KR102251287B1 - 5g beamforming antenna over a wide-band miniaturized by segmenting the substrate-integrated-waveguide structure into layers and stacking them - Google Patents

Abstract

According to one embodiment of the present invention, provided are a 5G small terminal using zigzag stacking technique after separating a substrate integrated structure into segments which are element functions, and area-reduced beamforming antennas for repeaters, which are broadband beamforming antennas covering all frequency bands from 26.5GHz to 28.9GHz planned for 5G communication service and are miniaturized beamforming antenna structures which greatly reduce the overall size of the antenna by applying an unprecedented folded structure which stacks layers back and forth (in zigzag) between an input port and an output port rather than a signal flow direction.

Description

5G BEAMFORMING ANTENNA OVER A WIDE-BAND MINIATURIZED BY SEGMENTING THE SUBSTRATE-INTEGRATED-WAVEGUIDE STRUCTURE INTO LAYERS AND STACKING THEM}

The present invention advances the function and structure of a beamforming antenna system, and more particularly, is a broadband beamforming antenna operating in all frequency bands from 26.5GHz to 28.9GHz planned for 5G communication service, and is a general phase such as microstrip. For multilayered board-type feed beamforming antennas with low radiation loss rather than arrays, a single layer has a large area, so it maintains the entire function, but is divided into segments, which are functional elements, and then stacked into unprecedented phased array feed beamforming antennas. The present invention relates to a method to propose a beamforming antenna structure in which the overall size of the antenna is significantly reduced by applying a folded structure.

Mobile communication technology has evolved over the years. The first generation wireless communication network is based on analog technology, and the second generation communication introduces digital technology using standards such as GSM and CDMA. In terms of performance, 2G added basic text transmission and limited wireless data capabilities and voice services. However, it was difficult to surf the web freely with 2G mobile devices.

3G, a third-generation communication network, is able to transmit small-sized data such as video by adding a high-speed data communication function using W-CDMA. However, high data rates, such as streaming video, suffered from slower problems than Wi-Fi or wireless LANs that most users compare to.

LTE (Long Term Evolution)-based 4G communication is significantly improved in terms of data volume compared to 3G, and provides a maximum data rate of up to 10 times. In addition, mobile service providers have implemented LTE-A, which can theoretically double the LTE speed.

In 2015, ITU-R (International Telecommunication Union-Radiocommunication) determined IMT-2020 (International Mobile Telemcommunications-2020) as the official name of 5G mobile communication, and a target performance and 5G service scenario were proposed.

1 shows a comparison of the main functions of IMT-Advanced (4G) and IMT-2020 (5G).

As shown in Figure 1, the 5G technical performance requirements proposed by ITU-R are the highest data rate of 20Gbps, latency within 1ms, maximum mobility of 500km/h, spectrum efficiency 3 times higher than that of 4G of IMT-Advanced, 1km. It can be seen that the connection density of 1 million per ^{2 and the user experience transmission speed of 100 Mbps or more are improved.}

Beamforming is one of the core technologies of 5G wireless communication, and radio wave transmission efficiency and frequency reusability are essential to satisfy the technical performance shown in FIG. 1. To improve this characteristic, a directional radiation pattern should be used for the antenna and a beamforming function should be provided.

The beamforming antenna should have good directivity and gain, and should have good energy transfer efficiency. Therefore, efficient beamforming systems are being researched around the world, and improved performance results are being published.

2 shows an integrated 28 GHz array (array) operated with a four element LTE MIMO antenna.

FIG. 2 shows a small-sized antenna for hybridization of 5G and LTE-A communication modes. The antenna is LTE-A from the side of a flat substrate Integrated waveguide Butler matrix beamforming antenna. It is a four multi-input multi-output chip antenna that works for.

3 shows a dual-layer multi-beam antenna, and is a structure in which the flow of the port 1 and port 4 series is divided up and down while maintaining the signal flow direction as in the conventional structure. Although it is a two-story structure, the size reduction effect is insignificant because the area, especially the length, of the structure is the same as that of the existing structure. In contrast, in the present invention, the signal flow direction is divided into elements, the segments are separated into layers, and the length and area are drastically reduced by stacking the layers and electrically connecting the input port and the output port direction back and forth (zigzag), There is a big difference. Ultimately, for a repeater that repeats this structure, it is possible to reduce the size to a degree that other techniques cannot match.

4 shows a flat Rotman lens for a 5G beamforming antenna.

4, in the main stage of the design, the arcs of the input and output ports of the Rotman lens are determined according to the concept of the light path. Adhering to the trifocal approach, the rays from the three focal points follow the equation in which the solution forms the input and output curves. Together with these arcs, the geometric information for the delay lines is determined to generate a beam pointing to three angles: high, medium and low.

With the development of such communication technology, the number of wireless communication service subscribers is rapidly increasing, and as user demands for high-quality and broadband data communication increase, mmWave technology is being proposed as one of the technologies to meet these demands. The technology is a technology that utilizes an ultra-high frequency broadband that exceeds the frequency band currently used for commercial mobile communication.

Since the hardware to which the mmWave technology is applied is inevitably required to be miniaturized, an antenna design technique that can be further miniaturized while satisfying the characteristics of a basic frequency band as an antenna is required.

The present invention is to solve the problems of the prior art as described above, and to provide a broadband and compact beamforming antenna including all frequency bands from 26.5GHz to 28.9GHz planned for 5G communication service.

In particular, for a substrate-integrated phased array feed beamforming antenna with a small radiation loss but a large area due to a single layer, the elements are segmented in the direction of signal flow, and the layers are stacked in a zigzag method that moves back and forth between the input port and the output port. We propose an unprecedented folded structure that is conjoined through a slot to help broadband and maintains the beamforming function, thereby presenting a miniaturized beamforming antenna that significantly reduces the overall size of the antenna.

An area reduction beamforming antenna for a 5G small terminal and a repeater using a structural segment separation zigzag folded stacking technique according to an embodiment of the present invention for achieving the above technical problem,

The signal transmission part of the SIW Butler matrix including a quadrature coupler, a cross over, and a phase shifter, formed based on a substrate integrated waveguide (SIW). A folded SIW Butler matrix consisting of a plurality of layers by being divided (segmented) into at least two parts based on the reference and stacked in a zigzag folded form between the input port and the output port; And

And a radiator connected to an output port at one end of the SIW Butler matrix.

An area-reduced beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention is formed at an input port of the other end of the SIW Butler matrix, It may further include a strip-SIW transition.

In addition, in the reduced-area beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention, the folded SIW Butler matrix,

It may include a plurality of SIW-SIW vertical transitions electrically coupling separated portions of two vertically adjacent layers among the plurality of layers. For reference, it is also a feature of the present invention that Vias (metal pins) of each layer do not interfere with performing the entire function even if they are not aligned with Vias of other layers.

In addition, in the area reduction beamforming antenna for 5G small terminals and repeaters using the structure separation and stacking technique according to an embodiment of the present invention, the SIW Butler matrix may be an 8×8 SIW Butler matrix.

In addition, in the reduced-area beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention, the radiator includes a microstrip patch antenna,

The microstrip patch antenna,

A modified E-shaped patch antenna pattern formed on an uppermost layer of the plurality of layers; And

And a SIW-microstrip transition formed on a lowermost layer of the plurality of layers and connected to the SIW transmission line,

The modified E-shaped patch antenna pattern may be fed by indirect coupling through the SIW-microstrip transition.

In addition, in the reduced-area beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention, the microstrip-SIW transition may include a tapered microstrip line.

In addition, in the area reduction beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention, the SIW-SIW vertical transition,

A via wall positioned in an upper layer of two vertically adjacent layers of the plurality of layers and a lower layer below the upper layer; And

A slot may be spaced apart from the via wall by a predetermined distance and formed in the metal clad between the upper layer and the lower layer. This slot is a very important element in the present invention, and in the general SIW Butler matrix structure, element functions are gathered in one layer, so that area reduction is impossible. It is stacked according to the direction, and the length cannot be shortened, or the cost increases due to the need for FPCB lines and process steps to connect the output of one layer to the input of the other layer). It plays a very important role in connecting the layers while maintaining the broadband characteristics (to satisfy the impedance matching and required phase value of the partial and entire structure). The shape of the slot may change depending on the situation.

In addition, in the reduced-area beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention, the phase shifter,

Including 67.5° phase shifter, 22.5° phase shifter and 45° phase shifter,

The phase shifter may perform a time advance shift.

In addition, in the area reduction beamforming antenna for 5G small terminals and repeaters using the structure separation and stacking technique according to an embodiment of the present invention, the folded SIW Butler matrix is separated and overlapped based on the interruption of the SIW Butler matrix. It consists of an upper layer and a lower layer,

The SIW Butler matrix may be separated based on an interruption by dividing the position of the right angle coupler into two parts.

According to the present invention as described above, it is possible to provide a low profile beamforming antenna system for 5G communication. The antenna beam is formed in 8 directions by an 8×8 Butler matrix beamforming network. The antenna of the present invention may be manufactured based on a substrate integrated waveguide (SIW).

The SIW structure applied in the present invention has an advantage in RF component design. Compared to the conventional waveguide, it can be manufactured using a printed circuit board (PCB) technology, and since the existing waveguide is manufactured using a mold technology, the SIW structure according to the present invention has the advantage of low manufacturing cost and low weight. . In addition, the electrical loss is less than that of the microstrip structure.

The antenna of the present invention provides a right angle coupler, a crossover, and a phase shifter as necessary components, and by combining these components, a Butler matrix having 8 inputs and 8 outputs can be provided. In particular, in order to meet the necessity of precise phase adjustment in the millimeter wave (mmWave) domain, each SIW phase shifter is precisely optimized in the present invention, and also minimizes the area of the phase shifter, and provides a phase shift required only for a straight pattern, not a curved pattern. Can be provided to satisfy.

In order to minimize the size of a general linear 8×8 Butler matrix, the present invention proposes a folded structure that is allocated as a layer after segment separation and stacked in a zigzag manner, and the folded structure is applied using a SIW-SIW vertical transition. The SIW-SIW vertical transition is a slot for electrical coupling and impedance matching and phase satisfaction formed in the metal clad between the upper and lower layers by a predetermined distance from the closed metal via (post) wall formed on the adjacent upper and lower layers and the via wall. It is composed of and electrically connects the upper layer and the lower layer so that the frequency band to which energy is to be transmitted is transmitted. As a result of this treatment, the length of the SIW structure can be drastically reduced.

In addition, in the present invention, by applying the E-shaped patch antenna, it is possible to solve the problem of isolation from a microstrip patch antenna having a narrow band as well as a size reduction. The E-shaped patch antenna has a wider operating frequency band above 2.4GHz. Therefore, the structure proposed in the present invention has the advantage of having a high antenna beam uniformity from 26.5 GHz to 28.9 GHz.

1 shows the main function contrast of IMT-Advanced (4G) and IMT-2020 (5G),
Figure 2 shows an integrated 28GHz array operated with a four-element LTE MIMO antenna,
3 shows a dual layer (no length reduction effect) multi-beam antenna,
4 shows a flat Rotman lens for a 5G beamforming antenna,
5 shows the geometry of the microstrip transmission line,
6 shows a rectangular waveguide structure,
7 shows a structure of a substrate integrated waveguide (SIW),
8 shows an array antenna composed of two dipoles,
9 shows the topology of a Butler matrix having 4 inputs and 4 outputs,
10 shows an example of a right angle coupler of the microstrip,
11 shows the operation of the circuit of the right angle coupler according to the signal input of port 1,
12 shows a separate circuit of the right angle coupler in the even mode,
13 shows a separate circuit of the right angle coupler in odd mode,
14 shows the topology of an 8×8 Butler matrix,
15 shows an example of a microstrip patch antenna,
16 shows the electromagnetic field of the microstrip line,
17 shows the actual length of a patch antenna having a fringing effect,
18 shows a modeled SIW transmission line,
19 shows S-parameters of a linear pattern SIW transmission line according to a via spacing,
20 shows the electromagnetic field distribution of the SIW transmission line according to the parameter s,
21 shows S-parameters of a linear pattern SIW transmission line according to a waveguide width,
22 shows the electromagnetic field distribution of the SIW transmission line according to the parameter a,
23 shows a SIW right angle coupler proposed in the present invention,
24 shows the S-parameters of the SIW right angle coupler of FIG. 23,
25 shows the electromagnetic field distribution of the right angle coupler proposed by 28GHx,
26 shows the SIW crossover proposed in the present invention,
27 shows the S-parameter and electromagnetic field distribution for the crossover of FIG. 26,
28 shows a 67.5° SIW phase shifter in the present invention,
29 shows S-parameters for the 67.5° SIW phase shifter of FIG. 28,
30 shows a 22.5° SIW phase shifter in the present invention,
31 shows S-parameters for the 22.5° SIW phase shifter of FIG. 30,
FIG. 32 shows electromagnetic field distributions of the 67.5° SIW phase shifter of FIG. 28 and the 22.5° SIW phase shifter of FIG. 30,
33 shows an externally located 45° phase shifter in the present invention,
34 shows S-parameters for the 45° phase shifter of FIG. 33,
35 shows the electromagnetic field profile,
36 shows a microstrip-waveguide transition in the present invention,
37 shows the S-parameter of FIG. 36,
38 shows a combined structure of each SIW configuration according to the present invention,
39 (a) to 39 (h) show S-parameters for each port in the embodiment of FIG. 28,
40 shows the electromagnetic field distribution of the 8×8 SIW Butler matrix of FIG. 38,
41 shows a microstrip patch antenna according to the present invention,
FIG. 42 shows the reflection loss and 3D radiation pattern of the microstrip patch antenna according to the embodiment of FIG. 41,
43 shows a patch antenna array to which a Butler matrix structure having a transition function according to the present invention is applied,
44 shows S-parameters of an antenna to which the SIW Butler matrix according to the embodiment of FIG. 43 is applied,
FIG. 45 shows the distribution of electromagnetic fields at each port of the antenna to which the SIW Butler matrix according to the embodiment of FIG. 43 is applied,
46 shows a 3D beam pattern of the SIW Butler matrix according to the embodiment of FIG. 43,
FIG. 47 shows the far field gain of the SIW Butler matrix according to the embodiment of FIG. 43,
48 shows the concept of an antenna miniaturization scheme proposed in the present invention,
49 shows a SIW-SIW vertical transition structure according to the present invention,
50 shows the parameters for FIG. 49,
51 shows the return loss and insertion loss of the SIW-SIW vertical transition according to FIG. 50,
FIG. 52 shows a structure of an 8×8 folded SIW Butler matrix according to a reduced area beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention.
FIG. 53 shows S-parameters for each port of the 8×8 folded SIW Butler matrix according to the embodiment of FIG. 52,
54 shows a modified E-shaped patch antenna according to the present invention,
55 shows the return loss of the modified E-shaped patch antenna of FIG. 54,
56 shows a far-field radiation pattern of the modified E-shaped patch antenna according to the embodiment of FIG. 54,
57 shows an 8×8 folded SIW Butler matrix synthesized with a modified E-shaped antenna according to the present invention,
58 shows the structure of an 8×8 folded SIW Butler matrix synthesized with a modified E-shaped antenna according to the present invention,
59 shows the S-parameters for the embodiment of FIG. 57,
60 shows a 3D beam pattern for the embodiment of FIG. 58,
61 shows the uniformity of the antenna beam pattern from the lowest frequency to the highest frequency for FIG. 60,
62 shows an implementation example of an 8×8 SIW Butler matrix beamforming antenna fabricated according to the present invention,
63 shows an implementation example of an 8×8 folded SIW Butler matrix beamforming antenna fabricated according to the present invention,
FIG. 64 shows a size contrast between the embodiment of FIG. 62 and the embodiment of FIG. 63,
65 shows the S-parameter measurement result for the embodiment of 62,
66 shows a result of measuring a far-field radiation pattern for the embodiment of FIG. 62,
67 shows the S-parameter measurement result for the embodiment of 63,
68 shows a result of measuring a far-field radiation pattern for the embodiment of FIG. 63,
69 shows a result of measuring a far-field radiation pattern for each frequency for the embodiment of 63,
70 shows a general concept of an antenna miniaturization scheme proposed in the present invention,
FIG. 71 shows an implementation example of an actually manufactured 8×8 folded SIW Butler matrix beamforming antenna that is divided into two parts and three parts, respectively, and stacked according to the antenna miniaturization technique of FIG. 70.

In order to explain the present invention and the operational advantages of the present invention and the object achieved by the implementation of the present invention, the following describes a preferred embodiment of the present invention and looks at with reference thereto.

First, the terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention, and expressions in the singular may include a plurality of expressions unless the context clearly indicates otherwise. In addition, in the present application, terms such as "comprise" or "have" are intended to designate the existence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other It should be understood that the presence or addition of features, numbers, steps, actions, components, parts, or combinations thereof, does not preclude the possibility of preliminary exclusion.

In describing the present invention, when it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

The present invention proposes a millimeter wave (mmWave) beamforming antenna system for 5G communication and a miniaturized antenna structure for the same. The antenna according to the present invention has been proposed to meet the requirements of the following [Table 1], and is a broadband beamforming antenna system including all frequency bands from 26.5GHz to 28.9GHz planned for 5G communication service. In addition, as a compact beamforming antenna structure, the size can be significantly reduced by applying a folded structure in which the signal flow function is divided into segments and layers are stacked in a zigzag manner between the input port and the output port.

Prior to describing the beamforming antenna system according to the present invention, a base technology for understanding each configuration of the present invention will be first described, and then each configuration of the beamforming antenna system according to the present invention will be described in detail.

As a base technology for the antenna design of the present invention, 1.1. Transmission Line, 1.2. Phased Array Antenna, 1.3. Let's first look at the Butler Matrix.

1.1. Transmission line

1.1.1. Microstrip transmission line

Microstrip transmission lines are often used in antennas for economical efficiency, and microstrip transmission lines consist of a dielectric substrate and a metal pattern. Because the metal strip is printed using PCB technology, it is relatively inexpensive and easy to manufacture.

5 shows the geometry of the microstrip transmission line.

A strip of width W is printed on a substrate with a thickness d and a relative permittivity ε _r. The electromagnetic field is mainly distributed inside the dielectric substrate and between the ground plane. The phase velocity and propagation constant may be defined as in [Equation 1] and [Equation 2] below.

1.1.2. Rectangular waveguide

Rectangular waveguides are mainly used as transmission lines in the microwave region. In recent years, flat transmission lines such as microstrips are being used instead of waveguides according to the trend of reduction and integration. However, for systems that handle high power and sophisticated tests, waveguides are still used effectively. Rectangular waveguides can be commercialized by standard waveguide frequency bands.

6 shows a rectangular waveguide structure.

As shown in FIG. 6, in general, the waveguide has a length in the x-axis direction longer than the y-axis. In the rectangular waveguide structure, TM and TE modes exist, and TEM modes cannot exist. For frequencies lower than the cutoff frequency, the propagation constant becomes an imaginary value and propagation does not proceed. In the TE _mn mode, the x-axis and y-axis components of the E field may be defined by the following [Equation 3] and [Equation 4].

In addition, in the TE _mn mode, the x-axis and y-axis components of the H field may be defined by the following [Equation 5] and [Equation 6].

Here, the propagation constant β may be calculated by the following [Equation 7], k _c denotes a cutoff wavenumber, and may be expressed by the following [Equation 8].

Since the wave number must be k> k _c in order for the electromagnetic wave to propagate, the cutoff frequency fc _mn can be calculated according to the following [Equation 9].

_{Therefore, in TE 10} mode, which is a dominant mode, the cutoff frequency may be as shown in [Equation 10] below.

1.1.3. Substrate Integrated Waveguide

Conventional planar transmission lines such as microstrip lines, strip lines, and coplanar waveguides can be implemented with a substrate integrated circuit (SIC) structure in the same processing technique.

Substrate Integrated Waveguide (SIW) also belongs to the SIC category. SIW is a technology that implements a waveguide structure using through-hole metal vias on a substrate.

7 shows the structure of a substrate integrated waveguide (SIW).

On both sides of the substrate, there are metallic clads 10 and 20 and metallic vias 30 connecting the clads.

For the design of the SIW, the substrate thickness h and the relative permittivity ε _r are considered constant, and as three main parameters determining the action and effect, the SIW in FIG. 7 is the width a, the diameter d of the metal via, and It has a distance s between metal vias. In general, for SIW having a width a, the cutoff frequency is determined by the thickness h of the substrate.

These SIWs are non-standard waveguides, but the rectangular waveguides have standard dimensions and do not support transverse magnetic TM mode propagation, but only allow propagation in _{TE n0 mode.} This is because there is no current flowing along the two sidewalls.

The cutoff frequency can be obtained by the least squares approach according to the following [Equation 11], where c ₀ is the speed of light in free space.

The thickness only affects the Q-factor. The SIW structure can be analyzed with a rectangular waveguide filled with the same substrate using the same width w. The basic equivalent width w can be obtained by the following [Equation 12], but more precisely, it can be obtained by the following [Equation 13]. This is because this does not include the effect of the diameter-to-width ratio.

The distance s between the metal vias should be set so that there is no band gap beyond the band of interest. When s satisfies the condition of [Equation 14], a band gap does not occur.

The impedance of SIW Z ₀ can be expressed by the following [Equation 15], where η is _{an intrinsic impedance having a relative dielectric constant ε r} of a dielectric material, and can be expressed by the following [Equation 16].

Changing Z ₀ is related to the tolerances of other parameters, and the worst operation can be calculated as shown in [Equation 17] below.

In the equation 17], △ a, △ h , △ ε r, △ s and d is the maximum error for each of a, h, ε _r, s and d. In addition, S ^z ₀ is an impedance sensitivity parameter. In SIW impedance, the tolerance effect of a, h and ε _r is greater than that of s and d.

1.2. Phased Array Antenna

1.2.1. Antenna array

The radiation pattern of a single radiating element generally has a large beamwidth and low directivity. By compensating for this, in order to obtain a radiation pattern with high directivity, it is possible to increase a gain by arranging a plurality of radiation elements. An antenna in which several radiating elements are arranged is called an array antenna, and the total radiating system of the array antenna is the sum of the radiation vectors of each radiating element. The array can be implemented in various shapes such as linear, flat and circular.

Figure 8 shows an array antenna composed of two dipoles, Figure 8 (a) shows an infinite dipole array, (b) shows a far field approximation.

Assuming an array antenna composed of two small dipoles arranged horizontally on the z-axis as shown in FIG. 8, the sum of the electric fields for them can be expressed by the following [Equation 18].

Where β is the phase difference between the two elements. The input amplitude of the two dipoles is the same. In FIG. 8, the conditions of the far-field approximation are the following [Equation 19] to [Equation 22].

According to the following [Equation 23], the total radiation field of the array is equal to the multiplication of the radiation field of a single element by the array factor (AF). Here, the array factor AF may be expressed by the following [Equation 24].

1.2.2. Analog feeding system.

The phased array antenna is composed of many radiating elements, which are sequentially fed to the radiating elements and use a phase shifter. Also, variable amplitude control is sometimes provided for pattern formation.

The antenna beam is formed by shifting the phase of the EM wave from the radiating element by providing constructive, destructive interference to steer each beam in the intended direction. Accordingly, the phased array antenna electrically controls the beam of the physically fixed antenna.

A power supply system is a network that connects antenna inputs to radiators. This is to transmit power to the antenna element or to collect a signal from the antenna element. Feeding must be performed while the excitation of the phase and amplitude required for the required radiating performance is maintained.

In addition, the power supply network may include a switch or other device to scan the beam, select among different antenna beam shapes, or switch between active sectors.

1.3. Butler Matrix

1.3.1. 4×4 Butler Matrix

The Butler Matrix forms N consecutive antenna beams in an array of N elements.

The conventional Butler matrix is formed by an arrangement of symmetric 3dB directional couplers. By adding an appropriate phase shifter to the network, a Butler beamformer can be realized.

이다.Butler matrix has the input 2 ^P 2 and ^P output. The number of directional couplers required for an array with N elements is

to be.

In order to implement a planar structure Butler matrix having only one plane, cross over couplers are required. 9 shows the topology of a Butler matrix with 4 inputs and 4 outputs.

The 90° quadrature coupler is also called a 90° hybrid coupler. This is a directional coupler having four ports having a phase difference of 90° at the two output ports, and may be implemented as a microstrip or strip line as shown in FIG. 10. When the signal is input to port 1, the signal is at half the power (3dB) of port 2, and the difference in output phase is 90°. Meanwhile, port 4 is isolated.

[Equation 25] below represents a matrix of a right angle coupler. The right angle coupler has a symmetrical structure because all ports can be used as input ports.

11 shows a circuit of a right-angle coupler when a signal with amplitude A _{1 = 1 is input to port 1.} This circuit can be analyzed separately in even mode and odd mode.

12 shows a separate circuit of the right angle coupler in even mode, and FIG. 13 shows a separate circuit of the right angle coupler in odd mode. When the circuits of FIG. 12 and FIG. 13 are combined, the state of the circuit is obtained as shown in FIG. 11, and the response characteristics to supply of the even mode and the odd mode are summed.

The amplitude of the emerging wave at each port of the right-angled coupler may be expressed by the following [Equation 26] to [Equation 29].

Where Г _e,o and T _e,o are the even and odd mode reflection and transmission coefficients for the two port networks. In the even mode circuit, Г _e and T _e can be obtained by multiplying the ABCD matrix according to the following [Equation 30] to [Equation 32].

In the same way, Г _o and T _o can be obtained through the following [Equation 33] to [Equation 35].

In addition, values of the following [Equation 36] to [Equation 39] can be obtained by substituting _{Г e,o} and T _e,o in [Equation 26] to [Equation 28].

1.3.2. 8×8 Butler Matrix

Increasing the number of elements in the array makes the Butler matrix feeding network more complex. For example, a feed network with 64 elements would require 192 directional couplers and 160 fixed phase shifters. For a network with 8 elements, 12 directional couplers and 8 fixed phase shifters are used.

14 shows the topology of an 8×8 Butler matrix.

The phase shifts required by the fixed phase shifter are 67.5°, 22.5° and 45°. Table 2 below shows the phase output of an ideal 8×8 Butler matrix. When a signal is input to port 1, the phase difference of each adjacent output port becomes -22.5. When signals are input to each port 2, 3, and 4, the phase difference between each adjacent output port is +157.5°, -112.5° and +67.5°, respectively. The results of inputting signals to ports 5, 6, 7 and 8 respectively indicate opposite results for each output when the inputs are ports 1, 2, 3, and 4 as shown in Table 2 below.

1.4. Microstrip patch antenna

The microstrip patch antenna has a structure with parallel metal surfaces on both sides of the insulator. In general, one wide surface is used as a ground plane and the other pattern is used as a radiating element as shown in FIG. 15.

Microstrip patch antennas use PCB printing technology, so they are relatively thin, easy to manufacture, and inexpensive. In addition, resonant frequency, polarization, impedance, etc. can be variously implemented by selecting a mode according to the pattern of the radiating element, and an antenna parameter can be changed by combining an active element such as a varactor diode.

The type of insulating substrate used in the microstrip patch antenna design differs depending on the dielectric constant, hardness and loss characteristics. In general, when the dielectric constant of the substrate is low and the thickness is large, the antenna bandwidth is wide and the efficiency is improved. However, it is expensive and the weight and volume increase. Conversely, if a substrate having a high dielectric constant and a thin substrate is used, the bandwidth becomes narrower and the efficiency decreases. However, since the size of the antenna element can be reduced, it is important to properly configure the antenna according to the use environment of the antenna.

Among the microstrip patch antennas, the square patch is the most widely used pattern. An appropriate transmission line model can be used to analyze a square patch antenna. The transmission line model represents a microstrip antenna with two slots separated by a transmission line of a specific length with low impedance.

Since the rectangular patch antenna is a finite structure with a width W, a length L, and a height h, a fringing effect occurs at the end of the structure. The fringing effect is determined by the size of the patch, the height of the substrate, and the dielectric constant ε _r. The resonant frequency of the patch antenna depends on the fringing effect.

16 shows the electromagnetic field of the microstrip line.

As shown in FIG. 16, the electromagnetic field appears almost in the center of the substrate. Since part of the radio wave propagates to the substrate and another part of the radio wave propagates into the air, the effective dielectric constant ε _reff is used to calculate the propagation due to fringing of the line. The static value of the effective dielectric constant can be obtained through the following [Equation 40].

Due to the fringing effect, the size of the patch is electrically larger than its actual physical size. Therefore, as shown in FIG. 17, it is calculated by adding the actual physical patch length. The effective length is as shown in [Equation 41] below.

In addition, L is related to the effective dielectric constant, the width of the patch, and the height of the substrate, and can be expressed as Equation 42 below.

In the mode TM ₀₁₀ , the resonant frequency of the patch antenna can be obtained through the following [Equation 43].

When considering the fringing effect, [Equation 43] may be expressed again as [Equation 44] below.

When [Equation 44] is multiplied by a weight, it can be expressed as [Equation 45] below.

And, q may be expressed by the following [Equation 46].

q is called a fringing factor, and as the thickness of the substrate increases, fringing increases and the effective length increases, so that the resonance frequency decreases.

In the present invention, based on the above-described base technology, each antenna element is presented and combined to implement a beamforming antenna system. After looking at the antenna elements proposed in the present invention, the beamforming according to the present invention is combined and combined. Let's take a look at the antenna system.

First, an antenna element proposed in the present invention will be described. The antenna elements proposed in the present invention are antenna elements based on the substrate integrated waveguide (SIW) described above.

2.1. SIW Transmission Line

In the microwave domain, transmission lines are key to a successful circuit design. The basic straight pattern SIW transmission line can be modeled through software CST Microwave Studio 2016 (CST-MWS). Rogers duroid RT5880 applied in the embodiment of the present invention uses a substrate having a thickness of 0.254 mm, and dielectric constant and loss tangent are 2.2 and 0.0009, respectively.

18 shows a modeled SIW transmission line, and Table 3 below shows a design target for a straight line pattern of the SIW transmission line.

The diameter of the metallic via is set to 0.5mm, so it can be easily used in general PCB manufacturing.

19 shows S-parameters of a linear pattern SIW transmission line according to a via spacing.

In the 28GHz band, the spacing s between vias is optimized to prevent a band gap, and it can be seen that the S-parameter changes according to the metal via spacing to select the parameter s. The band gap appears to have a return loss of less than -30dB at both observed frequencies when the spacing is 1.5 mm and the selected s value is 0.75 mm.

20 shows the electromagnetic field distribution of the SIW transmission line according to the parameter s. In FIG. 20, (a) is a case where the parameter s is 1.5 mm, and (b) is a case where the parameter s is 0.75 mm.

21 shows S-parameters of a linear pattern SIW transmission line according to a waveguide width, and FIG. 22 shows an electromagnetic field distribution of a SIW transmission line according to a parameter a. In FIG. 22, (a) is a case where a parameter a is 5.0, and (b) is a case where a parameter a is 6.0.

The width of waveguide a determines the cutoff frequency of the SIW transmission line. It is observed that the cutoff frequency is changed according to the parameter a according to [Equation 9]. The parameter a was selected as 6.0mm, and the cutoff frequency showed that the return loss was less than -30dB in all target frequency bands. It is desirable that the cutoff frequency be set to a sufficiently low cutoff frequency for the convenience of subsequent component design.

In an embodiment of the present invention, the final selected values of the diameter and spacing of the metal via and the width of the waveguide are 0.5 mm, 0.75 mm, and 6.0 mm, respectively. The return loss and insertion loss of the structure with the finally selected value were found to be less than -33dB and more than -0.06dB in the target frequency band, respectively.

2.2. SIW Quadrature Coupler

The SIW right angle coupler is a type of directional coupler with 4 ports. There is a characteristic that the input signal is divided into two signals of half power with a difference of 90°. And the other ports become separate ports.

23 shows a SIW right angle coupler proposed in the present invention.

Based on the above-described transmission line, an aperture having parameters qv and qh as shown in (b) of FIG. 23 was optimized. In the embodiment of the present invention, parameters qv and qh were set to 10.4 mm and 7.7 mm, respectively.

The return loss was less than -28.5dB, and S _2,1 and S _3,1 were found to be about -3dB with the same power distribution across the target frequency. The phase difference between the output ports is 90.15° at 28GHz.

24 shows the S-parameters of the SIW right angle coupler of FIG. 23. In FIG. 24, S _4,1 denotes an insulation level between two inputs. 25 shows the electromagnetic field distribution of a right angle coupler proposed at 28GHz. As shown in FIG. 25, it can be seen that power distribution is good and insulation is high.

2.3. SIW Cross over

In the ideal topology of the Butler matrix, the crossover component does not affect the phase matrix. However, for a Butler matrix, especially a planar implementation, crossover is required because the input signals do not overlap and cannot go to the opposite side.

In the present invention, the SIW crossover is a four-port coupler, and transmits an input signal to a diagonal output port. 26 shows the SIW crossover proposed by the present invention. The SIW crossover of FIG. 26 is based on the SIW transmission line discussed above. It has a couple region composed of parameters ch and cv as shown in (b) of FIG. 26. In the embodiment of the present invention, the values of ch and cv were set to 9 mm and 12 mm, respectively.

FIG. 27 shows S-parameters and electromagnetic field distributions for the crossover of FIG. 26.

As shown in (a) of FIG. 27, it can be seen that the return loss is less than -25dB in the frequency band 26.5GHz to 29.75GHz. The minimum value of _{S 3,1} , which means insertion loss, is -0.24dB. (B) of FIG. 27 shows a function of a crossover proposed in 28GHz.

2.4. SIW Phase Shifter

In the case of the topology of the 8×8 Butler matrix as shown in FIG. 14, the number of phase shifters is eight.

If the Butler matrix feeding network is ideal, there is no phase shift in the crossover. However, in the actual Butler matrix, the crossover has a fixed phase shift. Therefore, it is necessary to optimize each phase shifter in consideration of the phase shift of the crossover.

2.4.1. 67.5° phase shifter

FIG. 28 shows the 67.5° SIW phase shifter in the present invention, and FIG. 29 shows the S-parameters for the 67.5° SIW phase shifter of FIG. 28.

The SIW phase shifter of FIG. 28 is designed based on a SIW transmission line. In addition, in (b) of FIG. 28, the distance of the via p1 is adjusted to finely adjust the output phase. In the embodiment of the present invention, parameter a was set to 6.0 mm and p1 was set to 6.5 mm.

29 shows S parameters for the 67.5° phase shifter of FIG. 28.

2.4.2. 22.5° phase shifter

The phase shifter proposed in the present invention is designed for time advance shift. Compared to the time delay shifter type, there is no need to increase the overall length, so more physical space is not required. Although the bandwidth is relatively narrow, it can be sufficiently applied when the required bandwidth is still satisfied.

30 shows a 22.5° SIW phase shifter in the present invention.

In the present invention, parameters a, pb1, and pb2 of the phase shifter in FIG. 30(b) were set to 5.25 mm, 6.0 mm and 5.8 mm, respectively.

In FIG. 31 (a) shows the S-parameter for the 22.5° SIW phase shifter of FIG. 30, and (b) is the phase difference between the 67.5° SIW phase shifter of FIG. 28 and the 22.5° SIW phase shifter of FIG. 30 Represents.

As shown in (a) of FIG. 31, S _1,1 is less than -30dB and S _2,1 exceeds -0.073dB from 25.5GHz to 30.3GHz. And, as shown in (b) of FIG. 31, the phase difference between the 67.5° SIW phase shifter and the 22.5° SIW phase shifter is 45°.

FIG. 32 shows the electromagnetic field distribution of the 67.5° SIW phase shifter of FIG. 28 and the 22.5° SIW phase shifter of FIG. 30, the left side shows the electromagnetic field distribution of the 67.5° SIW phase shifter, and the right side shows the electromagnetic field of the 22.5° SIW phase shifter Shows the distribution.

2.4.3. 45° phase shifter

There are several considerations when designing a 45° phase shifter. In the topology shown in FIG. 14, the 45° phase shifter appears to be the same, but the physical length of the 45° phase shifter different from the 45° phase shifter located outside in the actual Butler matrix is different. Therefore, it must be designed in a different way in consideration of this.

FIG. 33 shows an externally located 45° phase shifter in the present invention, and FIG. 34 shows S-parameters for the 45° phase shifter of FIG. 33.

The length of the externally located 45° phase shifter is the same as the crossover length of 3 times. Since the crossover has a slight phase shift, it is necessary to adjust the phase shift according to the realized structure as well as the 45° phase shift.

2.5. Microstrip-SIW transition

A transition is required for the connection between the SIW structure and the microwave connector. The microstrip line is suitable for exciting a waveguide because the electromagnetic fields of two different structures are oriented in substantially the same direction and have a profile as shown in FIG. 35.

36 shows the microstrip-waveguide transition in the present invention, and FIG. 37 shows the S-parameter of FIG. 36.

In the present invention, the input impedance of the microstrip was set to 50 Ω as the parameter w50. As shown in FIG. 36, in the present invention, the transition structure is formed as a tapered microstrip line having parameters tap W and tap L in a waveguide mode. The taper serves to convert the quasi-TEM mode of the microstrip line into the TE _{10 mode in the waveguide.}

In the embodiment of the present invention, the parameters of the tapered microstrip lines w50, tapW and tapL were formed to be 0.75mm, 4.0mm and 4.7mm.

As shown in FIG. 37, it can be seen that a return loss of less than -20dB and an insertion loss of -0.26dB or more appeared in all bands of the target frequency.

Next, a method of configuring a SIW beamforming network through the assembly of the antenna components described above will be described.

3.1. 8×8 SIW Butler Matrix

The SIW Butler matrix feeding network may be implemented as an assembly of SIW components proposed in the present invention as discussed above.

Each designed component must be correctly positioned according to the topology shown in FIG. 14. Since the Butler matrix feeding network is a symmetrical structure, the SIW structure is also formed to be symmetrical. In the ideal case, the Butler matrix feeding network is a lossless network, but there is always a finite insertion loss because all components of the Butler matrix are lossy.

In the present invention, an 8×8 SIW Butler matrix was proposed to meet the design goals of Table 4 below.

In the present invention, the SIW Butler matrix targets a return loss of less than -15dB from 26.5GHz to 28.9GHz.

38 shows the combined structure of each SIW configuration according to the present invention.

In the ideal case of the Butler matrix, we use 8 fixed phase shifters with 12 directional couplers and 16 crossovers. In the real case, 6 phase shifters are added before the output ports due to the phase shift of the crossover.

The SIW Butler matrix 100 of FIG. 38 is configured by assembling the antenna elements according to the present invention described above, an input port 110, a right angle coupler 130, a 67.5° SIW phase shifter 140, and a 22.5° SIW A phase shifter 160, a 45° SIW phase shifter 150a, 150b, an additional phase shifter 170, and an output port 120 are combined in an assembly.

The substrate was Rogers duroid RT5880 of the same method as previously described, and a 0.254mm-thick substrate was applied. In the example of FIG. 38, the length of the entire structure is set to 135.5 mm and the width is set to 48.5 mm.

39(a) to 39(h) show S-parameters for each port for the embodiment of FIG. 28, and Table 5 below shows the phase difference results of each port.

When port 4 is input, the maximum phase error is 0.09λ. The results of ports 1 and 8, the results of ports 2 and 7, the results of ports 3 and 6, and the results of ports 4 and 5 are symmetrically the same because the physical structure is symmetric.

40 shows the electromagnetic field distribution of the 8×8 SIW Butler matrix of FIG. 38. 40A illustrates a case of port 1, (b) a case of port 2, (C) a case of port 3, and (d) a case of port 4. Referring to FIG.

3.2. Synthesis of radiating elements and feeding networks

In the present invention, an antenna beam forming system is implemented by adding a radiation element to the Butler matrix described above.

41 shows a microstrip patch antenna according to the present invention.

In FIG. 41, a microstrip patch antenna is used as a radiating element. The resonant frequency of the patch antenna was set to 28 GHz. In the embodiment of FIG. 41, since the patch shape is square, patch_W and patch_L were set to 3.5 mm as the design parameter of the patch antenna. In consideration of the connection between the SIW and the microstrip, a transition was applied. The parameters inset, tap_L and tap_W for impedance matching were set to 1.2mm, 3.0mm and 3.0mm, respectively.

42 illustrates reflection loss and 3D radiation pattern of the microstrip patch antenna according to the embodiment of FIG. 41.

As shown in FIG. 42, an excellent return loss of -20dB or less is exhibited at 28GHz, and the antenna gain was confirmed to be 7.198dB at 28GHz.

43 shows a patch antenna array to which a Butler matrix structure having a transition function according to the present invention is applied.

In the patch antenna array 200 to which the Butler matrix structure is applied, the SIW Butler matrix 100 according to the embodiment of FIG. 38 is applied, and since there are 8 output ports, the number of patch antennas is 8. According to the structure of the Butler matrix proposed in the present invention, the shape of the patch antenna array is linearly arranged as shown in FIG. 43.

In the implementation of the embodiment of FIG. 38, in order to compare the similarity between the actual product and the measurement, the conductor material was changed from PEC to copper, and the antenna was connected to the output port. In addition, the microstrip-SIW transition 210 is added to the input port for connecting the microwave connector, and the microstrip patch antenna 250 described above is installed at the output port for power supply. In the example of FIG. 43, the total length L_m1 is set to 214 mm, and the width W_m1 is set to 72.9 mm.

FIG. 44 shows the S-parameters of the antenna to which the SIW Butler matrix according to the embodiment of FIG. 43 is applied, and FIG. 45 shows the electromagnetic field distribution at each port of the antenna to which the SIW Butler matrix according to the embodiment of FIG. 43 is applied, FIG. 46 shows a 3D beam pattern of the SIW Butler matrix according to the embodiment of FIG. 43, and FIG. 47 shows a far field gain of the SIW Butler matrix according to the embodiment of FIG. 43.

Table 6 below shows the gain at 28 GHz of the antenna to which the SIW Butler matrix according to the embodiment of FIG. 43 is applied, and Table 7 below shows the results in the main lobe direction.

In the antenna to which the SIW Butler matrix according to the embodiment of FIG. 43 is applied, since the angle of the outermost main beam is ±49°, the coverage range of the beamforming antenna is 98°.

As described above, the beamforming antenna proposed by the present invention shows an 8-direction beam capable of covering a 98° front range, and it can be seen that it can be sufficiently applied to a repeater for 5G communication.

Further, the present invention proposes an antenna capable of reducing return loss at all target frequencies while further reducing the size and extending the bandwidth to a broadband for application to a mobile device. This will be described with reference to the following embodiments.

4.1. SIW-SIW Vertical Transition

Antenna miniaturization has always been a matter of tremendous coordination and challenge. Although many design techniques have been proposed for miniaturization of antennas, in general, there is a disadvantage in that the bandwidth is narrowed or performance is degraded when miniaturization is performed.

In order to minimize the SIW Butler matrix according to the present invention described above, the antenna design technique proposed in the present invention is to divide and reconstruct the antenna structure. In this regard, FIG. 48 illustrates a concept of an antenna miniaturization technique proposed to provide an area-reduced beamforming antenna for a 5G small terminal and a repeater using a structure separation and stacking technique according to an embodiment of the present invention.

As shown in (a) of FIG. 48, the SIW Butler matrix structure is divided into areas of Part 1 and Part 2, and as shown in (b) of FIG. 48, the divided portion is folded to form a multi-layered antenna. You will be reconstructed.

FIG. 70 shows a general concept of an antenna miniaturization scheme proposed in the present invention. As shown in FIG. 70(a), the SIW Butler matrix structure is divided into two parts based on a dividing line, and FIG. As shown in (b), the divided portions are folded and stacked to reconstruct a multi-layered antenna.

In addition, as shown in (b) of FIG. 70, the SIW Butler matrix structure is divided into three parts based on two dividing lines, and the divided parts are folded and stacked as shown in Fig. 70(b). It is reconstructed with a multi-layered antenna.

The dividing lines for dividing the SIW Butler matrix structure into a plurality of parts are signal transmission parts that do not significantly affect the operation of the SIW Butler matrix structure when the SIW Butler matrix structure is divided into a plurality of parts. It is preferable to be.

FIG. 71 shows an implementation example of an actually fabricated 8×8 folded SIW Butler matrix beamforming antenna that is divided into two parts and three parts, respectively, folded and stacked according to the antenna miniaturization technique of FIG. 70.

(A) of FIG. 71 shows an ungrounded 8x8 SIW Butler matrix beamforming antenna, and (b) of FIG.71 is an 8x8 SIW Butler matrix according to the antenna miniaturization technique shown in (a) of FIG. Figure 71(c) shows an 8x8 folded SIW Butler matrix beamforming antenna in which the beamforming antennas are folded once and stacked, and FIG.71(c) is an 8x8 SIW Butler according to the antenna miniaturization technique shown in FIG.70(b). It shows an 8×8 folded SIW Butler matrix beamforming antenna in which the matrix beamforming antenna is folded twice and stacked.

As shown in FIGS. 70 and 71, the more the SIW Butler matrix beamforming antenna is folded, the smaller the size may be.

In one embodiment of the present invention, an 8×8 folded SIW Butler matrix beamforming antenna formed by folding and stacking the SIW Butler matrix beamforming antenna once will be described. However, the present invention is not limited to an 8×8 folded SIW Butler matrix beamforming antenna that is folded and stacked once, and a folded SIW Butler matrix beamforming antenna that is folded and stacked a plurality of times may be provided.

In order to fold the Butler matrix discussed above, two SIW transmission lines must be connected vertically. 49 shows a SIW-SIW vertical transition structure according to the present invention. The SIW-SIW vertical transition is a via wall positioned in an upper layer of two vertically adjacent layers and a lower layer under the upper layer, and a metal clad between the upper layer and the lower layer by being spaced a predetermined distance from the via wall. Including the slots formed in the upper layer and the lower layer, the frequency band to which energy is to be transmitted is transmitted between the upper layer and the lower layer by electrically connecting the upper layer and the lower layer.

FIG. 50 shows the parameters for FIG. 49, and as shown in FIG. 50, the length, width, and position of the slot are indicated by Slot_L, Slot_W, and Slot_O, respectively. In the embodiment of the present invention, Slot_L is set to 3mm, Slot_W is set to 0.2mm, and Slot_O is set to 3.7mm. The location of the slot (Slot_O) represents the distance away from the via wall.

According to the length (Slot_L), width (Slot_W), and position (Slot_O) of the slot of the SIW-SIW vertical transition structure, the frequency band in which energy is to be transferred between the upper layer and the lower layer through the slot is adjusted.

Therefore, when a target frequency band in which energy is to be transmitted between the upper layer and the lower layer is set, the length of the slot of the SIW-SIW vertical transition structure so that energy is transmitted between the upper layer and the lower layer through the slot according to the set target frequency band. Adjust (Slot_L), width (Slot_W) and position (offset) (Slot_O).

51 shows the return loss and insertion loss of the SIW vertical transition according to FIG. 50.

4.2. 8×8 folded SIW Butler Matrix

The miniaturized SIW Butler matrix can be implemented by stacking two separate parts. 52 shows the structure of an 8×8 folded SIW Butler matrix proposed in the present invention.

As shown in (a) of FIG. 52, the 8×8 folded SIW Butler matrix 300 divides the position of the right-angled coupler at the center into two parts and separates it into a first part 310 and a second part 350. .

In addition, as shown in (b) of FIG. 52, the folded SIW Butler matrix 400 is formed by overlapping the first part 310 and the second part 350, wherein the separated plane is filled with a via wall. The transition described above is applied.

As shown in (c) of FIG. 52, since the Butler matrix feeding network proposed in the present invention is symmetric, the SIW structure is also configured to be symmetric.

The 8×8 folded SIW Butler matrix presented in the present invention was designed to satisfy the return loss, insulation, and phase errors shown in Table 8 below.

53 shows S-parameters for each port of the 8×8 folded SIW Butler matrix according to the embodiment of FIG. 52.

In the 8×8 folded SIW Butler matrix according to the embodiment of FIG. 52, the phase difference result of each port is shown in Table 9 below, and the maximum phase error is 0.091λ when port 4 is input.

4.3. E-shaped patch antenna for broadband

Since the microstrip patch antenna described above has a narrow band and does not satisfy the requirements for all target frequencies, it is difficult to cover a broadband through a microstrip patch antenna according to a single layer design. However, you can improve this problem by adding a PCB layer.

The folded Butler matrix structure proposed in the present invention has a multi-layered characteristic compared to the basic Butler matrix structure. Using these advantages, the E-shaped patch antenna shown in FIG. 54 is proposed in the present invention.

The SIW transmission line 520 and the SIW-microstrip transition 530 are formed on the substrate of the lower layer 510, and the E-shaped patch antenna pattern 560 is formed on the substrate of the upper layer 550.

The E-shaped pattern is fed by indirect coupling from the transition. As the substrate used, Rogers RT5880, which is the same as the above Butler matrix, was applied. [Table 10] below shows design targets for a broadband antenna, and [Table 11] shows design parameters of an E-shaped patch antenna proposed in the present invention.

FIG. 55 shows the return loss of the E-shaped patch antenna of FIG. 54, and in the patch antenna according to the present invention, a return loss of less than -10 dB was obtained in a band from 26.4 GHz to 29.1 GHz.

Excellent reflection loss as well as antenna beam uniformity are important characteristics of antenna performance evaluation. FIG. 56 shows a long-distance radiation pattern of the E-shaped patch antenna according to the embodiment of FIG. 54. Looking at the radiation pattern results according to the target frequency for the E-shaped patch antenna according to the embodiment of FIG. 54, it can be seen that all radiation patterns satisfy the formation of the antenna radiation pattern.

4.4. Synthesis of radiating elements and feeding networks

FIG. 57 shows a folded SIW Butler matrix synthesized with an E-shaped antenna according to the present invention, and FIG. 58 shows a structure of an 8×8 folded SIW Butler matrix synthesized with an E-shaped antenna according to the present invention.

Looking at the structure of the 8×8 folded SIW Butler matrix, (a) of FIG. 57 is a front direction, and a first part 400a and a patch antenna 500a of the SIW Butler matrix are formed on the upper layer. 57(b) is a rear direction, and a second part 400b and a rear part of the SIW Butler matrix are not shown on the lower layer, but the SIW transmission line and the SIW-microstrip transition 500b are formed.

In the embodiment of FIG. 57, the total length L_m2 of the antenna is 120 mm and the width is 72.9 mm. Therefore, compared to the single-layered structure, the length of the folded structure is about 56%.

59 shows S-parameters for the embodiment of FIG. 57.

As shown in FIG. 59, in the operating frequency band, the return loss is less than -15dB and the insulation is improved to less than -10dB.

FIG. 60 shows the 3D beam pattern for the embodiment of FIG. 58, and FIG. 61 shows the uniformity of the antenna beam pattern from the lowest frequency to the highest frequency for FIG. [Table 12] shows antenna gains at each port for each frequency.

As shown in FIG. 61, it can be seen that the radiation pattern uniformity of the antenna according to the embodiment of FIG. 58 is excellent, and the antenna beam is not deformed from the lowest frequency of 26.5 GHz to the highest frequency of 28.9 GHz. Got it.

4.5. Antenna implementation and performance measurement

62 shows an implementation example of an 8×8 SIW Butler matrix beamforming antenna fabricated according to the present invention.

The implemented antenna of FIG. 62 has a total length of 214 mm and a width of 72.9 mm. The K-connector is connected to the microstrip transition for measurement.

63 shows an implementation example of an 8×8 folded SIW Butler matrix beamforming antenna fabricated according to the present invention.

The implemented antenna of FIG. 63 has a total length of 120 mm and a width of 72.9 mm.

62 and 63 are implemented by applying PCB technology.

FIG. 64 shows the size comparison between the implementation example of FIG. 62 (left antenna) and the implementation example of FIG. 63 (center antenna).

As shown in FIG. 64, the straight pattern of the Butler matrix beamforming antenna of FIG. 62 exceeds the size of the mobile phone, but the folded structure of the Butler matrix beamforming antenna of FIG. 63 may be made smaller than that of the mobile phone.

65 shows a result of measuring the S-parameter for the embodiment of 62, and FIG. 66 shows the result of measuring a far-field radiation pattern for the embodiment of FIG. 62. Table 13 below shows the gain measurement results for the embodiment of 62.

As shown in FIG. 65, it can be seen that the measured return loss of the linear pattern SIW Butler matrix beamforming antenna exhibits a good return loss of less than -10 dB in the target frequency band. As shown in FIG. 66, it can be seen that the measured far-field radiation patterns have similar results at each symmetric input port.

67 shows the results of measuring the S-parameter for the embodiment of 63, and FIG. 68 shows the results of measuring the far-field radiation pattern for the embodiment of FIG. 63. Table 14 below shows the antenna gain measurement results for the embodiment of FIG. 63.

Further, FIG. 69 is a result of measuring a far-field radiation pattern for each frequency for the embodiment of FIG. 63, and Table 15 below shows the result of measuring an antenna gain for each frequency.

As shown in FIG. 69, it can be seen that the 8×8 folded SIW Butler matrix beamforming antenna according to the present invention has relatively superior antenna beam uniformity compared to the linear structure.

As described above, the present invention proposes a low profile beamforming antenna system for 5G communication. The antenna beam is formed in 8 directions by an 8×8 Butler matrix beamforming network. The antenna of the present invention may be manufactured based on a substrate integrated waveguide (SIW).

The SIW structure has an advantage in RF component design. Compared to conventional waveguides, it can be manufactured using a printed circuit board (PCB) technology, and since the existing waveguides are manufactured using mold technology, manufacturing costs are high, whereas the SIW structure according to the present invention has a low manufacturing cost and low weight. There is a light advantage. In addition, the electrical loss is less than that of the microstrip structure.

The antenna of the present invention presents a right angle coupler, a crossover, and a phase shifter as necessary components, and combines these components to present a Butler matrix having 8 inputs and 8 outputs. For the 8x8 Butler matrix to work properly, it requires precise phase adjustment, especially in the mmWave region. Therefore, in the present invention, each SIW phase shifter is precisely optimized. In addition, it is proposed to minimize the area of the phase shifter and satisfy the required phase shift only in a straight pattern, not a curved pattern.

In order to minimize the size of a general linear 8×8 Butler matrix, the present invention proposes a folded structure, where the folded structure is applied using a SIW vertical transition. The SIW vertical transition consists of a closed metal post wall and an impedance matching slot connecting the upper and lower layers. As a result of this treatment, the length of the SIW structure was reduced by 44% from 214 mm to 120 mm.

In addition, in the present invention, by applying the E-shaped patch antenna, not only the size reduction but also the isolation problem from the microstrip patch antenna having a narrow band is solved. The E-shaped patch antenna has a wider operating frequency band above 2.4GHz. Therefore, the structure proposed in the present invention has a high antenna beam uniformity from 26.5GHz to 28.9GHz.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

10, 20: metal clad,
30: metal via,
40: dielectric substrate,
100: SIW Butler Matrix,
110: input port,
120: output port,
130: right angle coupler,
140: 67.5° SIW phase shifter,
150a, 150b: 45° SIW phase shifter,
160: 22.5° SIW phase shifter,
170: additional phase shifter,
200: patch antenna array,
210: microstrip-SIW transition,
250: microstrip patch antenna,
300: 8×8 folded SIW Butler matrix,
310: the first part,
350: second part,
400: 8×8 folded SIW Butler matrix,
400a: the first part of the SIW Butler matrix,
400b: the second part of the SIW Butler matrix,
500a: patch antenna,
500b: SIW-microstrip transition,
510: lower layer,
520: SIW transmission line,
530: SIW-microstrip transition,
550: upper layer,
560: E-shaped patch antenna pattern.

Claims (9)

The signal transmission part of the SIW Butler matrix including a quadrature coupler, a cross over, and a phase shifter, formed based on a substrate integrated waveguide (SIW). Folded SIW consisting of multiple layers by dividing into at least two or more parts and stacking them in a folded form, that is, segmenting the signal flow element functions and stacking them in a zigzag manner between input and output ports to maintain performance and reduce size. Butler Matrix; And
Including a radiator connected to an output port of one end of the SIW Butler matrix,
The folded SIW Butler matrix,
And a plurality of SIW-SIW vertical transitions electrically coupling separated portions of two vertically adjacent layers among the plurality of layers as slots satisfying a phase relationship between impedance matching and output in a broadband,
The SIW-SIW vertical transition,
A via wall positioned in an upper layer of two vertically adjacent layers among the plurality of layers and a lower layer below the upper layer; And
And a slot formed in a metal clad between the upper layer and the lower layer by being spaced a predetermined distance from the via wall. The method of claim 1,
It is formed in the input port of the other end of the SIW Butler matrix,
An area reduction beamforming antenna for 5G small terminals and repeaters using a structure-separated zigzag stacking technique, further comprising a microstrip-SIW transition for connection with a microwave connector. delete The method of claim 1,
The SIW Butler matrix,
An area-reduced beamforming antenna for 5G small terminals and repeaters using a structure-separated zigzag stacking technique, which is an 8×8 SIW Butler matrix. The method of claim 1,
The radiator includes a microstrip patch antenna,
The microstrip patch antenna,
A modified E-shaped patch antenna pattern formed on an uppermost layer of the plurality of layers; And
And a SIW-microstrip transition formed on a lowermost layer among the plurality of layers and connected to the SIW transmission line,
The modified E-shaped patch antenna pattern is fed by indirect coupling through the SIW-microstrip transition. The method of claim 2,
The microstrip-SIW transition,
An area-reduced beamforming antenna for 5G small terminals and repeaters using a structure-separated zigzag stacking technique, comprising a tapered microstrip line. delete The method of claim 1,
The phase shifter,
Including 67.5° phase shifter, 22.5° phase shifter and 45° phase shifter,
The phase shifter is a reduced-area beamforming antenna for a 5G small terminal and a repeater using a structure-separated zigzag stacking technique, characterized in that the phase shifter performs a time advance shift. The signal transmission part of the SIW Butler matrix including a quadrature coupler, a cross over, and a phase shifter, formed based on a substrate integrated waveguide (SIW). Folded SIW consisting of multiple layers by dividing into at least two or more parts and stacking them in a folded form, that is, segmenting the signal flow element functions and stacking them in a zigzag manner between input and output ports to maintain performance and reduce size. Butler Matrix; And
And a radiator connected to an output port of one end of the SIW Butler matrix,
The folded SIW Butler matrix consists of an upper layer and a lower layer by being separated and overlapped based on the interruption of the SIW Butler matrix,
The SIW Butler matrix is a reduced area beamforming antenna for a 5G small terminal and a repeater using a structure-separated zigzag stacking technique, characterized in that the position of the right-angle coupler is divided into two parts and separated based on an interruption.

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