CN209526203U - Broadband double-circle polarization micro-strip turns waveguide feed antenna system - Google Patents

Abstract

The utility model discloses a kind of antenna systems, comprising: electric bridge, upper layer metal, top substrate layer, underlying substrate, lower metal, radiation patch, mode converter, circular waveguide, metallic vias；The antenna system is Multilayer Structure, with being followed successively by upper layer metal from top to bottom, top substrate layer, underlying substrate, lower metal；The radiation patch is located on the upside of the top substrate layer, and the mode converter is placed in the top of the radiation patch and is connected to the circular waveguide above it；The electric bridge constitutes feeding network, and two ports of the electric bridge are between the top substrate layer and the underlying substrate.Broadband, double-circle polarization can be realized in millimeter wave frequency band using the feed antenna system of the utility model, guarantee that transmitting-receiving port has good isolation, the mode conversion that microstrip antenna turns circular waveguide is realized simultaneously, structure is simple and efficient, and circular polarisation performance is not changed, the feed that can be used as multiple types antenna uses.

Description

Broadband Dual Circularly Polarized Microstrip-to-Waveguide Feed Antenna System

technical field

The utility model relates to the technical field of antennas, in particular to a wide-band double-circular polarization 77GHz microstrip-to-waveguide feed source antenna system.

Background technique

In the prior art, millimeter-wave radar technology has been widely used in automotive radar, security imaging, scene monitoring radar, level measurement and other fields. The main advantages of millimeter wave radar technology are: high tracking accuracy and spatial resolution; high Doppler resolution and speed measurement accuracy; strong target recognition and imaging capabilities; good anti-interference ability .

The early radar technology was mainly based on pulse radar technology, but pulse radar technology has obvious disadvantages: for example, the transmission power requires a lot of power, the transmission and reception needs to be switched, there are detection blind spots, the volume is large, and it is easy to be intercepted and so on. The continuous wave (Continuous Wave, CW) radar overcomes these shortcomings, and has the advantages of simple structure, small size, low power, etc., so it is more and more widely used. Continuous wave radar can have various modulation methods, among which frequency modulation continuous wave (FMCW) radar is the most widely used. Compared with the pulse radar system, the frequency modulation continuous wave radar has been paid more and more attention due to its characteristics of no distance blind zone, high receiving sensitivity, strong anti-interference ability, high resolution, small power requirement, and simple structure. However, there are still many challenges in the technical development of continuous wave radar. First, since the FM continuous wave radar requires the transmit-receive (TX/RX) terminals to work at the same time, in order to keep the transmit-receive (TX/RX) ports from interfering with each other to obtain Good working performance has higher requirements for the isolation of the transceiver port between the transmit-receive (TX/RX) port, which adds difficulty to the design of the back-end millimeter wave device; secondly, the resolution of the FM continuous wave radar Determined by the bandwidth of the radar antenna, in order to ensure the high sensitivity and resolution of the receiving port, the receiving antenna needs to use a broadband antenna as much as possible, which brings challenges to the design of the transceiver antenna.

In the practical application of millimeter-wave radar, such as the level measurement system, the requirements for the antenna are high gain and small beam angle (3°), which can improve the link gain, increase the range and reduce interference. In this type of application scenarios, lens antennas, horn antennas, reflector antennas, etc. become better choices, because in the 77GHz frequency band, the above-mentioned antennas are usually small in size and can be actually processed and applied. At present, most of the radio frequency chips at the core of the millimeter-wave radar system are monolithic microwave integrated circuits (Monolithic Microwave Integrated Circuit, MMIC for short), and their packaging forms are mainly Ball Grid Array (BGA) packaging. It can be seen that the radio frequency system of radar can be divided into the feed system with MMIC, feeder, and antenna as the core, and the focusing system with lens/horn as the core. The design of the feeder and antenna after the transmit-receive (TX/RX) port of the RF chip is crucial. The primary challenge is how to convert the 77GHz frequency band signal from a planar transmission line structure to a traditional waveguide structure or other three-dimensional structure, and further stimulate the lens or horn, so as to achieve high-gain radiation; secondly, the electromagnetic wave wavelength of 77GHz is only 3.9mm, whether it is printed circuit board (Printed Circuit Board, referred to as PCB) process or numerical control (Computer Numerical Control, referred to as CNC) process, the processing accuracy of the antenna The design has a great influence. How to design a highly robust antenna to adapt to the corresponding processing accuracy is another key point. In the frequency-modulated continuous wave (FMCW) radar system in the millimeter wave band, the main challenges of antenna design include: operating bandwidth; transmit-receive isolation; conversion of planar transmission line structure to transmit/receive structure; robust design.

Referring to Figure 1A-Figure 1D, in the prior art, in order to achieve transceiver isolation, the antenna feed network system usually adopts the following schemes: a 3dB bridge scheme as shown in Figure 1A; a circulator as shown in Figure 1B scheme; the coupler scheme as shown in FIG. 1C; the dual-antenna scheme as shown in FIG. 1D.

However, the inventors have found through research that in the circulator solution, the characteristics of the ferrite material will change dramatically in the 77GHz frequency band, so it is difficult to implement it by using a PCB process. In the dual-antenna solution, one antenna is used for reception and transmission; theoretically, as long as the two antennas are far enough apart, the isolation can be very good; but as a product design, two antennas are bound to be required Double the space; especially in the 77GHz radar design, in order to achieve a longer communication distance, the size of the antenna is larger, and the two antennas will inevitably occupy a larger space, making the product structure more bloated. Therefore, in the prior art, circulators or dual antennas are used in order to achieve transceiver isolation. The circulator will cause the gain loss of the antenna, and the dual antenna system will increase the size of the antenna, and it will also cause the antenna to lose its directivity. gain loss.

Since the receiving end and the transmitting end of FMCW radar work at the same time, the antenna mostly uses a linearly polarized antenna, which leads to poor isolation between the receiving and transmitting ports and affects the performance of the antenna. To solve this problem, a circulator can be added to improve the isolation of the transceiver port, but the circulator will bring additional attenuation and reduce the sensitivity of the antenna; or, different antennas are used at the transceiver end, but this method will cause Increase the size of the device and reduce the antenna gain due to directivity problems.

As shown in Figure 2, in the prior art, a rectangular-circle conversion scheme is often used for microstrip-to-waveguide conversion. Due to the symmetry of the circular waveguide, there is a phenomenon of polarization degeneracy, which will excite various modes, and due to the circular waveguide’s different Continuity is more likely to excite higher-order modes; and since the main mode TE10 mode of the rectangular waveguide is very similar to the main mode TE11 mode of the circular waveguide, the mode conversion can be well realized and the high-order mode can be reduced through the oblong conversion structure shown in Figure 2. Therefore, it has better working performance; however, the scheme shown in Figure 2 destroys the circular symmetry and cannot generate circularly polarized waves. As shown in Figure 3, in the prior art, the depth of the short-circuit piston is often adjusted for impedance matching through the excitation method of the microstrip probe, so that the energy coupled into the circular waveguide can be maximized; however, in the scheme in Figure 3 It is necessary to add a short-circuit piston, which brings certain difficulties to its processing design in the 77GHz millimeter-wave frequency band, and because it is directly converted from the microstrip to the circular waveguide, it is very easy to generate high-order modes, and its working bandwidth cannot reach the system. design needs.

In the prior art, the microstrip antenna usually uses a single-layer patch direct excitation method, which is simple in design and processing, but the working bandwidth is narrow, usually less than 5%, and the robustness is not high due to the narrow bandwidth , is easily restricted by machining accuracy, and cannot realize broadband design.

Utility model content

Based on this, in order to solve the technical problems in the prior art, an antenna system is proposed.

The antenna system includes a bridge, an upper metal ground, an upper substrate, a lower substrate, a lower metal ground, a radiation patch, a mode converter, and a circular waveguide; the antenna system has a multi-layer board structure, and the order from top to bottom is the upper layer Metal ground, upper substrate, lower substrate, lower metal ground; the radiation patch is located on the upper side of the upper substrate, the mode converter is placed above the radiation patch and connected to the circular waveguide above it ; The two ports of the bridge are located between the upper substrate and the lower substrate.

In one embodiment, the mode converter is a conical waveguide, and the mode converter completes the mode transition from the microstrip line to the conical waveguide and finally to the circular waveguide, and realizes TM01 under the excitation of the radiation patch Mode to TE11 mode gradient.

In one embodiment, wherein, the upper metal ground is ring-shaped and located at the edge of the inner diameter of the mode converter; the antenna system has a plurality of metal vias, and the metal vias are arranged in a ring, Around the outer edge of the upper metal ground, the metal via hole passes through the upper substrate and the lower substrate from top to bottom.

In one embodiment, the electric bridge constitutes a feeding network, and the electric bridge has a first port, a second port, a third port, and a fourth port; the first port and the second port are respectively receiving ports Or the emission port; the third port and the fourth port are located between the upper substrate and the lower substrate, below the radiation patch and separated from the radiation patch by the upper substrate .

In one embodiment, the electric bridge is a 3dB electric bridge; a signal is input from the first port or the second port, and the amplitude is generated at the third port and the fourth port by the 3dB electric bridge double-ended excitation signals that are equal and have a phase difference of 90 degrees, so as to generate circularly polarized waves; the third port and the fourth port feed the radiation patch through a coupling feeding method.

In one embodiment, the antenna system is applied in frequency modulated continuous wave radar;

In one embodiment, the operating frequency of the antenna system is 77GHz;

In one embodiment, the antenna system can be used as a feed source for a lens antenna or a horn antenna.

Implement the utility model embodiment, will have following beneficial effect:

The utility model adopts the coupling feeding mode, and the double-port signals with the same amplitude and 90-degree phase difference are generated by the bridge feeding network to simultaneously excite the radiation patch to generate circularly polarized waves, and use circularly polarized waves to reflect echo polarization The reverse feature realizes the polarization isolation of the transceiver end and ensures the isolation of the transceiver port. The antenna system of the present utility model also includes a conical mode converter with simple structure, good performance and high conversion efficiency, which realizes the mode transition from microstrip line to conical waveguide, and finally to standard circular waveguide. In the broadband microstrip antenna Under the action of excitation, the gradual change of the microstrip antenna from TM01 mode to TE11 mode is realized by adding a mode converter, which reduces the coupling effect of the waveguide to the microstrip antenna and reduces the generation of high-order modes, so the bandwidth of the antenna system is directly changed by the double circle The excitation of the polarized microstrip antenna is determined, which reduces the coupling interference of the traditional circular waveguide.

The utility model proposes a feed antenna system with wide frequency band, dual circular polarization, and microstrip conversion to circular waveguide. The dual rotation direction of the receiving and receiving end signals can ensure that the receiving and receiving ports of the antenna system maintain a high degree of isolation. At the same time, the antenna system uses a A very simple transition structure from microstrip to waveguide, which can improve the gain of the antenna and the sensitivity of the receiver as the feed source of the lens antenna or horn antenna.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are only some embodiments of the utility model, and those skilled in the art can also obtain other drawings based on these drawings without creative work.

in:

FIG. 1A is a schematic diagram of an antenna feeding network system realized by using a 3dB bridge in the prior art.

FIG. 1B is a schematic diagram of implementing an antenna feeding network system using a circulator in the prior art.

FIG. 1C is a schematic diagram of implementing an antenna feeding network system using a coupler in the prior art.

FIG. 1D is a schematic diagram of implementing an antenna feeding network system using dual antennas in the prior art.

Fig. 2 is a schematic diagram of a rectangle conversion structure in the prior art;

3A is a front view of a microstrip-to-waveguide structure excited by a microstrip probe in the prior art;

3B is a left view of the microstrip-to-waveguide structure excited by the microstrip probe in the prior art;

Fig. 4 is the perspective view of the antenna system in the utility model;

Fig. 5 is a side view of the antenna system in the utility model;

Fig. 6 is the top view of the antenna system in the utility model;

Including, antenna system 1, electric bridge 2, upper metal ground 3, upper substrate 4, lower substrate 5, lower metal ground 6, radiation patch 7, mode converter 8, circular waveguide 9, metal via hole 10, first port 21 , second port 22 , third port 23 , and fourth port 24 .

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. example. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

The utility model discloses a feed source antenna system with high isolation, wide frequency band and microstrip-to-waveguide working in the 77GHz frequency band.

4 and 5, the antenna system 1 includes a bridge 2, an upper metal ground 3, an upper substrate 4, a lower substrate 5, a lower metal ground 6, a radiation patch 7, a mode converter 8, a circular waveguide 9, Metal via 10;

Referring to the side view of the antenna system 1 shown in FIG. 5, the antenna system 1 is a multi-layer board structure, and the upper layer metal ground 3, the upper layer substrate 4, the lower layer substrate 5, and the lower layer metal ground 6 are sequentially arranged from top to bottom; The radiation patch 7 is located on the upper side of the upper substrate 4, and the mode converter 8 is placed above the radiation patch 7 and connected to the circular waveguide 9 above it; wherein, the mode converter 8 is a circular frustum Shaped waveguide for realizing gradual conversion from TM01 mode to TE11 mode;

Wherein, the upper metal ground 3 is ring-shaped and located at the edge of the inner diameter of the mode converter 8; the antenna system 1 has a plurality of metal vias 10, and the metal vias 10 are arranged in a ring around the At the outer edge of the upper metal ground 3 , the metal via hole 10 passes through the upper substrate 4 and the lower substrate 5 from top to bottom. The metal vias 10 are used to reduce the generation of surface waves, and there are no metal vias 10 at the feeder microstrip line of the bridge 2 feeder network to ensure no interference.

4-6, the bridge 2 constitutes a feed network, the bridge 2 has a first port 21, a second port 22, a third port 23, and a fourth port 24; wherein, the first The port 21 and the second port 22 are respectively a receiving port or a transmitting port, that is, when the first port 21 is a receiving port, the second port 22 is a transmitting port, or when the second port 22 is a receiving port. The first port 21 is a transmitting port; the third port 23 and the fourth port 24 are located between the upper substrate 4 and the lower substrate 5, below the radiation patch 7 and in contact with the The radiation patches 7 are separated from the upper substrate 4;

Wherein, the electric bridge 2 is a 3dB electric bridge; by the first port 21 or the second port 22 input signal, by the 3dB electric bridge at the third port 23, the fourth port 24 to generate equal amplitude and a double-ended excitation signal with a phase difference of 90 degrees, thereby generating circularly polarized waves; the upper substrate 4 is separated between the third port 23 and the fourth port 24 and the radiation patch 7, through coupling The feeding mode feeds the radiation patch 7;

The 3dB bridge is also called the same-frequency combiner, which can continuously sample the transmission power along a certain direction of the transmission line, divide the input signal at the input port of the bridge into two equal-amplitude signals with a 90-degree phase difference and Output; 3dB bridge is used for multi-signal combination to improve the utilization rate of output signal;

The antenna system 1 in the utility model adopts a multi-layer board design, feeds the radiation patch 7 through the feed network composed of the bridge 2 through the coupling feed mode, and uses an appropriate impedance matching technology to realize impedance matching. The antenna system The operating bandwidth of 1 can be increased by 50%-70% compared with the single-layer feeding method, which not only improves the operating bandwidth of the system, but also improves the robustness of the system.

The antenna system 1 is applied to the frequency modulation continuous wave radar. The antenna system 1 is a dual circularly polarized antenna. The circularly polarized wave emitted by the radar will change the direction of rotation when it is reflected back. The existence of polarization isolation to ensure the isolation of the transceiver port. The generation of surface waves is reduced by adding metal vias 10 , and it can be seen through simulation that this structure increases the bandwidth of the antenna, making the bandwidth of the antenna reach 16%.

The mode converter 8 in the utility model is a transition structure from microstrip to waveguide with simple structure and high conversion efficiency, which realizes the conversion from microstrip to circular waveguide 9 . Due to the limitation of the working frequency, many conversion methods in the prior art cannot be used in the 77GHz frequency band, such as the rectangular transition method used in the commonly used microstrip to waveguide, because the TE10 mode of the rectangular waveguide is very close to the TE11 mode of the circular waveguide. The structure of the rectangular waveguide has enough bandwidth to avoid the generation of high-order modes. However, in the technical solution of the utility model, the rectangular waveguide structure cannot be used due to the need for circular polarization transmission, and the direct transition of the circular waveguide will excite higher-order modes, and the strong coupling effect of the circular waveguide will affect the performance of the radiation patch. Parameters have an effect that reduces the operating bandwidth. Therefore, an efficient and simple mode converter is very important. The technical solution of the utility model realizes the gradual conversion of the microstrip from the TM01 mode to the TE11 mode by adding the mode converter 8. Compared with the direct conversion of the ordinary circular waveguide, its bandwidth has obvious The improvement can minimize the interference to the radiation patch 7.

The pattern of the microstrip radiating from the circular waveguide will be slightly deteriorated. On the one hand, it is caused by the poor return loss of the antenna port. On the other hand, there will still be certain high-order modes in the transition section, which will have a negative impact on the pattern. , by increasing the height of the mode converter (conical waveguide) or lengthening the length of the circular waveguide to attenuate the high-order mode during transmission, or adding a corrugated structure to the part of the mode converter (conical waveguide) can effectively reduce the direction of the high-order mode Figure impact.

Considering the processing factor, the technical solution of the utility model adopts the extended circular waveguide 9 and the mode converter 8 to speed up the attenuation of the high-order mode. From the comparison results of the pattern before and after the waveguide extension, it can be seen that the symmetry and equalization of the pattern after the extension are good. The improvement shows that the axial ratio performance has also been improved from the side. From the overall axial ratio simulation results of the antenna system 1, it can be seen that the 3dB axial ratio bandwidth has reached 10%, and the performance is good.

Implement the utility model embodiment, will have following beneficial effect:

The utility model discloses a 77GHz dual circularly polarized microstrip feed source antenna system converted to a circular waveguide, the simulated axial ratio of 3dB bandwidth is 10%, which meets the requirement of broadband circular polarization and has better robustness , which has better anti-interference ability than the linearly polarized antenna. Using the characteristic of circular polarization echo to change the direction of rotation, it has the advantage of innate polarization isolation and ensures the isolation of the transceiver port. At the same time, the antenna system has a mode converter with simple structure and high conversion efficiency, which can realize the conversion from micro to waveguide, reduce the interference of high-order modes, and ensure the broadband requirements of the antenna system. The overall antenna system has good radiation performance. It is widely used and can be used as the feed source of various antennas such as lens antennas and horn antennas, effectively improving the gain of the antenna and the sensitivity of the receiver.

The above embodiments are only used to illustrate the technical solutions of the present utility model, and are not intended to limit it; although the utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be applied to the foregoing embodiments Modifications to the technical solutions described in the examples, or equivalent replacement of some of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (7)

1. An antenna system, characterized in that, The antenna system includes a bridge, an upper metal ground, an upper substrate, a lower substrate, a lower metal ground, a radiation patch, a mode converter, and a circular waveguide; the antenna system has a multi-layer board structure, and the order from top to bottom is the upper layer Metal ground, upper substrate, lower substrate, lower metal ground; the radiation patch is located on the upper side of the upper substrate, the mode converter is placed above the radiation patch and connected to the circular waveguide above it ; The two ports of the bridge are located between the upper substrate and the lower substrate. 2. Antenna system according to claim 1, characterized in that, Wherein, the mode converter is a conical waveguide, and the mode converter completes the mode transition from the microstrip line to the conical waveguide and finally to the circular waveguide, and realizes the transition from the TM01 mode to the TE11 mode under the excitation of the radiation patch. gradient. 3. Antenna system according to claim 2, characterized in that, Wherein, the upper metal ground is ring-shaped and located at the edge of the inner diameter of the mode converter; the antenna system has a plurality of metal vias, and the metal vias are arranged in a ring around the upper metal ground At the outer edge, the metal via holes pass through the upper substrate and the lower substrate from top to bottom. 4. The antenna system according to claim 1, characterized in that, Wherein, the electric bridge constitutes a feeding network, and the electric bridge has a first port, a second port, a third port, and a fourth port; the first port and the second port are respectively receiving ports or transmitting ports; The third port and the fourth port are located between the upper substrate and the lower substrate, below the radiation patch and separated from the radiation patch by the upper substrate. 5. Antenna system according to claim 4, characterized in that, Wherein, the electric bridge is a 3dB electric bridge; by the first port or the second port input signal, by the 3dB electric bridge at the third port and the fourth port, the amplitude is equal and the phase difference is A 90-degree double-ended excitation signal to generate a circularly polarized wave; the third port and the fourth port feed the radiation patch through a coupling feeding method. 6. The antenna system according to any one of claims 1-5, characterized in that, The antenna system is applied in frequency modulation continuous wave radar. 7. The antenna system according to claim 1 or 2, characterized in that, The operating frequency of the antenna system is 77GHz.