CN109378592B - A broadband antenna array feed network with stable beamwidth and low side lobes - Google Patents

Abstract

The invention discloses a broadband antenna array feed network with stable beam width and low side lobes, which includes first, second and third dielectric substrates arranged from top to bottom, the upper surface of the first dielectric substrate and the third dielectric substrate A floor is provided on the lower surface, first and second conductor layers are respectively provided on the lower surface of the first dielectric substrate and the upper surface of the third dielectric substrate, and part of the microstrip transmission lines on the first and second conductor layers are formed as phase shifters. A part of the microstrip transmission lines on the conductor layer forms a power divider, and the remaining microstrip transmission lines on the first and second conductor layers together with the second dielectric substrate form two frequency selection circuits. The first conductor layer is connected to an input port and a second dielectric substrate. Three output ports, the second conductor layer is connected to the first, second, fourth and fifth output ports. The invention realizes that the radiation beam has the characteristics of low side lobes, good bandwidth characteristics, stable radiation direction, and has the advantages of simple design, stable performance, and low cost.

Description

A broadband antenna array feed network with stable beamwidth and low side lobes

Technical field

The present invention relates to the technical field of antenna feeding, and in particular, to a broadband antenna array feeding network with stable beam width and low side lobes.

Background technique

Due to the rapid development of wireless communications in recent years, whether it is the popularization of 4G technology, the popularity of the Internet of Things, or the imminent arrival of 5G, wireless technology will usher in another peak period of vigorous development. On the other hand, with the rapid development of electronic information, people have higher and higher requirements for communication quality, such as higher frequency bandwidth, narrower and constant beam width, and lower side lobe radiation. The current technology to solve these problems mainly involves the development of antennas with various performances and antenna feed networks. Therefore, the research on antenna feed networks has become one of the hot spots in recent years.

At present, a common and convenient method to achieve wide-bandwidth is to use devices with wide-band characteristics such as 3dB couplers and power splitters; and a common method to achieve lower side-lobe radiation of antenna arrays is to make the amplitude of the output port conical. Shape distribution, higher in the middle and lower on both sides.

In 2016, Krzysztof Wincza and others published a paper entitled "Broadband Scalable Antenna Arrays With ConstantBeamwidths Fed by Frequency-Selective Networks" in "IEEE Transactions On Antenna andPropagation". They used a three-layer stacked structure to realize a 3dB coupler with a wide frequency band. A circuit with frequency selective characteristics between f ₀ and 2f ₀ is used to form a broadband feed network with a stable beam width, but the side lobe radiation of this structure is relatively high, especially at low and high frequencies.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings and deficiencies of the existing technology, and propose a broadband antenna array feed network with stable beam width and low side lobes. The feed network uses an unequal power divider at the input end. To achieve a tapered amplitude distribution between the five output ports, the radiation beam has low side lobes, good bandwidth characteristics, stable radiation direction, and has the advantages of simple design, stable performance, and low cost.

In order to achieve the above object, the technical solution provided by the present invention is: a broadband antenna array feed network with stable beam width and low side lobes, including three dielectric substrates parallel to each other and arranged from top to bottom, respectively. It is a first dielectric substrate, a second dielectric substrate and a third dielectric substrate. A first floor is formed on the upper surface of the first dielectric substrate, and a first conductor layer is formed on the lower surface of the first dielectric substrate. The upper surface of the third dielectric substrate is A second conductor layer is formed, and a second floor is formed on its lower surface. A part of the microstrip transmission lines on the first conductor layer and the second conductor layer are formed as phase shifters, and a part of the microstrip transmission lines on the first conductor layer are formed. The strip transmission line is formed as a power splitter, and the remaining microstrip transmission lines on the first conductor layer and the second conductor layer together with the second dielectric substrate sandwiched in the middle constitute two mutually symmetrical frequency selection circuits, and the first The conductor layer is connected to an input port and a third output port, the second conductor layer is connected to a first output port, a second output port, a fourth output port and a fifth output port, and all output ports have different characteristics at different frequencies. signal distribution to obtain a wider operating frequency band and a stable radiation beam.

Furthermore, the power splitter has a cross-shaped structure. When a signal is input from the input port, the power of the output ports on both sides is the same, and the power of the middle output port is the sum of the output powers of both sides.

Further, the frequency selection circuit is composed of two 3-dB directional couplers and two low-pass filters, wherein the two low-pass filters are located between the two 3-dB directional couplers and are connected to the two directional couplers respectively. A 3-dB directional coupler connection.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. This feed network achieves stable radiation beam width and low side lobes in a wide frequency band, and has good impedance matching within the passband.

2. This feed network is composed of a three-layer structure. The coupler can easily obtain high coupling degree to produce a wider bandwidth, and it is easy to debug.

3. This feed network is based on the existing broadband feed network improvement, without adding additional devices, and the structure is simple and clear.

4. The overall structure of this feed network is compact, the processing is simple, the weight is light, the processing cost is low, and it has good application prospects.

Description of drawings

Figure 1 is a schematic cross-sectional view of the feed network structure of the present invention.

Figure 2 is a wiring diagram of the feed network structure of the present invention.

Figure 3 is a diagram of the power splitter structure and its transmission characteristics used in the feed network of the present invention.

Figure 4 is a diagram of the frequency selection circuit structure and its transmission characteristics used in the feed network of the present invention.

Figure 5 is a diagram of the overall transmission characteristics of the feed network of the present invention.

Figure 6 shows the comparison results of the antenna array radiation pattern before and after the feed network is improved.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Referring to Figures 1 and 2, the broadband antenna array feed network with stable beam width and low side lobes provided by this embodiment includes three dielectric substrates parallel to each other and arranged from top to bottom, respectively. The first dielectric substrate 16, the second dielectric substrate 17 and the third dielectric substrate 18; the first floor 15 is formed on the upper surface of the first dielectric substrate 16, and the first conductor layer 20 is formed on the lower surface. A second conductor layer 21 is formed on the upper surface of the dielectric substrate 18 , and a second floor 19 is formed on the lower surface thereof. A portion of the microstrip transmission lines on the first conductor layer 15 and the second conductor layer 16 are formed into phase shifters 10 , 11, 12, 13, 14. A part of the microstrip transmission lines on the first conductor layer 20 is formed into a power splitter 7, and the remaining microstrip transmission lines on the first conductor layer 20 and the second conductor layer 21 are connected to the clip. The second dielectric substrate 17 in the middle together constitutes two mutually symmetrical frequency selection circuits 8 and 9. The first conductor layer 20 is connected to the input port 1 and the third output port 4, and the second conductor layer 21 is connected to There are a first output port 2, a second output port 3, a fourth output port 5 and a fifth output port 6, and all output ports have different signal distributions at different frequencies to obtain a wider operating frequency band and stable radiation. beam.

The structure of the power divider is shown in Figure 3. It is a cross-shaped structure. When a signal is input from the input port, the power of the output ports on both sides is the same, and the power of the middle output port is the sum of the output powers of both sides.

The structure of the frequency selection circuit is shown in Figure 4. It consists of two 3-dB directional couplers and two low-pass filters. The two low-pass filters are located between the two 3-dB directional couplers, and Connect to the two 3-dB directional couplers respectively. Its characteristic is that at high frequency, the signal is output to the output port on the right, while at low frequency, the signal is output to the output port on the left, and the transmission characteristics transition smoothly at the intermediate frequency.

The input port of the power divider 7 is connected to the input port 1 of the entire feed network. The left and right output ports of the power divider 7 are respectively connected to two frequency selection circuits 8 and 9. The lower left port of the frequency selection circuit 8 is connected to the frequency selection circuit. The lower right corner ports of circuit 9 are connected to 50Ω impedance matching. The two output ports of frequency selection circuit 8 are connected to the first output port 2 and the second output port 3 respectively through phase shifters 10 and 11. The two output ports of frequency selection circuit 9 The output ports are respectively connected to the fourth output port 5 and the fifth output port 6 through phase shifters 13 and 14, and the intermediate output of the power divider 7 is connected to the third output port 4 through the phase shifter 12 port. The phase shifter is composed of 50Ω impedance microstrip lines of different lengths. The different lengths of the microstrip lines meet the condition that the phase difference between the output ports is near 0°.

The input port 1, the first output port 2, the second output port 3, the third output port 4, the fourth output port 5 and the fifth output port 6 are all microstrip lines with an impedance of 50Ω. The dielectric constant ε _r of the first dielectric substrate 16 and the third dielectric substrate 18 is 2.55, the loss tangent is 0.0029, and the thickness h ₁ =1.5 mm. The dielectric constant ε _r of the second dielectric substrate 17 is 2.55 and the loss tangent is 0.0029. is 0.0029, and the thickness h ₂ =0.25 mm.

Referring to Figure 5, the simulation results of the transmission parameters of the above-mentioned feed network in this embodiment are shown, in which Figure (a) is the amplitude distribution diagram, and Figure (b) is the phase difference distribution diagram. The distribution of the S61 is the same as that of the S21, and the distribution of the S51 is the same as that of the S31. As can be seen from the figure, in the operating frequency band from 2GHz to 4GHz, S11 is less than -20dB, achieving good impedance matching. At low frequency, the signal is mainly distributed in output port 2, output port 4 and output port 6, and the power of output port 6 is twice that of output ports 2 and 4, and the phase difference between output ports 2, 4 and 6 is 0° Nearby; at high frequency, the signal is mainly distributed at output port 3, output port 4 and output port 5, and the power of output port 4 is twice that of output ports 3 and 5. The phase difference between output ports 3, 4 and 5 around 0°. The transmission characteristics transition smoothly in the mid-band, thus achieving stable radiation beam width and low side-lobe levels in a wide operating frequency band.

Referring to Figure 6, the radiation pattern calculated by connecting the output port of the above-mentioned feed network to a 5-element linear antenna array in this embodiment is shown. The spacing between the antenna array elements is 1/1 in vacuum at low frequency f ₀ . 3 wavelengths. Figure (a) shows the radiation pattern before improvement, and Figure (b) shows the radiation pattern after improvement. It can be seen that both have achieved stable beam width, but the former has a higher side lobe level, while the latter has a higher side lobe. The level reaches below -15dB.

In summary, the present invention uses unequal power dividers to reasonably allocate the amplitude of the output port of the feed network to reduce the side lobe level of the antenna array radiation. It has flexible design, small size, low cost, stable output signal, and The output signal has a small side lobe level, which has practical application value and is worthy of promotion.

The above-described embodiments are only preferred embodiments of the present invention and do not limit the scope of the present invention. Therefore, any changes made based on the shape and principle of the present invention should be covered by the protection scope of the present invention.

Claims (1)

1. A broadband antenna array feed network with stable beam width and low side lobes, characterized by: including three dielectric substrates parallel to each other and arranged from top to bottom, namely a first dielectric substrate and a second dielectric substrate. A dielectric substrate and a third dielectric substrate. The first dielectric substrate has a first floor formed on its upper surface and a first conductor layer formed on its lower surface. The third dielectric substrate has a second conductor layer formed on its upper surface. A second floor is formed on the lower surface, a part of the microstrip transmission lines on the first conductor layer and the second conductor layer are formed as phase shifters, and a part of the microstrip transmission lines on the first conductor layer are formed as a power splitter, The remaining microstrip transmission lines on the first conductor layer and the second conductor layer, together with the second dielectric substrate sandwiched in between, constitute two mutually symmetrical frequency selection circuits, and the first conductor layer is connected to an input port and a third Three output ports, the second conductor layer is connected to a first output port, a second output port, a fourth output port and a fifth output port, and all output ports have different signal distributions at different frequencies to obtain a wider The operating frequency band and stable radiation beam; the power divider has a cross-shaped structure. When the signal is input from the input port, the power of the output ports on both sides is the same, and the power of the middle output port is the sum of the output powers of both sides; the frequency selection The circuit consists of two 3-dB directional couplers and two low-pass filters. The two low-pass filters are located between the two 3-dB directional couplers and are coupled with the two 3-dB directional couplers respectively. device connection.