CN112748426A

CN112748426A - Monopulse sum-difference network for long-distance high-resolution radar system

Info

Publication number: CN112748426A
Application number: CN202011560176.4A
Authority: CN
Inventors: 吴泽威; 袁浩俊; 张冉; 王敏行; 蒲友雷; 罗勇
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2021-05-04
Anticipated expiration: 2040-12-25
Also published as: CN112748426B

Abstract

The invention discloses a monopulse sum-difference network for a long-distance high-resolution radar system, and belongs to the field of monopulse radars. The sum-difference network is designed according to a feed network required by a single-pulse radar antenna, is a slot gap waveguide structure and comprises three input ports, a load port, two first-stage 0/180-degree electric bridges, two second-stage 0/180-degree electric bridges and four output ports; TE₁₀The module is input through an input port, first sum and difference operation is completed through a first-stage 0 degree/180 degree electric bridge to output two paths of first-stage signals, second sum and difference operation is completed through two second-stage 0 degree/180 degree electric bridges to output four paths of second-stage signals, and finally the four paths of second-stage signals are output through four output ports. The invention completes low-error 90-degree phase shift by changing the propagation constant of the slot gap waveguide through the phase shifter, and can provide four paths of amplitudesThe feed signal with small phase error also has the advantages of high power, low loss, miniaturization and the like, and is favorable for being integrated into a monopulse radar antenna system.

Description

Monopulse sum-difference network for long-distance high-resolution radar system

Technical Field

The invention relates to the field of monopulse radars, in particular to a monopulse sum-difference network for a long-distance high-resolution radar system.

Technical Field

The monopulse radar antenna is a high-precision tracking antenna, and is widely applied to the military field due to the fact that the information data rate acquisition speed is high and the monopulse radar antenna has certain anti-interference capacity. The sum and difference network is one of the most critical devices of the monopulse radar antenna. The sum-difference network forms sum-difference beams by feeding the radiation antenna, and then compares the sum difference of signals received by the radar antenna, so as to obtain an angle error signal and realize the tracking and positioning of the target. Currently, the commonly used single pulse sum and difference network is mainly composed of waveguide magic ts. The monopulse sum-difference network composed of the waveguide magic T can easily realize performance indexes such as port return loss, isolation degree and amplitude-phase consistency and the like on a microwave frequency band. However, such a structure in which the devices are sequentially cascaded through a single functional device is complicated and is not easily integrated with other circuits. As the operating frequency increases, the impact of device processing and mounting errors on the performance of the sum and difference network becomes significantly exacerbated. The sum and difference network structure is subjected to planar design, so that integrated processing is facilitated, and the process implementation difficulty is reduced. Therefore, the use of a planarized sum and difference network architecture is becoming increasingly popular at high frequency bands.

At present, researchers at home and abroad mainly design a planar sum-difference network through four 3dB electric bridges and four 90-degree phase shifters, and the sum-difference network with the structure can output signals to a monopulse radar antenna only through two times of sum-difference operation. Hongwei and the like are designed based on the substrate integrated waveguide sum and difference network, and the structure is compact and the processing difficulty is low [ Hongwei, Liu-ice ] single-pulse substrate integrated waveguide slot array antenna: china, 200610096845.0[ P ]].2007-03-28]. The electromagnetic field in the substrate integrated waveguide propagates in the dielectric substrate, but the dielectric substrate has large loss and lower breakdown voltage than air. Thus, based on substrate integrated wavesThe sum and difference network with the lead design has difficulty in achieving low loss and high power capacity. Rectangular waveguides have no dielectric loss and the cavity size is much larger than that of substrate integrated waveguides, and are generally used for designing high-power and low-loss devices. Thus, Pei Zheng et al uses a rectangular waveguide design sum and difference network. However, Pei Zheng et al designs a 90 ° phase shifter by using a delay line, which causes a phase delay varying with frequency, and is not suitable for designing a wideband sum-difference network with low phase error. Furthermore, the sum-difference network based on rectangular waveguide Design needs to be divided into multiple parts for processing, and the post-assembly difficulty is large [ Pei Zheng, Guo Qiang ZHao, Shen Heng Xu, et al "Design of a W-Band Full-Polarization monitoring foundry Antenna", IEEE Antennas and Wireless processing Letters, vol.31, No.6,2017]. Later researchers, Adri n Tamayo-Dom ienguz et al, based on the design of a sum-difference network with slot-gap waveguides having similar cavity dimensions as rectangular waveguides, could achieve high power and low loss. In addition, the structure does not need to have good electric contact between metal walls, only the periodic structure of the metal pins needs to be ensured, the processing cost can be reduced, and the assembly difficulty can be reduced. However, the 3dB bridge and 90 phase shifter design of Adri n T-amayo-Dom I anguez et al have poor amplitude-phase consistency, resulting in a relative bandwidth of the sum-difference network of 0.7%, an amplitude error of 1dB, a phase error of 10 ° [ Adri n Tamayo-Dom I anguez, Jos e-Manuel Fern de z-Gonz a lez, Manual Sierra-

“3-D-Printed Modifified Butler Matrix Based on Gap Waveguide at W-Band for Monopulse Radar”IEEE Transaction on Microwave Theory and Techniques,vol.68,no.3,Mar 2020]. The sum and difference network formed by the 3dB electric bridge and the phase shifter has compact structure and is easy to integrate. However, the working bandwidth of the planar sum-difference network is narrow under the condition of low amplitude phase error, mainly because the design mode of the used 3dB electric bridge and the phase shifter is not suitable for designing the broadband sum-difference network with low amplitude phase error. And the existing sum-difference network is difficult to give consideration to low loss, high power and wide frequency band, and limits the performance of the single-pulse radar antenna.

Disclosure of Invention

The invention provides a broadband sum-difference network which is simple and compact in structure, high in power capacity and low in loss and can effectively improve the performance of a monopulse radar antenna, and aims to solve the problems that a sum-difference network in the prior art is complex in structure and not easy to integrate, and a planar sum-difference network has narrow working bandwidth, low power capacity, high loss and the like under the condition of low amplitude phase error.

In order to achieve the purpose, the invention adopts the following technical scheme:

a single pulse sum-difference network for a long-distance high-resolution radar system is a slot gap waveguide structure and comprises three input ports, a load port, two primary 0/180 electric bridges, two secondary 0/180 electric bridges and four output ports; the load port is used for absorbing energy, and standard rectangular waveguide TE₁₀The mode is input through an input port, first sum and difference operation is completed through a first-stage 0 degree/180 degree electric bridge to output two paths of first-stage signals, second sum and difference operation is completed through two second-stage 0 degree/180 degree electric bridges to output four paths of second-stage signals, and finally the four paths of second-stage signals are output through four output ports respectively.

The first-stage 0/180 DEG bridge (5-2) comprises a first 3dB bridge (5-1) and a first phase shifter (7-1) arranged at an output port of the first 3dB bridge; the two-stage 0 degree/180 degree electric bridge (5-4) comprises a second 3dB electric bridge (5-3), a third H face 90 degree turning structure (6-3) connected with an output port of the second 3dB electric bridge (5-3), and a second phase shifter (7-2) arranged at an input section or an output section of the third H face 90 degree turning structure (6-3), and when the phase shifter is arranged at the output section, the plane size of the sum-difference network can be effectively reduced.

Two output ports of the primary 0 degree/180 degree electric bridge (5-2) are respectively connected with input ports of the secondary 0 degree/180 degree electric bridge through a second H surface 90 degree turning structure (6-2).

Further, the output ports of the third H-surface 90-degree turning structures (6-3) are respectively connected with the 90-degree turning structures (6-4) in the form of rectangular waveguides, and the tail ends of the 90-degree turning structures in the form of rectangular waveguides are output ports of the sum-difference network. A 90 turn structure in the form of a rectangular waveguide can further reduce the planar size of the sum and difference network.

Further, a first H-surface 90-degree turning structure (6-1) is arranged between the three input ports, one load port and the first-stage 0/180-degree electric bridge.

Further, the first H-face 90-degree turning structure (6-1), the second H-face 90-degree turning structure (6-2) and the third H-face 90-degree turning structure (6-3) are 90-degree right-angle turning structures in the form of slot gap waveguides, and the turning radius of the 90-degree right-angle turning structures is the size of the wide edge of the slot gap waveguides.

Furthermore, the slot gap waveguide structure is composed of an upper metal plate, a lower metal plate and metal cylinders which are periodically arranged, wherein the bottom ends of the metal cylinders are fixedly connected with the lower metal plate, and the top ends of the metal cylinders are smaller than lambda than the upper metal plate_gA gap of/4, wherein_gIs the waveguide wavelength. At this time, the high-impedance surface formed by the metal cylinder can make the electromagnetic field be confined in the propagation path of the slot-gap waveguide. And the top of the metal cylinder does not need to contact with the metal plate above, so that the processing difficulty and the assembly difficulty can be reduced. In order to satisfy the high impedance condition and low loss TE of the metal cylinder₁₀Single-mode transmission, the size of the cavity formed by the metal cylinder and the metal plate is the size of the rectangular waveguide of the standard Ka wave band, and the period of the metal cylinder is lambda_g/4～λ_gAnd/2, the diameter of the metal cylinder is 0.3-0.5 times of the period.

Furthermore, the first phase shifter and the second phase shifter are formed by periodic metal pins, and the propagation constant of the slot gap waveguide is changed by adjusting the size of the periodic metal pins, so that the phase difference of 90 degrees exists between the side of the E surface where the periodic metal pins are placed and the side where the periodic metal pins are not placed. Compared with the side without the periodic metal pins, the phase difference theta between the side of the slot gap waveguide with the periodic metal pins arranged on the E surface is beta multiplied by L, beta is the propagation constant difference of the two structures, and L is the longitudinal length of the periodic metal pin structure.

Further, the height, the interval and the diameter of the periodic metal pins are all set at lambda_g20 to lambda_gAnd/10.

Furthermore, the height and the number of the periodic metal pins in each row at the two longitudinal ends of the periodic metal pins are gradually reduced to complete impedance matching, so that the uniform variation of the propagation constant of the slot gap waveguide in a wide frequency band is maintained, and the phase shift precision of the phase shifter in the wide frequency band is also ensured.

Furthermore, the first 3dB electric bridge and the second 3dB electric bridge have the same structure, the coupling mode is H-plane single-hole coupling, and each of the first 3dB electric bridge and the second 3dB electric bridge includes a coupling hole, two input side waveguides and two output side waveguides, which are symmetrically arranged at two sides of the coupling hole, and two ends of a circle of metal cylinder outside the coupling hole are fixedly connected with upper and lower metal plates; the output side waveguide is also provided with a matching pin for further optimizing the isolation of the 3dB bridge.

According to the H-plane single-hole coupling theory, only TE can exist in the coupling hole₁₀And TE₂₀Mode when TE₁₀And TE₂₀When the phase difference of the two modes is 90 degrees, the output port outputs two paths of signals with equal amplitude and 90-degree phase difference. TE₁₀Of the waveguide wavelength

And TE₂₀Of the waveguide wavelength

And longitudinal length l of coupling hole₁It should satisfy:

the working principle of the sum and difference network of the invention is as follows:

the sum and difference network is designed according to the feed network required by the monopulse radar antenna. A monopulse radar antenna typically consists of four antenna sub-arrays distributed in four quadrants. Four signals with the same amplitude need to be input into the four antenna sub-arrays, and the phase difference of the input signals of the four antenna sub-arrays determines the beam shape output by the monopulse radar antenna. And when the phase difference of the input signals of the four antenna sub-arrays is 0 degree, the monopulse radar antenna outputs sum beams to acquire the distance information of the target. When the phase difference between the two antenna sub-arrays positioned in the same side quadrant and the other two antenna sub-arrays is 180 degrees, the monopulse radar antenna outputs a difference beam to acquire angle information of different planes. The 0/180 degree bridge can output two paths of signals with equal amplitude and same phase or equal amplitude and opposite phase. Thus, a sum and difference network can be formed with four 0 °/180 ° bridges. The sum and difference network with the structure can carry out two times of sum and difference operation to output four paths of signals, and provides required feed signals for the sum and difference beams of the monopulse radar antenna.

The sum-difference network of the invention consists of two first-stage 0 degree/180 degree electric bridges and two second-stage 0 degree/180 degree electric bridges, TE is input from a standard Ka wave band rectangular waveguide₁₀In the mode, first sum and difference operation is completed through a first-stage 0 degree/180 degree electric bridge to output two paths of signals with equal amplitude and in phase or equal amplitude and opposite phase, and then second sum and difference operation is completed through two second-stage 0 degree/180 degree electric bridges to output four paths of signals required to be fed by the monopulse antenna. Since the phase shifter performs a 90 ° phase shift by changing the propagation constant of the slot-gap waveguide, this way a low-error 90 ° phase shift can be achieved over a wide frequency band. Therefore, the sum and difference network can provide four paths of feed signals with small amplitude and phase errors.

Compared with the prior art, the invention has the following advantages:

1. the sum and difference network is of a slot gap waveguide structure, does not need to have good electric contact with the whole structure, and reduces the processing difficulty and the assembly difficulty. And the slot gap waveguide has a cavity size similar to that of the rectangular waveguide, and can realize high power and low loss.

2. The sum-difference network of the invention combines a planar sum-difference network by utilizing a 3dB electric bridge and a phase shifter, and is beneficial to being integrated into a single-pulse radar antenna system.

3. The 3dB bridge designed by the invention is in an H-plane single-hole coupling mode, and the problem of poor amplitude consistency of the existing sum-difference network under the condition of a wide frequency band is solved. And the H-plane single-hole coupling mode can ensure that the main waveguide and the auxiliary waveguide are in the same plane, thereby being beneficial to reducing the overall size of the sum-difference network.

4. The phase shifter designed by the invention can complete 90-degree phase delay by changing the waveguide dispersion. Compared with a phase shifter utilizing a delay line principle, the method can realize low-error 90-degree phase shift under the condition of a wide frequency band, solves the problems of narrow band and large phase error of the existing sum and difference network, and is favorable for improving the anti-interference capability of a monopulse radar antenna.

Drawings

FIG. 1 is a schematic diagram of the structure of the sum and difference network of the present invention

FIG. 2 is an internal block diagram of the sum and difference network of the present invention

FIG. 3 is a cross-sectional block diagram of an embodiment of a sum and difference network of the present invention

FIG. 4 is a cross-sectional block diagram of a 3dB bridge for a sum and difference network of the present invention

FIG. 5 is a cross-sectional view of a 90 phase shifter for a sum and difference network according to the present invention

FIG. 6 is a cross-sectional view of a 90 turn of the H-plane of a slot gap waveguide for a sum and difference network of the present invention

FIG. 7 is a diagram showing simulation results of amplitudes from a sum port to four output ports of a sum-difference network according to the present invention

FIG. 8 is a schematic diagram showing simulation results of phase difference between one output port and other output ports of the sum and difference network according to the present invention

The reference numbers illustrate: 1 is a waveguide flange, 2 is a positioning pin A and 3 of an output port, 4 is a positioning pin B, 5-1 is a first 3dB bridge, 5-2 is a first-stage 0/180-degree bridge, 5-3 is a second 3dB bridge, 5-4 is a second-stage 0/180-degree bridge, 6-1 is a first H-face 90-degree turning structure, 6-2 is a second H-face 90-degree turning structure, 6-3 is a third H-face 90-degree turning structure, 6-4 is a rectangular waveguide-shaped 90-degree turning structure, 7-1 is a first 90-degree phase shifter, 7-2 is a second 90-degree phase shifter, 8 is a matching structure at an input end of the 3dB bridge, 9 is a matching structure at an output end of the 3dB bridge, 10-1-10-4 is a circle of metal cylinder outside a coupling hole, and 11 is a matching pin of a waveguide at an output side, 12 is a primary matching structure of the phase shifter, 13 is a secondary matching structure of the phase shifter, and 14 is a main phase shifting structure of the 90-degree phase shifter. A is a sum port of a sum-difference network, B is a dip port of the sum-difference network, C is a variance port of the sum-difference network, D is a load port of the sum-difference network, E is a sum-difference network output port E, F is a sum-difference network output port F, G is a sum-difference network output port G, and H is a sum-difference network output port H.

Detailed Description

The invention will be described in further detail below with reference to the accompanying drawings, which illustrate an embodiment of a monopulse sum-difference network for a long-range, high-resolution Ka-band radar system operating at 27.2GHz-34GHz, without limiting the scope of the invention.

As shown in fig. 1, the present invention is a monopulse sum and difference network for a long-range, high-resolution Ka-band radar system. This sum and difference network can provide a feed signal with low amplitude phase error for the monopulse radar antenna. The Ka-band standard rectangular waveguide transmission link is connected into an input port of a sum-difference network through a waveguide flange 1, and a positioning pin A of an output port is used for an antenna structure after accurate connection. The assembly screw 3 and the positioning pin B ensure the assembly precision of the whole structure.

As shown in fig. 3, the sum and difference network structure includes a first 3dB bridge 5-1, a second 3dB bridge 5-3, a first 90 ° turn 6-1, a second 90 ° turn 6-2, a third 90 ° turn 6-3, a 90 ° turn 6-4 in the form of a rectangular waveguide, a first 90 ° phase shifter 7-1, and a second 90 ° phase shifter 7-2.

Taking a sum port as an example, a standard rectangular waveguide of Ka wave band is connected into the sum port A through a waveguide flange 1, and TE is input from the standard rectangular waveguide of Ka wave band₁₀Mode-to-slot gap waveguides. TE₁₀After entering the slot gap waveguide, the mode firstly passes through a first 90-degree turning structure 6-1 and then passes through a first 3dB electric bridge 5-1 to output two paths of TE with equal amplitude₁₀After the mode, two paths of TE with equal amplitude and same phase are output through a first 90-degree phase shifter 7-1₁₀Mode(s). The two paths of TE with equal amplitude and same phase₁₀The mode is input into two second 3dB bridges 5-3 through two second 90-degree turning structures, and the two paths of TE₁₀The mode outputs four paths of equal-amplitude TE after passing through two second 3dB electric bridges 5-3₁₀Mode, TE of equal amplitude for the four ways₁₀The mode respectively passes through a third 90-degree turning structure 6-3, a second 90-degree phase shifter 7-2 and a rectangular waveguide 90-degree turning structure 6-4 in sequence to output four paths and the likeTE with same amplitude₁₀Mode(s). Thus, the input and output signals of the sum port may be denoted as a ═ E + F + G + H. The pitch signal and the variance signal enter the sum and difference network through a B port and a C port respectively to complete two sum and difference operations, an input signal and an output signal of the pitch port can be represented as B + E + G-F-H, and an input signal and an output signal of the variance port can be represented as C + E + F-G-H.

As shown in FIG. 4, the first-level 3dB bridge and the second-level 3dB bridge have the same structure and are H-plane single-hole coupled 3dB bridges, the whole structure is bilaterally symmetrical, the H plane is composed of metal cylinders which are periodically arranged, the diameter of each cylinder is 1.5mm, the height of each cylinder is 3.356mm, the E plane is composed of two parallel metal plates, one metal plate is used for placing the metal cylinders, and a gap of 0.2mm is kept between the other metal plate and the metal cylinders. The size of a cavity enclosed by the metal cylinders at two sides of the waveguide and the upper metal plate and the lower metal plate is 7.112mm multiplied by 3.556 mm. The 3dB electric bridge enables the metal cylinders at two sides to approach the coupling holes through the matching structure 8 to complete impedance matching of the input port. The diameter of a circle of six metal cylinders which are symmetrically distributed at the left and the right outside the coupling hole is 1.5mm, the height of the six metal cylinders is 3.556mm, and the size and the relative position of the six metal cylinders are related to the amplitude performance of the 3dB bridge output. The relative circle center distances between the metal cylinders 10-1 to 10-4 are respectively l₁＝12.8mm，l₂＝7.16mm，l₃＝4.4mm，l₄6.95 mm. TE through coupling hole₁₀The pattern passes through the matching structure 9 and the matching pin 11 to the output port of the bridge, the matching pin 11 having a diameter of 1.1mm and a height of 0.35 mm.

As shown in fig. 5, the 90 ° phase shifter is composed of a slot gap waveguide and periodic metal pins. The cavity dimensions of the slot-gap waveguide are 7.112mm by 3.556 mm. All metal cylinders of the H-face were 1.5mm in diameter and 3.356mm in height. The longitudinal spacing of the metal cylinders was 3mm and the transverse spacing was 3.5 mm. The metal pins are placed on the E-plane metal plate of the slot-gap waveguide. The metal pin completes the impedance matching of the 90 DEG phase shifter in the longitudinal direction of the slot gap waveguide through the primary matching structure 12, the secondary matching structure 13 and the main phase shifting structure 14. The slot gap waveguide having the metal pin structure performs a phase change of 90 ° compared to the slot gap waveguide without the metal pin. The metal pins of the primary matching structure 12 have a diameter of 0.76mm, a height of 0.21mm and a longitudinal periodic spacing of 1.17 mm. The metal pins of the secondary matching structure 13 have a diameter of 0.76mm and a height of 0.26mm, and the longitudinal and transverse periodic spacings are 1.17mm and 1.16mm, respectively. The metal pins of the main phase shifting structure 14 have a diameter of 0.76mm and a height of 0.3mm, and the longitudinal and transverse periodic spacings are 1.17mm and 1.16mm, respectively.

As shown in FIG. 6, the turning structure of the H-face of the slot-gap waveguide is a right-angle turn with a turning radius of 8.3 mm.

FIG. 7 shows the simulation results of the amplitudes of the sum and difference network sum and port output signals, and the amplitude of the four output signals from 27.2GHz to 34GHz is not consistent to be less than 0.26 dB.

Fig. 8 is a simulation result of phase difference between one of the output signals and the other three output signals of the sum-difference network, and the phase inconsistency of the four output signals from 27.2GHz to 34GHz is less than ± 3 °.

The above examples are merely for convenience of illustration, and the present invention is also applicable to the sum and difference network based on slot-gap waveguide in other frequency bands, and any other changes, modifications, substitutions, combinations and simplifications which do not depart from the spirit and principle of the present invention should be regarded as equivalent substitutions and shall be included in the protection scope of the present invention.

Claims

1. A single pulse sum-difference network for a long-distance high-resolution radar system is a slot gap waveguide structure and comprises three input ports, a load port, two primary 0/180 electric bridges, two secondary 0/180 electric bridges and four output ports; the load port is used for absorbing energy, and standard rectangular waveguide TE₁₀The mode is input through an input port, first sum and difference operation is completed through a first-stage 0 degree/180 degree electric bridge to output two paths of first-stage signals, then second sum and difference operation is completed through two second-stage 0 degree/180 degree electric bridges to output four paths of second-stage signals, and finally the four paths of second-stage signals are respectively output through four output ports;

the first-stage 0/180 DEG bridge (5-2) comprises a first 3dB bridge (5-1) and a first phase shifter (7-1) arranged at an output port of the first 3dB bridge; the two-stage 0 DEG/180 DEG electric bridge (5-4) comprises a second 3dB electric bridge (5-3), a third H-surface 90 DEG turning structure (6-3) connected with an output port of the second 3dB electric bridge (5-3), and a second phase shifter (7-2) arranged at an input section or an output section of the third H-surface 90 DEG turning structure (6-3);

two output ports of the first-stage 0 degree/180 degree electric bridge (5-2) are respectively connected with input ports of the second-stage 0 degree/180 degree electric bridge through a second H-surface 90 degree turning structure (6-2);

and a first H-surface 90-degree turning structure (6-1) is arranged between the three input ports, one load port and the first-stage 0/180-degree electric bridge.

2. A monopulse sum-difference network for a long range high resolution radar system according to claim 1, characterized in that the output ports of the third H-plane 90 ° turn structures (6-3) are connected to 90 ° turn structures (6-4) in the form of rectangular waveguides, respectively, and the 90 ° turn structures in the form of rectangular waveguides end at the output ports of the sum-difference network.

3. A monopulse sum-difference network for a long range high resolution radar system according to claim 1, characterized in that the first H-plane 90 ° turn (6-1), the second H-plane 90 ° turn (6-2) and the third H-plane 90 ° turn (6-3) are 90 ° quarter turns in the form of slot-gap waveguides with a turn radius of the broadside dimension of the slot-gap waveguides.

When the phase shifter is arranged at the output section, the plane size of the sum and difference network can be effectively reduced.

4. The monopulse sum-difference network for a long-range high-resolution radar system as claimed in claim 1, wherein said slot-gap waveguide structure is composed of upper and lower metal plates and a periodically arranged metal cylinder, the bottom end of said metal cylinder is fixedly connected to the lower metal plate, and the top end of said metal cylinder has a value smaller than λ with respect to the upper metal plate_gA gap of 4, the size of the cavity formed by the metal cylinder and the metal plate is the size of a rectangular waveguide of a standard Ka wave band, and the period of the metal cylinder is lambda_g/4～λ_gA metal cylinder diameter of 0.3 to 0.5 times the period, where lambda_gIs the waveguide wavelength.

5. The monopulse sum and difference network for a long-range high-resolution radar system according to claim 1 or 4, wherein the first phase shifter and the second phase shifter are formed of periodic metal pins, and the propagation constant of the slot gap waveguide is changed by adjusting the size of the periodic metal pins so that the side of the E-plane on which the periodic metal pins are placed is 90 ° out of phase with the side on which the periodic metal pins are not placed; compared with the side without the periodic metal pins, the phase difference theta between the side of the slot gap waveguide with the periodic metal pins placed on the E surface is beta multiplied by L, beta is the propagation constant difference of two sides, and L is the longitudinal length of the periodic metal pin structure.

6. The monopulse sum and difference network for a long range high resolution radar system according to claim 5, wherein the height and number of periodic metal pins per row at both longitudinal ends of said periodic metal pins are gradually decreased.

7. The monopulse sum-difference network for a long range high resolution radar system according to claim 6, wherein the height, spacing and diameter of said periodic metal pins are set at λ_g20 to lambda_gAnd/10.

8. The monopulse sum-difference network for a long-distance high-resolution radar system as claimed in claim 1, wherein the first 3dB bridge and the second 3dB bridge are identical in structure, and are coupled in a manner of H-plane single-hole coupling, each of which comprises a coupling hole, two input-side waveguides and two output-side waveguides symmetrically arranged at two sides of the coupling hole, and two ends of a circle of metal cylinders outside the coupling hole are fixedly connected with upper and lower metal plates; the output side waveguide is also provided with a matching pin.

9. For long distances as in claim 8Monopulse sum-difference networks for high resolution radar systems, characterised by a time delay between coupling of TE in the holes₁₀And TE₂₀When the phase difference of the two modes is 90 degrees, the output port outputs two paths of signals with equal amplitude and 90-degree phase difference; TE₁₀Waveguide wavelength of mode

And TE₂₀Of the waveguide wavelength

And longitudinal length l of coupling hole₁Satisfies the following conditions: