Active phased array radar system

Abstract

The invention discloses an active phased array radar system, and relates to the technical field of radars. The system comprises an antenna unit, a TR assembly, a transmit-receive processing unit and a wave control unit. A feed network and a sum-difference network are integrated in the TR assembly. The sum-difference network comprises a broadband sum-difference device formed by arraying four 180-degree strip line bridges, a sum port and a difference port of a first bridge are respectively used as a sum port and a pitch difference port of the sum-difference device, and two equally divided arm ports of the first bridge are respectively connected to sum ports of a second bridge and a third bridge. Equally-divided arm ports of the second bridge and the third bridge are respectively used as four quadrant ports, difference ports of the second bridge and the third bridge are respectively connected to two equally-divided arm ports of the fourth bridge, and a sum port of the fourth bridge is used as an azimuth difference port of the sum-difference device. According to the invention, the problem that the metal waveguide sum-difference device is difficult to integrate with the tile-type radar antenna is thoroughly solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of radar technology, and particularly relates to a two-dimensional "tile type" active phased array radar system. BACKGROUND

[0002] In a radar system, sum-difference angle measurement is a key technology for realizing high-precision target positioning and tracking. The principle is to process target echo signals and use the "difference pattern null depth" generated by the sum-difference network to accurately indicate the target direction. The deeper the null depth, the stronger the antenna's ability to suppress signals in that direction, and the higher the angle measurement accuracy provided.

[0003] In terms of specific workflow, the sum-difference network plays a core role in the transmission and reception stages:

[0004] When transmitting: the signal from the transmitter is input from the sum port of the sum-difference network through a circulator, and is divided into four paths, which then excite the feed networks of the four quadrants to drive the T / R components to radiate energy into space.

[0005] When receiving: the RF signals from the antenna array are combined by the feed networks of the four quadrants, forming four downlink signals that are sent to the sum-difference network. The sum-difference network forms the sum beam, azimuth difference beam and elevation difference beam accordingly, and then sends them to the receiver through the circulator for subsequent processing.

[0006] To meet the urgent needs of modern radars for higher null depth, better angle / range measurement accuracy, lighter weight and higher integration, the development of sum-difference networks is moving towards broadband, lightweight and easy integration. Traditional sum-difference networks generally use metal waveguide structures, which have excellent performance but are high in profile, large in volume and heavy in weight, making it difficult to integrate with the current mainstream microstrip patch antenna (tile type antenna array). This often results in the need for independent installation space for the sum-difference network and interconnection with the antenna feed network through a large number of RF connectors, ultimately leading to a complex structure and low integration of the entire radar system. SUMMARY

[0007] In view of the problems of large volume, high profile and difficulty in integrated with tile type microstrip antenna array of traditional metal waveguide sum-difference network in the prior art, the present application aims to provide a highly integrated active phased array radar system.

[0008] The core of the application is that four 180° stripline electric bridge cascade groups are adopted to form a novel stripline broadband sum-difference device.

[0009] The application is achieved by the following technical scheme: an active phased array radar system, comprising an antenna unit, a TR component, a transceiver processing unit and a wave control unit; a feed network and a sum-difference network are integrated in the TR component; an input end of the feed network is connected with the antenna unit; an output end of the sum-difference network is connected with the transceiver processing unit; the wave control unit is connected with a control end of the TR component.

[0010] The sum-difference network comprises a sum-difference device composed of a first electric bridge, a second electric bridge, a third electric bridge and a fourth electric bridge; the first electric bridge, the second electric bridge, the third electric bridge and the fourth electric bridge are all 180° stripline electric bridges.

[0011] The sum port of the first electric bridge is used as the sum port of the sum-difference device; the difference port of the first electric bridge is used as the pitch difference port of the sum-difference device; the two equal division arm ports of the first electric bridge are respectively connected to the sum port of the second electric bridge and the sum port of the third electric bridge.

[0012] The two equal division arm ports of the second electric bridge are respectively used as the first quadrant port and the second quadrant port; the difference port of the second electric bridge and the difference port of the third electric bridge are respectively connected to the two equal division arm ports of the fourth electric bridge; the two equal division arm ports of the third electric bridge are respectively used as the third quadrant port and the fourth quadrant port.

[0013] The sum port of the fourth electric bridge is used as the azimuth difference port of the sum-difference device.

[0014] In the embodiment, a single 180° electric bridge has one sum port, one difference port and two equal division arm ports; when a signal is input from the sum port, the signals to the two equal division arm ports are equal in amplitude and in phase; when a signal is input from the difference port, the signals to the two equal division arm ports are equal in amplitude and opposite in phase. Based on the characteristics of the 180° electric bridge, through two-stage cascade, the initial equal-amplitude and in-phase signal is reasonably distributed and transmitted to the four quadrant ports:

[0015] (1) Sum port excitation: After the signal is input from the sum port of the first bridge, it is divided into two excitation signals with equal amplitude and in phase by the first bridge; one of the excitation signals is input from the sum port of the second bridge, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the second bridge (corresponding to the first quadrant port and the second quadrant port); the other excitation signal is input from the sum port of the third bridge, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the third bridge (corresponding to the third quadrant port and the fourth quadrant port).

[0016] Since the two excitation signals output from the two equally divided arm ports of the first bridge are equal in amplitude and phase, and the second and third bridges are both operating in the equal in amplitude and phase mode of the input ports, the signals obtained at the first, second, third, and fourth quadrant ports are all equal in amplitude and phase, thus forming a beam.

[0017] (2) Azimuth difference port excitation: After the signal is input from the sum port (i.e. the azimuth difference port of the sum and difference device) of the fourth bridge, it is divided into two excitation signals with equal amplitude and in phase by the fourth bridge; one of the excitation signals is input from the difference port of the second bridge, and generates an output with equal amplitude and opposite phase on the two equally divided arm ports of the second bridge (corresponding to the first quadrant port and the second quadrant port); the other excitation signal is input from the difference port of the third bridge, and generates an output with equal amplitude and opposite phase on the two equally divided arm ports of the third bridge (corresponding to the third quadrant port and the fourth quadrant port).

[0018] Since the signals at the first and fourth quadrant ports originate from the second and third bridges respectively, and the two excitation signals are in phase, their absolute phases are the same. Similarly, the signals at the second and third quadrant ports also have the same absolute phase, but are opposite to those at the first and fourth quadrant ports. Therefore, the signals from the azimuth difference ports to (signals at the first and fourth quadrant ports) and (signals at the second and third quadrant ports) are of equal amplitude and opposite phase, forming an azimuth difference beam.

[0019] (3) Pitch difference port excitation: After the signal is input from the difference port of the first bridge (i.e. the pitch difference port of the sum and difference device), it is divided into two excitation signals with equal amplitude and opposite phase by the first bridge; one of the excitation signals is input from the sum port of the second bridge, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the second bridge (corresponding to the first quadrant port and the second quadrant port); the other excitation signal is input from the sum port of the third bridge, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the third bridge (corresponding to the third quadrant port and the fourth quadrant port).

[0020] Since the signals of the first-quadrant port and the second-quadrant port are equal in amplitude and in phase, the signals of the third-quadrant port and the fourth-quadrant port are also equal in amplitude and in phase, but the two excitation signals are equal in amplitude and opposite in phase. Therefore, the (signal of the first-quadrant port, signal of the second-quadrant port) is equal in amplitude and opposite in phase to the (signal of the third-quadrant port, signal of the fourth-quadrant port), which realizes that the tilt-difference port is equal in amplitude and opposite in phase to the (signal of the first-quadrant port, signal of the second-quadrant port) and (signal of the third-quadrant port, signal of the fourth-quadrant port), forming a tilt-difference beam required for tilt-plane angle measurement.

[0021] The sum-and-difference device of the application is composed of four 180° stripline electric bridges, which is a broadband circuit form itself, and can further improve the bandwidth by selecting an electric bridge (such as Lange electric bridge) with ultra-wide working bandwidth, solving the problem of narrow bandwidth in traditional design.

[0022] The sum-and-difference device of the application is composed of four 180° stripline electric bridges. Since the stripline is a planar transmission line structure, the sum-and-difference device can be integrally manufactured by standard printed circuit board (PCB) process, realizing low profile and thinness of the overall circuit. The PCB form sum-and-difference device is integrated with the feeding network in the T / R module, so as to realize high integration and conformal integration with the tile type radar array in the form of microstrip patch antenna. The design not only completely abandons the independent metal waveguide sum-and-difference device and a large number of RF connectors in the traditional scheme, significantly reduces the system weight and structural complexity, but also has the engineering advantages of simple processing, low cost and good consistency, and fundamentally solves the technical difficulty that the traditional sum-and-difference device is difficult to realize high-density integration with the tile type radar antenna.

[0023] Further, the 180° stripline electric bridge is a four-port network, including a sum port, a difference port, a first equal-division arm port and a second equal-division arm port; the internal circuit of the 180° stripline electric bridge is composed of 1 / 4λ transmission lines with characteristic impedance, and forms a ring network; wherein λ represents wavelength, and the ring network is configured as:

[0024] So that the signals input from the first equal-division arm port and the second equal-division arm port reach the sum port through two paths with equal electric length, realizing equal-amplitude and in-phase synthesis;

[0025] So that the signals input from the first equal-division arm port and the second equal-division arm port reach the difference port through two paths with a phase difference of 180°, realizing equal-amplitude and opposite-phase synthesis.

[0026] The application realizes the equal-length in-phase path from two equal-division arm ports to the sum port and the half-wavelength difference anti-phase path to the difference port by the ring network composed of 1 / 4 lambda transmission lines with characteristic impedance, thereby ensuring that the 180° stripline electric bridge can stably and efficiently complete equal-amplitude in-phase and equal-amplitude anti-phase synthesis of signals in structure. This not only provides high-purity and high-consistency sum and difference signals for the radar system and lays the foundation for high-precision angle measurement, but also has the characteristics of low profile and easy processing due to the planar structure based on the stripline, which is very beneficial to the integration with the TR component and the microstrip antenna, and effectively supports the core requirements of high performance and high integration of the tile-type radar system.

[0027] Further, the ring network of the 180° stripline electric bridge is a two-stage ring composed of first to eighth 1 / 4 lambda transmission lines; the first 1 / 4 lambda transmission line connects the first equal-division arm port and the sum port; the second 1 / 4 lambda transmission line connects the sum port and the second equal-division arm port; the third, fourth and fifth 1 / 4 lambda transmission lines are connected in series between the second equal-division arm port and the difference port; the sixth and seventh 1 / 4 lambda transmission lines are connected in series between the difference port and the first equal-division arm port; the eighth 1 / 4 lambda transmission line is bridged between the nodes of the third and fourth 1 / 4 lambda transmission lines and the nodes of the sixth and seventh 1 / 4 lambda transmission lines; and the first, second, third and seventh 1 / 4 lambda transmission lines all have a first characteristic impedance, the fourth and sixth 1 / 4 lambda transmission lines all have a second characteristic impedance, the eighth 1 / 4 lambda transmission line has twice the first characteristic impedance, and the fifth 1 / 4 lambda transmission line has twice the second characteristic impedance; the first characteristic impedance is not equal to the second characteristic impedance.

[0028] In this embodiment, the higher the ring level of the 180° stripline electric bridge, the higher the bandwidth and the greater the loss. The 180° stripline electric bridge with a two-stage ring has low loss while achieving a bandwidth of more than 15% in the Ku band.

[0029] The application significantly expands the working bandwidth (for example, more than 15% in the Ku band) while controlling the insertion loss at a low level on the basis of ensuring the equal-amplitude in-phase and anti-phase synthesis function of signals, thereby achieving an excellent balance between wideband performance and signal attenuation and meeting the dual requirements of high spectral utilization and high signal integrity of the sum and difference network of modern wideband radar systems.

[0030] Further, the sum and difference device is implemented by a multi-layer printed circuit board, which at least includes a top layer, an intermediate layer and a bottom layer; the stripline conductors of the first electric bridge, the second electric bridge, the third electric bridge and the fourth electric bridge are formed in the intermediate layer, and the top layer and the bottom layer are ground layers.

[0031] The application integrates the lead bands of all four electric bridges in the middle signal layer of the multilayer printed circuit board, and uses the top and bottom layers as ground shielding, so that the high compactness and low profile of the whole sum-difference device are realized, the signal crosstalk and radiation loss are effectively suppressed, the good amplitude and phase consistency between the electric bridges is ensured, the electric bridges can be directly embedded in the feed network inside the TR assembly as a high-density integrated standard module, and a key process implementation path is provided for realizing the high performance and high reliability integrated integration of the tile type radar system.

[0032] Further, the top layer is provided with a microstrip line and a radio frequency connector connected with the microstrip line, and the microstrip line is connected with the strip line lead band of the middle layer through a vertical interconnection structure.

[0033] The application sets the microstrip line and the radio frequency connector on the top layer, and realizes the electrical connection with the strip line lead band of the middle layer through the vertical interconnection structure, so that a standard and reliable external radio frequency interface is provided for the whole sum-difference device module, the interconnection with the external TR assembly and the antenna unit is facilitated, the high integration and shielding advantages brought by the multilayer PCB structure are maintained, and the effective unification between the high-performance circuit and the convenient system integration is realized.

[0034] Further, the sum port, the pitch difference port, the azimuth difference port, the first quadrant port, the second quadrant port, the third quadrant port and the fourth quadrant port of the sum-difference device are all connected with the radio frequency connector to form an independent functional accessory.

[0035] The application sets the standard radio frequency connector on all key ports of the sum-difference device, so that it can become an independent plug-and-play functional module; this not only greatly facilitates the system assembly, testing and maintenance, improves the production efficiency and reliability, but also ensures that the high-performance sum-difference device can be used as a highly integrated internal component and as a standard external module to flexibly adapt to different radar system architectures.

[0036] Further, the feed network and the sum-difference network in the TR assembly are made of an integrated multilayer circuit process, so that the feed network and the sum-difference network are integrated in the same multilayer circuit substrate in physical structure, and are connected with the feed lines of the transmit channel and the receive channel of the TR assembly.

[0037] The application realizes direct interconnection between the feeding network and the sum-difference network without connectors and jumpers and high-density connection with the TR component feeding line by adopting the integrated multilayer circuit process to integrate the feeding network and the sum-difference network in the same multilayer circuit substrate. This fundamentally eliminates the parasitic parameters, loss and uncertainty introduced by the discrete interconnection between the modules, greatly improves the signal integrity, amplitude and phase consistency and reliability of the whole radio frequency front end, and realizes significant optimization of the system volume, weight and power consumption, thereby providing a key engineering implementation path for constructing a high-performance and high-integration tile active phased array radar.

[0038] Further, the difference port of the fourth electric bridge is connected with a matching load.

[0039] Further, the first electric bridge, the second electric bridge, the third electric bridge and the fourth electric bridge have the same structural size and electrical performance parameters.

[0040] The application ensures that the four 180° strip line electric bridges constituting the sum-difference device are completely consistent in structural size and electrical performance parameters, fundamentally guarantees that the sum-difference network has extremely high amplitude and phase consistency when processing four quadrant signals, and significantly improves the quality of the sum beam and the difference beam formed finally, thereby laying a key foundation for the radar system to realize high-precision and high-sensitivity angle measurement and tracking performance.

[0041] Further, the antenna unit includes an antenna array divided into four sub-arrays; the four sub-arrays of the antenna array are respectively connected with the four input ends of the feeding network; and the four output ends of the feeding network are respectively connected to the first quadrant port, the second quadrant port, the third quadrant port and the fourth quadrant port of the sum-difference device.

[0042] The application constructs a clear and symmetrical four-quadrant sum-difference beam forming link by explicitly dividing the antenna unit into four sub-arrays and connecting them to the four quadrant ports of the sum-difference device through the feeding network, which not only realizes efficient partitioning and signal synthesis of the antenna aperture and ensures the excellent performance of the sum and difference beam patterns, but also provides a stable and reliable physical and signal foundation for the whole radar system to realize high-precision monopulse angle measurement.

[0043] Compared with the prior art, the application has the following beneficial effects:

[0044] The active phased array radar system provided by the application has the core innovation of integrating a wideband and difference device based on a stripline bridge.

[0045] The wideband and difference device of the application adopts a stripline planar circuit form, has the characteristics of low profile and light weight, can be directly integrated in a multilayer feed network of a T / R module, completely solves the problem that a traditional metal waveguide and difference device is difficult to be integrated with a current tile type radar antenna, and significantly improves the integration degree of a radar system.

[0046] Thanks to the excellent characteristics of the stripline bridge, the and difference device of the application can stably work in a relative bandwidth of more than 15% (such as a Ku band), and ensures the performance consistency of a radar system at different frequencies. Since a symmetrical circuit topology and the same elements are adopted, the and difference device of the application has excellent amplitude and phase consistency between channels, which is crucial for forming a deep zero deep difference beam, thereby providing a single pulse radar with extremely high angle measurement accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only one embodiment of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0048] Figure 1 is a structural block diagram of an active phased array radar system in an embodiment of the application;

[0049] Figure 2 is a structural schematic diagram of a 180° stripline bridge with a three-level loop in an embodiment of the application;

[0050] Figure 3 is a structural schematic diagram of a stripline wideband and difference device in an embodiment of the application;

[0051] Figure 4 is a structural schematic diagram of a 180° stripline bridge with a two-level loop in an embodiment of the application;

[0052] Figure 5 is a schematic diagram of a stripline wideband and difference structure used alone in embodiments of the invention;

[0053] Figure 6 is a stripline wideband and difference layer stack diagram implemented through a multilayer printed circuit board in embodiments of the invention;

[0054] Figure 7 is a 180° stripline bridge standing wave curve in embodiments of the invention;

[0055] Figure 8 is a 180° stripline bridge and difference port isolation curve in embodiments of the invention;

[0056] Figure 9 is a 180° stripline bridge and port amplitude consistency schematic in embodiments of the invention;

[0057] Figure 10 is a 180° stripline bridge and port phase consistency schematic in embodiments of the invention;

[0058] Figure 11 is a 180° stripline bridge difference port amplitude consistency schematic in embodiments of the invention;

[0059] Figure 12 is a 180° stripline bridge difference port phase consistency schematic in embodiments of the invention;

[0060] Figure 13 is a stripline wideband and difference and port, azimuth difference port, and elevation difference port standing wave curve in embodiments of the invention;

[0061] Figure 14 is a stripline wideband and difference each quadrant port standing wave curve in embodiments of the invention;

[0062] Figure 15 is a stripline wideband and difference each port isolation curve in embodiments of the invention;

[0063] Figure 16 is a stripline wideband and difference receive and port-quadrant port amplitude consistency schematic in embodiments of the invention;

[0064] Figure 17 is a stripline wideband and difference receive and port-quadrant port phase consistency schematic in embodiments of the invention;

[0065] Figure 18 is a stripline wideband and difference azimuth difference port-quadrant port amplitude consistency schematic in embodiments of the invention;

[0066] Figure 19is a schematic diagram of azimuth difference port-quadrant port phase consistency of a stripline broadband and difference device in an embodiment of the invention;

[0067] Figure 20 is a schematic diagram of elevation difference port-quadrant port amplitude consistency of a stripline broadband and difference device in an embodiment of the invention;

[0068] Figure 21 is a schematic diagram of elevation difference port-quadrant port phase consistency of a stripline broadband and difference device in an embodiment of the invention;

[0069] Figure 22 is a received and normalized pattern of a stripline broadband and difference device in an embodiment of the invention;

[0070] Figure 23 is a received azimuth difference normalized pattern of a stripline broadband and difference device in an embodiment of the invention;

[0071] Figure 24 is a received elevation difference normalized pattern of a stripline broadband and difference device in an embodiment of the invention.

[0072] BRIEF DESCRIPTION OF DRAWINGS: 1 - first bridge, 11 - sum port of first bridge, 12 - difference port (elevation difference port) of first bridge, 2 - second bridge, 21 - second split arm port (second quadrant port) of second bridge, 22 - first split arm port (first quadrant port) of second bridge, 3 - third bridge, 31 - second split arm port (third quadrant port) of third bridge, 32 - first split arm port (fourth quadrant port) of third bridge, 4 - fourth bridge, 41 - difference port (load port) of fourth bridge, 5 - RF connector. DETAILED DESCRIPTION

[0073] The technical solutions in the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0074] The technical solutions of the present application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and some embodiments may not be described again for the same or similar concepts or processes.

[0075] The present application provides a highly integrated two-dimensional active phased array radar system, which is particularly suitable for "tile type" radar applications with strict requirements on weight, volume and profile.

[0076] As Figure 1As shown, the radar system mainly includes an antenna unit, a TR assembly, a transceiving processing unit and a wave control unit. These units form a complete radio frequency signal transceiving and processing link through a specific connection relationship.

[0077] Antenna unit: a planar array in the form of microstrip patch antenna, which can be divided into four independent sub-arrays (first quadrant to fourth quadrant). The antenna unit is used to radiate radar beams to space and receive echo signals from targets.

[0078] TR assembly: the core integrated component of the present application, which integrates a feed network and a sum-difference network inside and is made integrally through a multi-layer printed circuit board (PCB) process, realizing high-density integration. The TR assembly has multiple external interfaces:

[0079] Radio frequency end: connected to each radiating element or sub-array of the antenna unit through multiple independent radio frequency channels.

[0080] Control end: connected to the wave control unit, receiving control instructions (such as phase shift and attenuation control codes) required for beam scanning.

[0081] Signal end: connected to the transceiving processing unit through the output end of the internal sum-difference network.

[0082] Specifically, the feed network integrated inside the TR assembly is connected to each radiating element or sub-array of the antenna unit, used for power distribution when transmitting and signal synthesis when receiving. The output end (usually four-way, corresponding to four antenna sub-arrays) of the feed network is connected to the input end of the internally integrated sum-difference network.

[0083] The sum-difference network is the key to realizing the monopulse angle measurement function of the present application, which is specifically composed of four 180° strip-line bridges of first, second, third and fourth according to a specific topology connection. The sum-difference network has seven key ports: one sum port, one azimuth difference port, one elevation difference port, and four quadrant ports corresponding to the four sub-arrays of the antenna. The function of the sum-difference network is to process and synthesize the four-way signals from the four antenna sub-arrays into sum signal, azimuth difference signal and elevation difference signal in real time in the receiving state. These three signals together constitute all the information required for monopulse angle measurement.

[0084] Wave control unit: connected to the control end of the TR assembly, which calculates and generates corresponding control codes according to the beam pointing instructions of the radar system, sends them to each channel inside the TR assembly through the control end, realizes accurate control of the amplitude and phase of the transmitted / received signal, and thus completes beam scanning and shaping.

[0085] Transceiving processing unit: connected to the output port of the sum-difference network in the TR assembly. Its main functions include:

[0086] In the transmitting period: the radar intermediate frequency transmitting signal is generated, and after up-conversion, is fed into the sum port of the hybrid network through the circulator, is distributed after the network, and excites the TR component and the antenna radiation;

[0087] In the receiving period: the sum and difference three-way radio frequency echo signals from the TR component and the output of the hybrid network are received, and after down-conversion, analog-to-digital conversion and other processing, the angle information of the target is finally calculated based on the amplitude and phase relationship of the sum and difference signals.

[0088] The working principle of the radar system is as follows:

[0089] The transmitting process: the transmitting signal generated by the transceiver processing unit is input from the sum port of the hybrid network, is distributed through the internal bridge of the network, is output from the four quadrant ports in the form of equal amplitude and in-phase, and is distributed to each TR channel through the feeding network, and after amplification, is radiated to space by the antenna unit.

[0090] The receiving process: the echo signals received by the four sub-arrays of the antenna unit are amplified and phase-adjusted by the TR channel, and are preliminarily synthesized into four signals by the feeding network, and are input into the four quadrant ports of the hybrid network. The hybrid network combines the four signals into one sum signal and two difference signals (azimuth difference and elevation difference) in real time according to the fixed phase relationship inside. The three signals are output to the transceiver processing unit for subsequent processing, and the azimuth angle and elevation angle deviation of the target relative to the radar beam axis can be accurately calculated by comparing the amplitude ratio (monopulse ratio) of the sum and difference channel signals.

[0091] The present application successfully replaces the traditional large and heavy metal waveguide hybrid by highly integrating the feeding network and the hybrid network inside the TR component and adopting the planarized stripline bridge scheme. This design greatly simplifies the system structure, reduces a large number of radio frequency connectors and cables, realizes the low profile, light weight and high reliability of the radar front end, and perfectly adapts to the integration needs of modern tile type active phased array radar.

[0092] The 180° bridge (ring bridge) is a kind of microwave passive device, which is composed of 3 90° branches and 1 270° branch to form a ring structure, realizes the generation of 180° phase difference of the input signal at the output end, and has the port isolation function, and is widely used in power distribution, signal synthesis and monopulse feeding network scenes.

[0093] As Figure 2As shown, the 180° stripline electric bridge of the embodiment is a four-port network, including a sum port Port3, a difference port Port4, a first equal-division arm port Port1 and a second equal-division arm port Port2; the internal circuit of the 180° stripline electric bridge is composed of 1 / 4λ transmission lines (i.e. quarter-wavelength transmission lines) with characteristic impedance, and forms a ring network. The ring network is configured as:

[0094] So that the signals input from the first equal-division arm port Port1 and the second equal-division arm port Port2 reach the sum port Port3 through two paths ① and ② with equal electric length, realizing equal-amplitude and in-phase synthesis to form a sum signal; similarly, when a signal is input from the sum port Port3, the signals output from the first equal-division arm port Port1 and the second equal-division arm port Port2 are equal-amplitude and in-phase.

[0095] So that the signals input from the first equal-division arm port Port1 and the second equal-division arm port Port2 reach the difference port Port4 through two paths ③ and ④ with electric length difference of half a wavelength, generating a 180° phase difference, realizing equal-amplitude and anti-phase synthesis to form a difference signal; similarly, when a signal is input from the difference port Port4, the signals output from the first equal-division arm port Port1 and the second equal-division arm port Port2 are equal-amplitude and anti-phase.

[0096] Figure 3 The 180° stripline electric bridge in the above formula has three levels of loops, and Z0, Z1, Z2 and Z3 all represent the characteristic impedance of the corresponding transmission line. The transmission lines corresponding to the characteristic impedances Z1, Z2 and Z3 are all 1 / 4λ transmission lines, and the transmission line corresponding to the characteristic impedance Z0 can be an arbitrary wavelength transmission line.

[0097] Based on the above characteristics of the 180° stripline electric bridge, four 180° stripline electric bridges are connected in a specific array to form a four-quadrant sum-difference device, which can simultaneously generate a high-gain sum beam, an azimuth difference beam for azimuth angle measurement and an elevation difference beam for elevation angle measurement. As shown in Figure 3 As shown, the stripline broadband sum-difference device provided by the embodiment of the application includes a first electric bridge 1, a second electric bridge 2, a third electric bridge 3 and a fourth electric bridge 4, and the first electric bridge 1, the second electric bridge 2, the third electric bridge 3 and the fourth electric bridge 4 are all 180° stripline electric bridges.

[0098] The sum port 11 of the first bridge is the sum port of the sum-difference device, the difference port 12 of the first bridge is the pitch difference port of the sum-difference device, the two equal-arm ports of the first bridge 1 are connected to the sum ports of the second bridge 2 and the third bridge 3 respectively; the two equal-arm ports of the second bridge 2 are the first quadrant port 22 and the second quadrant port 21 respectively; the difference port of the second bridge 2 and the difference port of the third bridge 3 are connected to the two equal-arm ports of the fourth bridge 4 respectively; the two equal-arm ports of the third bridge 3 are the third quadrant port 31 and the fourth quadrant port 32 respectively; and the sum port of the fourth bridge 4 is the azimuth difference port of the sum-difference device.

[0099] Based on the characteristics of the 180° bridge, the initial equal-amplitude and in-phase signal is reasonably distributed and transmitted to the four quadrant ports through two-stage cascade:

[0100] Sum port excitation: after the signal is input from the sum port of the first bridge 1, the first bridge 1 distributes it into two equal-amplitude and in-phase excitation signals; one of the excitation signals is input from the sum port of the second bridge 2, and equal-amplitude and in-phase outputs are generated on the two equal-arm ports (corresponding to the first quadrant port 22 and the second quadrant port 21) of the second bridge 2; the other excitation signal is input from the sum port of the third bridge 3, and equal-amplitude and in-phase outputs are generated on the two equal-arm ports (corresponding to the third quadrant port 31 and the fourth quadrant port 32) of the third bridge 3.

[0101] Since the two excitation signals output from the two equal-arm ports of the first bridge 1 are equal-amplitude and in-phase, and the second bridge 2 and the third bridge 3 both work in the equal-amplitude and in-phase mode of the sum port input, the signals obtained at the first quadrant port 22, the second quadrant port 21, the third quadrant port 31 and the fourth quadrant port 32 are all equal-amplitude and in-phase, forming a sum beam.

[0102] Azimuth difference port excitation: after the signal is input from the sum port of the fourth bridge 4 (i.e. the azimuth difference port of the sum-difference device), the fourth bridge 4 distributes it into two equal-amplitude and in-phase excitation signals; one of the excitation signals is input from the difference port of the second bridge 2, and equal-amplitude and opposite-phase outputs are generated on the two equal-arm ports (corresponding to the first quadrant port 22 and the second quadrant port 21) of the second bridge 2; the other excitation signal is input from the difference port of the third bridge 3, and equal-amplitude and opposite-phase outputs are generated on the two equal-arm ports (corresponding to the third quadrant port 31 and the fourth quadrant port 32) of the third bridge 3.

[0103] Since the signals of the first quadrant port 22 and the fourth quadrant port 32 come from the second electric bridge 2 and the third electric bridge 3 respectively, and the two excitation signals are in phase, the absolute phases of the signals of the first quadrant port 22 and the fourth quadrant port 32 are the same. Similarly, the absolute phases of the signals of the second quadrant port 21 and the third quadrant port 31 are also the same, but opposite to the absolute phases of the signals of the first quadrant port 22 and the fourth quadrant port 32. Therefore, the azimuth difference port to (the signals of the first quadrant port 22 and the fourth quadrant port 32) and (the signals of the second quadrant port 21 and the third quadrant port 31) are equal amplitude and opposite phase, forming an azimuth difference beam.

[0104] The elevation difference port excitation: after the signal is input from the difference port 12 (i.e. the elevation difference port of the hybrid) of the first electric bridge, the signal is distributed by the first electric bridge 1 into two equal amplitude and opposite phase excitation signals; one of the excitation signals is input from the sum port of the second electric bridge 2, and equal amplitude and in-phase outputs are generated on the two equal arm ports (corresponding to the first quadrant port 22 and the second quadrant port 21) of the second electric bridge 2; the other excitation signal is input from the sum port of the third electric bridge 3, and equal amplitude and in-phase outputs are generated on the two equal arm ports (corresponding to the third quadrant port 31 and the fourth quadrant port 32) of the third electric bridge 3.

[0105] Since the signals of the first quadrant port 22 and the second quadrant port 21 are equal amplitude and in phase, and the signals of the third quadrant port 31 and the fourth quadrant port 32 are also equal amplitude and in phase, but the two excitation signals are equal amplitude and opposite phase. Therefore, (the signals of the first quadrant port 22 and the second quadrant port 21) and (the signals of the third quadrant port 31 and the fourth quadrant port 32) are equal amplitude and opposite phase, realizing that the elevation difference port 12 to (the signals of the first quadrant port 22 and the second quadrant port 21) and (the signals of the third quadrant port 31 and the fourth quadrant port 32) are equal amplitude and opposite phase, forming an elevation difference beam required for elevation plane angle measurement.

[0106] Since the hybrid of the application adopts a strip line form, the profile is low, can be integrated with the multi-layer feed network of the T / R module, the processing is simple, and the cost is low. The hybrid of the application is composed of four 180° strip line electric bridges, the structure is symmetrical, the amplitude consistency is good, and the S parameter (scattering parameter) is optimal.

[0107] In the specific embodiments of the application, as Figure 4As shown in the figure, the annular network of the 180° stripline bridge adopted by the first to fourth bridges is a two-level loop formed by the first to eighth 1 / 4λ transmission lines; the first 1 / 4λ transmission line connects the first split-arm port and the sum port; the second 1 / 4λ transmission line connects the sum port and the second split-arm port; the third, fourth and fifth 1 / 4λ transmission lines are connected in series between the second split-arm port and the difference port; the sixth and seventh 1 / 4λ transmission lines are connected in series between the difference port and the first split-arm port; and the eighth 1 / 4λ transmission line bridges between the nodes of the third and fourth 1 / 4λ transmission lines and the nodes of the sixth and seventh 1 / 4λ transmission lines.

[0108] The first, second, third and seventh 1 / 4λ transmission lines all have a first characteristic impedance Z1, the fourth and sixth 1 / 4λ transmission lines all have a second characteristic impedance Z2, the eighth 1 / 4λ transmission line has a first characteristic impedance Z1 doubled, and the fifth 1 / 4λ transmission line has a second characteristic impedance Z2 doubled; the first characteristic impedance Z1 is not equal to the second characteristic impedance Z2. The eighth 1 / 4λ transmission line can be composed of two 1 / 4λ transmission lines with the first characteristic impedance Z1, and the fifth 1 / 4λ transmission line can be composed of two 1 / 4λ transmission lines with the second characteristic impedance Z2.

[0109] The higher the loop level of the 180° stripline bridge, the higher the bandwidth and the greater the loss. The 180° stripline bridge adopted by the first to fourth bridges has a two-level loop, which has low loss while achieving a bandwidth of more than 15% in the Ku band.

[0110] In the specific embodiments of the present application, as shown in Figure 5 and Figure 6 The sum-difference device is implemented by a multi-layer printed circuit board, which at least includes a top layer TOP, a middle layer A02 and a bottom layer BOT; wherein the stripline conductors of the first bridge 1, the second bridge 2, the third bridge 3 and the fourth bridge 4 are formed in the middle layer A02, and the top layer TOP and the bottom layer BOT are ground layers.

[0111] As shown in Figure 6 The sum-difference device implemented by the multi-layer printed circuit board has a total thickness of only 1.205 mm, greatly reducing the profile height.

[0112] The sum-and-difference device is realized by a multilayer printed circuit board, and a fundamental transformation from a three-dimensional structure to a two-dimensional plane circuit of the sum-and-difference device is realized, which enables the sum-and-difference device to be seamlessly integrated into a tile phased array antenna, conformally mounted with a T / R module and a radiation unit, and is a key technology for realizing thinness and conformality of a radar antenna array surface. The sum-and-difference device can be directly designed and manufactured in a multilayer feed network of the T / R module itself as one wiring layer. This completely eliminates all external connectors, cables and mounting structures, greatly improves system integration and reliability, and reduces potential failure points.

[0113] In the specific embodiments of the present application, as shown in Figure 5 , a microstrip line and a radio frequency connector 5 connected with the microstrip line are arranged on the top layer TOP, and the microstrip line is connected with a strip line guide of the middle layer through a vertical interconnection structure. In this embodiment, the vertical interconnection structure is a copper-plated via hole VIA1 or a blind hole VIA2 or a coaxial via.

[0114] In this embodiment, as shown in Figure 5 , the sum port, the elevation difference port, the azimuth difference port, the first quadrant port, the second quadrant port, the third quadrant port and the fourth quadrant port of the sum-and-difference device are all connected with radio frequency connectors to form an independent functional accessory for separate use.

[0115] In the specific embodiments of the present application, the difference port 41 of the fourth bridge is connected with a matching load. In this embodiment, the matching load is welded at the end of the microstrip line of the top layer TOP of the multilayer printed circuit board.

[0116] In order to verify the effect of the present application, the 180° strip line bridge and the strip line broadband sum-and-difference device are measured, and the S parameter data are obtained, as shown in Figures 7 to 24 .

[0117] As can be seen from Figure 7 , the standing wave of each port of the 180° strip line bridge is relatively optimal, and the bandwidth meets the demand.

[0118] As can be seen from Figure 8 , the sum port-difference port isolation of the 180° strip line bridge is relatively optimal, which can reduce the interference of the sum port and the difference port radio frequency signals in the bridge, and ensure that the isolation between each port of the sum-and-difference device obtained by the strip line bridge array is relatively optimal, and further ensure that the interference of the sum-and-difference device port radio frequency signals in the bridge is less.

[0119] As can be seen from Figure 9 , the amplitude consistency of the sum port to the two equal arm ports of the 180° strip line bridge is relatively optimal, which ensures the amplitude consistency of the sum port of the sum-and-difference device obtained by the strip line bridge array, and further ensures that the receiving and directional pattern of the phased array radar antenna is good.

[0120] Depend on Figure 10 It can be seen that the phase consistency between the sum port of the 180° stripline bridge and the ports of the two equally divided arms is better, which ensures the phase consistency of the sum port of the sum and difference device obtained by the stripline bridge array, and thus ensures that the phased array radar antenna has better reception and radiation pattern.

[0121] Depend on Figure 11 It can be seen that the amplitude consistency from the difference port of the 180° stripline bridge to the ports of the two equally divided arms is better, which ensures the amplitude consistency of the difference port of the sum and difference device obtained by the stripline bridge array, and thus ensures that the zero depth of the received elevation difference pattern and received azimuth difference pattern of the phased array radar antenna is better, which is more beneficial to the radar's positioning performance.

[0122] Depend on Figure 12 It can be seen that the phase consistency from the difference port of the 180° stripline bridge to the ports of the two equally divided arms is better, which ensures the phase consistency of the difference port of the sum and difference device obtained by the stripline bridge array, and thus ensures that the zero depth of the received elevation difference pattern and the received azimuth difference pattern of the phased array radar antenna is better, which is more beneficial to the radar's positioning performance.

[0123] Depend on Figure 13 It can be seen that the VSWR of the sum port, azimuth port and elevation port of the stripline broadband sum and difference device are better, indicating that the reflected radio frequency signal has less impact on the devices at the back end of the sum and difference device.

[0124] Depend on Figure 14 It can be seen that the VSWR of each quadrant port of the stripline broadband sum and difference device is better, which can better match the power divider network of the radar antenna and reduce the radio frequency signal loss caused by mismatch.

[0125] Depend on Figure 15 It can be seen that the stripline broadband sum and difference circuit has better isolation, which can better reduce the radio frequency signal interference of each port inside the sum and difference circuit and enhance the suppression capability inside the radar.

[0126] Depend on Figure 16 It can be seen that the stripline broadband sum differencer has better reception and port-quadrant port amplitude consistency, which ensures better reception and radiation pattern of the phased array radar antenna.

[0127] Depend on Figure 17 It can be seen that the stripline broadband sum differencer has better reception and port-quadrant port phase consistency, which ensures good reception and pattern sidelobes and beam pointing consistency of the phased array radar antenna.

[0128] Depend on Figure 18It can be seen that the azimuth difference port-quadrant port amplitude consistency of the stripline broadband summer is better, which ensures that the zero depth of the receiving azimuth difference of the phased array radar antenna is deeper, the level amplitude of the radar's receiving pattern and azimuth difference pattern is suppressed more, and the radar's positioning lateral is more sensitive.

[0129] Depend on Figure 19 It can be seen that the azimuth difference port-quadrant port of the stripline broadband summer has better phase consistency, which ensures that the zero depth of the received azimuth difference of the phased array radar antenna is deeper and the zero depth angle is consistent. The radar's received signal and radiation pattern have greater suppression of the level amplitude of the azimuth difference radiation pattern, and the radar's positioning lateral is more sensitive.

[0130] Depend on Figure 20 It can be seen that the amplitude consistency between the elevation difference port and the quadrant port of the stripline broadband summer is better, which ensures that the zero depth of the received elevation difference of the phased array radar antenna is deeper, the level amplitude of the radar's received radiation pattern and the elevation difference radiation pattern is suppressed more, and the radar's positioning lateral is more sensitive.

[0131] Depend on Figure 21 It can be seen that the phase consistency between the elevation difference port and the quadrant port of the stripline broadband sum difference device is better, which ensures the consistency of the zero depth and zero depth angle of the received elevation difference of the phased array radar antenna. The level amplitude of the radar's received radiation pattern and the elevation difference radiation pattern is suppressed more, and the radar's positioning lateral is more sensitive.

[0132] Depend on Figure 22 It can be seen that the stripline broadband sum and difference receiver has good sidelobe suppression and left-right symmetry of the radiation pattern, and has good anti-interference capability in radar positioning and direction finding.

[0133] Depend on Figure 23 It can be seen that the zero depth of the azimuth difference pattern received by the stripline broadband sum difference receiver is better than 40dB, and the radar has good positioning lateral performance in practical engineering applications.

[0134] Depend on Figure 24 It can be seen that the zero depth of the elevation difference pattern received by the stripline broadband sum difference receiver is better than 40dB, and the radar has good positioning lateral performance in practical engineering applications.

[0135] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An active phased array radar system, characterized in that, The radar system includes an antenna unit, a TR module, a transceiver processing unit, and a beam control unit; the TR module integrates a feed network and a sum-difference network, the input of the feed network is connected to the antenna unit, and the output of the sum-difference network is connected to the transceiver processing unit; the beam control unit is connected to the control terminal of the TR module. The sum-difference network includes a sum-difference device composed of a first bridge, a second bridge, a third bridge, and a fourth bridge, wherein the first bridge, the second bridge, the third bridge, and the fourth bridge are all 180° stripline bridges. The sum port of the first bridge serves as the sum port of the sum-difference converter, the difference port of the first bridge serves as the pitch difference port of the sum-difference converter, and the two equally divided arm ports of the first bridge are respectively connected to the sum port of the second bridge and the sum port of the third bridge. The two equally divided arm ports of the second bridge serve as the first quadrant port and the second quadrant port, respectively; the difference port of the second bridge and the difference port of the third bridge are respectively connected to the two equally divided arm ports of the fourth bridge. The two equally divided arm ports of the third bridge serve as the third quadrant port and the fourth quadrant port, respectively. The sum port of the fourth bridge serves as the azimuth difference port of the sum difference device.

2. The active phased array radar system according to claim 1, characterized in that, The 180° stripline bridge is a four-port network, including a sum port, a difference port, a first equal-arm port, and a second equal-arm port. The internal circuit of the 180° stripline bridge consists of 1 / 4λ transmission lines with characteristic impedance, forming a ring network. Here, λ represents the wavelength. The ring network is configured as follows: This ensures that the electrical lengths of the two paths from the first and second equally divided arm ports to the sum port are equal, thus achieving equal amplitude and in-phase synthesis. This causes the two paths of signals input from the first and second equal-division arm ports to reach the difference port to have an electrical length difference of half a wavelength, resulting in a 180° phase difference and achieving equal-amplitude anti-phase synthesis.

3. The active phased array radar system according to claim 2, characterized in that, The ring network of the 180° stripline bridge is a two-level loop composed of the first to the eighth 1 / 4λ transmission lines. The first 1 / 4λ transmission line connects the first equal-arm port to the sum port; the second 1 / 4λ transmission line connects the sum port to the second equal-arm port; the third, fourth, and fifth 1 / 4λ transmission lines are connected in series between the second equal-arm port and the difference port; the sixth and seventh 1 / 4λ transmission lines are connected in series between the difference port and the first equal-arm port; the eighth 1 / 4λ transmission line bridges the node between the third and fourth 1 / 4λ transmission lines and the node between the sixth and seventh 1 / 4λ transmission lines. Furthermore, the first, second, third, and seventh 1 / 4λ transmission lines all have a first characteristic impedance; the fourth and sixth 1 / 4λ transmission lines all have a second characteristic impedance; the eighth 1 / 4λ transmission line has twice the first characteristic impedance; and the fifth 1 / 4λ transmission line has twice the second characteristic impedance. The first characteristic impedance and the second characteristic impedance are not equal.

4. The active phased array radar system according to claim 1, characterized in that, The sum and difference circuit is implemented through a multilayer printed circuit board, which includes at least a top layer, an intermediate layer, and a bottom layer; wherein the strip conductors of the first bridge, the second bridge, the third bridge, and the fourth bridge are formed in the intermediate layer, and the top layer and the bottom layer are ground layers.

5. The active phased array radar system according to claim 4, characterized in that, The top layer has microstrip lines and radio frequency connectors connected to the microstrip lines. The microstrip lines are connected to the strip conductors of the middle layer through a vertical interconnect structure.

6. The active phased array radar system according to claim 5, characterized in that, The sum port, pitch difference port, azimuth difference port, first quadrant port, second quadrant port, third quadrant port and fourth quadrant port of the sum and difference device are all connected to the radio frequency connector.

7. The active phased array radar system according to claim 4, characterized in that, The power supply network and the sum and difference network in the TR component are fabricated on the multilayer printed circuit board using an integrated multilayer circuit process, so that the power supply network and the sum and difference network are physically integrated in the same multilayer circuit board and connected to the feed lines of the transmit channel and receive channel of the TR component.

8. The active phased array radar system according to claim 1, characterized in that, The differential port of the fourth bridge is connected to a matched load.

9. The active phased array radar system according to claim 1, characterized in that, The first, second, third, and fourth bridges have the same structural dimensions and electrical performance parameters.

10. The active phased array radar system according to claim 1, characterized in that, The antenna unit includes an antenna array divided into four subarrays; the four subarrays of the antenna array are respectively connected to the four input terminals of the feed network; the four output terminals of the feed network are respectively connected to the first quadrant port, the second quadrant port, the third quadrant port and the fourth quadrant port of the sum and difference device.

Images