An active phased array radar system

Abstract

This invention discloses an active phased array radar system, relating to the field of radar technology. The system includes an antenna element, a transceiver module (TR), a transceiver processing unit, and a wave control unit. The TR element integrates a feed network and a sum / difference network. The sum / difference network includes a broadband sum / difference device composed of four 180° stripline bridges: the sum and difference ports of the first bridge serve as the sum and elevation difference ports of the sum / difference device, respectively; the two equally spaced arm ports of the first bridge are connected to the sum ports of the second and third bridges, respectively; the equally spaced arm ports of the second and third bridges serve as the four quadrant ports; the difference ports of the second and third bridges are connected to the two equally spaced arm ports of the fourth bridge; and the sum port of the fourth bridge serves as the azimuth difference port of the sum / difference device. This invention completely solves the problem of integrating metal waveguide sum / difference devices with tile-type radar antennas.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, and in particular relates to a two-dimensional "tile-type" active phased array radar system. Background Technology

[0002] In radar systems, sum-difference angle measurement is a key technology for achieving high-precision target positioning and tracking. Its principle lies in processing the target echo signal and using the zero depth of the "difference pattern" (i.e., the depth of the point with the lowest radiation intensity in the pattern) generated by the sum-difference network to accurately indicate the target's azimuth. The deeper the zero depth, the stronger the antenna's ability to suppress the signal in that direction, thus providing higher angle measurement accuracy.

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

[0004] During transmission: The signal from the transmitter is circulated and input from the sum port of the sum and difference network. It is then divided into four equal paths, which in turn excite the feed networks of the four quadrants, driving the T / R components to radiate energy into space.

[0005] During reception: The downlink RF signal from the antenna array is combined by the feed network of the four quadrants to form four downlink signals, which are then sent to the sum and difference network. The sum and difference network forms the sum beam, azimuth difference beam and elevation difference beam accordingly, and then sends them to the receiver for further processing via the circulator.

[0006] To meet the urgent demands of modern radar for higher zero depth, better angle / range 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, while offering excellent performance, have high profiles, large size, and heavy weight, making them difficult to integrate with current mainstream microstrip patch antennas (tile-type antenna arrays). This typically results in sum-difference networks requiring dedicated installation space and interconnection with the antenna feed network via numerous RF connectors, ultimately leading to a complex radar system structure and low integration. Summary of the Invention

[0007] To address the problems of large size, high profile, and difficulty in integrating traditional metal waveguide sum and difference devices with tile-type microstrip antenna arrays in existing technologies, this invention aims to provide a highly integrated active phased array radar system.

[0008] The core of this invention lies in the use of four cascaded 180° stripline bridges to form a novel stripline broadband sum and difference circuit. This sum and difference circuit can be directly embedded inside the TR component, efficiently processing signals from all four quadrants of the antenna. It possesses significant advantages such as wide operating bandwidth, good amplitude and phase consistency, low profile, and ease of integration with planar circuits. This not only greatly improves the system's integration and lightweight level but also effectively overcomes the engineering limitations of traditional waveguide structures in terms of bandwidth and profile height, possessing significant engineering application value.

[0009] The present invention solves the above-mentioned technical problems through the following technical solution: an active phased array radar system, comprising an antenna element, a TR component, a transceiver processing unit, and a beam control unit; the TR component integrates a feed network and a sum-difference network, the input end of the feed network is connected to the antenna element, and the output end of the sum-difference network is connected to the transceiver processing unit; the beam control unit is connected to the control end of the TR component;

[0010] 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.

[0011] 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.

[0012] 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.

[0013] The sum port of the fourth bridge serves as the azimuth difference port of the sum difference device.

[0014] In this embodiment, a single 180° bridge has one sum port, one difference port, and two equally divided arm ports. When a signal is input from its sum port, the signals to the two equally divided arm ports are of equal amplitude and in phase; when a signal is input from its difference port, the signals to the two equally divided arm ports are of equal amplitude and out of phase. Based on this characteristic of the 180° bridge, by cascading two stages, the initial equal-amplitude and in-phase signals are rationally 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 from the first and second quadrant ports are of equal amplitude and in phase, and the signals from the third and fourth quadrant ports are also of equal amplitude and in phase, but the two excitation signals are of equal amplitude and out of phase, (the signals from the first and second quadrant ports) and (the signals from the third and fourth quadrant ports) are of equal amplitude and out of phase. This achieves equal amplitude and out of phase from the pitch difference port to (the signals from the first and second quadrant ports) and (the signals from the third and fourth quadrant ports), forming the pitch difference beam required for pitch plane angle measurement.

[0021] The sum and difference circuit of this invention is composed of a specific array of four 180° stripline bridges, which is itself a broadband circuit form. At the same time, bridges with ultra-wide operating bandwidth (such as Lange bridges) can be selected to further increase the bandwidth, thus solving the problem of narrow bandwidth in traditional designs.

[0022] The sum and difference device of this invention consists of four cascaded 180° stripline bridges. Since the stripline is a planar transmission line structure, the sum and difference device can be integrated using standard printed circuit board (PCB) technology, achieving a low profile and thin profile for the overall circuit. This PCB-based sum and difference device is integrated with the feed network within the T / R assembly, enabling highly integrated and conformal integration with tile-type radar arrays in the form of microstrip patch antennas. This design not only completely eliminates the independent metal waveguide sum and difference device and its numerous associated RF connectors found in traditional solutions, significantly reducing system weight and structural complexity, but also offers engineering advantages such as ease of fabrication, lower cost, and better consistency. It fundamentally solves the technical challenge of achieving high-density integration of traditional sum and difference devices with tile-type radar antennas.

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

[0024] 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.

[0025] 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.

[0026] This invention utilizes a ring network composed of 1 / 4λ transmission lines with characteristic impedance to precisely achieve equal-length in-phase paths from the two equally divided arm ports to the sum port, and a half-wavelength difference out-of-phase path to the difference port. Structurally, this ensures that the 180° stripline bridge can stably and efficiently synthesize signals with equal amplitude in-phase and equal amplitude out-of-phase characteristics. This not only provides radar systems with high-purity, high-consistency sum and difference signals, laying the foundation for high-precision angle measurement, but its planar structure based on striplines inherently possesses low profile and ease of fabrication, making it highly suitable for integrated integration with TR components and microstrip antennas. This effectively supports the core requirements of tile-type radar systems for high performance and high integration.

[0027] Furthermore, the ring network of the 180° stripline bridge is a two-level loop composed of the first to the eighth 1 / 4λ transmission lines; wherein, the first 1 / 4λ transmission line connects the first equal arm port and the sum port; the second 1 / 4λ transmission line connects the sum port and 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; and 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.

[0028] In this embodiment, the higher the loop level of the 180° stripline bridge, the higher the bandwidth and the greater the loss. The 180° stripline bridge with a two-level loop achieves a bandwidth of over 15% in the Ku band while maintaining low loss.

[0029] This invention employs a second-stage ring network structure with specific impedance configuration, which significantly expands the operating bandwidth (e.g., achieving over 15% bandwidth in the Ku band) while ensuring the signal equal-amplitude, in-phase, and out-of-phase synthesis functions, and keeps the insertion loss at a low level. This achieves an excellent balance between broadband performance and signal attenuation, meeting the dual requirements of modern broadband radar systems for high spectral utilization and high signal integrity of sum-difference networks.

[0030] Furthermore, the sum and difference device 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.

[0031] This invention integrates the conductors of all four bridges into the middle signal layer of a multilayer printed circuit board, and uses the top and bottom layers as ground shields. This not only achieves a highly compact and low-profile sum and difference circuit, but also effectively suppresses signal crosstalk and radiation loss, ensuring good amplitude and phase consistency between the bridges. This allows it to be directly embedded into the feed network inside the TR component as a high-density integrated standard module, thus providing a key process implementation path for achieving high-performance and high-reliability integrated tile radar systems.

[0032] Furthermore, a microstrip line and an RF connector connected to the microstrip line are provided on the top layer, and the microstrip line is connected to the stripline conductor of the middle layer through a vertical interconnect structure.

[0033] This invention provides a standard and reliable external RF interface for the entire sum and difference module by setting microstrip lines and RF connectors on the top layer and using a vertical interconnect structure to achieve electrical connection with the middle layer stripline conductors. This facilitates interconnection with external TR components and antenna units, while maintaining the high integration and shielding advantages of the multi-layer PCB structure. This achieves an effective balance between high-performance circuitry and convenient system integration.

[0034] Furthermore, 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 to form an independent functional accessory.

[0035] This invention enables the sum and difference device to become an independent, plug-and-play functional module by setting standard radio frequency connectors at all key ports. This not only greatly facilitates system assembly, testing and maintenance, and improves production efficiency and reliability, but also ensures that the high-performance sum and difference device can be used as a highly integrated internal component or as a standard external module to flexibly adapt to different radar system architectures.

[0036] Furthermore, the multilayer printed circuit board containing the power supply network and the sum and difference network in the TR component is manufactured 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.

[0037] This invention integrates the feed network and the sum / difference network onto the same multilayer circuit board using an integrated multilayer circuit process, achieving direct interconnection between the two without connectors or jumpers, as well as high-density connection to the TR component feed lines. This fundamentally eliminates parasitic parameters, losses, and uncertainties introduced by discrete interconnections between modules, significantly improving the signal integrity, amplitude and phase consistency, and reliability of the entire RF front-end. Simultaneously, it achieves significant optimization of system size, weight, and power consumption, providing a crucial engineering implementation path for building high-performance, highly integrated tile-type active phased array radar.

[0038] Furthermore, the differential port of the fourth bridge is connected to a matched load.

[0039] Furthermore, the first, second, third, and fourth bridges have the same structural dimensions and electrical performance parameters.

[0040] This invention ensures that the four 180° stripline bridges constituting the sum and difference network are completely identical in structural dimensions and electrical performance parameters, thereby fundamentally guaranteeing that the sum and difference network has extremely high amplitude and phase consistency when processing signals in the four quadrants. This significantly improves the quality of the final sum and difference beams, laying a key foundation for radar systems to achieve high-precision and high-sensitivity angle measurement and tracking performance.

[0041] Furthermore, 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.

[0042] This invention constructs a clear and symmetrical four-quadrant sum-difference beamforming link by clearly dividing the antenna element into four subarrays and precisely connecting them to the four quadrant ports of the sum and difference beamformer through a feed network. This not only achieves efficient partitioning and signal synthesis of the antenna aperture and ensures excellent performance of the sum and difference beamformer, but also provides a stable and reliable physical and signal foundation for the entire radar system to achieve high-precision single-pulse angle measurement.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] The core innovation of the active phased array radar system provided by this invention lies in the integration of a broadband sum and difference converter based on a stripline bridge. This broadband sum and difference converter uses four 180° stripline bridges connected in a specific array configuration. Its operating principle is based on two fundamental characteristics of the 180° bridge: when a signal is input from the sum port, its two equally divided arm ports output signals of equal amplitude and in phase; when a signal is input from the difference port, its two equally divided arm ports output signals of equal amplitude and out of phase. Through a carefully designed array topology, these four 180° stripline bridges are interconnected, and the above-mentioned basic phase relationships are logically synthesized to construct a complete four-quadrant sum and difference converter, capable of simultaneously generating a high-gain sum beam, an azimuth difference beam for azimuth angle measurement, and an elevation difference beam for elevation angle measurement.

[0045] The broadband sum and difference device of this invention adopts a stripline planar circuit form, which has the characteristics of low profile and light weight. It can be directly integrated into the multi-layer feed network of the T / R module, which completely solves the problem that traditional metal waveguide sum and difference devices are difficult to integrate with current tile-type radar antennas, and significantly improves the integration of radar system.

[0046] Thanks to the excellent characteristics of the stripline bridge itself, the sum and difference device of this invention can operate stably within a relative bandwidth exceeding 15% (such as the Ku band), ensuring the performance consistency of the radar system at different frequencies. Due to the use of a symmetrical circuit topology and identical components, the sum and difference device of this invention exhibits excellent amplitude and phase consistency between channels, which is crucial for forming deep zero-depth difference beams, thus providing extremely high angle measurement accuracy for monopulse radar. Attached Figure Description

[0047] To more clearly illustrate the technical solution of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0049] Figure 2 This is a schematic diagram of a 180° stripline bridge structure with three-level loops in an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the stripline broadband sum and differencer structure in an embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of a 180° stripline bridge structure with a two-stage loop in an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the stripline broadband sum and differencer structure used alone in an embodiment of the present invention;

[0053] Figure 6 This is a stack-up diagram of a sum and difference device implemented using a multilayer printed circuit board in an embodiment of the present invention;

[0054] Figure 7 This is the standing wave curve of the 180° stripline bridge in an embodiment of the present invention;

[0055] Figure 8 This is the isolation curve of the 180° stripline bridge and differential port in an embodiment of the present invention;

[0056] Figure 9 This is a schematic diagram of the 180° stripline bridge and port amplitude consistency in an embodiment of the present invention;

[0057] Figure 10 This is a schematic diagram of the 180° stripline bridge and port phase consistency in an embodiment of the present invention;

[0058] Figure 11 This is a schematic diagram of the amplitude consistency of the differential port of the 180° stripline bridge in an embodiment of the present invention;

[0059] Figure 12 This is a schematic diagram of the phase consistency of the differential port of the 180° stripline bridge in an embodiment of the present invention;

[0060] Figure 13 These are the standing wave curves of the stripline broadband sum and difference device and port, azimuth difference port and elevation difference port in the embodiments of the present invention;

[0061] Figure 14 These are the standing wave curves of each quadrant port of the stripline broadband sum and difference device in this embodiment of the invention;

[0062] Figure 15 These are the isolation curves of each port of the stripline broadband sum and differencer in this embodiment of the invention;

[0063] Figure 16 This is a schematic diagram of the amplitude consistency between the receiving port and the quadrant port of the stripline broadband sum and differencer in an embodiment of the present invention.

[0064] Figure 17 This is a schematic diagram of the stripline broadband sum differencer receiver and port-quadrant port phase consistency in an embodiment of the present invention;

[0065] Figure 18 This is a schematic diagram of the amplitude consistency between the azimuth difference port and the quadrant port of the stripline broadband sum difference device in an embodiment of the present invention;

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

[0067] Figure 20 This is a schematic diagram of the amplitude consistency between the pitch difference port and quadrant port of the stripline broadband sum difference device in an embodiment of the present invention;

[0068] Figure 21 This is a schematic diagram of the phase consistency between the pitch difference port and quadrant port of the stripline broadband sum difference device in an embodiment of the present invention;

[0069] Figure 22 This is the receiving and normalized radiation pattern of the stripline broadband sum differencer in this embodiment of the invention;

[0070] Figure 23 This is the normalized azimuth difference pattern of the stripline broadband sum difference receiver in this embodiment of the invention;

[0071] Figure 24 This is the normalized radiation pattern of the elevation difference received by the stripline broadband sum differencer in this embodiment of the invention.

[0072] Explanation of reference numerals in the attached diagram: 1-First bridge, 11-Sum port of the first bridge, 12-Difference port (pitch difference port) of the first bridge, 2-Second bridge, 21-Second arm port (second quadrant port) of the second bridge, 22-First arm port (first quadrant port) of the second bridge, 3-Third bridge, 31-Second arm port (third quadrant port) of the third bridge, 32-First arm port (fourth quadrant port) of the third bridge, 4-Fourth bridge, 41-Difference port (load port) of the fourth bridge, 5-RF connector. Detailed Implementation

[0073] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0075] This invention 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, size and profile.

[0076] like Figure 1As shown, the radar system mainly includes an antenna unit, a TR assembly, a transceiver processing unit, and a beam control unit. These units form a complete radio frequency signal transmission and processing link through specific interconnections.

[0077] Antenna element: A planar array in the form of a microstrip patch antenna, which can be divided into four independent subarrays (quadrants one through four). The antenna element is used to transmit beams to the space-based radiating radar and receive echo signals from targets.

[0078] The TR component is the core integrated component of this invention. It integrates the power supply network and the sum / difference network, and is manufactured using a multilayer printed circuit board (PCB) process to achieve high-density integration. The TR component has multiple external interfaces.

[0079] Radio frequency (RF) end: It is connected to each radiating element or subarray of the antenna unit through multiple independent RF channels.

[0080] Control unit: Connected to the beam control unit, it receives control commands (such as phase shift and attenuation control codes) required for beam scanning.

[0081] Signal terminal: Connected to the transceiver processing unit via the output of the internal sum and difference network.

[0082] Specifically, the feed network integrated within the TR component connects to the individual radiating elements or subarrays of the antenna unit at its input. This network is used to distribute signal power during transmission and to synthesize signals from the radiating elements during reception. The output of the feed network (typically four channels, corresponding to the four antenna subarrays) is connected to the input of the internally integrated sum and difference network.

[0083] The sum-difference network is key to realizing the monopulse angle measurement function of this invention. Specifically, it consists of four 180° stripline bridges connected in a specific topology. 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 antenna subarrays. The function of the sum-difference network is to process and synthesize the four signals from the four antenna subarrays in real time during reception to produce the sum signal, azimuth difference signal, and elevation difference signal. These three signals together constitute all the information required for monopulse angle measurement.

[0084] Beam control unit: Connected to the control terminal of the TR component, it calculates and generates corresponding control codes according to the beam pointing instructions of the radar system, and sends them to each channel inside the TR component through the control terminal to achieve precise control of the amplitude and phase of the transmitted / received signals, thereby completing beam scanning and shaping.

[0085] Transceiver processing unit: Connects to the output port of the sum and difference network in the TR component. Its main functions include:

[0086] During the transmission cycle: the radar intermediate frequency transmission signal is generated, and after up-conversion, it is fed into the sum port of the sum-difference network through devices such as circulators. After being distributed by the network, it excites the TR component and antenna radiation.

[0087] During the receiving period: the sum and difference three radio frequency echo signals from the TR component and the difference network output are received, and they are processed by downconversion, analog-to-digital conversion, etc. Finally, the angle information of the target is calculated based on the amplitude and phase relationship of the sum and difference signals.

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

[0089] Transmission process: The transmit signal generated by the transceiver processing unit is input from the sum port of the sum and difference network, distributed by the internal bridge of the network, and output from the four quadrant ports in an equal amplitude and in phase manner. It is then distributed to each TR channel through the feed network, amplified, and radiated into space by the antenna element.

[0090] Reception Process: The echo signals received by the four subarrays of the antenna unit are amplified by low noise and adjusted in amplitude and phase by the TR channel. The feed network then initially synthesizes these signals into four channels, which are input to the four quadrant ports of the sum and difference network. Based on its internal fixed phase relationship, the sum and difference network synthesizes the four signals in real time into one sum signal and two difference signals (azimuth difference and elevation difference). These three signals are output to the transceiver processing unit for further processing. By comparing the amplitude ratio (monopulsive ratio) of the sum and difference channel signals, the azimuth and elevation angle deviations of the target relative to the radar beam axis can be accurately calculated.

[0091] This invention successfully replaces the traditional bulky and heavy metal waveguide sum and difference devices by highly integrating the feed network and sum / difference network within the TR component and employing a planar stripline bridge scheme. This design greatly simplifies the system structure, reduces a large number of RF connectors and cables, and achieves a low profile, lightweight, and high reliability for the radar front end, perfectly meeting the integration requirements of modern tile-type active phased array radars.

[0092] A 180° bridge (ring bridge) is a microwave passive device that uses three 90° stubs and one 270° stub to form a ring structure, enabling the input signal to generate a 180° phase difference at the output. It also has port isolation capabilities and is widely used in power distribution, signal synthesis, and single-pulse power supply networks.

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

[0094] This ensures that the two paths ① and ② from the first equal-arm port Port1 and the second equal-arm port Port2 to the sum port Port3 have equal electrical lengths, achieving equal amplitude and in-phase synthesis to form a sum signal; similarly, when the signal is input from the sum port Port3, the signals output from the first equal-arm port Port1 and the second equal-arm port Port2 have equal amplitude and in-phase.

[0095] This causes the two paths ③ and ④ of the signals input from the first equal-arm port Port1 and the second equal-arm port Port2 to reach the difference port Port4 to have an electrical length difference of half a wavelength, resulting in a 180° phase difference, achieving equal amplitude and inverse phase synthesis to form a difference signal; similarly, when the signal is input from the difference port Port4, the signals output from the first equal-arm port Port1 and the second equal-arm port Port2 are equal amplitude and inverse phase.

[0096] Figure 3 The 180° stripline bridge in the diagram has three loops, where Z0, Z1, Z2, and Z3 represent the characteristic impedances of the corresponding transmission lines. The transmission lines corresponding to characteristic impedances Z1, Z2, and Z3 are all 1 / 4λ transmission lines, while the transmission line corresponding to characteristic impedance Z0 can be a transmission line of any wavelength.

[0097] Based on the aforementioned characteristics of the 180° stripline bridge, four 180° stripline bridges are specifically arrayed and connected to form a four-quadrant sum and difference beam, capable of simultaneously generating a high-gain sum beam, an azimuth difference beam for azimuth angle measurement, and an elevation difference beam for elevation angle measurement. For example... Figure 3 As shown, the stripline broadband sum and difference device provided in this embodiment of the invention includes a first bridge 1, a second bridge 2, a third bridge 3, and a fourth bridge 4, all of which are 180° stripline bridges.

[0098] The sum port 11 of the first bridge serves as the sum port of the sum-difference converter, and the difference port 12 of the first bridge serves as the pitch difference port of the sum-difference converter. The two equally divided arm ports of the first bridge 1 are respectively connected to the sum port of the second bridge 2 and the sum port of the third bridge 3. The two equally divided arm ports of the second bridge 2 serve as 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 respectively connected to the two equally divided arm ports of the fourth bridge 4. The two equally divided arm ports of the third bridge 3 serve as the third quadrant port 31 and the fourth quadrant port 32, respectively. The sum port of the fourth bridge 4 serves as the azimuth difference port of the sum-difference converter.

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

[0100] Sum-and-sum excitation: After the signal is input from the sum-and-sum port of the first bridge 1, it is divided into two excitation signals with equal amplitude and in phase by the first bridge 1; one of the excitation signals is input from the sum-and-sum port of the second bridge 2, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the second bridge 2 (corresponding to the first quadrant port 22 and the second quadrant port 21); the other excitation signal is input from the sum-and-sum port of the third bridge 3, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the third bridge 3 (corresponding to the third quadrant port 31 and the fourth quadrant port 32).

[0101] Since the two excitation signals output from the two equally divided arm ports of the first bridge 1 are equal in amplitude and phase, and the second bridge 2 and the third bridge 3 are both operating in the equal in amplitude and phase mode of the input port, 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 in amplitude and phase, thus forming a beam.

[0102] 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 4, it is distributed by the fourth bridge 4 into two excitation signals with equal amplitude and in phase; one of the excitation signals is input from the difference port of the second bridge 2, and generates an output with equal amplitude and opposite phase on the two equally divided arm ports of the second bridge 2 (corresponding to the first quadrant port 22 and the second quadrant port 21); the other excitation signal is input from the difference port of the third bridge 3, and generates an output with equal amplitude and opposite phase on the two equally divided arm ports of the third bridge 3 (corresponding to the third quadrant port 31 and the fourth quadrant port 32).

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

[0104] Pitch difference port excitation: After the signal is input from the difference port 12 of the first bridge (i.e., the pitch difference port of the sum difference device), it is distributed by the first bridge 1 into two excitation signals with equal amplitude and opposite phase; one of the excitation signals is input from the sum port of the second bridge 2, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the second bridge 2 (corresponding to the first quadrant port 22 and the second quadrant port 21); the other excitation signal is input from the sum port of the third bridge 3, and generates an output with equal amplitude and in phase on the two equally divided arm ports of the third bridge 3 (corresponding to the third quadrant port 31 and the fourth quadrant port 32).

[0105] Since the signals from the first quadrant port 22 and the second quadrant port 21 are of equal amplitude and in phase, and the signals from the third quadrant port 31 and the fourth quadrant port 32 are also of equal amplitude and in phase, but the two excitation signals are of equal amplitude and out of phase, (the signals from the first quadrant port 22 and the second quadrant port 21) and (the signals from the third quadrant port 31 and the fourth quadrant port 32) are of equal amplitude and out of phase. This achieves equal amplitude and out of phase for the signals from the pitch difference port 12 to (the signals from the first quadrant port 22 and the second quadrant port 21) and (the signals from the third quadrant port 31 and the fourth quadrant port 32), forming the pitch difference beam required for pitch plane angle measurement.

[0106] Because the sum and difference device of this invention adopts a stripline form with a low profile, it can be integrated with the multi-layer feed network of the T / R module, simplifying manufacturing and reducing costs. The sum and difference device of this invention is constructed using an array of four identical 180° stripline bridges, resulting in a symmetrical structure, good amplitude consistency, and superior S-parameters (scattering parameters).

[0107] In a specific embodiment of the present invention, such as Figure 4As shown, the ring network of the 180° stripline bridge used in the first to fourth bridges is a two-level loop composed of the first to eighth 1 / 4λ transmission lines; the first 1 / 4λ transmission line connects the first equal arm port and the sum port; the second 1 / 4λ transmission line connects the sum port and 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 is bridged between the node of the third and fourth 1 / 4λ transmission lines and the node 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 twice the first characteristic impedance Z1; and the fifth 1 / 4λ transmission line has twice the second characteristic impedance Z2. The first characteristic impedance Z1 and the second characteristic impedance Z2 are not equal. The eighth 1 / 4λ transmission line can be composed of two 1 / 4λ transmission lines with a characteristic impedance equal to the first characteristic impedance Z1, and the fifth 1 / 4λ transmission line can be composed of two 1 / 4λ transmission lines with a characteristic impedance equal to the second characteristic impedance Z2.

[0109] The higher the loop level of the 180° stripline bridge, the higher the bandwidth, but also the greater the loss. The 180° stripline bridges used in the first to fourth bridges have a two-stage loop, achieving a bandwidth of over 15% in the Ku band while maintaining low loss.

[0110] In a specific embodiment of the present invention, such as Figure 5 and Figure 6 As shown, the sum and difference circuit is implemented through a multilayer printed circuit board, which includes at least a top layer TOP, an intermediate layer A02, and a bottom layer BOT; wherein, the strip conductors of the first bridge 1, the second bridge 2, the third bridge 3, and the fourth bridge 4 are formed on the intermediate layer A02, and the top layer TOP and the bottom layer BOT are ground layers.

[0111] like Figure 6 As shown, the sum and difference device implemented through a multilayer printed circuit board has a total thickness of only 1.205mm, which greatly reduces the profile height.

[0112] The sum and difference circuit is implemented using a multi-layer printed circuit board, representing a fundamental shift from a three-dimensional structure to a two-dimensional planar circuit. This allows for seamless integration of the sum and difference circuit into tile-type phased array antennas, conformally mounting it with the T / R assembly and radiating elements. This is a key technology for achieving thinner and more conformal radar antenna arrays. The sum and difference circuit can be directly designed and manufactured within the multi-layer feed network of the T / R assembly itself, becoming one of its wiring layers. This completely eliminates all external connectors, cables, and mounting structures, greatly improving system integration, reliability, and reducing potential failure points.

[0113] In a specific embodiment of the present invention, such as Figure 5 As shown, a microstrip line and an RF connector 5 connected to the microstrip line are provided on the top layer (TOP). The microstrip line is connected to the stripline conductor of the middle layer through a vertical interconnect structure. In this embodiment, the vertical interconnect structure is a copper-plated through-hole VIA1, a blind via VIA2, or a coaxial via.

[0114] In this embodiment, as Figure 5 As shown, 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 RF connectors to form an independent functional accessory for standalone use.

[0115] In a specific embodiment of the present invention, a matching load is connected to the differential port 41 of the fourth bridge. In this embodiment, the matching load is soldered to the end of the microstrip line of the top layer (TOP) of the multilayer printed circuit board.

[0116] To verify the effectiveness of this invention, actual measurements were performed on a 180° stripline bridge and a stripline broadband sum-difference converter, and S-parameter data were obtained, such as... Figures 7 to 24 As shown.

[0117] Depend on Figure 7 It can be seen that the VSWR at each port of the 180° stripline bridge is better and the bandwidth meets the requirements.

[0118] Depend on Figure 8 It can be seen that the 180° stripline bridge has better isolation between the sum and difference ports, which can reduce the interference of the RF signals of the sum and difference ports inside the bridge. This ensures that the isolation between the ports of the sum and difference device obtained by the stripline bridge array is better, and thus ensures that the RF signals of each port of the sum and difference device have less interference inside.

[0119] Depend on Figure 9 It can be seen that the amplitude consistency between the sum port and the two equally divided arm ports of the 180° stripline bridge is better, which ensures the amplitude consistency of the sum port of the sum and difference device obtained by the stripline bridge array, and thus ensures better reception and radiation pattern of the phased array radar antenna.

[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 by 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; The 180° stripline 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 bridge consists of 1 / 4λ transmission lines with characteristic impedance, forming a ring network. Here, λ represents the wavelength, and 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-arm ports to 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. 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.

2. The active phased array radar system of claim 1, wherein, The sum and difference device 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.

3. The active phased array radar system of claim 2, wherein, 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.

4. The active phased array radar system of claim 2, wherein, 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 radio frequency connectors.

5. The active phased array radar system according to claim 2, 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.

6. 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.

7. 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.

8. 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.

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