Broadband high-integration millimeter wave multiple correlation receiving front end

Abstract

The invention provides a broadband high-integration millimeter wave multiple correlation receiving front end, and relates to the technical field of microwave radiometers. The high-integration broadband millimeter wave multiple correlation receiving front end comprises an integrated shell, a millimeter wave receiving front end, an intermediate frequency filtering and amplifying device, a distributed frequency synthesis device, an analog multiple correlation processing device and a power supply control device, the integrated shell is internally provided with a separation cavity, and the millimeter wave receiving front end, the intermediate frequency filtering and amplifying device, the distributed frequency synthesis device, the analog multiple correlation processing device and the power supply control device are arranged in the separation cavity in an integrated mode. And the output is connected with the millimeter wave receiving front end and provides system coherent millimeter wave local oscillation signals for the millimeter wave receiving front end. According to the millimeter wave comprehensive aperture radiometer array, generation, transmission and distribution of millimeter wave local oscillators are realized in each broadband millimeter wave multiple correlation receiving front end by adopting a distributed frequency synthesis technology, the architecture of the system is simplified, and the defects that the centralized transmission and distribution loss of the millimeter wave local oscillators in the traditional millimeter wave comprehensive aperture radiometer array is large, and self-excitation is easy are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave radiometers, in particular to the structure of a complex correlation receiving front end in a millimeter wave synthetic aperture radiometer array, and specifically to a broadband highly integrated millimeter wave complex correlation receiving front end. Background Art

[0002] Millimeter-wave aperture-synthetic radiometer arrays, independent of external radiation sources, can observe targets around the clock and are attracting increasing attention. As the fundamental component of a millimeter-wave aperture-synthetic radiometer array system, the broadband millimeter-wave complex-correlation receiving front end is responsible for low-noise amplification, phase-shift mixing, and complex-correlation processing of the weak microwave energy radiated by the observed target, generating a voltage signal proportional to the target's brightness temperature. Its performance directly impacts the performance of the aperture-synthetic radiometer array.

[0003] like Figure 1 The figure shows a conventional millimeter-wave aperture synthesis radiometer array design with N (typically N ≥ 8) complex correlation receiver front ends. Due to operating frequency constraints, existing millimeter-wave aperture synthesis radiometer array complex correlation receiver front ends typically employ a discrete design, achieving the required system functions through cascading single functional modules.

[0004] For example, an N-channel broadband millimeter-wave low-noise receiving front end is composed of N independent basic receiving units. The millimeter-wave low-noise amplifier, millimeter-wave pre-selection filter and millimeter-wave mixer chips in each basic receiving unit channel are cascaded and packaged in an airtight metal box using a micro-assembly process; the intermediate frequency filter amplification module is usually integrated using a hybrid integrated circuit process, and the 2N-channel intermediate frequency amplifier chip, digitally controlled attenuator chip and LC filter are integrated and packaged in another airtight packaged module using a hybrid integrated circuit process; and the 2N-channel analog complex correlation processing module uses a reflow soldering process to realize the cascade of packaged devices such as broadband balun, broadband analog multiplier, and operational amplifier on the printed circuit board, and uses a metal cavity for shielding; then the packaged different functional modules are fixed on the structural parts and interconnected through RF / low-frequency cables to form a millimeter-wave complex correlation receiving front end. The N-channel coherent local oscillator signals required for phase shift and mixing at the millimeter-wave complex correlation receiving front end are also centrally generated and distributed. The millimeter-wave frequency synthesis chip also uses a micro-assembly process to cascade the phase-locked loop chip, amplifier chip, power divider chip and filter chip and encapsulate them in an airtight metal box. After power division, the millimeter-wave local oscillator is sent to each functional module through an RF cable.

[0005] From the above description, it can be seen that the phase-shifted mixing local oscillator required by the complex correlation receiving front end inside the existing millimeter-wave synthetic aperture radiometer array adopts centralized generation, transmission and distribution, which has the disadvantage of large loss. It requires a multi-stage millimeter-wave amplification circuit cascade to compensate for the local oscillator power, which is prone to self-excitation and oscillation, restricting the expansion of the array of millimeter-wave synthetic aperture radiometer array. Summary of the Invention

[0006] (1) Technical problems solved In response to the deficiencies of the existing technology, the present invention provides a broadband highly integrated millimeter-wave complex correlation receiving front end, which solves the technical problem of large phase-shift mixing local oscillator loss required by the complex correlation receiving front end inside the existing millimeter-wave synthetic aperture radiometer array.

[0007] (2) Technical solution To achieve the above objectives, the present invention is implemented through the following technical solutions: The present invention provides a highly integrated broadband millimeter-wave complex correlation receiving front end, comprising: a dual-waveguide broadband impedance converter, an integrated housing with a compartment provided therein, and a millimeter-wave receiving front end integrated in the compartment, intermediate frequency filtering and amplification, distributed frequency synthesis, analog complex correlation processing, and power supply control. Wherein, the dual-waveguide broadband impedance converter is realized by overlapping a step impedance converter with a radio frequency insulator; The input of the distributed frequency synthesis is connected to the system synchronization reference signal, and the output is connected to the millimeter wave receiving front end to provide the millimeter wave receiving front end with a system-coherent millimeter wave local oscillator signal; The millimeter wave receiving front-end input is connected to the dual-path interference antenna through a dual-waveguide broadband impedance converter, and the output is connected to the intermediate frequency filter amplifier; The intermediate frequency filtering and amplification processes a pair of in-phase and a pair of orthogonal intermediate frequency signals and then outputs them to analog complex correlation processing; The power supply control provides low-noise, highly stable power supply for the millimeter wave receiving front end, intermediate frequency filtering and amplification, distributed frequency synthesis and analog complex correlation processing.

[0008] Preferably, the distributed frequency synthesis system includes a phase-locked crystal oscillator, a phase-locked loop chip, an active quadruple frequency chip, a MEMS filter, a low phase noise amplifier chip and a power divider chip; The phase-locked crystal oscillator generates a reference signal that is coherent with an external reference; The phase-locked loop chip and MEMS filter perform frequency multiplication and phase-locking processing on the reference signal to generate a high-quality, low-phase-noise X-band coherent local oscillator signal and perform filtering; The active quadruple frequency chip uses a direct synthesis method to generate a low phase noise local oscillator required for zero intermediate frequency system mixing in the millimeter wave frequency band.

[0009] Preferably, the intermediate frequency filtering and amplification includes four identical intermediate frequency filtering and amplification channels, each of which is equipped with a low-noise amplifier chip, a low-pass filter chip, a digitally controlled attenuator chip and an LC band-pass filter; the input end of the intermediate frequency filtering and amplification channel is connected to the output of the millimeter wave receiving front end, and the output end is connected to the analog complex correlation processing, and a pair of in-phase and a pair of orthogonal intermediate frequency signals are output to the analog complex correlation processing part after filtering and amplification processing.

[0010] Preferably, the analog complex correlation processing includes two completely identical analog correlation channels, which respectively perform correlation operations on a pair of in-phase intermediate frequency signals with a bandwidth of DC to N / 2 GHz and a pair of orthogonal intermediate frequency signals with a bandwidth of DC to N / 2 GHz, and output a pair of orthogonal IQ signals after active differential filtering.

[0011] Preferably, the power supply control is internally provided with a linear low-dropout voltage regulator, a voltage reference and a serial-to-parallel conversion circuit; The linear low-dropout voltage regulator is used to convert the positive and negative switching power generated by the external input DC-DC conversion into a high-precision, low-noise linear ±5V power supply for the circuit; The voltage reference provides a high-precision and high-stability reference voltage reference for high-performance broadband analog multipliers and active differential filtering; The serial-to-parallel conversion circuit includes an SPI control interface.

[0012] Preferably, the partition cavity comprises a double-sided cavity including a front cavity and a back cavity; the front cavity is equipped with a millimeter wave receiving front end, an intermediate frequency filtering and amplification, a distributed frequency synthesis and an analog complex correlation processing; the back cavity is equipped with a power supply control; Among them, the functional components arranged in the front cavity are completely isolated except for the slots necessary for interconnection; The power control in the back cavity and the millimeter wave receiving front end, intermediate frequency filtering and amplification, distributed frequency synthesis, and analog complex correlation processing in the front cavity are electrically connected by butt welding of high-temperature insulated wires.

[0013] Preferably, the millimeter wave receiving front end and the distributed frequency synthesis synthesis both adopt a microwave monolithic circuit integrated design, the chip corresponding to the millimeter wave receiving front end and the chip corresponding to the distributed frequency synthesis synthesis are assembled using a micro-assembly process, and the electrical signal transmission substrate used for assembly is a high-frequency complex dielectric board.

[0014] Preferably, the intermediate frequency filter amplifier adopts an MMIC microwave monolithic circuit and an LC package filter integrated design, is internally assembled using a hybrid integrated circuit process, and the electrical signal transmission substrate used for assembly is a glass fiber board.

[0015] Preferably, all devices in the analog complex correlation processing are assembled on an integrated board level using a reflow process, and a multi-layer PCB board made of glass fiber board is used as an electrical signal transmission substrate.

[0016] Preferably, all components in the power control are integrated at the board level by adopting a reflow soldering process, and a multi-layer PCB board made of glass fiber board is used as an electrical signal transmission substrate.

[0017] (3) Beneficial effects The present invention provides a broadband, highly integrated millimeter-wave complex correlation receiving front end. Compared with the existing technology, it has the following advantages: 1. The present invention adopts distributed frequency synthesis technology to realize the generation, transmission and distribution of millimeter-wave local oscillators in each broadband millimeter-wave complex correlation receiving front end, which simplifies the system architecture and solves the disadvantages of large losses and easy self-excitation in the centralized transmission and distribution of millimeter-wave local oscillators in traditional millimeter-wave synthetic aperture radiometer arrays.

[0018] 2. The broadband millimeter-wave complex-correlation receiving front-end of the present invention integrates multiple functional units, so that a single receiving front-end has complete system functions and can easily expand the array scale. The integrated design adopted inside the receiving front-end improves circuit integration and utilization, realizes a cable-free design, and minimizes volume, weight, and manufacturing costs, thereby ensuring that the overall volume, weight, and manufacturing cost of the synthetic aperture radiometer array can be greatly reduced, meeting the requirements of mass production and debugging, further promoting the engineering application of synthetic aperture radiometer arrays, and improving competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A block diagram of the broadband millimeter-wave complex correlation receiving front end for an existing conventional aperture synthesis radiometer array; Figure 2 A block diagram of the structure of a broadband, highly integrated millimeter-wave complex correlation receiving front end provided by an embodiment of the present invention; Figure 3 Schematic diagram of expanding N broadband millimeter-wave complex correlation receiving front ends in a synthetic aperture radiometer array provided by an embodiment of the present invention; Figure 4 This is a schematic diagram of the overall structure of a broadband, highly integrated millimeter-wave complex correlation receiving front end provided by an embodiment of the present invention; Figure 5 1 is an exploded schematic diagram of a broadband highly integrated millimeter-wave complex correlation receiving front end provided by an embodiment of the present invention; Figure 6 2 is a schematic structural diagram of a front-end cavity of a broadband, highly integrated millimeter-wave complex correlation receiving front end provided by an embodiment of the present invention; Figure 7 This is a schematic structural diagram of a broadband, highly integrated millimeter-wave complex correlation receiving front-end back cavity provided by an embodiment of the present invention; Figure 8 A circuit block diagram of a broadband, highly integrated millimeter-wave complex correlation receiving front end provided by an embodiment of the present invention; Figure 9 A block diagram of the millimeter wave receiving front end provided by an embodiment of the present invention; Figure 10 A block diagram illustrating the principle of distributed frequency synthesis according to an embodiment of the present invention; Figure 11 A block diagram of the principle of intermediate frequency filtering and amplification provided by an embodiment of the present invention; Figure 12 A block diagram illustrating the principle of simulated complex correlation processing provided by an embodiment of the present invention; Figure 13 A block diagram of the power supply control principle provided by an embodiment of the present invention; Among them, 1 is the front laser sealing cover; 2 is the back laser sealing cover; 3 is the shielding cover; 4 is the front screw-mounted cover; 5 is the back screw-mounted cover; 6 is the integrated metal shell; 7 is the dual-waveguide broadband impedance converter; 8 is the millimeter wave receiving front end; 9 is the intermediate frequency filtering and amplification; 10 is the distributed frequency synthesis; 11 is the analog complex correlation processing; 12 is the power control, the left power control unit 1201, and the right power control unit 1202. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] The embodiments of the present application provide a broadband, highly integrated millimeter-wave complex correlation receiving front-end, employing distributed coherent frequency synthesis technology to address the drawbacks of traditional millimeter-wave aperture synthesis radiometer arrays, such as high losses and susceptibility to self-excitation in centralized millimeter-wave local oscillator generation, transmission, and distribution. By employing an integrated design, multiple functional components are integrated into a broadband millimeter-wave complex correlation receiving front-end, enabling a single millimeter-wave complex correlation receiving front-end to possess complete system functionality. This fully utilizes available system resources and large-scale production technology, improving circuit integration and utilization, and addressing the technical issues of low integration and difficulty in array expansion in existing millimeter-wave complex correlation receiving front-ends used in aperture synthesis radiometer arrays.

[0023] The technical solution in the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows: The existing synthetic aperture radiometer array uses a broadband millimeter wave complex correlation receiving front end composed of Figure 1 , consisting of N-channel broadband millimeter-wave low-noise receiving front-end, 2N-channel intermediate frequency filter amplification modules and 2N-channel analog correlation processing modules. The main problems of this architecture in engineering are: First, the coherent local oscillator signals required for phase-shift mixing are generated by independently packaged frequency synthesizer modules. These millimeter-wave local oscillators are then transmitted to the receiving front ends of various broadband millimeter-wave switches via RF cables via power divider amplification. In the millimeter-wave band, local oscillator transmission losses are significant, requiring multi-stage cascaded circuits for compensation. This is prone to oscillation and self-excitation. RF cables also have limited isolation in the millimeter-wave band, resulting in significant local oscillator leakage. This results in poor electromagnetic compatibility and restricts the expansion of millimeter-wave synthetic aperture radiometer arrays.

[0024] 2. The millimeter wave complex correlation receiving front end for the synthetic aperture radiometer array basically adopts a separate design in the existing technology, and realizes the functions required by the system through the cascade of single functional modules. For example, the broadband millimeter-wave low-noise receiving front-end adopts a multi-chip micro-assembly process to cascade and package the millimeter-wave low-noise amplifier, millimeter-wave pre-selection filter and millimeter-wave mixer chips in a single basic receiving unit channel into an airtight metal box; the intermediate frequency filter amplification module usually integrates the intermediate frequency amplifier, digitally controlled attenuator and filter into another airtight packaged module using hybrid integrated circuit process technology; and the analog complex correlation processing module adopts a reflow soldering process to realize the cascade of packaged devices such as broadband balun, broadband analog multiplier and operational amplifier on the printed circuit board, and uses a metal cavity for shielding; the packaged different functional modules are then fixed on the structural parts to form the millimeter-wave complex correlation receiving front-end. Due to the large number of components used, large packaging volume, limited circuit density, low integration, and large area occupied by the microstrip board, the volume and weight of the existing millimeter-wave complex correlation receiving front-end cannot be effectively controlled. As a result, the millimeter-wave synthetic aperture radiometer array contains many connectors and a huge number of connecting cables, resulting in a large overall volume, heavy weight and high manufacturing cost.

[0025] From the above description, it can be seen that the existing millimeter-wave complex correlation receiving front-end used in the synthetic aperture radiometer array has large local oscillator loss in the millimeter-wave frequency band, and needs to be compensated by a multi-stage circuit cascade method. It is easy to cause oscillation and self-excitation, which restricts the increase in the number of millimeter-wave complex correlation receiving front-ends and limits the further expansion of the scale of the synthetic aperture radiometer array.

[0026] Furthermore, existing millimeter-wave complex correlation receiver front-ends are constructed using discrete components. Due to the large number of components, high packaging requirements, limited circuit density, low integration, and the large microstrip board area occupied, the volume and weight of the existing millimeter-wave complex correlation receiver front-end cannot be effectively controlled. As a result, the resulting integrated aperture radiometer array contains numerous connectors and a large number of connecting cables, resulting in a large overall size, weight, and high manufacturing cost. As the basic unit of the integrated aperture radiometer array, the volume, weight, manufacturing cost, and reliability of the millimeter-wave complex correlation receiver front-end are determined by its volume, weight, manufacturing cost, and manufacturing cost. Clearly, the millimeter-wave complex correlation receiver front-end constructed by cascading different functional modules is difficult to implement in practical engineering, thus limiting the application of integrated aperture radiometer arrays.

[0027] In summary, the key issues that need to be addressed in the design of a broadband millimeter-wave complex correlation receiving front-end for a synthetic aperture radiometer array are to carry out the integrated design of the broadband millimeter-wave complex correlation receiving front-end, solve the millimeter-wave local oscillator transmission problem, realize high-frequency cable-free interconnection, reduce system volume and weight, lower manufacturing costs, and meet the requirements of mass production and debugging. These are also the bottlenecks that restrict its application in actual engineering.

[0028] To address the above-mentioned issues, an embodiment of the present invention proposes a highly integrated broadband millimeter-wave complex correlation receiving front end for a synthetic aperture radiometer array. Utilizing distributed frequency synthesis technology, the millimeter-wave local oscillator that originally needed to be transmitted externally is simplified into an external reference signal. Distributed millimeter-wave local oscillator frequency synthesis is achieved through low-phase-noise phase-locked coordination and direct frequency multiplication processing within the broadband millimeter-wave complex correlation receiving front end, which greatly reduces the difficulty of local oscillator transmission and distribution, and facilitates the expansion of the scale of the synthetic aperture radiometer array.

[0029] It should be noted that, in the embodiment of the present invention, phase-shift mixing is adopted and the orthogonality of complex correlation detection is utilized to eliminate the influence of phase inconsistency within the radiometer system. Therefore, the system's low-frequency synchronous clock can be used as the reference signal for frequency synthesis, and distributed frequency synthesis technology is used in each broadband millimeter-wave complex correlation receiving front end to generate the required millimeter-wave mixing local oscillator, thereby realizing a distributed coherent design. This solves the drawbacks of large centralized transmission and distribution losses of millimeter-wave local oscillators and easy self-excitation within the traditional millimeter-wave comprehensive aperture radiometer array.

[0030] In addition, the original architecture is improved by adopting the idea of integrated integration. Through the combination of multi-chip microassembly / hybrid integrated circuit process / reflow soldering process, multiple functional components are integrated into the broadband millimeter-wave complex correlation receiving front-end module, so that each broadband millimeter-wave complex correlation receiving front-end can independently have complete system functions, fully utilizing the resources available in the system and large-scale production technology, improving circuit integration and utilization, minimizing the volume and weight of the broadband millimeter-wave complex correlation receiving front-end and reducing manufacturing costs, thereby ensuring that the overall volume, weight and manufacturing cost of the synthetic aperture radiometer array can be greatly reduced, meeting the requirements of mass production and debugging, further promoting the engineering application of synthetic aperture radiometer arrays, and improving competitiveness. In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0031] The embodiment of the present invention provides a highly integrated broadband millimeter wave complex correlation receiving front end, such as Figure 2As shown, it includes: a housing (in the embodiment of the present invention, the housing is preferably an integrated metal housing), a dual-waveguide broadband impedance converter, a millimeter wave receiving front end, an intermediate frequency filtering and amplification, a distributed frequency synthesis, an analog complex correlation processing and a power supply control; A compartment is provided inside the housing, and the compartment is used for integrating the millimeter wave receiving front end, intermediate frequency filtering and amplification, distributed frequency synthesis, analog complex correlation processing and power supply control; The dual-waveguide broadband impedance converter is realized by overlapping a stepped impedance converter with a radio frequency insulator, and the radio frequency insulator is welded to the input end face of the integrated housing to realize the airtight design of the millimeter wave complex correlation receiving front end; The input of the distributed frequency synthesis is connected to the reference signal, and the output is connected to the millimeter wave receiving front end to provide the millimeter wave local oscillator signal for the millimeter wave receiving front end; The millimeter wave receiving front-end input is connected to the dual-path interference antenna through a dual-waveguide broadband impedance converter, and the output is connected to the intermediate frequency filter amplifier; The intermediate frequency filtering and amplification processes a pair of in-phase and a pair of orthogonal intermediate frequency signals and then outputs them to analog complex correlation processing; The power supply control provides highly stable power supply for the millimeter wave receiving front end, intermediate frequency filtering and amplification, millimeter wave distributed frequency synthesis and analog complex correlation processing.

[0032] The highly integrated broadband millimeter-wave complex correlation receiving front end provided by the embodiment of the present invention integrates different functional components such as the millimeter-wave receiving front end, intermediate frequency filtering and amplification, distributed frequency synthesis, analog complex correlation processing and power supply control to form a basic unit of the synthetic aperture radiometer array. This basic unit has complete system functions. By increasing the number of highly integrated broadband millimeter-wave complex correlation receiving front ends, the scale expansion of the synthetic aperture radiometer array can be easily achieved, such as Figure 3 shown.

[0033] The following is a detailed description of the overall architecture and various functional components of the highly integrated broadband millimeter-wave complex correlation receiving front end: At the architectural level: The embodiment of the present invention provides a broadband highly integrated millimeter wave complex correlation receiving front end overall structure as shown in FIG. Figure 4 As shown, its exploded diagram is as follows Figure 5 As shown, the compartment inside the integrated metal shell is a double-sided cavity including a front cavity and a back cavity. The structures of the front cavity and the back cavity are as shown in FIG. Figure 6 、 Figure 7 shown.

[0034] The millimeter-wave receiving front end 8, intermediate frequency filtering and amplification 9, distributed frequency synthesis 10, and analog complex correlation processing 11 are arranged in the front cavity, while the power supply control 12 is located in the rear cavity. The design utilizes metal ribs to achieve physical shielding and isolation. Each functional component is completely isolated except for gaps at the interconnection points. This allows multiple modules to be installed in a single cavity, reducing component size and interconnect complexity while ensuring isolation between modules and preventing interference and spurious emissions from components within the link.

[0035] refer to Figures 4 to 7 The embodiment of the present invention provides a broadband, highly integrated millimeter-wave complex correlation receiving front end, which is composed of an integrated metal shell 6, a dual-waveguide broadband impedance converter 7, a front laser sealing cover plate 1, a back laser sealing cover plate 2, a shielding cover plate 3, a front screw-mounted cover plate 4, and a back screw-mounted cover plate 5. The RF input is electrically connected to the airtight RF insulator welded on the integrated shell by using a stepped impedance converter through the dual-waveguide broadband impedance converter 7. The low-frequency input and output of the airtight part are connected through a J30JMI airtight connector, and the input and output of the non-airtight part are connected through a J30JY rainproof connector. The shielding cover plate 3 and the internal partition of the integrated metal shell 6 form a connected front cavity, which isolates the circuits of different modules, reduces crosstalk between circuits, and improves the stability and reliability of the component. At the same time, the front laser sealing cover plate 1 and the back laser sealing cover plate 2 are added to meet the airtightness requirements of the cavity containing the chip, ensuring the stable and reliable operation of the internal MMIC chip.

[0036] Within the front cavity, both the millimeter-wave receiving front-end 8 and the millimeter-wave distributed frequency synthesizer 10 utilize an MMIC microwave monolithic integrated circuit design and are assembled internally using a micro-assembly process. To reduce transmission losses in the millimeter-wave frequency band, a high-frequency complex dielectric substrate, ROGERS5880, is used as the electrical signal transmission substrate. Furthermore, where the microstrip board is mounted, the integrated housing is slotted and cavity-formed to the microstrip board's profile. The bottom of the cavity is partially gold-plated. Because it operates at millimeter-wave frequencies, the microstrip board is made of ROGERS5880 sheet material with a dielectric constant of 2.2. To minimize the height difference between the microstrip board and the MMIC chip, the microstrip board is 0.254mm thick. The back of the microstrip board is gold-plated with ground copper and directly soldered to the gold-plated integrated housing at the cavity bottom, providing good grounding. The cavity depth where the microstrip board is soldered to the millimeter-wave receiving front-end 8 and the millimeter-wave distributed frequency synthesizer 10 is preferably 3mm deep and 3.6mm wide.

[0037] The IF filter amplifier 9 integrates an MMIC microwave monolithic circuit with an LC package filter. Internally assembled using a hybrid integrated circuit process, it uses an inexpensive FR4 substrate to minimize transmission losses and reduce costs. The bottom of the integrated housing, where the substrate is mounted, is partially gold-plated. To minimize the height difference between the substrate and the MMIC chip, the substrate thickness is set to 0.2mm. The back of the substrate is gold-plated with ground copper and directly soldered to the gold-plated bottom of the integrated housing, providing excellent grounding. Where the LC package filter is mounted, the integrated housing is slotted and cavity-formed to the filter's contour. The cavity depth is sufficient to allow for lap soldering to the substrate using filter input and output RF insulators. The filter bottom is padded with indium foil for excellent grounding. Installation is secured from the back of the integrated housing using screws, spring washers, and flat washers. The cavity depth and width of the IF filter amplifier where the substrate is soldered can be set to 5mm, simplifying assembly operations.

[0038] All components within the Analog Complex Correlation Processor 11 are assembled at the board level using a reflow soldering process. A low-cost FR4 (fiberglass) multilayer PCB is used as the substrate for electrical signal transmission, enhancing the design's integration. Furthermore, the multilayer PCB is implemented as a single-function packaged device and mounted directly within the module's front cavity using screws.

[0039] The rear cavity is divided into two chambers by metal ribs, housing the left and right sections of the power control unit 12. The left power control unit 1201 provides high-precision ±5V power, processed by a linear regulator, and phase-shift and attenuation code control after serial-to-parallel conversion to the millimeter-wave receiving front-end 8, the intermediate-frequency filtering and amplification module 9, and the millimeter-wave distributed frequency synthesis module 10. It is electrically connected to the front cavity using a sealed low-frequency insulator transition. A laser-sealed cover plate 2 is used to achieve partial airtightness in the rear cavity corresponding to the left power control unit 1201, further enhancing the reliability of the module containing the chip. The linear low-dropout voltage regulator, extremely low-noise, high-stability voltage reference, and serial-to-parallel conversion circuitry in the power control unit 12 are all implemented using surface-mount components using a reflow soldering process on a single FR-4 printed circuit board.

[0040] The right power control unit 1202 provides a high-precision +5V power supply and a high-precision, stable reference voltage to the analog complex correlation processor 11, processed by a linear regulator. Electrical connections are achieved between the front and back cavities using high-temperature insulated wires welded through the cavities. The back cavity corresponding to the right power control unit 1202 is sealed with a screw-mounted cover plate 2, further reducing costs.

[0041] The left power control unit 1201 and the right power control unit 1202 are connected via a J30JMI airtight connector, while the right power control unit 1202 is connected to the outside via a J30JY rainproof connector installed on the side wall of the integrated housing.

[0042] At the same time, it should be noted that the cavity containing the MMIC microwave monolithic circuit part adopts an airtight design, and the RF insulator, low-frequency insulator and low-frequency connector are all welded. The low-frequency electrical connection on the front and back sides of the cavity adopts a vertical transition method of the low-frequency insulator. The end face of the low-frequency insulator in the cavity part containing the chip adopts a flat-head gold-plated design, which can easily realize gold wire bonding with the MMIC chip and microstrip board. The other end can be welded to the corresponding functional pad on the power control printed circuit board in the back cavity after molding. Combined with the cover plate with local laser sealing on the front, the module containing the chip part can be locally airtight, which improves reliability while reducing costs.

[0043] The microstrip board / substrate where the chip is placed within the cavity requires slotting. A 0.2mm thick gold-plated molybdenum copper pad is inserted into the slot as a stress buffer. The molybdenum copper pad is cut to size according to the chip and soldered to the bottom of the integrated housing. The chip and the molybdenum copper pad are bonded using conductive adhesive, preferably H20E two-component conductive adhesive. Gold wire bonding is used for electrical interconnection between the MMIC microwave integrated circuits and between the MMIC chips and the microstrip board, improving integration and reducing module size.

[0044] like Figure 4 The main structural dimensions of the broadband highly integrated millimeter-wave complex correlation receiving front end are shown in the following table.

[0045] Table 1 Main structural dimensions of broadband highly integrated millimeter-wave complex correlation receiving front end During the implementation of this application, millimeter-wave radiometer circuits with different functions are integrated into an overall module through distributed frequency synthesis, microwave monolithic integration, structural integration design and process synthesis, so that the broadband millimeter-wave complex correlation receiving front end can independently have the complete functions of the system, simplify the connection relationship with the system, eliminate the separate module design and internal connecting cables, thereby achieving the purpose of reducing the overall weight and volume, ensuring the electrical indicators of the broadband highly integrated millimeter-wave complex correlation receiving front end while achieving miniaturization, and having the advantages of simple structure and low cost, which can easily realize the scale expansion of the synthetic aperture radiometer array.

[0046] At the functional circuit level: The circuit principle of the broadband highly integrated millimeter wave complex correlation receiving front end provided by the embodiment of the present invention is as follows Figure 8As shown in Figure 2. Among them, the principle block diagram of the millimeter wave receiving front end is as follows: Figure 9 As shown in the figure, Channel A and Channel B are identical; only Channel A is described here. Connected sequentially are a low-noise amplifier (LNA) N1, preselector filter Z1, LNA N2, and power divider N3. Power divider N3 splits the in-phase signal into two paths. One path is connected sequentially to attenuator N4, mixer N5, attenuator N6, and low-pass filter Z3, while the other path is connected sequentially to attenuator N7, mixer N8, attenuator N9, and low-pass filter Z4. N1 and N2 provide low-noise amplification of the weak target temperature radiation signal, achieving low noise and high gain. Z1 is a high-rectangular coefficient bandpass filter that provides frequency selectivity. Z3 and Z4 are low-pass filters that suppress leakage of the local oscillator signal. N4 and N7 are fixed attenuators that mitigate interstage standing waves and optimize intra-band fluctuations. The input local oscillator signal is connected to the power divider N34 in sequence. The power divider N34 splits the local oscillator signal into two paths with the same phase power. One path is sent to the local oscillator power divider N33 of the echo 2 channel, and the other path is connected in sequence to the local oscillator amplifier N25 and the local oscillator power divider N24. The power divider N24 again splits the local oscillator signal into two paths with the same phase power. One path is connected in sequence to the local oscillator amplifier N20, the phase shifter N19, the local oscillator amplifier N19 and the local oscillator port of the mixer N5, and the other path is connected in sequence to the local oscillator amplifier N21, the phase shifter N22, the local oscillator amplifier N23 and the local oscillator port of the mixer N8. N20, N21, and N25 are local oscillator driver amplifiers. They and the power divider N24 realize the active power division amplification of the local oscillator after the frequency doubling filter. N20 and N21 also provide reverse isolation of the local oscillator to prevent the standing wave pulling during the phase shift of the phase shifter from affecting the accuracy of the local oscillator phase shift. N19 and N22 are digitally controlled phase shifters that can achieve a phase shift range of 0° to 360° in the smallest step.

[0047] The active power division amplification function of the millimeter-wave local oscillator is integrated into the millimeter-wave receiving front end. The low phase noise amplifier chips N25 and N33, the power divider chips N34, N24, and N32 are combined with low-loss microstrip circuits to complete the active amplification and four-power division of the millimeter-wave low phase noise local oscillator.

[0048] N1 and N2 serve as the first-stage low-noise amplifiers in the broadband, highly integrated millimeter-wave complex-correlation receiver front-end. Their noise figure directly impacts the system's minimum sensitivity. The first-stage amplifier is the NC10229C-2640 low-noise amplifier, which boasts a 2.3dB noise figure and 22dB gain within the millimeter-wave frequency band. Its low noise figure and high gain contribute to a lower overall noise figure. N19 and N22 are digitally controlled phase shifters in the local oscillator branch, model WYD330370-6. Their phase shift accuracy is within 3°, demonstrating high precision.

[0049] Figure 10 The principle block diagram of the millimeter wave distributed frequency synthesis module is given. Figure 8From the circuit structure in the figure, the orthogonality of phase-shift mixing and complex correlation detection can be used to eliminate the inconsistency within the millimeter-wave complex correlation receiving front-end channel. Therefore, a simple distributed frequency synthesis method can be used to replace the centralized local oscillator generation and distribution.

[0050] Figure 10 The phase-locked crystal oscillator N101 generates a reference signal coherent with an external reference (a reference signal of different frequencies can be selected based on the external reference, for example, a 100MHz reference signal can be generated coherently with a 10MHz external reference). This signal is then passed through the low-phase-noise phase-locked loop chip N102 to generate a high-quality, low-phase-noise X-band coherent local oscillator signal. This signal then passes through the MEMS filter chip Z101, which suppresses spurious signals and harmonics generated by the PLL, improving the purity of the spectral output. The silicon-based bandpass filter, fabricated using MEMS technology, simplifies the synthesizer circuit structure, improves filtering effectiveness, and is compact and low-cost. The filtered signal is further amplified by the driver amplifier N103 before being input to the active quadrupling chip N104. Through direct frequency multiplication, the low-phase-noise local oscillator required for phase-shift mixing in the millimeter-wave band is generated. In addition to the phase-locked crystal oscillator, the entire frequency synthesis generation part uses four functional chips realized in an integrated housing through a micro-assembly process. It adopts a combination of active frequency multiplication and locking, and cooperates with the power division network integrated in the millimeter wave receiving front end using the same process to achieve highly integrated and low-cost distributed frequency synthesis, greatly reducing transmission losses and the number of cascaded amplifiers, thus solving the problems of large transmission losses of millimeter wave local oscillator signals and easy oscillations in multi-stage cascades.

[0051] In the implementation, the active quadrupler chip N104 was set to the WBD350400-B4, a low-power, high-harmonic-suppression, high-power quadrupler capable of outputting 12dBm within the millimeter-wave operating frequency range. The phase-locked loop (PLL) was set to the SIPL219, a broadband, low-phase-noise integrated phase-locked loop.

[0052] The intermediate frequency filtering and amplification module contains four completely identical amplification and filtering channels. It removes the DC from the signal output after phase shift mixing at the millimeter wave receiving front end and further filters and amplifies it to meet the requirements of the subsequent analog complex correlation processing for the input signal frequency and power range. Figure 11 This is a block diagram of the IF filtering and amplification principle. The diagram depicts IF channels 1, 2, 3, and 4, each identically. Only IF channel 1 is described here. Taking IF channel 1 as an example, the following connections are IF amplifier N111, bandpass filter Z111, digitally controlled attenuator N112, and IF amplifier N113. The inputs and outputs of N111 and N113 are AC-coupled to prevent the amplified DC components generated by zero-IF mixing from interfering with the subsequent analog complex correlation unit operations.

[0053] In an embodiment of the present invention, the bandpass filter Z111 uses a high-pass and low-pass LC filter, and the signal bandwidth is set to 0.1 GHz to N / 2 GHz. The reason for using a high-pass filter with a cutoff frequency of 0.1 GHz is that after zero intermediate frequency mixing, the additional phase noise brought by the local oscillator at 0.1 GHz is already much lower than the thermal noise of the channel. Therefore, the additional local oscillator noise introduced by the mixing of the in-band intermediate frequency signal can be ignored. N111 and N113 are broadband amplifiers on the intermediate frequency branch, with a setting model of NC11236C-106. Within the working frequency band, its fluctuation is less than 0.8dB, with good flatness. N112 is a digitally controlled attenuator, with a setting model of BW163. It has an internal integrated driver and does not require an external driver. While improving the circuit integration, it reduces the cost of components.

[0054] Figure 12 A block diagram of the analog complex correlation processing principle is presented. It comprises two identical analog correlation channels, each performing correlation operations on a pair of in-phase IF signals with a bandwidth of DC to N / 2 GHz and a pair of quadrature IF signals with a bandwidth of DC to N / 2 GHz. After active differential filtering, the resulting signals are output as a pair of quadrature IQ signals. After passing through the wideband analog multiplier, the signal energy is distributed over the DC to N / 2 GHz frequency range. Therefore, a low-pass filter with the lowest possible cutoff frequency is required to minimize channel noise, retaining only the bandwidth that matches the signal variation. The link input, output, and internal processing within the dual-channel complex correlation unit utilize a differential design to minimize potential common-mode interference. This design provides twice the amplitude of a single-ended signal at the same power supply voltage, along with improved linearity, addressing DC drift and common-mode interference suppression issues.

[0055] Figure 12 The in-phase and quadrature paths described in [1] are identical in hardware configuration; only the in-phase path is described here. Connected sequentially are broadband baluns N121 and N125, broadband high-performance multiplier N122, matching network 1, passive differential filter Z121, matching network 2, op amp N123, matching network 3, op amp N124, and the feedback network.

[0056] N121 and N125 are broadband baluns, converting two IF broadband signals into differential signals for output to the subsequent-stage broadband, high-performance multiplier N122. N122 multiplies the input signals, achieving broadband operation and high consistency. Matching network 1 matches the output impedance of N122 with the input impedance of the differential passive low-pass filter Z121. N123 and N124 are operational amplifiers, and matching network 2 matches the output impedance of the differential passive low-pass filter Z121 with the input impedance of N123. Matching network 3 provides inter-stage matching between op amps N123 and N124. The feedback network provides negative feedback and filtering for the op amp, forming an active differential low-pass filter together with N123 and N124.

[0057] In the embodiment of the present invention, N121 and N125 are set as the broadband unbalanced-balanced conversion circuit TC-1-13M+, N2 is set as the wide-band, high-performance, super-symmetrical analog multiplier ADL5391, N123 is set as the extremely high linearity and temperature stability precision instrumentation amplifier AD8139, and N124 is set as the low offset, high stability differential drive amplifier LTC1992.

[0058] Figure 13 The power supply control block diagram is presented, comprising linear low-dropout regulators N131, N132, and N133, an extremely low-noise and high-stability voltage reference N134, and a serial-to-parallel converter circuit N135. N131, N132, and N133 are linear low-dropout regulators that provide highly stable, low-noise +5V and -5V power supplies, respectively, to the millimeter-wave receiver front end, intermediate frequency filter, and distributed frequency synthesizer. N132 provides a highly stable, low-noise +5V power supply, also processed by a linear regulator, to the analog complex correlation processor. N134 provides a high-precision, highly stable reference voltage for the analog complex correlation processor, effectively ensuring the stability of the correlation output voltage. Furthermore, the power supply control circuit also includes a serial-to-parallel converter circuit N135, allowing an external host to operate the phase shifter within the millimeter-wave receiver front end and the digitally controlled attenuator within the intermediate frequency filter amplifier via an SPI interface. Furthermore, the serial-to-parallel converter circuit is implemented using a dedicated integrated circuit, simplifying the interface design. In this embodiment of the present invention, N131, N132, and N133 are configured as the low-noise, low-dropout XC5322BMAC, capable of providing a maximum output current of 3A. N134 is configured as the high-precision, highly stable reference voltage ADR431. N135 is preferably configured as the NC20415F, capable of providing a maximum of 24-bit parallel code output.

[0059] In summary, compared with the existing technology, the present invention has the following beneficial effects: 1. In the embodiment of the present invention, distributed frequency synthesis is achieved by integrating low phase-noise phase-locked generation inside the broadband millimeter-wave complex correlation receiving front end and combining it with direct synthesis frequency multiplication processing, which greatly reduces the difficulty of local oscillator transmission allocation and realizes the convenient expansion of the synthetic aperture radiometer array scale.

[0060] 2. The embodiment of the present invention integrates multiple functional components into a broadband millimeter-wave complex correlation receiving front-end module while ensuring the electrical performance indicators required by the system, so that a separate millimeter-wave complex correlation receiving front-end has complete system functions, can make full use of the resources and large-scale production technology that can be provided by the system, improve circuit integration and utilization, minimize the volume and weight of the broadband millimeter-wave complex correlation receiving front-end and reduce manufacturing costs, thereby ensuring that the overall volume, weight and manufacturing cost of the synthetic aperture radiometer array can be greatly reduced, meeting the requirements of mass production and debugging, further promoting the engineering application of synthetic aperture radiometer arrays, and improving competitiveness.

[0061] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A highly integrated broadband millimeter-wave complex correlation receiving front end, characterized in that: include: Dual-waveguide broadband impedance converter, an integrated housing with a cavity inside, and millimeter-wave receiving front-end, intermediate frequency filtering and amplification, distributed frequency synthesis, analog complex correlation processing, and power supply control integrated in the cavity; Wherein, the dual-waveguide broadband impedance converter is realized by overlapping a step impedance converter with a radio frequency insulator; The input of the distributed frequency synthesis is connected to the system synchronization reference signal, and the output is connected to the millimeter wave receiving front end to provide the millimeter wave receiving front end with a system-coherent millimeter wave local oscillator signal; The millimeter wave receiving front-end input is connected to the dual-path interference antenna through a dual-waveguide broadband impedance converter, and the output is connected to the intermediate frequency filter amplifier; The intermediate frequency filtering and amplification processes a pair of in-phase and a pair of orthogonal intermediate frequency signals and then outputs them to analog complex correlation processing; The power supply control provides low-noise, highly stable power supply for the millimeter wave receiving front end, intermediate frequency filtering and amplification, distributed frequency synthesis and analog complex correlation processing.

2. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to claim 1, characterized in that: The distributed frequency synthesis system includes a phase-locked crystal oscillator, a phase-locked loop chip, an active quadruple frequency chip, a MEMS filter, a low phase noise amplifier chip and a power divider chip; The phase-locked crystal oscillator generates a reference signal that is coherent with an external reference; The phase-locked loop chip and the MEMS filter perform frequency multiplication and phase-locked filtering on the reference signal to generate a high-quality, low-phase-noise X-band coherent local oscillator signal and perform filtering; The active quadruple frequency chip uses a direct synthesis method to generate a low phase noise local oscillator required for zero intermediate frequency system mixing in the millimeter wave frequency band.

3. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to claim 1, characterized in that: The intermediate frequency filter amplifier comprises four identical intermediate frequency filter amplifier channels, each of which is internally provided with a low noise amplifier chip, a low-pass filter chip, a digitally controlled attenuator chip and an LC band-pass filter; The input end of the intermediate frequency filtering and amplifying channel is connected to the output of the millimeter wave receiving front end, and the output end is connected to the analog complex correlation processing, and a pair of in-phase and a pair of orthogonal intermediate frequency signals are output to the analog complex correlation processing part after filtering and amplification processing.

4. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to claim 1, wherein: The analog complex correlation processing includes two completely identical analog correlation channels, which respectively perform correlation operations on a pair of in-phase intermediate frequency signals with a bandwidth of DC to N / 2 GHz and a pair of orthogonal intermediate frequency signals with a bandwidth of DC to N / 2 GHz, and output a pair of orthogonal IQ signals after active differential filtering.

5. The highly integrated broadband millimeter-wave complex correlation receiving front end according to claim 1, characterized in that: The power supply control is internally provided with a linear low voltage dropout regulator, a voltage reference and a serial-to-parallel conversion circuit; The linear low-dropout voltage regulator is used to convert the positive and negative switching power generated by the external input DC-DC conversion into a high-precision, low-noise linear ±5V power supply for the circuit; The voltage reference provides a high-precision and high-stability reference voltage reference for high-performance broadband analog multipliers and active differential filtering; The serial-to-parallel conversion circuit includes an SPI control interface.

6. The highly integrated broadband millimeter-wave complex correlation receiving front end according to any one of claims 1 to 5, characterized in that: The partition cavity comprises a double-sided cavity including a front cavity and a back cavity; the front cavity is equipped with a millimeter wave receiving front end, an intermediate frequency filtering and amplification, a distributed frequency synthesis and an analog complex correlation processing; the back cavity is equipped with a power supply control; Among them, the functional components arranged in the front cavity are completely isolated except for the grooves required for interconnection; The power control in the back cavity and the millimeter wave receiving front end, intermediate frequency filtering and amplification, distributed frequency synthesis, and analog complex correlation processing in the front cavity are electrically connected by butt welding of high-temperature insulated wires.

7. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to any one of claims 1 to 5, characterized in that: The millimeter wave receiving front end and the distributed frequency synthesis synthesis both adopt a microwave monolithic circuit integrated design. The chip corresponding to the millimeter wave receiving front end and the chip corresponding to the distributed frequency synthesis synthesis are assembled using a micro-assembly process, and the electrical signal transmission substrate used in the assembly is a high-frequency complex dielectric board.

8. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to any one of claims 1 to 5, characterized in that: The intermediate frequency filter amplifier adopts an MMIC microwave monolithic circuit and an LC package filter integrated design, is internally assembled using a hybrid integrated circuit process, and the electrical signal transmission substrate used for assembly is a glass fiber board.

9. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to any one of claims 1 to 5, characterized in that: All devices in the analog complex correlation processing are assembled on an integrated board level using a reflow soldering process, and a multi-layer PCB board made of glass fiber board is used as an electrical signal transmission substrate.

10. The highly integrated broadband millimeter-wave complex correlation receiving front-end according to any one of claims 1 to 5, characterized in that: All components in the power control are assembled on an integrated board level using a reflow soldering process, and a multi-layer PCB made of glass fiber board is used as an electrical signal transmission substrate.

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