Device for measuring mutual coupling coefficient between active sub-arrays of sub-array level digital array antenna

Abstract

The invention particularly relates to a measuring device for measuring a mutual coupling coefficient between active sub-arrays in a sub-array level digital array antenna. The device comprises a radiation irradiation unit, a fixed attenuation plate, a sub-array level digital array antenna, an orthogonal demodulation unit and a signal processing unit. A fixed attenuation plate with known attenuation is introduced into a receiving path of a reference subarray, the other subarray is terminated through a matched load, the phase of the subarray is kept orthogonal to the reference subarray, and mixed signals output by the reference subarray are subjected to IQ orthogonal demodulation to obtain I and Q baseband components; and the signal processing unit calculates a mutual coupling coefficient between the sub-arrays based on the I and Q amplitude difference in combination with a fixed attenuation value. The measuring device can quickly and accurately quantify non-antenna radiation coupling caused by a radio frequency link, feed, a power supply / ground loop and the like under the condition of eliminating the influence of antenna radiation coupling, facilitates system-level online calibration, and is suitable for an active phased array and digital beam forming system of a microwave frequency band.

Description

Technical Field

[0001] This invention belongs to the field of active phased array and digital array antenna testing and measurement technology, specifically relating to a device for measuring and obtaining the mutual coupling coefficient between active subarrays in a subarray-level digital array antenna caused by non-antenna radiation factors such as radio frequency links, feed networks, power supplies, and grounding. Background Technology

[0002] With the rapid development of digital beamforming (DBF) technology, radar, satellite communication and wireless detection systems are gradually evolving from traditional analog beam control to digital arrays.

[0003] Beamforming (DBF) represents a core evolutionary direction in modern phased array technology, marking a fundamental shift in beam control from traditional "hardware-defined" to "software-defined." Its basic principle is as follows: First, the analog signal received by each independent RF channel is down-converted and directly digitized. Then, in the digital domain (typically in an FPGA or DSP), a software algorithm applies precise and dynamically reconfigurable complex weights to the digital signal stream of each channel (simultaneously controlling amplitude and phase). Finally, the weighted signals from all channels are vector-summed. This processing mechanism brings revolutionary advantages: it can simultaneously generate multiple independent high-gain beams, greatly improving the system data rate; it can also form deep nulls in the direction of interference sources in real time through adaptive algorithms, achieving excellent spatial filtering and anti-interference capabilities; simultaneously, digital calibration can compensate for inherent amplitude and phase errors in the hardware, improving the purity and accuracy of beamforming.

[0004] To achieve the engineering and cost feasibility of large-scale digital arrays, active subarrays have become the fundamental physical building block of the system. It is a highly integrated, fully functional RF front-end subsystem. Specifically, an active subarray is not simply a combination of antennas; it typically integrates the following components: 1. Antenna element array: It consists of multiple antenna elements (such as microstrip patches) arranged at a specific spacing (such as half wavelength) (e.g., 4×4, a total of 16), which are responsible for the radiation and reception of electromagnetic waves.

[0005] 2. TR Component Cluster: Each antenna element or a small cluster of elements (e.g., 2×2) connects to one TR channel. Modern technology commonly uses multi-channel integrated TR chips, where a single chip contains multiple independent transmit amplifiers, low-noise amplifiers, digital phase shifters and attenuators, as well as transmit and receive switches.

[0006] 3. Feeding and combining network: The subarray contains a sophisticated microwave transmission line network (such as microstrip lines or striplines). During reception, this network combines the output signals of all TR channels in the analog RF domain, ultimately converging the energy of the entire subarray to one or a very few RF output ports; during transmission, the reverse power distribution is performed.

[0007] Therefore, each active subarray is itself a small analog phased array, which forms a fixed or small-range-scanning "sub-beam" by controlling the amplitude and phase of its internal multiple elements. This modular design is the physical and engineering basis for building any large-scale phased array.

[0008] Subarray-level digital arrays are a hybrid architecture that combines the advantages of analog and digital technologies, aiming to balance the extreme performance of pure digital arrays with the significant engineering challenges. Their core feature lies in the strategic placement of digital nodes.

[0009] In this architecture, the signal processing flow is clearly divided into two stages: Phase 1: Analog Subarray Beamforming. Each active subarray acts as an independent analog front-end, amplifying, phase-shifting, and synthesizing multi-channel signals within itself, and outputting one (or several) analog radio frequency signals representing the overall response of that subarray.

[0010] The second stage: Digital beamforming. Immediately following the analog output of each active subarray, a dedicated down-conversion and analog-to-digital conversion channel is set up. At this point, the signal is converted into a digital signal. The digital signals from all subarrays are then fed into a centralized digital beamforming processor. Here, the system weights and synthesizes these subarray-level digital signals (rather than thousands of unit-level signals) to ultimately achieve advanced functions such as agile scanning, multi-beaming, and adaptive beamforming at the system level.

[0011] This architecture is known as "hybrid beamforming." It significantly reduces the digitization requirements of massive cell channels through active subarrays, making it feasible in terms of system power consumption, data throughput, and manufacturing cost. At the same time, by retaining digital processing at the subarray level, it cleverly inherits the core advantages of digital beamforming in terms of flexibility, multi-beam, and anti-interference.

[0012] The superior performance of subarray-level digital arrays is based on the idealized assumption of signal independence and consistency in each subarray's digital channels. However, in high-density integration environments, the mutual coupling effects between active subarrays severely undermine this assumption. Besides spatial radiation coupling between antenna elements, non-antenna radiation coupling is even more insidious and challenging.

[0013] This type of non-antenna radiation coupling originates from the sophisticated internal structure of the system, and its coupling paths are complex and diverse: 1. RF link crosstalk: The RF output feeders of adjacent subarrays are arranged in parallel in a limited space, which causes energy leakage through electromagnetic induction.

[0014] 2. Power integrity coupling: On a shared power distribution network, the instantaneous current surge generated by a high-power TR component in one subarray during pulse operation will be modulated onto the power supply of other subarrays through the impedance of the power network.

[0015] 3. Ground loop coupling: An imperfect grounding system will create a common impedance. The fast switching current of one subarray will generate voltage fluctuations on the ground plane, which can be picked up by other subarrays and cause interference.

[0016] 4. Structural parasitic coupling: In complex multilayer PCBs, connectors and metal housings, the parasitic inductance and capacitance present form unexpected signal paths between subarrays.

[0017] These non-antenna radiation coupling paths can cause signals from one subarray to "leak" into another, resulting in crosstalk between channels. This is fatal for digital beamforming algorithms that rely on channel independence, as it introduces fixed amplitude and phase errors that are difficult to completely eliminate through conventional calibration. This ultimately manifests as beam pointing deviation, increased sidelobe levels, and severely limits the depth and convergence speed of adaptive nulls, making it impossible to fully realize the theoretical performance of DBF in reality.

[0018] In such systems, to study and measure the non-antenna radiation mutual coupling characteristics between subarrays, measurements are typically performed in receive mode. That is, both active subarrays under test operate in receive mode, while the remaining subarrays not involved in the measurement remain off or powered down to prevent interference from nonlinear factors in the transmit link and spatial radiation fields. Measurements performed in receive mode allow for a more accurate reflection of the coupling characteristics between electrical paths within the subarray, such as RF links, feed networks, and power grounding.

[0019] Currently, industry standards primarily rely on vector network analyzers (VNAs) or anechoic chamber field tests to calculate coupling coefficients by measuring the S-parameters (such as S21) of different subarrays or antenna elements under radiation conditions. However, this method suffers from the following significant problems: 1. Inability to distinguish between antenna radiation and non-antenna radiation coupling: When an active subarray operates in transmit mode, the measurement result is a vector superposition of the signals from two parallel paths: antenna radiation coupling and internal non-antenna radiation coupling. In actual measurements, the strong spatial radiation field completely overwhelms the weak non-antenna radiation coupling signals that need to be measured accurately, resulting in a distorted, mixed parameter that fails to reflect the true internal electrical isolation performance. This method cannot provide accurate non-antenna radiation mutual coupling coefficients for system design and calibration.

[0020] 2. The testing environment is complex and highly dependent on equipment: It usually requires a large darkroom or near-field scanning system, and online calibration cannot be achieved in a system-level environment.

[0021] 3. Test accuracy is greatly affected by system noise: When multiple subarrays work simultaneously, signal superposition and beam interference can cause fluctuations in measurement results.

[0022] The performance of subarray-level digital arrays is highly dependent on the isolation and consistency of the signal links between active subarrays. Therefore, accurately measuring the mutual coupling characteristics between subarrays is a critical issue in system design and calibration. In view of this, there is an urgent need to develop a novel device that can accurately measure the non-antenna radiating mutual coupling coefficients between active subarrays while effectively eliminating the influence of coupling between radiating elements. This device should not only accurately reflect the actual electrical coupling characteristics between subarray-level channels but also provide robust and reliable data support for the system design, amplitude and phase consistency calibration, and performance optimization of subarray-level digital arrays.

[0023] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0024] The purpose of this invention is to provide a device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna. This device can accurately measure the mutual coupling coefficient between active subarrays caused by non-antenna radiation factors such as RF links, feed networks, power supplies, and grounding, under the condition of eliminating the influence of electromagnetic coupling between radiating elements. This provides a reliable basis for channel consistency analysis, beam calibration, and system-level online calibration of digital array systems.

[0025] This invention introduces a fixed attenuator plate into the receiving path of the reference subarray and utilizes IQ quadrature demodulation and digital signal processing algorithms to calculate the mutual coupling coefficient between subarrays based on the amplitude difference between the I and Q signals, thereby achieving quantitative measurement of non-antenna radiated mutual coupling. This device effectively solves the problems in existing technologies such as difficulty in distinguishing between antenna radiated and non-antenna radiated coupling, insufficient measurement accuracy, and complex testing environments.

[0026] To achieve the above objectives, the present invention provides a highly integrated lens antenna, comprising: a radiation illumination unit, a fixed attenuation plate, a subarray-level digital array antenna, an active subarray, a matched load, an orthogonal demodulation unit, and a signal processing unit; The radiation illumination unit is disposed above the sub-array digital array antenna array surface and is used to radiate a test signal with stable amplitude and consistent phase to the sub-array digital array antenna. The subarray-level digital array antenna comprises multiple active subarrays, one of which serves as a reference subarray and the other as a leaky subarray. The leaky subarray is terminated by a matched load, and its phase remains orthogonal to that of the reference subarray. The fixed attenuation plate is disposed on the radiation path between the radiation irradiation unit and the reference subarray. Its attenuation value is fixed and pre-calibrated. It is used to attenuate the main signal received by the reference subarray to a specific level to prevent it from drowning out the coupling signal of the leakage subarray. The input terminal of the quadrature demodulation unit is connected to the output terminal of the reference subarray, and is used to perform quadrature downconversion and filtering on the mixed radio frequency signal containing the main signal and the coupling signal, and output I-channel and Q-channel baseband signals. The signal processing unit is connected to the output of the quadrature demodulation unit and is used to perform amplitude calculation and differential processing on the I and Q baseband signals. Based on the amplitude difference and the attenuation value of the fixed attenuation plate, the mutual coupling coefficient between the subarrays is calculated.

[0027] In some exemplary embodiments, the radiating illumination unit is one of a horn antenna, a Vivaldi antenna, or a waveguide antenna, and its operating frequency band covers the receiving frequency band of the active subarray.

[0028] In some exemplary embodiments, the fixed attenuation plate is a flat plate structure arranged on the radiation path, preferably a thin-film type fixed attenuator with a fixed attenuation value obtained through calibration experiments, typically ranging from 20 to 40 dB.

[0029] In some exemplary embodiments, the fixed attenuation plate may also be an absorbing material plate, a dielectric film, or other equivalent attenuation plate structure.

[0030] In some exemplary embodiments, several fixed attenuation plates (2) with different attenuation values ​​may be provided and replaced according to the estimated mutual coupling strength to optimize the system measurement range.

[0031] In some exemplary embodiments, the quadrature demodulation unit includes an IQ mixer and a low-pass filter; the IQ mixer is used to decompose the input radio frequency signal into I and Q signals with a 90° phase difference, and the low-pass filter is used to filter out high-frequency components and output a smooth baseband signal.

[0032] In some exemplary embodiments, the signal processing unit includes an analog-to-digital converter (ADC) and a digital signal processor (DSP).

[0033] In some exemplary embodiments, the resolution of the analog-to-digital converter (ADC) determines the measurement accuracy of the system; when a 12-bit ADC is used, the overall accuracy of the mutual coupling coefficient measurement is 0.5 dB.

[0034] In some exemplary embodiments, when the subarray-level digital array antenna contains more than two active subarrays, by switching the subarray configuration, a pair of subarrays can be arbitrarily selected as the reference subarray and the leaking subarray respectively for mutual coupling measurement to obtain a complete subarray mutual coupling matrix.

[0035] Based on the above-described apparatus, the present invention also provides a method for measuring the mutual coupling coefficient, comprising the following steps: S1: A test signal with stable amplitude and consistent phase is radiated to the subarray-level digital array antenna through the radiation illumination unit; S2: The fixed attenuation board attenuates the reference subarray received signal to a specific level, preventing the main signal from saturating or drowning the coupled signal under test in the subsequent processing link, and ensuring that both signals are within the linear operating range of the quadrature demodulation unit. S3: The quadrature demodulation unit performs quadrature down-conversion and filtering on the mixed signal output from the reference subarray, and outputs I and Q baseband signals; S4: The signal processing unit calculates the amplitude values ​​M of the I and Q signals respectively. I and M Q Calculate the amplitude difference ΔM, and then apply the formula... Calculate and store the mutual coupling coefficient C, where A is the attenuation value of the fixed attenuation plate.

[0036] The highly integrated lens antenna provided in the embodiments of the present invention improves the passive net gain of the R-KR lens antenna by setting a dynamic adjustment module between the antenna output and the lens input. This module's gain compensation path compensates for the antenna's transmission loss and beamforming loss. Simultaneously, a calibration path is included in the dynamic adjustment module to calibrate the amplitude and phase of the antenna's subsequent lens, thus achieving the antenna channel amplitude and phase calibration function. By utilizing the dynamic adjustment module to implement both the calibration and gain compensation paths, and by co-packing the antenna and dynamic adjustment module onto a multilayer printed circuit board, a high degree of integration of the lens antenna is achieved, meeting the requirements for dynamically reconfigurable performance.

[0037] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0039] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 A schematic diagram showing the relative positions of the radiation irradiation unit, the fixed attenuation plate, and the active subarray; Figure 3 This is a diagram of the 256-channel subarray digital array antenna array. Figure 4 A block diagram showing the composition of active subarrays; Figure 5 This is a schematic diagram of the bottom of the active subarray; Figure 6 This is a schematic diagram illustrating the working principle of IQ mixing. Figure 7 Here is a flowchart of the mutual coupling coefficient measurement process; Icons: 1-Radiation unit; 2-Fixed attenuator; 3-Subarray digital array antenna; 4-Active subarray; 4a-Reference subarray; 4b-Leaking subarray; 5-Matching load; 6-Quadrature demodulation unit; 7-IQ mixer; 8-Low-pass filter; 9-Signal processing unit. Detailed Implementation

[0040] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the invention will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0041] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0042] like Figure 1-7 As shown, this embodiment provides a device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna. The device includes: a radiation illumination unit 1, a fixed attenuation plate 2, a subarray-level digital array antenna 3, a matching load 5, a quadrature demodulation unit 6, and a signal processing unit 9.

[0043] like Figure 1As shown, the radiation illumination unit 1 is a standard gain horn antenna, whose operating frequency band covers the receiving frequency band of the subarray-level digital array antenna. The input terminal of this unit is connected to an external signal source to radiate a stable and amplitude-controllable test signal to the active subarray.

[0044] Furthermore, in other embodiments, the radiation illumination unit may also employ a broadband Vivaldi antenna or waveguide antenna structure to adapt to the testing requirements of different frequency bands.

[0045] The fixed attenuation plate 2 is disposed in the radiation path between the radiation illumination unit 1 and the reference subarray 4a under test. Its core function is to attenuate the strong main signal incident on the reference subarray to a specific level using its pre-calibrated fixed attenuation value A. This ensures that the attenuated main signal is comparable in power level to the weak signal coupled through the non-antenna radiation path, thereby preventing the main signal from saturating or drowning out the coupled signal under test in the subsequent quadrature demodulation unit 6. This ensures that the quadrature demodulation unit operates within its linear range, thus avoiding nonlinear distortion caused by main signal saturation.

[0046] Preferably, the fixed attenuation plate 2 is a thin-film fixed-value attenuator arranged on the radiation path, whose attenuation value is fixed after experimental calibration, typically ranging from 20 to 40 dB. This attenuation plate achieves amplitude attenuation of the incident signal through spatial propagation loss, and features a simple structure and smooth frequency response. In other embodiments, the fixed attenuation plate can be an absorbing material plate, a dielectric diaphragm, or other equivalent attenuation plate structure. To adapt to different test scenarios, multiple attenuation plates with different attenuation values ​​can be equipped and flexibly replaced according to the estimated mutual coupling signal strength to optimize the system's measurement dynamic range and linear operating range.

[0047] like Figure 3 As shown, the subarray-level digital array antenna 3 described in this embodiment has a total of 256 channels, and its array surface consists of 16×16 antenna elements. The entire array is divided into 4×4 active subarrays 3, and each active subarray 4 consists of 4×4 antenna elements. In each active subarray 4, every 2×2 antenna elements correspond to one T / R (transmit / receive) chip, so each active subarray 3 contains 4 T / R chips, corresponding to 16 radiating element channels. All subarrays together constitute the system's 256 independent transmit / receive channels.

[0048] like Figure 4As shown, the active subarray 4 includes an antenna array, a T / R chip module, a phase shifting and attenuation control circuit, a power combining / distribution network, an RF interface, and a digital control interface. The T / R chip module integrates a low-noise amplifier, a transmit power amplifier, a digital phase shifter, and an adjustable attenuator, and can switch between receive and transmit modes. During the testing process of this invention, two of the active subarrays 4 under test are in receive mode, while the remaining active subarrays 4 are in a turned-off state to avoid affecting the measurement results.

[0049] like Figure 5 The diagram shows the bottom structure of the active subarray 4. The bottom circuit board includes multi-layer RF wiring and power / ground planes. The T / R chip is connected to the upper radiating unit through RF vias. The bottom is equipped with a digital control interface, a power connection port, and an RF output interface for connecting to the system's main control module and signal acquisition unit.

[0050] Furthermore, during testing, two active subarrays 4 were selected for measurement: one was designated as the reference subarray 4a, and the other as the leakage subarray 4b. The phase shifter of the reference subarray 4a was set to 0°, and its output was connected to the quadrature demodulation unit 6; the phase shifter of the leakage subarray 4b was set to 90°, and its output was terminated through the matched load 5. The two subarrays maintained a phase quadrature relationship, thereby forming a decomposable composite signal at the output of the reference subarray. The remaining subarrays not involved in the measurement remained off or powered off to avoid crosstalk.

[0051] The input of the quadrature demodulation unit 6 is connected to the output of the reference subarray 4a. Its core function is to decompose and convert the mixed RF input containing the main signal and the coupling signal into two baseband I / Q signals suitable for sampling.

[0052] In one specific implementation, the quadrature demodulation unit 6 may consist of a discrete IQ mixer 7 and a subsequent low-pass filter 8. The IQ mixer 7 performs quadrature down-conversion of the signal, outputting two analog I and Q signals with a 90° phase difference. Subsequently, the low-pass filter 8 filters out high-frequency spurious signals generated during mixing, ensuring that the baseband signal is smooth and meets the subsequent sampling bandwidth requirements.

[0053] Furthermore, in other embodiments, the quadrature demodulation unit 6 can be implemented using a single integrated quadrature demodulator chip. Such chips typically integrate a full set of functions, including a mixer, local oscillator, programmable filter, and amplifier, and can directly output a baseband signal suitable for sampling, which helps improve system integration and consistency.

[0054] The signal processing unit 9 is used to acquire the I and Q baseband signals output by the quadrature demodulation unit 6. Preferably, the signal processing unit 9 is an embedded signal processing platform, internally integrating an analog-to-digital converter (ADC) and a digital processor (DSP). Its processing flow is as follows: 1. Synchronously acquire I and Q baseband signals using ADC.

[0055] 2. Convert the acquired I and Q signals into amplitude values ​​M in decibels (dB). I and M Q According to the IQ demodulation principle, M I M characterizes the coupling signal strength of the leaky subarray. Q Characterizes the main signal strength of the reference subarray.

[0056] 3. Calculate the amplitude difference:

[0057] 4. Based on the known attenuation value A (dB) of the fixed attenuation plate 2, the mutual coupling coefficient between the active subarrays is calculated:

[0058] 5. Output of results: The signal processing unit can store, display or upload the calculated mutual coupling coefficient C to the host computer for unified analysis.

[0059] For multi-subarray systems, the complete subarray mutual coupling matrix can be quickly obtained by switching different combinations of reference subarrays and leaky subarrays and repeating the above process.

[0060] During testing, the radiating illumination unit 1 radiates a coherent signal to the subarray-level digital array antenna 3; the reference subarray 4a receives the main signal through the fixed attenuator 2 and outputs a composite signal. The leaking subarray 4b operates under 90° phase conditions, and its coupled signal leaks to the reference subarray link through the internal electrical path of the system. The output signal of the reference subarray is quadrature demodulated to form two amplitude signals, I and Q.

[0061] Signal processing unit 9 calculates the mutual coupling coefficient C based on the amplitude difference ΔM and the attenuation A, thereby obtaining the non-antenna radiation mutual coupling intensity between the corresponding subarrays. Batch calculation and real-time display can be achieved through the software control interface.

[0062] Furthermore, in a typical implementation, the AD sampling resolution of signal processing unit 9 determines the measurement accuracy of the system. When a 12-bit ADC is used, the overall accuracy of the mutual coupling coefficient measurement, considering system noise and calibration error, can reach approximately 0.5 dB, which meets the calibration and verification requirements of microwave band subarray systems.

[0063] In practical applications, the fixed attenuator plate can be a precisely calibrated thin-film fixed-value attenuator, with an attenuation value A typically ranging from 20 to 40 dB to ensure the coupled signal remains within the demodulator's dynamic range. The signal processing unit supports a remote communication interface, enabling it to work in conjunction with the array control host to achieve online system calibration and self-testing.

[0064] The embodiments of the present invention have the following comprehensive advantages: 1. Non-antenna radiation mutual coupling can be quantified independently: By using fixed attenuation and orthogonal demodulation, radiation path interference is avoided, and the measurement results can truly reflect the internal channel coupling of the system.

[0065] 3. Simple structure and high integration: The device has a modular design and can be embedded into existing array systems without the need for an anechoic chamber or external instruments.

[0066] 3. High accuracy and stability: The system noise is suppressed by digital signal processing algorithms, resulting in good repeatability and applicability to microwave frequency bands.

[0067] 4. High scalability: Automatic measurement switching can be achieved through control logic, and a complete mutual coupling matrix can be established to provide support for array beam calibration and error compensation.

[0068] In summary, this invention achieves high-precision quantitative measurement of inter-array coupling characteristics by combining fixed attenuation with digital computation. This method effectively eliminates spatial radiation interference, accurately reflects the electrical coupling characteristics between the receiving link and channels, and provides stable, reliable, and highly repeatable test results. Its compact structure allows for integration into active phased array antenna systems, enabling online measurement and in-situ calibration, and supports rapid inter-array coupling measurement via software control. This solution is suitable for microwave digital array systems, particularly array architectures with DBF functionality, and possesses excellent engineering feasibility and widespread application value.

[0069] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0070] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is defined only by the appended claims.

Claims

1. A device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna, characterized in that, include: Radiation illumination unit (1), fixed attenuation plate (2), subarray-level digital array antenna (3), active subarray (4), matching load (5), quadrature demodulation unit (6), and signal processing unit (9); The radiation illumination unit (1) is disposed above the array surface of the subarray digital array antenna (3) and is used to radiate a test signal with stable amplitude and consistent phase to the subarray digital array antenna. The subarray-level digital array antenna (3) includes multiple active subarrays (4), one of which serves as a reference subarray (4a) and the other as a leaky subarray (4b). The leaky subarray (4b) is terminated by a matched load (5) and its phase remains orthogonal to that of the reference subarray (4a). The fixed attenuation plate (2) is set on the radiation path between the radiation irradiation unit (1) and the reference subarray (4a). Its attenuation value is fixed and pre-calibrated. It is used to attenuate the main signal received by the reference subarray (4a) to a specific level to prevent it from drowning out the coupling signal of the leakage subarray (4b). The input terminal of the quadrature demodulation unit (6) is connected to the output terminal of the reference subarray (4a) and is used to perform quadrature downconversion and filtering on the mixed radio frequency signal containing the main signal and the coupling signal, and output I-channel and Q-channel baseband signals. The signal processing unit (9) is connected to the output of the quadrature demodulation unit (6) and is used to perform amplitude calculation and differential processing on the I and Q baseband signals. Based on the amplitude difference and the attenuation value of the fixed attenuation plate, the mutual coupling coefficient between the subarrays is calculated.

2. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, The radiation illumination unit (1) is one of a horn antenna, a Vivaldi antenna, or a waveguide antenna, and its operating frequency band covers the receiving frequency band of the active subarray.

3. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, The fixed attenuation plate (2) is a flat plate structure arranged on the radiation path. It is preferably a thin film type fixed attenuator with a fixed attenuation value, which is obtained by calibration experiment and has a typical range of 20 to 40 dB.

4. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, The fixed attenuation plate (2) can also be an absorbing material plate, a dielectric film, or other equivalent attenuation plate structure.

5. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 3 or 4, characterized in that, Several fixed attenuation plates (2) with different attenuation values ​​can be equipped and replaced according to the estimated mutual coupling strength to optimize the system measurement range.

6. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, The quadrature demodulation unit (6) includes an IQ mixer (7) and a low-pass filter (8); the IQ mixer (7) is used to decompose the input radio frequency signal into I and Q signals with a phase difference of 90°, and the low-pass filter (8) is used to filter out high-frequency components and output a smooth baseband signal.

7. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, The signal processing unit (9) includes an analog-to-digital converter (ADC) and a digital signal processor (DSP).

8. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, The resolution of the analog-to-digital converter (ADC) determines the measurement accuracy of the system; when a 12-bit ADC is used, the overall accuracy of the mutual coupling coefficient measurement is 0.5 dB.

9. The device for measuring the mutual coupling coefficient between active subarrays of a subarray-level digital array antenna according to claim 1, characterized in that, When the subarray-level digital array antenna (3) contains more than two active subarrays (4), by switching the subarray configuration, a pair of subarrays can be arbitrarily selected as the reference subarray (4a) and the leaky subarray (4b) respectively for mutual coupling measurement to obtain the complete subarray mutual coupling matrix.

10. A method for measuring the mutual coupling coefficient based on the device according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: A test signal with stable amplitude and consistent phase is radiated to the sub-array digital array antenna (3) through the radiation illumination unit (1); S2: The fixed attenuation plate (2) attenuates the received signal of the reference subarray to a specific level, preventing the main signal from saturating or drowning the coupled signal under test in the subsequent processing link, and ensuring that both signals are within the linear working range of the quadrature demodulation unit. S3: The quadrature demodulation unit (6) performs quadrature down-conversion and filtering on the mixed signal output by the reference subarray (4a) and outputs I and Q baseband signals; S4: The signal processing unit (9) calculates the amplitude values ​​M of the I and Q signals respectively. I and M Q Calculate the amplitude difference ΔM, and then apply the formula... Calculate and store the mutual coupling coefficient C, where A is the attenuation value of the fixed attenuation plate.

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