A switching time modulation harmonic direction finding device and method
By using PIN diodes and compensation networks in the RF switching unit and digital processing module, the impedance mismatch and distortion problems of RF switching modulation in high-frequency applications are solved, achieving high-precision and stable direction of arrival estimation, which is suitable for miniaturized and low-cost direction finding devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI UNIV
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-30
AI Technical Summary
Existing direction finding schemes based on radio frequency switch modulation are prone to impedance mismatch, cutoff leakage and conduction delay problems in high-frequency application scenarios, and lack effective distortion correction and signal reconstruction methods, resulting in limited direction finding accuracy and stability.
Using PIN diodes as RF switching devices, combined with a compensation network and control unit, an equivalent direction-finding signal is generated through time modulation, and a digital processing module is used for signal recovery and direction of arrival estimation. The system includes an RF switching unit, a control unit, an ADC acquisition module, and a digital processing module. Compensation capacitors and inductors are used to improve impedance matching, a high-speed comparator outputs a stable control signal, and the digital processing module performs signal recovery and direction of arrival estimation.
It achieves improved direction finding accuracy and stability under miniaturization and low cost conditions, reduces system complexity and cost, and improves the flexibility of engineering implementation.
Smart Images
Figure CN122307460A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radio frequency signal direction finding technology, and in particular to a switching time modulation harmonic direction finding device and method. Background Technology
[0002] With the rapid evolution of wireless communication, spectrum monitoring, target localization, and electronic reconnaissance technologies, direction-of-arrival (ROA) measurement technology has become a core supporting technology in key areas such as complex electromagnetic environment perception, unmanned platform detection, and space signal localization. As a core means of obtaining target spatial orientation information, the measurement accuracy, system complexity, and engineering implementation capabilities of direction-finding technology directly determine the application effectiveness of related equipment in real-world scenarios.
[0003] Existing direction-finding methods mainly include amplitude comparison direction-finding, phase difference direction-finding, and high-resolution direction-finding based on array signal processing. While these methods have certain advantages in different application scenarios, they typically require multiple receiving channels and have high requirements for inter-channel amplitude and phase consistency, synchronization accuracy, and hardware complexity, resulting in high system costs and significant implementation difficulties. These problems are even more pronounced in miniaturized, low-cost, and highly integrated application scenarios.
[0004] To address the hardware complexity of traditional multi-channel direction finding solutions, the industry is increasingly focusing on signal processing methods based on radio frequency switch modulation. The core idea of this approach is to apply specific modulation relationships to multiple input radio frequency signals through periodic time-domain control of radio frequency switches, transforming multi-channel parallel reception into single / few-channel time-division reception. This reduces the number of receiving links, lowers system size and cost, and improves integration and engineering flexibility, making it particularly suitable for miniaturized unmanned platforms and low-cost monitoring terminals.
[0005] However, existing direction-finding schemes based on radio frequency switch modulation still have many technical bottlenecks, making it difficult to balance hardware simplification and direction-finding performance: switch modulation sequences often use fixed-period on / off control, which can easily introduce problems such as impedance mismatch, cutoff leakage, and conduction delay in high-frequency applications, thus affecting the amplitude and phase consistency of the modulated signal; at the same time, the ability to recover the equivalent signal after sampling is insufficient, and there is a lack of effective compensation and reconstruction methods for switch modulation distortion, which limits the accuracy and stability of subsequent direction of arrival estimation; the digital processing algorithm has poor compatibility with the switch modulation mechanism, and there is a lack of targeted distortion correction and signal reconstruction strategies, which causes the harmonic characteristics of the recovered equivalent signal to be distorted, directly affecting the accuracy and stability of subsequent direction estimation. Summary of the Invention
[0006] The purpose of this invention is to provide a switching time modulation harmonic direction finding device and method that is simple in structure, stable in performance, and capable of recovering the equivalent direction finding signal and estimating the direction of arrival.
[0007] To achieve the above objectives, the present invention provides a switching time-modulated harmonic direction finding device, comprising a radio frequency (RF) switch unit, a control unit, an ADC acquisition module, and a digital processing module; the RF switch unit is used to periodically time-modulate multiple input RF signals and output a modulated RF signal; the control unit is connected to the RF switch unit and is used to output a preset switch control signal to drive the RF switch unit to perform on or off switching; the ADC acquisition module is used to perform analog-to-digital conversion on the modulated RF signal and output a digital sampling signal; the digital processing module is used to process the digital sampling signal, recover the equivalent direction finding signal, and complete the direction of arrival estimation.
[0008] Preferably, the RF switching unit includes a main RF transmission line, a PIN diode, a bias branch, and a compensation network; the PIN diode is connected in series in the middle of the main RF transmission line as an RF switching device; one end of the bias branch is connected to the PIN diode, and the other end is connected to the control unit, for injecting a control bias signal into the PIN diode; the compensation network is disposed on the main RF transmission line for compensating for high-frequency impedance mismatch and optimizing switch transmission and isolation performance.
[0009] Preferably, a series current-limiting resistor and a series choke inductor are sequentially connected in series along the control signal transmission direction on the bias branch; the series current-limiting resistor is used to limit the bias current and suppress control signal surges; the series choke inductor is used to transmit DC or low-frequency control signals and block radio frequency signal leakage.
[0010] Preferably, the compensation network includes a first compensation capacitor, a second compensation capacitor, and a compensation inductor; the first and second compensation capacitors are respectively disposed on the main RF transmission lines on both sides of the PIN diode to improve impedance matching and reduce reflection loss; the bias branch is also provided with a decoupling capacitor in parallel, which is located between the series choke inductor and the series current limiting resistor to bypass high-frequency components and improve the isolation between the bias branch and the main RF path; the compensation inductor is disposed adjacent to the main RF transmission line to optimize switch cutoff isolation performance and reduce conduction insertion loss.
[0011] Preferably, the control unit includes a high-speed comparator; the non-inverting input terminal of the high-speed comparator is connected to the input control signal through a first current-limiting resistor, and the inverting input terminal is connected to the voltage divider reference threshold voltage through a second current-limiting resistor; a first decoupling capacitor and a second decoupling capacitor are connected in parallel to the power supply terminal of the high-speed comparator for power supply filtering and voltage regulation; the output terminal of the high-speed comparator is connected to the input terminal of the bias branch and outputs a regular high and low level control signal.
[0012] The present invention also provides a switching time modulation harmonic direction finding method, comprising the following steps: S1. A radio frequency switching unit is used to perform time modulation of multiple input radio frequency signals with a preset period to generate a modulated radio frequency signal; S2. The modulated combined RF signal is converted from analog to digital by the ADC acquisition module to obtain a digital sampling signal; S3. The digital processing module processes the digital sampled signal using a built-in signal recovery algorithm to recover the equivalent direction finding signal; S4. Based on the reconstructed equivalent direction-finding signal, construct the sample covariance matrix and combine it with the preset direction-finding algorithm model to complete the estimation of the incoming wave direction.
[0013] Preferably, in S1, a high-speed switching control signal is output by the control unit to drive the PIN diode to achieve periodic on and off of the radio frequency path, thereby completing time modulation.
[0014] Preferably, in S3, the digital sampled signal is recovered through digital signal processing, and the equivalent direction finding signal is reconstructed according to the switching modulation sequence.
[0015] Therefore, the present invention employs the above-described switching time modulation harmonic direction finding device and method, which has the following technical advantages: (1) The present invention uses PIN diodes as the core switching device, in conjunction with a compensation network and control unit, eliminating the need for high-precision phase shifters and multi-channel parallel complete receiving links, thereby achieving system miniaturization and cost reduction while retaining the array direction finding capability.
[0016] (2) The present invention improves high-frequency impedance matching, reduces reflection loss, improves the cutoff isolation of the switch and reduces conduction insertion loss through the compensation network (compensation capacitor + compensation inductor); the current limiting resistor, choke inductor and decoupling capacitor of the bias branch work together to effectively suppress interference and ensure the stability of switch control.
[0017] (3) The control unit of the present invention adopts a structure of high-speed comparator and first decoupling capacitor and second decoupling capacitor, which can output high-speed control signal with stable amplitude and clear edge, reduce modulation period drift, and improve the stability and accuracy of time modulation.
[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the structure of the radio frequency switching unit in the switching time modulation harmonic direction finding device of the present invention; Figure 2 This is a schematic diagram of the control unit in a switching time modulation harmonic direction finding device of the present invention; Figure 3 This invention relates to a switching time modulation harmonic direction finding device that controls the modulation frequency to be... The direction finding results under the condition of a 20% duty cycle.
[0020] Figure Labels 1. RF switch unit; 11. Main RF transmission line; 12. PIN diode; 13. Bias branch; 131. Series current limiting resistor; 132. Series choke inductor; 133. Decoupling capacitor; 14. Compensation network; 141. First compensation capacitor; 142. Second compensation capacitor; 143. Compensation inductor; 2. Control unit; 21. High-speed comparator; 22. First current limiting resistor; 23. Second current limiting resistor; 24. Voltage divider reference threshold voltage; 25. First decoupling capacitor; 26. Second decoupling capacitor. Detailed Implementation
[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.
[0023] like Figures 1 to 3 As shown, a switching time modulation harmonic direction finding device includes an RF switch unit 1, a control unit 2, an ADC acquisition module, and a digital processing module. The modules work together to complete the modulation, acquisition, processing, and direction finding of RF signals.
[0024] The RF switch unit 1 is used to periodically time-modulate multiple input RF signals and output modulated RF signals. It includes a main RF transmission line 11, a PIN diode 12, a bias branch 13, and a compensation network 14. The main RF transmission line 11 is used to transmit multiple input RF signals. The PIN diode 12 is connected in series in the middle of the main RF transmission line 11 and serves as the core RF switch device. It controls the on / off state of the RF path by switching between on and off states.
[0025] One end of the bias branch 13 is connected to the PIN diode 12, and the other end is connected to the output terminal of the control unit 2. It is used to inject a DC bias signal into the PIN diode 12 to control its working state. A series current-limiting resistor 131 and a series choke inductor 132 are connected in series along the control signal transmission direction on the bias branch 13. The series current-limiting resistor 131 is used to limit the bias current to prevent the PIN diode 12 from being damaged by overcurrent, and at the same time to suppress the impact interference of the control signal. The series choke inductor 132 is used to transmit DC or low-frequency control signals and block the leakage of radio frequency signals to the bias branch 13. A decoupling capacitor 133 is also connected in parallel on the bias branch 13, located between the series choke inductor 132 and the series current-limiting resistor 131, to bypass the high-frequency components in the control signal and improve the isolation between the bias branch 13 and the main radio frequency path.
[0026] The compensation network 14 is disposed on the main RF transmission line 11 to compensate for high-frequency impedance mismatch and optimize the switching transmission and isolation performance. It includes a first compensation capacitor 141, a second compensation capacitor 142, and a compensation inductor 143. The first compensation capacitor 141 and the second compensation capacitor 142 are respectively connected in series on the main RF transmission line 11 on both sides of the PIN diode 12 to offset the impedance shift caused by the parasitic parameters of the PIN diode 12, improve impedance matching, and reduce reflection loss. The compensation inductor 143 is disposed parallel to the main RF transmission line 11 to suppress RF signal leakage in the cutoff state, optimize the cutoff isolation performance of the switch, and reduce insertion loss in the conduction state.
[0027] Control unit 2 is connected to the bias branch 13 of RF switch unit 1 and is used to output a preset switch control signal to drive RF switch unit 1 to perform on or off switching. Control unit 2 includes a high-speed comparator 21. The non-inverting input terminal of high-speed comparator 21 is connected to an external input control signal through a first current-limiting resistor 22. The inverting input terminal is connected to a voltage divider reference threshold voltage 24 (e.g., 5V, provided by a voltage divider resistor network) through a second current-limiting resistor 23 to realize threshold comparison and level shaping of the input control signal. The power supply terminal of high-speed comparator 21 is connected in parallel with a first decoupling capacitor 25 and a second decoupling capacitor 26 to filter out power supply noise, suppress transient fluctuations, realize voltage regulation, and ensure the stability of the comparator output signal. The output terminal of high-speed comparator 21 is directly connected to the input terminal of bias branch 13 to output a high-low level control signal with stable amplitude and clear edges to drive PIN diode 12 to quickly switch its working state.
[0028] The ADC acquisition module is used to perform analog-to-digital conversion on the modulated radio frequency signal and output a digital sampling signal. The ADC acquisition module uses a high-speed, high-precision ADC chip, and its input terminal is connected to the output terminal of the radio frequency switch unit 1. The sampling clock is provided by a high-precision crystal oscillator to ensure the stability of the sampling timing. After converting the analog modulated signal into a digital signal, it is transmitted to the digital processing module.
[0029] The digital processing module is used to process the digital sampled signal, recover the equivalent direction-finding signal, and complete the direction of arrival estimation. The digital processing module can use a signal recovery algorithm based on time modulation sequence to recover the modulated signal and use a multiple signal classification algorithm (MUSIC) to estimate the direction of arrival. Signal recovery algorithm (TMS signal recovery formula, which is existing technology): Let the harmonic observation vector extracted from the single-channel combined signal be... Wherein, the superscript T indicates the transpose operation; Q represents the highest order of the selected harmonics, and the harmonic observation vector y consists of 2Q+1 harmonic components from -Q to +Q order.
[0030] The original array received signal vector is Define the harmonic coefficient matrix (this matrix is obtained by Fourier expansion of the FPGA-controlled spatiotemporal coding sequence, and represents the mapping relationship between the modulation state of each array element and each order of harmonic components). in Indicates the first The element corresponds to the first The modulation coefficient of the second harmonic. Then, the combined observation and the original signal satisfy a linear relationship. Where y is the harmonic observation vector, x is the original array received signal vector, and A is the harmonic coefficient matrix. Noise term; Under the least squares criterion, the signal recovery problem can be written as: Its closed-form solution is in This indicates the conjugate transpose.
[0031] Multiple signal classification algorithm (MUSIC, existing technology) From the recovered array signal matrix The sample covariance matrix can be constructed. in, The sample covariance matrix represents the recovered signal. This represents the number of snapshots used to construct the sample covariance matrix. Indicates the first The sample number corresponding to each snapshot moment, superscript Indicates conjugate transpose; Its eigenvalues are decomposed into in, This is the eigenvector matrix, and each column... for A feature vector; This is an eigenvalue diagonal matrix, with diagonal elements... For the corresponding eigenvalues, they are usually arranged in descending order, i.e. .
[0032] If the estimated number of information sources is Then the former The eigenvectors corresponding to the large eigenvalues constitute the signal subspace. the remaining The eigenvectors constitute the noise subspace. For a uniform linear array, the angle of incidence is... The guiding vector at time is written as in For wave number, For the spacing between array elements, This is the operating wavelength.
[0033] Then the MUSIC spatial spectral function is right Traversing the angular domain, the angle corresponding to the peak of the spatial spectrum is the estimated angle of arrival (DOA). A switching time modulation harmonic direction finding method includes the following steps: S1. Radio frequency signal time modulation: The control unit 2 outputs a high-speed switching control signal with a preset period, which is injected into the PIN diode 12 through the bias branch 13 to drive the PIN diode 12 to realize the periodic conduction and cutoff of the radio frequency path. The conduction time and cutoff time are preset according to the modulation period and duty cycle to perform time modulation on the multiple input radio frequency signals and generate the modulated radio frequency signal. S2. Analog-to-digital conversion: The ADC acquisition module continuously samples the modulated RF signal at a preset sampling rate, converts the analog signal into a digital sampled signal, and transmits it to the digital processing module; S3. Equivalent direction finding signal recovery: The digital processing module processes the digital sampled signal through the built-in signal recovery algorithm, recovers the equivalent direction finding signals of each channel from the combined sampled signal according to the switching modulation sequence, and reconstructs the equivalent direction finding signal used for wave direction estimation; S4. Direction of Arrival Estimation: Based on the reconstructed equivalent direction-finding signal, a sample covariance matrix is constructed, and the direction of arrival is estimated using the Multiple Signal Classification (MUSIC) algorithm.
[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A switching time-modulated harmonic direction finding device, characterized in that: The system includes an RF switch unit, a control unit, an ADC acquisition module, and a digital processing module. The RF switch unit is used to periodically time-modulate multiple input RF signals and output a modulated RF signal. The control unit is connected to the RF switch unit and is used to output a preset switch control signal to drive the RF switch unit to perform on or off switching. The ADC acquisition module is used to perform analog-to-digital conversion on the modulated RF signal and output a digital sampled signal. The digital processing module is used to process the digital sampled signal, recover the equivalent direction-finding signal, and complete the direction of arrival estimation.
2. The switching time modulation harmonic direction finding device according to claim 1, characterized in that: The radio frequency switching unit includes a main radio frequency transmission line, a PIN diode, a bias branch, and a compensation network. The PIN diode is connected in series in the middle of the main radio frequency transmission line as a radio frequency switching device. One end of the bias branch is connected to the PIN diode, and the other end is connected to the control unit, which is used to inject a control bias signal into the PIN diode. The compensation network is set on the main radio frequency transmission line to compensate for high-frequency impedance mismatch and optimize the switching transmission and isolation performance.
3. The switching time modulation harmonic direction finding device according to claim 2, characterized in that: A series current-limiting resistor and a series choke inductor are sequentially connected in series along the control signal transmission direction on the bias branch; the series current-limiting resistor is used to limit the bias current and suppress control signal surges; the series choke inductor is used to transmit DC or low-frequency control signals and block radio frequency signal leakage.
4. The switching time modulation harmonic direction finding device according to claim 3, characterized in that: The compensation network includes a first compensation capacitor, a second compensation capacitor, and a compensation inductor; the first compensation capacitor and the second compensation capacitor are respectively disposed on the main RF transmission lines on both sides of the PIN diode to improve impedance matching and reduce reflection loss; the bias branch is also provided with a decoupling capacitor in parallel, which is located between the series choke inductor and the series current limiting resistor to bypass high-frequency components and improve the isolation between the bias branch and the main RF path. The compensation inductor is positioned near the main RF transmission line to optimize switch cutoff isolation performance and reduce conduction insertion loss.
5. The switching time modulation harmonic direction finding device according to claim 4, characterized in that: The control unit includes a high-speed comparator; the non-inverting input terminal of the high-speed comparator is connected to the input control signal through a first current-limiting resistor, and the inverting input terminal is connected to the voltage divider reference threshold voltage through a second current-limiting resistor; the power supply terminal of the high-speed comparator is connected in parallel with a first decoupling capacitor and a second decoupling capacitor for power supply filtering and voltage regulation; the output terminal of the high-speed comparator is connected to the input terminal of the bias branch and outputs a regular high and low level control signal.
6. A switching time modulation harmonic direction finding method, based on the direction finding device described in claim 5, characterized in that, Includes the following steps: S1. A radio frequency switching unit is used to perform time modulation of multiple input radio frequency signals with a preset period to generate a modulated radio frequency signal; S2. The modulated combined RF signal is converted from analog to digital by the ADC acquisition module to obtain a digital sampling signal; S3. The digital processing module processes the digital sampled signal using a built-in signal recovery algorithm to recover the equivalent direction finding signal; S4. Based on the reconstructed equivalent direction-finding signal, construct the sample covariance matrix and combine it with the preset direction-finding algorithm model to complete the estimation of the incoming wave direction.
7. The switching time modulation harmonic direction finding method according to claim 6, characterized in that: In S1, the control unit outputs a high-speed switching control signal to drive the PIN diode to achieve periodic on and off of the radio frequency path, thus completing time modulation.
8. The switching time modulation harmonic direction finding method according to claim 6, characterized in that: In S3, the digital sampled signal is recovered through digital signal processing, and the equivalent direction finding signal is reconstructed according to the switching modulation timing.