Wideband high-precision single-channel direction finding device and method based on time division multiplexing phase shift technique

Abstract

The application relates to the technical field of wireless communication signal direction finding, in particular to a wide-band high-precision single-channel direction finding device and method based on time division multiplexing phase shift technology. The device comprises an antenna array for receiving 20MHz-1GHz frequency band signals; an antenna signal processing unit for pre-processing the received 20MHz-1GHz frequency band signals before frequency conversion and centrally transmitting the pre-processed multi-channel signals to a single-channel radio frequency front end; the radio frequency front end is used in the mode of a superheterodyne receiver, and through two-stage frequency conversion, the multi-channel signals are down-converted to 10.7MHz output; a direction finding receiver is used for sampling the 10.7MHz signals output by the radio frequency front end by using a 16-bit high-precision ADC, performing preset algorithm processing through an FPGA, and outputting the calculated wave angle to a display control computer through a gigabit network port together with the received signal spectrum data. The application can reduce the complexity and cost of the equipment, improve the direction finding precision, enhance the anti-interference ability and improve the real-time performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication signal direction finding, and in particular to a wideband high-precision single-channel direction finding device and method based on time division multiplexing phase shift technology. BACKGROUND

[0002] In the field of wireless communication, accurate signal direction finding (direction finding) is a core requirement for applications such as spectrum monitoring, electronic countermeasures, navigation and positioning. Traditional direction finding technology mainly relies on a multi-channel architecture to obtain phase differences of signals through multiple independent receiving channels to calculate the angle of incidence, but existing technical solutions have significant defects:

[0003] High hardware complexity: multiple channels require independent configuration of components such as radio frequency links, analog-to-digital converters (ADCs), etc., resulting in large device size and skyrocketing costs (such as a wideband direction finding system from a foreign country with hardware costs exceeding one million yuan).

[0004] Channel consistency problem: hardware differences between channels (such as amplifier gain, filter characteristics) can introduce phase errors, affecting direction finding accuracy, especially in wide frequency bands.

[0005] Real-time constraints: multi-channel signal synchronization processing requires complex timing control, and processing delay increases significantly with the number of channels, making it difficult to meet dynamic signal monitoring requirements.

[0006] Among existing domestic and foreign technologies, foreign products (such as Germany's Rohde & Schwarz DDF007) have improved performance through wideband design and anti-interference algorithms, but still rely on a multi-channel architecture, with high costs; domestic systems (such as products from China Electronics 54th Research Institute) use spatial spectrum estimation technology, which simplifies some hardware but lacks direction finding accuracy below 200MHz. Similar solutions such as Nanjing Zhongxin Saikesi's "single-channel correlation interferometer direction finding" only calculate angles through amplitude correlation, without addressing the technical bottlenecks of wideband signal transmission and time division multiplexing, and have limited anti-interference capabilities in complex electromagnetic environments. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a wideband high-precision single-channel direction finding device and method based on time division multiplexing phase shift technology to solve the defects of traditional multi-channel direction finding systems in existing technologies, such as high device complexity, high cost, difficulty in ensuring channel consistency, and insufficient real-time performance.

[0008] According to a first aspect of an embodiment of the present application, a wideband high-precision single-channel direction finding device based on time division multiplexing phase shift technology is provided, which includes:

[0009] an antenna array, an antenna signal processing unit, a radio frequency front end, and a direction finding receiver.

[0010] The antenna array is used for receiving 20MHz-1GHz band signals;

[0011] The antenna signal processing unit is used for pre-processing the received 20MHz-1GHz band signals before frequency conversion, and transmitting the pre-processed multi-channel signals to a single-channel radio frequency front end;

[0012] The radio frequency front end is used to adopt a superheterodyne receiver mode, and through two-stage frequency conversion, the multi-channel signals are down-converted to 10.7MHz output;

[0013] The direction finding receiver is used to sample the 10.7MHz signal output by the radio frequency front end using a 16-bit high-precision ADC, and through FPGA, a preset algorithm is processed, and after the wave angle is calculated, the received signal spectrum data is output to a display control computer through a gigabit network port.

[0014] Further, the antenna array comprises:

[0015] The first circular array is a 6-element circular array with a radius of 0.5m and an array length of 0.76m, and is used for receiving 20MHz-200MHz band signals;

[0016] The second circular array is a 6-element circular array with a radius of 0.08m and an array length of 0.16m, and is used for receiving 200MHz-1GHz band signals;

[0017] The central omnidirectional dipole antenna is located at the center of the second circular array, and is used to provide a reference signal.

[0018] Further, the antenna signal processing unit comprises:

[0019] The first antenna signal processing unit is used for processing 20MHz-200MHz band signals, and comprises:

[0020] At least one low-noise amplifier, the input ends of which are independently connected to the antennas in the first circular array;

[0021] A combiner, the input end of which is connected to the output end of the low-noise amplifier, divides the antenna circular array signal, and one of the divided signals is synthesized as a reference signal as a first output, and the other is a second output;

[0022] A first gating switch, the first input end of which is connected to the second output end of the combiner;

[0023] A first phase shifter, the first input end of which is connected to the output end of the first gating switch, the second input end is connected to the first output end of the combiner, and the output end is connected to a preset switching gating switch;

[0024] The second antenna signal processing unit is used to process 200MHz~1GHz frequency band signals, including:

[0025] a second selection switch, whose input terminals are respectively connected to the 6-element dipole antennas in the second circular array;

[0026] The second phase shifter has a first input end connected to the output end of the second selection switch, a second input end connected to the central omnidirectional dipole antenna, and an output end connected to the switching selection switch.

[0027] Furthermore, the second antenna signal processing unit adopts a 6-element dipole antenna array and a 1-element omnidirectional dipole antenna structure;

[0028] Wherein, the output end of each antenna in the 6-element dipole antenna array is connected to an impedance matching circuit and then connected to the input end of the second selection switch;

[0029] The output end of the central omnidirectional dipole antenna is connected to the second input end of the second phase shifter after passing through an impedance matching circuit, and serves as a reference signal input end;

[0030] The second gating switch is used for time-sharing gating of any antenna signal in the 6-element dipole antenna array;

[0031] The second phase shifter uses a parallel resistor network to optimize the broadband characteristics of the 200MHz~1GHz frequency band to achieve four-phase switching of 0°, 90°, 180°, and 270°.

[0032] Furthermore, the radio frequency front end includes:

[0033] It consists of a frequency conversion channel unit, a local oscillator unit, a reference clock unit, a power supply unit and a main control unit.

[0034] Furthermore, the frequency conversion channel unit of the radio frequency front end includes:

[0035] The first frequency conversion channel is used to down-convert the 20MHz~1GHz RF signal to a 2GHz intermediate frequency; wherein the local oscillator frequency range is 2.02GHz~3GHz;

[0036] The second frequency conversion channel is used to down-convert the first intermediate frequency signal to a second intermediate frequency output of 10.7MHz using a fixed local oscillator of 2010.7MHz, and supports normal spectrum output.

[0037] Furthermore, the direction-finding receiver includes:

[0038] The ADC unit uses a 16-bit high-precision ADC to receive the 10.7MHz analog intermediate frequency signal output by the RF front end, and transmits it to the FPGA through a high-speed data bus after sampling;

[0039] The FPGA core processing unit integrates time-division multiplexing control, phase extraction, adaptive filtering, and angle calculation modules. It implements real-time signal processing through hardware acceleration and outputs direction-finding results to the Gigabit Ethernet port.

[0040] Gigabit network port unit: used to encapsulate FPGA processing results into Ethernet data frames and transmit them to the display and control computer, while receiving parameter settings from the display and control terminal and transmitting them back to the FPGA;

[0041] Power supply and clock unit: used to provide stable power supply and reference clock for each module to ensure the synchronization of ADC sampling and FPGA processing timing.

[0042] According to a second aspect of an embodiment of the present invention, there is provided a method for wideband, high-precision, single-channel direction finding based on time-division multiplexing phase-shifting technology, which is applied to any of the above-mentioned wideband, high-precision, single-channel direction finding devices based on time-division multiplexing phase-shifting technology, characterized in that the method comprises:

[0043] Receive 20MHz~1GHz frequency band signals;

[0044] Pre-processing the received 20MHz~1GHz frequency band signal before frequency conversion, and centrally transmitting the pre-processed multi-channel signal to a single-channel RF front end;

[0045] Using a superheterodyne receiver, the multi-channel signal is down-converted to 10.7 MHz output through two-stage frequency conversion;

[0046] A 16-bit high-precision ADC is used to sample the 10.7MHz signal output from the RF front end. The signal is processed by a preset algorithm through the FPGA. After the outgoing wave angle is calculated, the received signal spectrum is output to the display and control computer through the Gigabit network port.

[0047] Furthermore, the preset algorithm processing is performed by FPGA to calculate the outgoing wave angle, and the received signal spectrum is output to the display and control computer through the gigabit network port, including:

[0048] Based on the preset combiner amplitude formula, the phase difference between the array element and the reference signal is extracted from the ADC data;

[0049] A multi-baseline combination algorithm is used to combine phase difference data to calculate the incoming wave angle, and the received signal spectrum is output to the display and control computer through the Gigabit network port.

[0050] Furthermore, the preset combined amplitude formula includes:

[0051] (1)

[0052] Among them, E1, E2, E3, and E4 are the signal amplitudes after the incoming signal is phase-shifted by 0°, 90°, 180°, and 270° and then superimposed with the reference signal.

[0053] The technical solutions provided by the embodiments of the present invention may have the following beneficial effects:

[0054] This invention significantly reduces hardware complexity and cost through phase-shifting technology and a single-channel architecture for centralized transmission of wideband multi-channel signals. It replaces traditional multi-channel RF links with time-division multiplexing (TDDM) gating switches and single-channel phase shifters, while the single-channel architecture eliminates phase differences between channels. It improves direction-finding accuracy and real-time processing capabilities through a multi-baseline phase difference combination algorithm and a wideband antenna array design. Time-division multiplexing and FPGA hardware acceleration ensure real-time signal processing.

[0055] In addition, the RF front-end multi-stage filtering combined with the FPGA adaptive filtering algorithm enhances anti-interference capabilities, and the display and control end supports dynamic parameter adjustment to adapt to complex electromagnetic environments; the band antenna design achieves full frequency band coverage from 20MHz to 1GHz, solving the problem of broadband directionality degradation of traditional arrays. The modular design supports rapid deployment and maintenance, and the low power consumption characteristics are adapted to the application needs of multiple scenarios such as portable and vehicle-mounted.

[0056] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] 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.

[0058] Figure 1 1 is a schematic diagram showing the composition of a wide-band, high-precision, single-channel direction-finding device based on time-division multiplexing phase-shifting technology according to an exemplary embodiment;

[0059] Figure 2 is a schematic diagram of a 20 MHz to 1 GHz antenna array according to an exemplary embodiment;

[0060] Figure 3 is a block diagram showing the working principle of a multi-channel centralized transmission phase shifter direction finding system according to an exemplary embodiment;

[0061] Figure 4 is a principle block diagram of a 20 MHz to 200 MHz frequency band phase shifter according to an exemplary embodiment;

[0062] Figure 5 is a principle block diagram of a 200 MHz to 1 GHz frequency band phase shifter according to an exemplary embodiment;

[0063] Figure 6 is a working principle block diagram of a direction finding radio frequency front end according to an exemplary embodiment;

[0064] Figure 7 is a principle block diagram of a direction finding receiver according to an exemplary embodiment;

[0065] Figure 8 is a single channel phase difference calculation diagram according to an exemplary embodiment;

[0066] Figure 9 is a wave coming diagram of an antenna according to an exemplary embodiment;

[0067] Figure 10 is a flow diagram of a wideband high-precision single channel direction finding method based on time division multiplexing phase shift technology according to an exemplary embodiment. DETAILED DESCRIPTION

[0068] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers refer to the same or similar elements throughout the drawings. The embodiments described in the following exemplary embodiments are not meant to represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0069] Embodiment One

[0070] Referring to Figure 1 , Figure 1 is a wideband high-precision single channel direction finding device composition diagram based on time division multiplexing phase shift technology according to an exemplary embodiment, the device comprises:

[0071] an antenna array 10, an antenna signal processing unit 20, a radio frequency front end 30, a direction finding receiver 40;

[0072] The antenna array 10 is used to receive 20MHz~1GHz frequency band signals;

[0073] The antenna signal processing unit 20 is used to pre-process the received 20MHz~1GHz frequency band signals before frequency conversion, and transmit the pre-processed multi-channel signals to the single channel radio frequency front end 30;

[0074] The radio frequency front end 30 is used to adopt the mode of superheterodyne receiver, and through two-stage frequency conversion, the multi-channel signals are down-converted to 10.7MHz output;

[0075] The direction finding receiver 40 is configured to sample the 10.7MHz signal output by the radio frequency front end 30 using a 16-bit high-precision ADC, and perform preset algorithm processing through an FPGA. After the angle of arrival is calculated, the received signal spectrum is output to a display and control computer through a gigabit network port.

[0076] In a specific implementation, the antenna array 10 is configured to receive radio signals. The antenna signal processing unit 20 is responsible for signal impedance conversion, amplification, gating, phase shifting, and combining processing. The radio frequency front end 30 is responsible for down-converting and gain adjusting the received signal, and converting the radio frequency signal into a baseband signal. The direction finding receiver 40 is configured to sample and demodulate the signal, and output the angle of arrival according to a direction finding algorithm.

[0077] The antenna signal processing unit 20 is configured to perform pre-processing on the antenna signal before frequency conversion, including impedance matching, amplification, gating of multi-channel signals, phase shifting, and combining processing. The phase shifter technology can be used in phased array radar, radio signal direction finding, signal source output phase control, and other fields.

[0078] The radio frequency front end 30 adopts a superheterodyne receiver mode, and converts the signal to 10.7MHz through two-stage frequency conversion, and flexibly sets the signal gain through a gain digital adjustable chip.

[0079] The direction finding receiver 40 uses a 16-bit high-precision ADC to sample the radio frequency, and performs fast algorithm processing through an FPGA. After the angle of arrival is calculated, the received signal spectrum is output to a display and control computer through a gigabit network port.

[0080] In addition to angle and spectrum display, the display and control computer interface can set the receiving frequency point, single-channel radio frequency front end 30 gain, and digital filter bandwidth, to enhance the system's anti-interference performance and useful signal processing capability.

[0081] In a specific implementation, please refer to Figure 2 The antenna array 10 is configured to receive signals in the 20MHz-1GHz frequency band. Considering the direction finding accuracy and phase ambiguity, the antenna array 10 is designed as two partial circular arrays, which are respectively for the 20MHz-200MHz and 200MHz-1GHz frequency bands.

[0082] In one embodiment, the antenna signal processing unit 20 includes:

[0083] The first antenna signal processing unit is configured to process signals in the 20MHz-200MHz frequency band, and includes:

[0084] The at least one low-noise amplifier has an input end independently connected to an antenna in the first circular array.

[0085] A combiner, whose input end is connected to the output end of the low noise amplifier, splits the antenna circular array signal, and synthesizes a reference signal into one path as the first output and the other path as the second output;

[0086] a first gating switch, a first input end of which is connected to the second output end of the combiner;

[0087] a first phase shifter, having a first input end connected to the output end of the first gating switch, a second input end connected to the first output end of the combiner, and an output end connected to a preset switching gating switch;

[0088] The second antenna signal processing unit is used to process 200MHz~1GHz frequency band signals, including:

[0089] a second selection switch, whose input terminals are respectively connected to the 6-element dipole antennas in the second circular array;

[0090] The second phase shifter has a first input end connected to the output end of the second selection switch, a second input end connected to the central omnidirectional dipole antenna, and an output end connected to the switching selection switch.

[0091] For specific implementation, please refer to Figure 3 The antenna signal processing unit 20 includes a 20MHz~200MHz antenna signal processing unit and a 200MHz~1GHz antenna signal processing unit. Among them, the 20MHz~200MHz antenna signal processing unit first matches the multi-channel signal impedance to 50Ω through an impedance 4:1 transformation, and then after amplification by the low noise amplifier LNA and 1-to-2 power division, one signal is combined as a reference signal, and the other enters the selection switch, and the time-division switching of a certain array element signal is turned on and enters the phase shifter for 0°, 90°, 180°, and 270° phase shifting. The phase shifting process is an analog phase shift, which is achieved by switching the diode selection through the time-division control signal. This part is the key technology of the antenna signal processing unit 20. Figure 4 、 Figure 5 The phase-shifted signal is combined with the reference signal and then switched to a gate switch to control whether the signal is passed to the RF front-end 30 module.

[0092] More specifically, the second antenna signal processing unit adopts a 6-element dipole antenna array 10 and a 1-element omnidirectional dipole antenna structure;

[0093] Wherein, each antenna output end of the 6-element dipole antenna array 10 is connected to the input end of the second selection switch after passing through an impedance matching circuit;

[0094] The output end of the central omnidirectional dipole antenna is connected to the second reference signal input end of the second phase shifter after passing through an impedance matching circuit;

[0095] The second gating switch is used to time-share gating any antenna signal in the 6-element dipole antenna array 10;

[0096] The second phase shifter uses a parallel resistor network to optimize the broadband characteristics of the 200MHz~1GHz frequency band to achieve four-phase switching of 0°, 90°, 180°, and 270°.

[0097] Specifically, the 200MHz~1GHz antenna signal processing unit adopts a 6-element dipole antenna array 10 and a 1-element omnidirectional dipole antenna structure. The 6-element array signal enters the selection switch after impedance matching, and the time-division switching of a certain array element signal is turned on, and enters the phase shifter for 0°, 90°, 180°, and 270° phase shifting. The phase-shifted signal is combined with the signal received by the central omnidirectional reference array element, and the selection switch is switched to control whether the signal is transmitted to the RF front-end 30 module.

[0098] For details, please refer to Figure 4 In this application, the function of the phase shifter is to achieve 0°, 90°, 180°, and 270° phase shifts on the input signal. First, the signal is divided into two paths by a power divider, and the 90° phase shift function is achieved through different capacitor and inductor values. Then, the inversion and signal channel selection are achieved by controlling the PIN diodes D1 to D8. For example, when D1 and D4 are turned on, the signal phase shifts by 0°; when D2 and D3 are turned on, the signal enters the balun in the opposite direction, and the signal phase shifts by 180°; when D5 and D8 are turned on, the signal phase shifts by 90°; when D6 and D7 are turned on, the signal phase shifts by 270°.

[0099] More specifically, the operating principle of the 200MHz to 1GHz phase shifter is the same as that of the 20MHz to 200MHz phase shifter, except that the link with a 0° phase shift has multiple parallel resistors.

[0100] In specific implementation, the 20MHz-200MHz frequency band phase shifter shown in the figure uses a power divider to split the input signal into two paths, creating 0° / 180° and 90° / 270° phase-shifted links, respectively. The uplink achieves a 0° or 180° phase shift by controlling the conduction state of PIN diodes D1-D4. The downlink utilizes an RC network to initially achieve a fixed 90° phase shift, then controls D5-D8 to achieve a 90° or 270° phase shift. The two signals are combined in a combiner and then synthesized with a reference signal in the final combiner, outputting a signal with four selectable phases: 0°, 90°, 180°, and 270°.

[0101] The core technology of this phase shifter utilizes the switching characteristics of PIN diodes and hardware circuits (such as baluns and LC networks) to achieve precise phase control across a wide bandwidth, meeting the multi-phase signal requirements of direction-finding algorithms. Its hardware design offers significant advantages: the balun improves impedance matching performance across a wide bandwidth and reduces phase error; the use of power dividers and combiners supports single-channel time-sharing processing of multi-element signals, significantly simplifying the hardware architecture and reducing cost and size.

[0102] Need to explain, Figure 5 The 200MHz-1GHz phase shifter operates on a similar principle to its lower-frequency counterparts, both utilizing a power splitter to achieve four-phase shifting in two paths. The difference lies in the addition of a parallel resistor to the high-frequency 0° link to optimize impedance matching and signal attenuation, ensuring phase shift accuracy across the 200MHz-1GHz bandwidth and addressing the high-frequency performance degradation of traditional phase shifters. Structurally, the signal undergoes power splitting, two-path phase shifting (0° / 180° and 90° / 270°), and combining. The combined signal is then combined with a reference signal to produce a four-phase signal, providing phase difference data for the direction-finding algorithm.

[0103] The RF front end 30 is used to convert RF signals into a baseband signal frequency range suitable for digital signal processing. The amplifier gain is adjusted to ensure that signals of different strengths can be effectively amplified without distortion. The RF front end 30 consists of a frequency conversion channel unit, a local oscillator unit, a reference clock unit, a power supply unit, and a main control unit. It adopts a secondary frequency conversion scheme. The detailed working principle block diagram is shown in the figure. Figure 6 shown.

[0104] In specific implementation, the module uses a two-frequency conversion scheme to convert the 20MHz~1GHz RF signal to a 10.7MHz intermediate frequency. The first frequency conversion uses a high local oscillator with an adjustable local oscillator frequency of 2.02GHz~3GHz, and an intermediate frequency output of 2GHz; the second frequency conversion also uses a high local oscillator with a fixed local oscillator frequency of 2010.7MHz. The second intermediate frequency output is 10.7MHz, and the output is a positive spectrum output.

[0105] In practice, the direction-finding RF front-end 30 operates as follows: the 20MHz-1GHz RF signal (RF_IN) is initially filtered by a 1GHz low-pass filter, its intensity is dynamically adjusted by an adjustable attenuator, and after amplification and secondary filtering by a two-stage RF amplifier, it enters the first frequency conversion phase: mixing with a 2.02GHz-3GHz adjustable local oscillator (LO) to generate a 2GHz IF. This is then subjected to dielectric filtering and amplification by the IF. It then enters the second frequency conversion phase: mixing with a fixed 2010.7MHz LO to generate a 10.7MHz IF. This is then subjected to multiple stages of IF amplification, 10.7MHz filtering, and adjustable attenuation, ultimately outputting IF_OUT (10.7MHz). Simultaneously, the MCU controls the LO frequency and module parameters, provides synchronization timing with a reference clock, and converts the +12V power supply to power each module, ensuring efficient frequency conversion and preprocessing of the broadband signal. This provides a stable IF signal for the subsequent phase difference calculation and angle resolution of the direction-finding receiver 40, supporting the device's high-precision direction-finding performance.

[0106] More specifically, the direction-finding RF front-end 30 converts the 20MHz~1GHz broadband signal into a uniform 10.7MHz fixed intermediate frequency through two frequency conversions. It is compatible with single-channel ADC sampling and FPGA processing to simplify hardware design. The fixed second intermediate frequency facilitates the development of digital filters, and the adjustable attenuator and multi-stage amplification ensure that the signal dynamic range is distortion-free, thereby improving the direction-finding accuracy. At the same time, the multi-stage filtering structure of 1GHz low-pass filter, dielectric filter, and 10.7MHz bandpass is combined with MCU dynamic control to effectively suppress out-of-band interference and adapt to complex electromagnetic environments, realizing the synergy of the technical advantages of broadband adaptation, high stability and strong anti-interference capability, and providing reliable support for the precise signal processing of the subsequent direction-finding receiver 40.

[0107] In one embodiment, a program is written in the direction-finding receiver 40 using the digital signal processing software Vivado to implement time-division multiplexing control, phase extraction, and adaptive filtering algorithms. By programming the switching sequence of each antenna element, the signal is accurately transmitted to the single-channel RF front-end 30 in sequence. A phase extraction algorithm is written to calculate the phase of the received baseband signal and obtain the phase difference between adjacent antenna element signals. The filtering coefficient is adjusted based on the characteristics of the interference signal to suppress the interference signal.

[0108] See also Figure 7In specific implementation, the direction finding receiver 40 mainly performs ADC sampling, FPGA data processing, digital communication interface and antenna driving interface. The ADC selects a 16-bit ADC with a sampling rate of 125 Mbps, which can sample a 10.7 MHz intermediate frequency signal low pass; the FPGA is an A7 series chip of xilinx, which meets the requirements of direction finding algorithm processing and spectrum display; the network port is designed with a gigabit network chip, which meets the transmission rate requirement; the control and driving part of the antenna mainly uses an NPN transistor driving circuit, which improves the driving ability of the FPGA.

[0109] In the direction finding receiver 40, the time division multiplexing control, phase extraction and adaptive filtering algorithm are realized by using the digital signal processing software vivado to write programs. The switching timing of the switch is controlled by programming to ensure that the signal of each antenna unit can be accurately transmitted to the single-channel radio frequency front end 30 in turn. The phase extraction algorithm is written to calculate the phase of the received baseband signal and obtain the phase difference of each baseline antenna unit signal. According to the characteristics of the interference signal, the filtering coefficient is adjusted to suppress the interference signal.

[0110] In specific implementation, the application adopts the phase shift technology based on wideband multi-channel signal centralized transmission. When used in a single-channel direction finding device, compared with a multi-channel system, the number of hardware is greatly reduced, the complexity and cost of the equipment are reduced, and the error caused by inconsistency between channels is also reduced. According to the principle of single-channel direction finding, the signals of each array element are phase-shifted and combined with the reference signal, the signal amplitude is extracted, the phase difference between the reference signal and each array element received signal is calculated according to the algorithm, and the appropriate measurement baseline is selected according to the phase difference, and the phase difference between different array elements is calculated to calculate the angle of arrival. The single-channel phase difference algorithm is as follows.

[0111] Figure 8 As shown in the figure, the reference signal is A, the incoming wave signal is B, E1, E2, E3 and E4 are the signal amplitudes of the signals B after being phase-shifted by 0°, 90°, 180° and 270° and then superimposed with the reference signal A, and the angle of arrival is calculated according to the amplitudes. The angle of arrival is mainly calculated according to the following formula.

[0112] According to the principle of vector synthesis, they satisfy the following formula:

[0113]

[0114]

[0115] (1)

[0116]

[0117] From the above formula, we can get:

[0118]

[0119] (2)

[0120] Thus, the phase difference between each antenna element and the reference element can be obtained:

[0121] (3)

[0122] The above formula can be used to calculate the phase difference between the reference array element and each array element. Then, by selecting different baselines and subtracting the signals between the array elements, the influence of the system's inherent phase difference can be eliminated and the outgoing wave angle can be calculated.

[0123] See also Figure 9 If baselines 1-4, 2-5, and 3-6 are used to calculate the incoming wave, the following formula is obtained, where θ is the incoming wave angle, E11 represents the amplitude of antenna A1's phase shift of 0°, E12 represents the amplitude of antenna A1's phase shift of 90°, E13 represents the amplitude of antenna A1's phase shift of 180°, E21 represents the amplitude of antenna A2's phase shift of 0°, E22 represents the amplitude of antenna A2's phase shift of 90°, and so on.

[0124] According to the schematic diagram, the calculation formula is as follows:

[0125] (4)

[0126] Divide the above formula 2 by formula 1, and divide formula 3 by formula 1:

[0127] (5)

[0128] θ can be calculated using the following two formulas. The average of the two θs is the angle of the incoming wave.

[0129] (6)

[0130] In practice, calculating the incoming wave angle is a core function of the direction-finding system. Its core role is to accurately determine the incident direction of wireless signals, providing key spatial parameters for scenarios such as spectrum monitoring and electronic countermeasures. Using the phase difference algorithm and multi-baseline combination model described in this application, the angle calculation directly verifies the effectiveness of the wideband phase-shifting technology and single-channel architecture, ensuring a direction-finding accuracy of ≤1.5° RMS within the 20MHz to 1GHz frequency band, becoming a core metric for measuring system performance.

[0131] In practical applications, the angle of incoming waves provides decision-making support in multiple fields: in spectrum management, it combines the signal spectrum to form a "frequency-azimuth" two-dimensional monitoring capability, helping to identify illegal emission sources and interference distribution; in military scenarios, real-time calculated angle data can quickly locate the direction of enemy communications or radar equipment, providing dynamic azimuth guidance for electronic countermeasures and strike operations; in the field of communications and navigation, this angle is used to calibrate antenna pointing, distinguish multipath signals, and optimize wireless link coverage and positioning accuracy.

[0132] Specifically, from a technical perspective, the calculation of incoming wave angles relies on multi-element phase difference data from the antenna array 10. A multi-baseline algorithm eliminates individual element errors, optimizing spatial resolution. This data forms a closed loop with the pure intermediate frequency (IF) signal output by the RF front-end 30. This high-quality signal ensures angle calculation accuracy, and the angle result feeds back into the adaptive filtering module to dynamically suppress noise in the direction of interference. Furthermore, angle data is transmitted to the display and control system via a Gigabit Ethernet port, forming a closed loop of "calculation-display-parameter adjustment" for human-computer interaction, enhancing the system's intelligent adaptability in complex environments.

[0133] More specifically, the method and hardware implementation for calculating the incoming wave angle are one of the core innovations. This approach replaces traditional multi-channel solutions with a single-channel time-division multiplexing architecture, reducing hardware complexity and cost. This approach leverages FPGA hardware acceleration algorithms (such as inverse tangent lookup tables and parallel multipliers) for real-time processing, thus overcoming the cost-efficiency trade-off between existing technologies. The angle calculation algorithm and logic design constitute the technical foundation of this application, ensuring its irreplaceable position in the field of wideband signal direction finding.

[0134] In one embodiment, see Figure 10 , Figure 10 This is a flow chart of a wideband, high-precision, single-channel direction finding method based on time-division multiplexing phase-shifting technology according to an exemplary embodiment. The method includes:

[0135] S1. Receive 20MHz~1GHz frequency band signals;

[0136] S2. The received 20MHz~1GHz frequency band signal is pre-processed before frequency conversion, and the pre-processed multi-channel signal is centrally transmitted to the single-channel RF front end 30;

[0137] S3 uses a superheterodyne receiver, through secondary frequency conversion, the multi-channel signal is down-converted to 10.7MHz output;

[0138] S4. Use a 16-bit high-precision ADC to sample the 10.7 MHz signal output from the RF front end 30, perform a preset algorithm processing through the FPGA, calculate the outgoing wave angle, and output it to the display and control computer through the gigabit network port together with the received signal spectrum.

[0139] More specifically, the preset algorithm processing is performed by FPGA to calculate the outgoing wave angle and output the received signal spectrum to the display and control computer through the gigabit network port, including:

[0140] Based on the preset combiner amplitude formula, the phase difference between the array element and the reference signal is extracted from the ADC data;

[0141] A multi-baseline combination algorithm is used to combine phase difference data to calculate the incoming wave angle, and the received signal spectrum is output to the display and control computer through the Gigabit network port.

[0142] In specific implementation, Figure 8 As shown in Figure 1, the reference signal is A, the incoming signal is B, and E1, E2, E3, and E4 are the amplitudes of signal B after phase shifting by 0°, 90°, 180°, and 270°, and then adding them to the vector of reference signal A. The incoming signal angle is calculated based on these amplitudes. This calculation is primarily based on the following formula.

[0143] According to the principle of vector synthesis, they satisfy the above formula (1):

[0144] From the above formula (1), we can get formula (2):

[0145] From this, the phase difference formula between each antenna array element and the reference array element can be obtained, referring to the above formula (3):

[0146] The above formula can be used to calculate the phase difference between the reference array element and each array element. Then, by selecting different baselines and subtracting the signals between the array elements, the influence of the system's inherent phase difference can be eliminated and the outgoing wave angle can be calculated.

[0147] See also Figure 9 If baselines 1-4, 2-5, and 3-6 are used to calculate the incoming wave, the following formula is obtained, where θ is the incoming wave angle, E11 represents the amplitude of antenna A1's phase shift of 0°, E12 represents the amplitude of antenna A1's phase shift of 90°, E13 represents the amplitude of antenna A1's phase shift of 180°, E21 represents the amplitude of antenna A2's phase shift of 0°, E22 represents the amplitude of antenna A2's phase shift of 90°, and so on.

[0148] According to the schematic diagram, the calculation formula is as shown in formula (4);

[0149] Divide formula 2 by formula 1, and divide formula 3 by formula 1 to obtain formula (5).

[0150] After that, two formulas of θ can be calculated, and the angle of arrival is obtained by averaging the two θs, as shown in formula (6).

[0151] In one embodiment, based on the phase shift technology of wideband multi-channel signal centralized transmission, the phase shift of each array element signal is combined with the reference signal to extract the signal amplitude, the phase difference between the reference signal and the received signal of each array element is calculated according to the algorithm, the appropriate measurement baseline is selected according to the phase difference, the phase difference between different array elements is calculated, and the angle of arrival is calculated.

[0152] In specific implementation, the calculation of the angle of arrival is the core function of the direction finding system, and the core role is to accurately determine the incident direction of the wireless signal, to provide a key spatial parameter for spectrum monitoring, electronic countermeasure and the like. Through the phase difference algorithm and the multi-baseline combination model in the present application, the angle calculation result directly verifies the effectiveness of the wideband phase shift technology and the single-channel architecture, ensures that the device realizes a direction finding precision of ≤1.5°RMS in a frequency band of 20MHz-1GHz, and becomes a core index for measuring the performance of the system.

[0153] Specifically, the above device and method provided by the embodiments of the present application can reduce the complexity and cost of the equipment, improve the direction finding precision, enhance the anti-interference capability, and improve the real-time performance.

[0154] It can be understood that the same or similar parts in the above embodiments can be mutually referred to, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0155] It should be noted that, in the description of the present application, the terms "first", "second" and the like are only used for description purpose, and cannot be understood as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is at least two.

[0156] Any process or method descriptions in flow charts or otherwise described herein can be understood as representing code modules, segments, or portions of code which include one or more executable instructions for implementing specific logic functions (or steps) in the process, and the various embodiments of the present application include additional implementations in which the order of execution or the specific logic functions (or steps) can be changed, including by having the steps performed at least partially concurrently with, in reverse order of presented, or in other orders, depending on the functionality involved as would be understood by one skilled in the art.

[0157] It should be understood that various components of the present invention may be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods may be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof may be used: a discrete logic circuit having logic gate circuits for implementing logic functions on data signals, an application-specific integrated circuit having suitable combinational logic gate circuits, a programmable gate array (PGA), a field-programmable gate array (FPGA), etc.

[0158] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0159] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing module, or each unit may exist physically separately, or two or more units may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or in the form of software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium.

[0160] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0161] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0162] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A broadband, high-precision, single-channel direction-finding device based on time-division multiplexing phase-shifting technology, characterized in that: The device comprises: Antenna array, antenna signal processing unit, RF front end, direction finding receiver; The antenna array is used to receive signals in the 20MHz to 1GHz frequency band; The antenna signal processing unit is used to pre-process the received 20MHz to 1GHz frequency band signal before frequency conversion, and centrally transmit the pre-processed multi-channel signal to the single-channel RF front end; The RF front end is used to down-convert the multi-channel signal to 10.7 MHz output through two-stage frequency conversion by adopting a superheterodyne receiver; The direction-finding receiver is used to sample the 10.7MHz signal output by the RF front end using a 16-bit high-precision ADC, perform a preset algorithm processing through the FPGA, calculate the outgoing wave angle, and output the received signal spectrum data to the display and control computer through the gigabit network port; The antenna signal processing unit includes: The first antenna signal processing unit is used to process signals in the 20 MHz to 200 MHz frequency band, including: at least one low-noise amplifier, whose input terminals are independently connected to the antennas in the first circular array; A combiner, whose input end is connected to the output end of the low noise amplifier, splits the antenna circular array signal, and synthesizes a reference signal into one path as the first output and the other path as the second output; a first gating switch, a first input end of which is connected to the second output end of the combiner; a first phase shifter, having a first input end connected to the output end of the first gating switch, a second input end connected to the first output end of the combiner, and an output end connected to a preset switching gating switch; The second antenna signal processing unit is used to process signals in the 200 MHz to 1 GHz frequency band, including: a second selection switch, whose input terminals are respectively connected to the 6-element dipole antennas in the second circular array; The second phase shifter has a first input end connected to the output end of the second selection switch, a second input end connected to the central omnidirectional dipole antenna, and an output end connected to the switching selection switch.

2. The device according to claim 1, characterized in that The antenna array comprises: The first circular array is a 6-element circular array with a radius of 0.5m and an array length of 0.76m, used to receive signals in the 20MHz to 200MHz frequency band; The second circular array is a 6-element circular array with a radius of 0.08m and an array length of 0.16m, used to receive signals in the 200MHz to 1GHz frequency band; The central omnidirectional dipole antenna is located at the center of the second circular array and is used to provide a reference signal.

3. The device according to claim 1, characterized in that The second antenna signal processing unit adopts a 6-element dipole antenna array and a 1-element omnidirectional dipole antenna structure; Wherein, the output end of each antenna in the 6-element dipole antenna array is connected to an impedance matching circuit and then connected to the input end of the second selection switch; The output end of the central omnidirectional dipole antenna is connected to the second input end of the second phase shifter after passing through an impedance matching circuit, and serves as a reference signal input end; The second gating switch is used for time-sharing gating of any antenna signal in the 6-element dipole antenna array; The second phase shifter uses a parallel resistor network to optimize the broadband characteristics of the 200MHz to 1GHz frequency band, and is used to achieve four-phase switching of 0°, 90°, 180°, and 270°.

4. The device according to claim 1, characterized in that The radio frequency front end includes: It consists of a frequency conversion channel unit, a local oscillator unit, a reference clock unit, a power supply unit and a main control unit.

5. The device according to claim 4, characterized in that The frequency conversion channel unit of the radio frequency front end includes: The first frequency conversion channel is used to up-convert the 20 MHz to 1 GHz radio frequency signal to a 2 GHz intermediate frequency; wherein the local oscillator frequency range is 2.02 GHz to 3 GHz; The second frequency conversion channel is used to down-convert the first intermediate frequency signal to a second intermediate frequency output of 10.7MHz using a fixed local oscillator of 2010.7MHz, and supports normal spectrum output.

6. The device according to claim 1, characterized in that The direction-finding receiver comprises: The ADC unit uses a 16-bit high-precision ADC to receive the 10.7MHz analog intermediate frequency signal output by the RF front end, and transmits it to the FPGA through a high-speed data bus after sampling; The FPGA core processing unit integrates time-division multiplexing control, phase extraction, adaptive filtering, and angle calculation modules. It implements real-time signal processing through hardware acceleration and outputs direction-finding results to the Gigabit Ethernet port. Gigabit network port unit: used to encapsulate FPGA processing results into Ethernet data frames and transmit them to the display and control computer, while receiving parameter settings from the display and control terminal and transmitting them back to the FPGA; Power supply and clock unit: used to provide stable power supply and reference clock for each module to ensure the synchronization of ADC sampling and FPGA processing timing.

7. A wideband high-precision single-channel direction finding method based on time-division multiplexing phase-shifting technology, applied to a wideband high-precision single-channel direction finding device based on time-division multiplexing phase-shifting technology as claimed in any one of claims 1 to 6, characterized in that: The method comprises: Receive 20MHz~1GHz frequency band signals; Pre-processing the received 20MHz to 1GHz frequency band signal before frequency conversion, and centrally transmitting the pre-processed multi-channel signal to a single-channel RF front end; Using a superheterodyne receiver, the multi-channel signal is down-converted to 10.7 MHz output through two-stage frequency conversion; A 16-bit high-precision ADC is used to sample the 10.7MHz signal output from the RF front end. The signal is processed by a preset algorithm through the FPGA. After the outgoing wave angle is calculated, the received signal spectrum data is output to the display and control computer through the Gigabit Ethernet port.

8. The method according to claim 7, characterized in that The preset algorithm processing is performed by FPGA to calculate the outgoing wave angle, and the received signal spectrum data is output to the display and control computer through the gigabit network port, including: Based on the preset combiner amplitude formula, the phase difference between the array element and the reference signal is extracted from the ADC data; A multi-baseline combination algorithm is used to combine phase difference data to calculate the incoming wave angle, and the received signal spectrum data is output to the display and control computer through the Gigabit network port.

9. The method according to claim 8, characterized in that The preset combined amplitude formula includes: Among them, E1, E2, E3, and E4 are the signal amplitudes after the incoming signal is phase-shifted by 0°, 90°, 180°, and 270° and then superimposed with the reference signal.

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