A hand-held spatial spectrum direction finding receiver and method of direction finding

Abstract

The application discloses a handheld space spectrum direction-finding receiver and a direction-finding method thereof, and belongs to the technical field of radio direction finding. The receiver comprises a receiving antenna array, a balance device group, an attitude detection control module, a radio frequency receiving link and a baseband processing system, etc. The receiving antenna array is manually rotated, and the rotating angle is obtained in combination with the attitude detection module; the balance device group is used for maintaining the polarization state of the antenna and reconstructing the layout form. The direction-finding method comprises system channel calibration, multi-attitude signal acquisition and covariance matrix calculation, and space spectrum search based on maximum likelihood estimation; the array flow model under the geodetic coordinate system is established, the covariance matrix sequence obtained after multiple rotations is subjected to joint spectrum estimation, and high-precision direction finding of the azimuth and the elevation angle of a single signal and multiple signals with the same frequency is realized. The application takes into account the handheld portability and the direction-finding performance, and is suitable for field operation, emergency communication and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of radio direction finding technology, and particularly relates to a handheld space spectrum direction finding receiver and its direction finding method. Background Technology

[0002] Currently, radio direction finding technology plays a crucial role in the detection, location, and management of unknown signals. Handheld direction finding receivers, due to their portability and flexibility, are widely in demand in scenarios such as field operations, emergency communications, and on-site inspections. However, existing handheld direction finding receivers are limited by size, power consumption, and cost, resulting in significant design and performance bottlenecks.

[0003] Currently, most mainstream handheld devices employ single-antenna rotational direction finding or amplitude / phase comparison-based direction finding systems based on simple, small-scale antenna arrays. These traditional technical solutions have the following inherent drawbacks:

[0004] 1. Inability to perform direction finding for multiple signals at the same frequency: When multiple signals at the same frequency exist, traditional direction finding methods will result in direction finding errors or indicate incorrect intermediate angles, making it impossible to distinguish and independently locate multiple signal sources. Its theoretical direction finding resolution is limited by the classical Rayleigh limit, making it difficult to overcome the limitations of physical aperture.

[0005] 2. Weak or absent elevation angle direction finding capability: Most simple array designs can only provide azimuth (horizontal direction) information and cannot measure elevation angle (vertical direction). Although some have attempted to perform two-dimensional direction finding, due to limitations in array configuration and algorithms, there are problems such as low elevation angle direction finding accuracy and inability to effectively distinguish between elevation and depression angles, making it difficult to meet the needs of complex electromagnetic environments and three-dimensional spatial positioning.

[0006] 3. The contradiction between performance and portability: Although large-scale fixed-station spatial spectrum estimation technology can achieve high-resolution, high-precision two-dimensional direction finding, its massive antenna arrays and complex computing systems cannot be ported to handheld devices. How to achieve spatial spectrum direction finding performance comparable to large systems while maintaining the handheld portability of the device has always been a technical challenge in this field.

[0007] Therefore, there is an urgent need to develop a handheld direction-finding receiver and direction-finding method that combines portability and high performance, breaking through the limitations of existing technologies in direction-finding dimension, resolution, and multi-signal processing capabilities. Summary of the Invention

[0008] This invention proposes a handheld spatial spectrum direction finding receiver and its direction finding method to solve the problems of traditional handheld direction finding receivers in terms of direction finding dimension, resolution and multi-signal processing capabilities.

[0009] To achieve the above objectives, the present invention proposes a handheld spatial spectrum direction finding receiver, comprising: a receiving antenna array 10 composed of multiple antenna array elements, a balancing device group 20 composed of multiple balancing devices, a balancing device control module 30, an attitude detection control module 40, a switch matrix 50, a multi-channel receiver module 60, a multi-channel ADC module 70, a baseband signal processing module 80, a calibration source module 90, a human-computer interaction module 100, a GPS module and antenna 110, a compass 120, a level 130, and an accelerometer 140;

[0010] The receiving antenna array 10 is composed of multiple antenna array elements;

[0011] The balancing device group 20, consisting of multiple balancing devices, is used to adjust the physical orientation of the antenna array elements.

[0012] The balancing device control module 30 is connected to the balancing device group 20;

[0013] The attitude detection and control module 40 is connected to the compass 120 and the level 130 to acquire the real-time angle information of the device; the attitude detection and control module 40 is also connected to the GPS module, the antenna 110, and the accelerometer 140 to determine the position information of the device; the attitude detection and control module 40 further controls the balancing device group 20 through the balancing device control module 30 to maintain or precisely adjust the polarization state of the antenna array elements when the device attitude changes.

[0014] The radio frequency receiving link includes a switch matrix 50, a multi-channel receiver module 60, and a multi-channel ADC module 70 connected in sequence; the input terminal of the switch matrix 50 can be selectively connected to the receiving antenna array 10 or a calibration source module 90.

[0015] The baseband signal processing module 80 is connected to the multi-channel ADC module 70 and the attitude detection and control module 40, respectively, and is used to control system operation, perform channel calibration, and perform spatial spectrum calculation based on signal data under multiple attitudes to achieve direction finding.

[0016] The GPS module, antenna 110, compass 120, level 130, and accelerometer 140 provide position and angle data for the attitude detection and control module 40.

[0017] The calibration source module 90 is used to output a standard calibration signal to realize system channel calibration.

[0018] The human-computer interaction module 100 is used to display the direction finding results and receive user operation commands.

[0019] Furthermore, each balancing device in the balancing device group 20 is coupled to at least one antenna element and is able to adjust and maintain the corresponding antenna element at any desired angle relative to the device body in response to the command of the balancing device control module 30.

[0020] Furthermore, the entire handheld device containing the receiving antenna array 10 is rotated in three-dimensional space by manual or mechanical means. The rotation angle data obtained by the attitude detection and control module 40 is used to reconstruct the antenna array layout to enhance the joint estimation capability of azimuth and elevation angles, and maintain direction finding accuracy when the elevation angle is close to 0°, thereby achieving effective differentiation between elevation and depression angles.

[0021] Furthermore, the baseband signal processing module 80 adopts a spatial spectrum direction finding system based on maximum likelihood estimation, and outputs direction finding results of direction finding degree and spectral peak size through spectrum search operation.

[0022] Furthermore, the receiving antenna array 10 is physically and electrically connected to the host via a Type-C quick-plug interface, which supports integrated signal transmission and power supply.

[0023] Furthermore, the digital signal output by the multi-channel ADC module 70 in the radio frequency receiving link is processed by DDC to generate a complex digital signal sequence for covariance matrix calculation.

[0024] A direction finding method for a handheld space spectrum direction finding receiver includes the following steps:

[0025] S1: System channel calibration. The calibration source sends a calibration signal, the switch matrix switches to the calibration channel, and the calibration signal is received by the multi-channel RF receiver module and the multi-channel ADC module. After DDC processing, K sets of complex digital signal row sequences are obtained: ,..., Where K is the number of antenna elements in the receiving antenna array.

[0026] The calibration covariance matrix was calculated. One of them is:

[0027] H denotes the conjugate transpose of a complex matrix;

[0028] in: .

[0029] S2: Manually rotate (with minor external movements allowed) the entire handheld device, and use a compass, level, etc., to obtain the rotation angle at this time, and record it as follows. , where n represents the nth rotation. Simultaneously, the balancing device is adjusted to maintain the orientation of the antenna elements.

[0030] in, , Defined using a spherical coordinate system based on the Earth: the X-axis is due east, the Y-axis is due north, and the Z-axis is upward. The angle between the spherical coordinate system and the Z-axis. The angle between the x-axis and the x-axis in a spherical coordinate system.

[0031] S3: The switch matrix is ​​switched to the receiving antenna array input for processing the received air signals. After DDC operations, K sets of complex digital signal row sequences are obtained: ,..., The calibrated signal covariance matrix is ​​calculated. , where n represents the nth rotation. Any one of the terms is:

[0032]

[0033] in: .

[0034] S4: Repeat S2~S3 multiple times to obtain multiple sets of calibrated signal covariance matrix sequences: { ... }. Where N represents the total number of rotations.

[0035] S5: Employ the maximum likelihood estimation spatial spectrum direction finding algorithm to perform spectrum search operations and output direction finding results, including directionality and spectral peak size.

[0036] Assume there are M incoming wave direction values ​​to be searched: ,in .

[0037] Initial positions of K antenna elements Represented by coordinate variables , where k .

[0038] Initial angle of receiving antenna array The array undergoes N rotations, with rotation angles of respectively. At this time, it can be based on The new positions of the array elements can be further calculated. , where k , The calculation method is as follows:

[0039] Initial angle of receiving antenna array At that time, the base of the receiving antenna array relative to the geodetic rectangular coordinate system is:

[0040]

[0041] Rotation angle Afterwards, the basis of the receiving antenna array relative to the geodetic rectangular coordinate system becomes:

[0042]

[0043] No. The position vector of each antenna element can be represented as:

[0044]

[0045] No. A unit vector representing the direction of incoming waves can be used to represent:

[0046]

[0047] so, exist The components on are:

[0048]

[0049] That is the first The incoming wave arrived from the first direction. The distance difference between each array element and the distance to the origin.

[0050] The corresponding array manifold vector can then be calculated. In particular, for an ideal omnidirectional antenna element that is uncoupled and unobstructed, the theoretical array manifold matrix can be written as a K-row, M-column matrix:

[0051]

[0052] in The imaginary unit, λ is the wavelength.

[0053] At this point, when performing spatial spectrum direction finding, N covariance matrices can be constructed. , .

[0054] Based on the spatial spectrum direction finding algorithm of maximum likelihood estimation, through

[0055]

[0056] in, This means that when the objective function is maximized, The value of , Represents the trace of a matrix.

[0057] For: when the initial angle of the receiving antenna array Rotation angle of receiving antenna array The direction and angle of the incoming wave In this case, the corresponding array manifold column matrix , projection matrix .

[0058] The obtained As the direction of incoming waves The solution. At this point... The corresponding value is recorded as the spectral peak value.

[0059] Beneficial effects

[0060] 1. Supports direction finding of multiple signals at the same frequency: The spatial spectrum direction finding system based on maximum likelihood estimation breaks through the Rayleigh limit and can effectively distinguish multiple signal sources at the same frequency, achieving independent positioning;

[0061] 2. Achieve high-precision two-dimensional direction finding: By rotating the receiving antenna array to reconstruct the layout, and combining it with a balancing device to maintain the polarization state, high direction finding accuracy is maintained even when the elevation angle is close to 0°, and the depression angle and elevation angle can be effectively distinguished.

[0062] 3. Balancing portability and performance: It adopts a handheld design, with quick-plug and lightweight antenna array. Through multi-attitude signal acquisition and joint spectrum estimation, it achieves direction-finding performance comparable to large fixed stations without expanding the array size.

[0063] 4. Easy to operate: The manual rotation of the receiving antenna array is suitable for field operation scenarios, and the system automatically completes calibration, calculation and spectrum search, reducing the user's operating threshold. Attached Figure Description

[0064] Figure 1 This is a block diagram illustrating the principle of the handheld spatial spectrum direction-finding receiver of the present invention.

[0065] Figure 2 This is a schematic diagram of the direction finding method of the handheld spatial spectrum direction finding receiver of the present invention. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0067] Example 1: Hardware configuration of a handheld spatial spectrum direction-finding receiver, see [link / reference]. Figure 1The schematic diagram of the handheld spatial spectrum direction finding receiver is shown below. The main structure and connections are as follows: The receiving antenna array 10 is electrically connected to the balancing device control module 30. The attitude detection control module 40 receives signals from the GPS module, antenna 110, compass 120, level 130, and accelerometer 140, and the attitude detection control module 40 is linked to the balancing device group 20 via the balancing device control module 30. One end of the switch matrix 50 can be optionally connected to the receiving antenna array 10 or the calibration source module 90, and the other end is sequentially connected to the multi-channel receiver module 60 and the multi-channel ADC module 70, ultimately connecting to the baseband signal processing module 80. Details of each component are as follows:

[0068] 1. Receiving antenna array 10: It adopts 5 uncoupled and unobstructed ideal omnidirectional antenna elements, with the element spacing being 1 / 2 of the signal wavelength;

[0069] 2. Balancing device group 20: 5 miniature motorized balancing gimbals (corresponding to 5 antenna elements), with a response accuracy of ±0.1°;

[0070] 3. Attitude detection and control module 40: Employs a MEMS compass (azimuth accuracy ±0.5°), a dual-axis level (pitch accuracy ±0.1°), a GPS module (positioning accuracy ±1m), and a triaxial accelerometer;

[0071] 4. RF receiver link: The switch matrix 50 adopts a single-pole double-throw RF switch, the multi-channel receiver module 60 operates in the frequency band of 200MHz-6GHz, and the multi-channel ADC module 70 has a sampling rate of 100MSps and a resolution of 16bit.

[0072] 5. Baseband signal processing module 80: It adopts an embedded processor (1.8GHz), runs on a Linux operating system, and has a pre-compiled maximum likelihood estimation algorithm program;

[0073] 6. Interface: The receiving antenna array 10 is connected to the host via a Type-C interface, supporting 5V / 2A power supply and high-speed data transmission.

[0074] Example 2: See Figure 2 The flowchart of the direction finding method is shown below. The main relationships are as follows: S1 corresponds to system channel calibration, S2~S4 correspond to multi-attitude signal acquisition and covariance matrix calculation, and S5 corresponds to maximum likelihood estimation spectrum search. Each step corresponds to the operation details of S1~S5 in the instruction manual.

[0075] Furthermore, the algorithm implementation examples will be used to further illustrate:

[0076] Taking the case where the number of array elements K=5, the number of incoming wave directions M=3, and the number of receiving antenna array rotations N=20 as an example. Specifically, the antenna array elements are assumed to be ideal omnidirectional antenna elements without coupling or obstruction. The specific processing steps of the algorithm are as follows:

[0077] S1: System channel calibration. The calibration source sends a calibration signal, the switch matrix switches to the calibration channel, and the calibration signal is received by the multi-channel RF receiver module and the multi-channel ADC module. After DDC processing, 20 sets of complex digital signal row sequences are obtained: ,..., .

[0078] The calibration covariance matrix was calculated. One of them is:

[0079]

[0080] in: .

[0081] S2: Manually rotate (with minor external movements allowed) the entire handheld device, and use a compass, level, etc., to obtain the rotation angle at this time, and record it as follows. , where n represents the nth rotation. Simultaneously, the balancing device is adjusted to maintain the orientation of the antenna elements.

[0082] in, , Defined using a spherical coordinate system based on the Earth: the X-axis is due east, the Y-axis is due north, and the Z-axis is upward. The angle between the spherical coordinate system and the Z-axis. The angle between the x-axis and the x-axis in a spherical coordinate system.

[0083] S3: The switch matrix is ​​switched to the receiving antenna array input for processing the received air signals. After DDC calculation, five sets of complex digital signal row sequences are obtained: ,..., The calibrated signal covariance matrix is ​​calculated. One of them is:

[0084]

[0085] in: .

[0086] S4: Repeat steps S2-S3 a total of 20 times to obtain multiple sets of calibrated signal covariance matrix sequences: { }

[0087] S5: Use the maximum likelihood estimation spatial spectrum direction finding algorithm to perform spectrum search operation and output direction finding results, such as orientation and spectral peak size.

[0088] Assume the three incoming wave direction values ​​to be searched are: ,in .

[0089] Initial positions of the 5 antenna elements Represented by coordinate variables , where k .

[0090] Initial angle of receiving antenna array The array underwent 20 rotations, with rotation angles of... At this time, it can be based on The new positions of the array elements can be further calculated. , where k , The calculation method is as follows:

[0091] Initial angle of receiving antenna array At that time, the base of the receiving antenna array relative to the geodetic rectangular coordinate system is:

[0092]

[0093] Rotation angle Then, the basis of the receiving antenna array relative to the geodetic rectangular coordinate system:

[0094]

[0095] No. The position vectors of the antenna array elements are:

[0096]

[0097] No. Unit vector of incoming wave direction:

[0098]

[0099] so, exist The components on are:

[0100]

[0101] That is the first The incoming wave arrived from the first direction. The distance difference between each array element and the distance to the origin.

[0102] The corresponding array manifold vector can then be calculated. In particular, for an ideal omnidirectional antenna element that is uncoupled and unobstructed, the theoretical array manifold matrix can be written as a 5x3 matrix:

[0103]

[0104] in The imaginary unit, λ is the wavelength.

[0105] At this point, when performing spatial spectrum direction finding, 20 covariance matrices can be constructed. , .

[0106] Based on the spatial spectrum direction finding algorithm of maximum likelihood estimation, through

[0107]

[0108] in, This means that when the objective function is maximized, The value of .

[0109] For: when the initial angle of the receiving antenna array Rotation angle of receiving antenna array The direction and angle of the incoming wave In this case, the corresponding array manifold column matrix , projection matrix .

[0110] The obtained As the direction of incoming waves The solution. At this point... The corresponding value is recorded as the spectral peak value.

[0111] Output results: The baseband signal processing module 80 displays the azimuth, elevation and peak values ​​of the incoming wave direction through the human-computer interaction module 100. The accuracy of the direction finding results is: azimuth ±0.3°, elevation ±0.5°, and the positions of three co-frequency signal sources can be clearly distinguished.

[0112] This embodiment verifies the feasibility of the present invention. In unobstructed outdoor scenarios, this handheld receiver can achieve high-precision two-dimensional direction finding of multiple signals on the same frequency, and the device weighs less than 1.5 kg and has a battery life of more than 8 hours, which is fully suitable for the use needs of field operations and emergency communication scenarios.

Claims

1. A handheld spatial spectrum direction-finding receiver, characterized in that, include: Receiver antenna array, balancing device group, balancing device control module, attitude detection and control module, RF receiver link and baseband signal processing module: The receiving antenna array (10) is composed of multiple antenna array elements; The balancing device group (20) consists of multiple balancing devices and is used to adjust the physical orientation of the antenna array elements; The balancing device control module (30) is connected to the balancing device group (20); The attitude detection and control module (40) is connected to the compass (120) and the level (130) to obtain the real-time angle information of the device; the attitude detection and control module (40) is also connected to the GPS module, the antenna (110), and the accelerometer (140) to determine the position information of the device; the attitude detection and control module (40) further controls the balance device group (20) through the balance device control module (30) to maintain or precisely adjust the polarization state of the antenna array elements when the device attitude changes; The radio frequency receiving link includes a switch matrix (50), a multi-channel receiver module (60), and a multi-channel ADC module (70) connected in sequence; the input of the switch matrix (50) can be selectively connected to the receiving antenna array (10) or a calibration source module (90). The baseband signal processing module (80) is connected to the multi-channel ADC module (70) and the attitude detection and control module (40) respectively, and is used to control system operation, perform channel calibration and perform spatial spectrum calculation based on signal data under multiple attitudes to achieve direction finding.

2. A handheld spatial spectrum direction-finding receiver according to claim 1, characterized in that, Each balancing device in the balancing device group (20) is coupled to at least one antenna element and is able to adjust and maintain the corresponding antenna element at any desired angle relative to the device body in response to the command of the balancing device control module (30).

3. A handheld spatial spectrum direction-finding receiver according to claim 1, characterized in that, The entire handheld device containing the receiving antenna array (10) is rotated in three-dimensional space by manual or mechanical means. The rotation angle data obtained by the attitude detection and control module (40) is used to reconstruct the antenna array layout to enhance the joint estimation capability of azimuth and elevation angles, and maintain direction finding accuracy when the elevation angle is close to 0°, so as to achieve effective differentiation between elevation and depression angles.

4. A handheld spatial spectrum direction-finding receiver according to claim 1, characterized in that, The baseband signal processing module (80) adopts a spatial spectrum direction finding system based on maximum likelihood estimation, and outputs the direction finding results of orientation degree and spectral peak size through spectrum search operation.

5. A handheld spatial spectrum direction-finding receiver according to claim 1, characterized in that, The receiving antenna array (10) is physically and electrically connected to the host through a Type-C quick-plug interface, which supports integrated signal transmission and power supply.

6. A handheld spatial spectrum direction-finding receiver according to claim 1, characterized in that, The digital signal output by the multi-channel ADC module (70) in the radio frequency receiving link is processed by DDC to generate a complex digital signal sequence for covariance matrix calculation.

7. A direction-finding method for a handheld spatial spectrum direction-finding receiver as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Control the switch matrix (50) to switch to the calibration source module (90), receive the calibration signal, process it through the radio frequency receiving link, obtain the calibration signal data, and calculate the calibration parameters; S2: Manually rotate the entire handheld device containing the receiving antenna array (10) to change the spatial attitude of the receiver. Record the current rotation angle (φn, θn) through the attitude detection and control module (40), and at the same time maintain the polarization orientation of the antenna array elements unchanged through the balance device control module (30) and the balance device group (20). S3: Control the switch matrix (50) to switch to the receiving antenna array (10) to receive the space signal. After processing by the radio frequency receiving link, obtain the space signal data under the current attitude, and calculate the calibrated signal covariance matrix using the calibration parameters. ; S4: Repeat steps S2~S3 N times to obtain multiple sets of calibrated signal covariance matrix sequences under different spatial attitudes. ... }; S5: Based on the signal covariance matrix sequence { ... The array manifold vectors and their corresponding attitudes are used to perform spectral search operations through the maximum likelihood estimation spatial spectrum direction finding algorithm, and the direction finding results are output.

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