Phased array radar and its receiving channel amplitude and phase test method and system

Abstract

This invention discloses a phased array radar and its receiving channel amplitude and phase testing method and system. The testing method includes: the radar under test transmitting a pulse signal to an area with a fixed reflector; calculating the phase difference caused by the path difference of each antenna element when the radar antenna receives the echo from the reflector; adjusting the servo azimuth angle of the radar under test to the azimuth of the reflector echo; changing the transmitted beam to a single beam with the transmitted beamwidth consistent with the received beamwidth; fixing the transmitted beam position; scanning with the radar under test; acquiring N sets of amplitude and phase values; and calculating the amplitude and phase of N receiving channels based on the phase difference caused by the path difference of each antenna element and the amplitude and phase values ​​of each set. This invention can perform complete testing of the entire receiving channel, can be tested in the field, and can be tested at any time after the radar leaves the factory.

Description

Technical Field

[0001] This invention belongs to the field of radar testing technology, and in particular relates to a phased array radar and its receiving channel amplitude and phase testing method and system. Background Technology

[0002] Phased array radars consist of multiple receiving channels, each containing antenna receiving elements and a receiver. The number of channels typically ranges from dozens to tens of thousands. Ensuring the consistency of amplitude and phase across all channels is a fundamental prerequisite for the normal operation of a phased array radar. However, during mass production, it is impossible to guarantee that the amplitude and phase of each channel are completely consistent, and it is also impossible to guarantee that the amplitude and phase of each channel will remain constant during radar use. This is a practical problem that must be faced in engineering practice. Therefore, amplitude and phase compensation is required for each channel during radar commissioning and use. To compensate for amplitude and phase differences between channels, the amplitude and phase values ​​of each channel must first be accurately tested. The following are some existing methods for testing the amplitude and phase of phased array radar receiving channels:

[0003] (1) Instrument testing method. This method uses a network analyzer to test the amplitude and phase difference of each receiver one by one. Since the network analyzer cannot test the amplitude and phase differences between antenna receiving elements, this method cannot perform a complete test of the entire receiving channel; and when there are many channels, testing each channel one by one with an instrument is very labor-intensive and prone to test errors.

[0004] (2) Anechoic Chamber Testing Method. This method uses a microwave anechoic chamber to scan and test the amplitude and phase of all channels, obtaining the amplitude and phase values ​​of the entire receiving channel, including the antenna receiving elements. Although this method provides a complete test, it requires a specialized microwave anechoic chamber, which is very expensive to build. Furthermore, this test cannot be performed once the radar leaves the factory, resulting in a large workload, high cost, and long testing cycle. For example, see patent document CN114047485A, entitled "Rapid Detection System, Method, Equipment, and Storage Medium for Phased Array Radar Anechoic Chamber."

[0005] (3) Field calibration tower test. This method involves constructing a calibration tower at a distance of tens to hundreds of meters from the radar. The calibration tower radiates a signal with known characteristics to the radar. After each channel of the radar receives the signal, the amplitude and phase values ​​of each channel can be calculated. This method is the same as the anechoic chamber test method, which is also a complete test of the receiving channel. However, the construction cost of the calibration tower is high, and this test cannot be performed once the radar leaves the factory. Summary of the Invention

[0006] The purpose of this invention is to provide a phased array radar and its receiving channel amplitude and phase testing method and system to solve the problems of large testing workload, high testing cost, and long testing cycle of traditional testing methods, as well as the problem that the radar cannot be tested after leaving the factory.

[0007] This invention solves the above-mentioned technical problems through the following technical solution: a method for testing the amplitude and phase of a phased array radar receiving channel, comprising the following steps:

[0008] The radar under test transmits pulse signals toward an area with a fixed reflector, wherein the distance between the reflector and the radar under test is greater than 2d. 2 / λ, where d is the spacing between adjacent antenna elements of the radar under test, and λ is the operating wavelength of the radar under test.

[0009] Calculate the phase difference caused by the path difference of each antenna element when the radar antenna under test receives the echo from the reflector, wherein the echo from the reflector refers to the signal of the pulse signal reflected to the radar under test after passing through the reflector.

[0010] The servo azimuth angle of the radar under test is adjusted to the azimuth of the reflector echo, the transmit beam is changed to a single beam and the transmit beam width is consistent with the receive beam width, the transmit position is fixed, and the radar under test scans.

[0011] Obtain N sets of amplitude and phase values, where N is the number of radar antenna array elements under test;

[0012] The amplitude and phase of N receiving channels are calculated based on the phase difference caused by the path difference of each antenna element and the amplitude and phase values ​​of each group.

[0013] Furthermore, the formula for calculating the phase difference caused by the path difference of the i-th antenna element is:

[0014]

[0015] in, The phase difference is caused by the path difference of the i-th antenna element, and φ is the angle between the radar antenna array surface under test and the horizontal plane. θ is the angle between the reflected object's echo and the horizontal plane, f is the operating frequency of the radar under test, and c is the speed of light.

[0016] Furthermore, the operating frequency f of the radar under test is measured by a spectrum analyzer; the spacing d between adjacent antenna elements is measured by calipers; and the angle φ between the antenna array surface of the radar under test and the horizontal plane is measured by a protractor.

[0017] Furthermore, the angle between the reflected echo and the horizontal plane The specific testing method is as follows:

[0018] An isolated reflector conforming to the far-field principle is placed within the scanning range of the radar being tested;

[0019] The radar under test performs a normal scan and acquires the echo map of the reflected object;

[0020] The azimuth and elevation angle of the reflected object echo are determined based on the reflected object echo diagram. The elevation angle is the angle between the reflected object echo and the horizontal plane.

[0021] Furthermore, the distance between the reflector and the radar under test is greater than 10km, and there are no other reflectors with echoes within 10km radially in front of or behind the reflector.

[0022] Furthermore, the signal-to-noise ratio of the reflected object echo is greater than 50 dB.

[0023] Furthermore, the formulas for calculating the amplitude and phase of the i-th receiving channel are as follows:

[0024]

[0025] Among them, G i ' represents the amplitude of the i-th receiving channel, η i ' represents the phase of the i-th receiving channel. The phase difference caused by the path difference of the i-th antenna element, (G i ,η i ) represents the amplitude and phase values ​​of the i-th group, G i Let η be the amplitude in the i-th group of amplitude and phase values. i The phase is the phase in the i-th group of amplitude and phase values.

[0026] Based on the same inventive concept, the present invention also provides a phased array radar receiving channel amplitude and phase testing system, comprising:

[0027] The signal transmitting unit is configured to transmit pulse signals toward an area with a fixed reflector, wherein the distance between the reflector and the radar under test is greater than 2d. 2 / λ, where d is the spacing between adjacent antenna elements of the radar under test, and λ is the operating wavelength of the radar under test.

[0028] The first calculation unit is configured to calculate the phase difference caused by the path difference of each antenna element when the radar antenna under test receives the echo of the reflected object, wherein the echo of the reflected object refers to the signal of the pulse signal reflected to the radar under test after passing through the reflected object.

[0029] The adjustment unit is configured to adjust the servo azimuth angle of the radar under test to the azimuth of the reflector echo, change the transmitted beam to a single beam, and make the transmitted beam width consistent with the received beam width, and fix the transmitted beam position.

[0030] The acquisition unit is configured to acquire N sets of amplitude and phase values, where N is the number of radar antenna array elements under test;

[0031] The second calculation unit is configured to calculate the amplitude and phase of N receiving channels based on the phase difference caused by the path difference of each antenna array element and the amplitude and phase values ​​of each group.

[0032] Based on the same inventive concept, the present invention also provides a phased array radar, including the phased array radar receiving channel amplitude and phase testing system as described above.

[0033] Beneficial effects

[0034] Compared with the prior art, the advantages of the present invention are as follows:

[0035] The present invention provides a phased array radar and its receiving channel amplitude and phase testing method and system, which can perform complete testing of the entire receiving channel, can be tested in the field, and can be tested at any time after the radar leaves the factory without any additional cost. The testing is simple and convenient. Attached Figure Description

[0036] To more clearly illustrate the technical solution of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the far-field principle in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the radar structure in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram illustrating the principle of amplitude and phase value calculation for the receiving channel in an embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The technical solutions of this application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0042] Far-field principle: A spherical wave emitted from the transmitting antenna travels a certain distance to reach the antenna under test. When the distance l between the transmitting antenna and the antenna under test is greater than 2d...2 When d = λ, it can be considered that the antenna under test receives an approximate plane wave, where d is the spacing between antenna elements and λ is the wavelength of the spherical electromagnetic signal.

[0043] For radar, the emitted signal is reflected back after passing through a ground target. The reflected signal is then received by the radar antenna. According to the far-field principle, if the distance between the ground target and the radar is greater than 2d... 2 When the distance is / λ, the ground object reflection signal (or ground object echo) received by the radar can be considered as a plane wave signal, such as Figure 1 As shown. Figure 1 In this context, φ represents the angle between the radar antenna array and the horizontal plane (unit: °). θ is the angle between the ground object echo and the horizontal plane (unit: °), θ is the angle between the ground object echo and the radar antenna array (unit: °), d is the spacing between adjacent radar antenna elements (unit: mm), L is the signal path difference between adjacent antenna elements (unit: m), and the numbers 1, 2, 3, 4, ..., 61, 62, 63, 64 represent the 64 antenna elements of the radar antenna array.

[0044] The reflective object includes ground features, a standard sphere, or other reflective bodies. In this embodiment, a ground feature is used as the reflective object.

[0045] from Figure 1 As can be seen from the data, when the object echo is a plane wave, the signals received by the 64 antenna elements are in the same direction, and the signal path difference between adjacent antenna elements is L. Let the signal path difference between the bottommost adjacent antenna elements be 0, and then increase the path difference of each antenna element upwards by L. Then the path difference S of the i-th antenna element is:

[0046] S=(i-1)L (1)

[0047] Based on the path difference, it can be converted into the phase difference and amplitude difference between antenna elements. Figure 1 Formulas (2) and (3) can be obtained:

[0048] L=d*sinθ (2)

[0049]

[0050] Based on the relationship between path difference and phase, we can obtain:

[0051]

[0052] Substituting equations (1) to (3) into equation (4), we obtain the phase difference caused by the path difference of the i-th antenna element as:

[0053]

[0054] Substituting the relationship between wavelength and frequency, c = λf, into equation (5), we can further obtain the phase difference caused by the path difference of the i-th antenna element as:

[0055]

[0056] Where f is the radar operating frequency, and c is the speed of light (3 × 10⁻⁶). 8 m / s.

[0057] When the radar's operating state is determined, all parameters in equation (6) are constant values, meaning that the phase difference of the ground object echo received by each antenna array element can be calculated for subsequent calculations.

[0058] The amplitude difference between ground object echoes reaching each antenna element depends on the attenuation of the electromagnetic wave over the path difference L. The attenuation of X-band electromagnetic waves in natural air is <1dB per kilometer. The spacing between antenna elements of X-band phased array radar is very small, on the order of millimeters, so the path difference L is much less than 1km, and the amplitude difference between ground object echoes reaching the 64 antenna elements can be ignored.

[0059] Each antenna element corresponds to one receiving channel of the radar, and each receiver has one AD acquisition channel, such as... Figure 2 As shown, when the antenna array elements receive ground object echoes, once the amplitude and phase differences between each antenna array element are known, the amplitude and phase values ​​of each receiving channel can be calculated through the AD acquisition unit and signal processing module.

[0060] The phase-array radar receiving channel amplitude and phase testing method provided in this embodiment of the invention includes the following steps:

[0061] Step 1: The radar under test transmits pulse signals to the area with fixed ground features.

[0062] According to the far-field principle, the distance between the ground object and the radar being measured must be greater than 2d. 2 / λ, where d is the spacing between adjacent antenna elements of the radar under test, and λ is the operating wavelength of the radar under test.

[0063] Step 2: Calculate the phase difference caused by the path difference of each antenna element when the radar antenna receives the ground object echo. The specific calculation formula is Equation (6). The amplitude difference can be ignored.

[0064] In equation (6), all parameters are known quantities. The operating frequency f of the radar under test is measured by a spectrum analyzer and can be measured after the radar is manufactured. The distance d between adjacent antenna elements is measured by calipers and can be measured after the radar antenna is manufactured. The angle φ between the antenna array of the radar under test and the horizontal plane is measured by a protractor and can be determined after the radar is debugged. The angle φ is the antenna elevation angle.

[0065] In this embodiment, the angle between the ground feature echo and the horizontal plane... The specific testing method is as follows:

[0066] 2.1: Set up isolated ground features that conform to the far-field principle within the scanning range of the radar being tested.

[0067] It conforms to the far-field principle, that is, the distance between the ground object and the radar being measured is greater than 10km; isolated ground object, that is, ground object with no other echo within 10km radially in front and behind.

[0068] 2.2: The radar under test performs a normal scan and acquires ground feature echo maps.

[0069] When the weather is clear, the radar will scan normally, and the ground feature echo map will be displayed on the radar echo display interface.

[0070] 2.3: Determine the azimuth and elevation angle of the ground feature echo based on the ground feature echo map. The elevation angle is the angle between the ground feature echo and the horizontal plane.

[0071] The radar echo display interface shows the azimuth and elevation of ground features. The azimuth and elevation of the ground feature echo can be directly read from the interface. The azimuth is used to adjust the servo azimuth angle in step 3, and the elevation angle is the angle between the ground feature echo and the horizontal plane. The signal-to-noise ratio of ground feature echoes should be relatively high, preferably greater than 50dB.

[0072] Substituting the parameters into equation (6), the phase difference caused by the path difference of the 1 to 64 linear array elements is calculated respectively. This represents the phase difference of the ground object echo entering the i-th antenna element. Since the amplitude difference is negligible, the phase difference between the amplitude and the phase of the i-th antenna element is denoted as .

[0073] Step 3: Adjust the servo azimuth angle of the radar under test to the azimuth of the ground object echo, change the transmit beam to a single beam, and make the transmit beam width consistent with the receive beam width. Fix the transmit position and scan the radar under test.

[0074] When a phased array radar is working normally, the transmitted beam switches rapidly in azimuth and elevation, and the direction of the transmitted beam is constantly changing. However, the test in this application only focuses on the reflected signal of ground targets. Therefore, it is necessary to fix the transmitted beam in the direction where the ground target is located and only scan in that direction. This can greatly reduce the complexity of receiving data processing.

[0075] Step 4: Read N sets of amplitude and phase values, where N is the number of radar antenna elements under test.

[0076] In this embodiment, N = 64. The amplitude and phase values ​​of the i-th group are denoted as (G i ,η i ), G i Let η be the amplitude in the i-th group of amplitude and phase values. iLet G be the phase in the i-th group of amplitude and phase values. i ,η i ) represents the amplitude and phase of the ground object reflected signal or ground object echo after passing through the i-th antenna receiving element and then the i-th receiver.

[0077] Step 5: Calculate the amplitude and phase of N receiving channels based on the phase difference caused by the path difference of each antenna element and the amplitude and phase values ​​of each group.

[0078] like Figure 3 As shown, in this embodiment, the formulas for calculating the amplitude and phase of the i-th receiving channel are:

[0079]

[0080] Among them, G i ' represents the amplitude of the i-th receiving channel, η i ' represents the phase of the i-th receiving channel. The phase difference caused by the path difference of the i-th antenna element, (G i ,η i ) represents the amplitude and phase values ​​of the i-th group, G i Let η be the amplitude in the i-th group of amplitude and phase values. i The phase is the phase in the i-th group of amplitude and phase values.

[0081] This invention allows for convenient amplitude and phase testing of the entire receiving channel, including the antenna, in the field. Antennas are complex devices, and their parameters and specifications are typically tested only in an anechoic chamber. Once the radar leaves the factory, it's no longer possible to test the amplitude and phase values ​​of the entire receiving channel, including the antenna receiving elements. After the radar has been operating in the field for a period of time, changes in the amplitude and phase consistency of the receiving channel are inevitable. At this point, testing the amplitude and phase of the receiving channel, including the antenna, and thus recompensating the channel, becomes impossible.

[0082] This invention utilizes the characteristics of the radar system itself to cleverly calculate the amplitude and phase values ​​of the radar receiving channel by receiving signals reflected back from objects in the far field. This provides a basis for recompensating the receiving channel and can effectively solve the practical problem of not being able to compensate for changes in the amplitude and phase of the receiving channel during radar use.

[0083] Based on the same inventive concept, embodiments of the present invention also provide a phased array radar receiving channel amplitude and phase testing system, comprising:

[0084] The signal transmitting unit is configured to transmit pulse signals toward an area with a fixed reflector, wherein the distance between the reflector and the radar under test is greater than 2d. 2 / λ, where d is the spacing between adjacent antenna elements of the radar under test, and λ is the operating wavelength of the radar under test.

[0085] The first calculation unit is configured to calculate the phase difference caused by the path difference of each antenna element when the radar antenna under test receives the echo of the reflector (as shown in equation (6)), wherein the echo of the reflector refers to the signal of the pulse signal reflected to the radar under test after passing through the reflector.

[0086] The adjustment unit is configured to adjust the servo azimuth angle of the radar under test to the azimuth of the reflector echo, change the transmitted beam to a single beam, and make the transmitted beam width consistent with the received beam width, and fix the transmitted beam position.

[0087] The acquisition unit is configured to acquire N sets of amplitude and phase values, where N is the number of radar antenna array elements under test;

[0088] The second calculation unit is configured to calculate the amplitude and phase of N receiving channels based on the phase difference caused by the path difference of each antenna array element and the amplitude and phase values ​​of each group (as shown in equation (7)).

[0089] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing the amplitude and phase of a phased array radar receiving channel, characterized in that, Includes the following steps: The measured radar emits pulse signals to the area provided with fixed reflectors, wherein the distance between the reflectors and the measured radar is greater than 2d 2 / λ, d is the distance between adjacent antenna elements of the measured radar, and λ is the working wavelength of the measured radar. Calculate the phase difference caused by the path difference of each antenna element when the radar antenna under test receives the echo from the reflector, wherein the echo from the reflector refers to the signal of the pulse signal reflected to the radar under test after passing through the reflector. The servo azimuth angle of the radar under test is adjusted to the azimuth of the reflector echo, the transmit beam is changed to a single beam and the transmit beam width is consistent with the receive beam width, the transmit position is fixed, and the radar under test scans. Obtain N sets of amplitude and phase values, where N is the number of radar antenna array elements under test; The amplitude and phase of N receiving channels are calculated based on the phase difference caused by the path difference of each antenna array element and the amplitude and phase values ​​of each group. The formula for calculating the phase difference caused by the path difference of the i-th antenna element is: Where, θ i Φ is the phase difference caused by the path difference of the i-th antenna element; Φ is the angle between the radar antenna array under test and the horizontal plane, which is measured by a protractor. θ is the angle between the reflected echo and the horizontal plane; f is the operating frequency of the radar under test; c is the speed of light. The angle between the reflected echo and the horizontal plane The specific testing method is as follows: An isolated reflector conforming to the far-field principle is placed within the scanning range of the radar being tested; The radar under test performs a normal scan and acquires the echo map of the reflected object; The azimuth and elevation angle of the reflected object echo are determined based on the reflected object echo diagram. The elevation angle is the angle between the reflected object echo and the horizontal plane.

2. The phase-array radar receiving channel amplitude and phase testing method according to claim 1, characterized in that, The operating frequency f of the radar under test is measured by a spectrum analyzer; the spacing d between adjacent antenna elements is measured by calipers.

3. The phase-array radar receiving channel amplitude and phase testing method according to claim 1, characterized in that, The distance between the reflector and the radar under test is greater than 10km, and there are no other reflectors with echoes within 10km radially in front of or behind the reflector.

4. The phase-array radar receiving channel amplitude and phase testing method according to claim 1, characterized in that, The echo signal-to-noise ratio of the reflector is greater than 50 dB.

5. The phase-array radar receiving channel amplitude and phase testing method according to any one of claims 1 to 4, characterized in that, The formulas for calculating the amplitude and phase of the i-th receiving channel are: (G i ,η i ) = (G i ,η i ) - (0,θ i ) = (G i ,η i -θ i ) where G i is the amplitude of the i-th receive channel, η i is the phase of the i-th receive channel, θ i is the phase difference caused by the path difference of the i-th antenna element, (G i , η i ) is the i-th set of amplitude and phase values, G i is the amplitude in the i-th set of amplitude and phase values, η i is the phase in the i-th set of amplitude and phase values.

6. A phased array radar receiver channel amplitude and phase testing system, comprising: The signal transmitting unit is configured to transmit a pulse signal to a region provided with a fixed reflector, wherein the reflector is greater than 2d away from the measured radar 2 / λ, d is the distance between adjacent antenna elements of the measured radar, and λ is the operating wavelength of the measured radar. The first calculation unit is configured to calculate the phase difference caused by the path difference of each antenna element when the radar antenna under test receives the echo from a reflected object, wherein the echo from the reflected object refers to the signal reflected back to the radar under test after the pulse signal passes through the reflected object; wherein the formula for calculating the phase difference caused by the path difference of the i-th antenna element is: Where, θ i Φ is the phase difference caused by the path difference of the i-th antenna element; Φ is the angle between the radar antenna array under test and the horizontal plane, which is measured by a protractor. θ is the angle between the reflected echo and the horizontal plane; f is the operating frequency of the radar under test; c is the speed of light. The angle between the reflected echo and the horizontal plane The specific testing method is as follows: An isolated reflector conforming to the far-field principle is placed within the scanning range of the radar under test; the radar under test scans normally and acquires the echo map of the reflector; the azimuth and elevation angle of the reflector echo are determined based on the echo map, where the elevation angle is the angle between the reflector echo and the horizontal plane. The adjustment unit is configured to adjust the servo azimuth angle of the radar under test to the azimuth of the reflector echo, change the transmitted beam to a single beam, and make the transmitted beam width consistent with the received beam width, and fix the transmitted beam position. The acquisition unit is configured to acquire N sets of amplitude and phase values, where N is the number of radar antenna array elements under test; The second calculation unit is configured to calculate the amplitude and phase of N receiving channels based on the phase difference caused by the path difference of each antenna array element and the amplitude and phase values ​​of each group.

7. A phased array radar, characterized in that: Includes the phased array radar receiving channel amplitude and phase testing system as described in claim 6.

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