A Direction Finding Method of an Interferometer Related to a Direction Finding and Positioning System

Abstract

The present invention discloses a direction finding method for an interferometer related to a direction finding and positioning system, comprising: establishing a mapping relationship between an incident angle and a steering vector, and constructing a steering vector library; a terminal broadcasting a data packet signal with flag information and a sine wave according to a protocol; after a base station receives and recognizes the flag information, controlling a radio frequency switch to time-divisionally select and connect antennas in a preset order to receive the sine wave signal in the data packet signal; then preprocessing the received signal to eliminate the phase difference caused by radio frequency channels and transceiver carrier frequency mismatch and constructing a multi-channel received signal; based on a two-dimensional hierarchical search algorithm, combining with the steering vector library to obtain a steering vector, calculating a signal S and its energy, and taking the angle with the strongest energy as an estimated value of the signal arrival angle. The present invention can enable the base station to quickly obtain an accurate estimation of the arrival angle of the terminal broadcast signal, and has low complexity and cost.

Description

Technical Field

[0001] The present invention relates to the technical field of radio signal direction finding, and particularly relates to an interferometer direction finding method related to a direction finding and positioning system. Background Art

[0002] The purpose of radio direction finding is to detect the incoming wave direction of a radiation source, and it has wide applications in military and civilian fields, such as electronic reconnaissance, radar, secondary radar, mobile communication, indoor positioning, etc. Compared with other direction finding methods, the phase interferometer direction finding method has the advantages of simple structure and easy implementation. Compared with other arrays, the circular array has a higher array surface space utilization rate in two-dimensional direction finding. In most cases, a uniform circular array is generally used.

[0003] When the direction finding and positioning system applies the phase interferometer direction finding algorithm at the base station front end, it faces problems such as a large number of channels, a large amount of data, and poor real-time performance. The present invention optimizes the base station antenna array design and adopts a time division mode to design the antenna channel gating sequence of a single receiving processor, reducing the base station cost and the amount of data. However, at the same time, it changes the received signal model, resulting in the inability to use the phase interferometer direction finding algorithm. Therefore, the present invention establishes a mapping relationship between the incident angle and the steering vector according to information such as the base station arrival angle observation range, angle observation step length, direction finding antenna array manifold, and carrier wavelength, and constructs a steering vector library; the present invention reconstructs the received signal model according to the antenna channel gating sequence design; the present invention designs an M-level two-dimensional hierarchical search strategy based on the principle of minimizing the total number of searches, and uses the elevation angle and azimuth angle corresponding to the maximum energy at the Mth level as the arrival angle estimation value. The present invention can enable the base station to quickly obtain an accurate estimation of the arrival angle of the terminal broadcast signal, with low complexity and cost. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the present invention provides an interferometer direction finding method related to a direction finding and positioning system, which can enable the base station to quickly obtain an accurate estimation of the arrival angle of the terminal broadcast signal, and has the technical characteristics of low complexity.

[0005] In order to achieve the above invention purpose, the technical solution adopted to solve its technical problems is as follows:

[0006] An interferometer direction finding method related to a direction finding and positioning system includes the following steps:

[0007] Step S1: Establish a mapping relationship between the incident angle and the steering vector according to the base station arrival angle observation range, angle observation step length, direction finding antenna array manifold, and carrier wavelength information, and construct a steering vector library;

[0008] Step S2: The terminal broadcasts a data packet signal with flag information, and the data packet signal contains a continuous sine wave signal for direction finding;

[0009] Step S3: After the central communication antenna of the base station receives and recognizes the flag information, the base station controls the RF switch to sequentially select and connect the direction-finding antenna and the communication antenna to receive the sine wave signal in the data packet signal at different times according to a preset order;

[0010] Step S4: Perform preprocessing on the received signal to eliminate the phase differences caused by the phase differences of the RF channels and the transceiver carrier frequency mismatches, and construct the multi-channel received signal R;

[0011] Step S5: Based on the two-dimensional hierarchical search algorithm, combine the steering vector library to obtain the steering vector A, and calculate S = A H R, and its energy, and take the angle with the strongest energy as the estimated value.

[0012] Furthermore, the step S1 includes the following steps:

[0013] Step S11: The base station includes an array antenna, which is composed of a communication antenna element and N direction-finding antenna elements. The direction-finding antennas are evenly distributed along a circle with a radius of R = λ / 2, where λ is the carrier wavelength. The element interval in radians is ω = 2π / N, and they are numbered 1, 2,..., N in sequence. And element 1 is on the X-axis, and the communication antenna element is located at the center of the uniform circular array and is numbered 0;

[0014] Step S12: The elevation angle θ is the angle between the signal incident direction and the XOY plane. Its maximum value, minimum value, and step length are θ max , θ min and θ step ;

[0015] The azimuth angle is the angle between the projection of the signal incident direction on the XOY plane and the X-axis. Its maximum value, minimum value, and step length are and

[0016] The steering vector corresponding to the elevation angle θ and the azimuth angle is:

[0017]

[0018] where,

[0019]

[0020] Step S13: According to the observation ranges [θ min , θ max of the elevation angle and the azimuth angle and the step length θ step and and Construct a guidance vector library of all pitch angle and azimuth angle combinations.

[0021] Furthermore, the step S2 includes the following steps:

[0022] Step S21: the mark information at least includes a MAC address for identifying and distinguishing the terminal and a characteristic identification code for identifying a sine wave;

[0023] Step S22: The sine wave signal s(t) is generated by modulating the direction finding information code, and the frequency is f sin , that is, s(t) = exp{j2πf sin t}.

[0024] Furthermore, the step S3 includes the following steps:

[0025] Step S31: The radio frequency switch selects the communication antenna to receive the space radio signal;

[0026] Step S32: when a characteristic identification code for identifying a sine wave is detected, the base station controls the radio frequency switch to time-select the direction-finding antenna and the communication antenna to receive the sine wave signal in a preset order;

[0027] Step S33: the preset array element gating sequence is that the communication antenna array element, the direction finding antenna array element, the communication antenna array element, and the direction finding antenna array element are alternately gated. Optionally, the gating sequence is cycled for several rounds, and finally the communication antenna array element is gated.

[0028] Step S34: gating time T sw , and 2f sin T sw is an integer;

[0029] Step S35: The receiving wavelength of the selected array element is λ, which is determined by the antenna array elevation angle θ and azimuth angle When the sine wave signal s(t) is in the direction, there exists s(t-2T sw )=exp{j(2πf sin t-2π·2f sin T sw )}=exp{j2πf sin t}=s(t);

[0030] When the communication antenna is selected, that is, i=0,n=0,2,...,2N-2,

[0031] y i (t) = s(t-nT sw )exp{j2πΔf(t-nT sw )},

[0032] When the direction-finding antenna is gated, that is, when \(i = 1,\cdots,N\) and \(n = 1,3,\cdots,2N - 1\),

[0033]

[0034] where \(\Delta f\) is the frequency difference caused by the transceiver carrier frequency mismatch;

[0035] Step S36: The transceiver carrier frequency mismatch is caused by the combined action of the Doppler frequency shift introduced by the relative motion between the terminal and the base station and the transceiver local oscillator mismatch.

[0036] Furthermore, the step S4 includes the following steps:

[0037] Step S41: Compensate the phase difference of the RF channel, and the phase difference is calibrated by a stationary signal source in the normal direction of the far field of the antenna array;

[0038] Step S42: Compensate the phase difference caused by the transceiver carrier frequency mismatch, and construct the multi-channel received signal \(r\) i (t), \(i = 1,2,\cdots,N\), satisfying:

[0039]

[0040] where \(\exp\{j\gamma\}\) is a constant, and we get:

[0041]

[0042] Furthermore, the step S5 includes the following steps:

[0043] Step S51: Adopt an M-level two-dimensional hierarchical search. According to the principle of minimizing the total search times, determine the range lengths, the number of segments, and the segment lengths of the pitch angles and azimuth angles at each level;

[0044] Step S52: Starting from the first level, according to the steering vectors \(A\) corresponding to the pitch angle and azimuth angle combinations in each segment of each level search, calculate all combinations \(S = A\) H \(R\) and its energy \(P=\sum|s\) i |\) 2 , \(s\) i is the \(i\)-th element in the data vector \(S\). Select the segment where the pitch angle and azimuth angle corresponding to the maximum energy are located as the search range for the next level until the M-th level;

[0045] Step S53: Take the pitch angle and azimuth angle corresponding to the maximum energy at the M-th level as the arrival angle estimation value.

[0046] Preferably, in the step S51, the minimization of the total search times determines the adoption of an M-level two-dimensional hierarchical search;

[0047] The range length of the pitch angle at the first level Number of segments Segment length

[0048] Length of the first - level azimuth range Number of segments Segment length

[0049] The number of combinations of the first - level pitch angle and azimuth angle is

[0050] Length of the m - th level pitch - angle range Number of segments Segment length

[0051] Length of the m - th level azimuth - angle range Number of segments Segment length

[0052] The number of combinations of the m - th level pitch angle and azimuth angle is

[0053] Length of the M - th level pitch - angle range Number of segments Segment length

[0054] Length of the M - th level azimuth - angle range Number of segments Segment length

[0055] The number of combinations of the M - th level pitch angle and azimuth angle is

[0056] Determine the number of segments of the pitch angle and azimuth angle at each level Satisfy:

[0057]

[0058] Due to the adoption of the above - mentioned technical solutions, compared with the prior art, the present invention has the following advantages and positive effects:

[0059] The method for interferometric direction finding related to a direction - finding and positioning system of the present invention can enable a base station to quickly obtain an accurate estimation of the arrival angle of a terminal broadcast signal, and has the technical feature of low complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following - described drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings. In the drawings:

[0061] Figure 1 It is a schematic flow chart of the interferometer direction finding method related to a direction finding and positioning system of the present invention;

[0062] Figure 2 It is a schematic diagram of the antenna array in the present invention. Specific embodiments

[0063] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0064] As Figure 1 shown, this embodiment discloses an interferometer direction finding method related to a direction finding and positioning system, including the following steps:

[0065] Step S1: According to information such as the arrival angle observation range of the base station, the angle observation step length, the manifold of the direction finding antenna array, and the carrier wavelength, establish a mapping relationship between the incident angle and the steering vector, and construct a steering vector library;

[0066] Step S2: The terminal broadcasts a data packet signal with flag information, and the data packet signal contains a continuous sine wave signal for direction finding;

[0067] Step S3: After the central communication antenna of the base station receives and recognizes the flag information, the base station controls the RF switch to time-divisionally select and connect the direction finding antenna and the communication antenna in a preset order to receive the sine wave signal in the data packet signal;

[0068] Step S4: Preprocess the received signal, eliminate the phase differences caused by the phase differences of the RF channels and the transceiver carrier frequency mismatches, and construct a multi-channel received signal R;

[0069] Step S5: Based on the two-dimensional hierarchical search algorithm, combine the steering vector library to obtain the steering vector A, calculate S = A H R, and its energy, and take the angle with the strongest energy as the estimated value.

[0070] Furthermore, the step S1 includes the following steps:

[0071] Step S11: The base station includes an array antenna, and the array antenna is composed of a communication antenna element and N direction finding antenna elements. The direction finding antennas are evenly distributed along a circumference with a radius of R = λ / 2, where λ is the carrier wavelength, the element interval in radians ω = 2π / N, and they are numbered 1, 2,..., N in sequence. And element 1 is on the X-axis, and the communication antenna element is located at the center of the uniform circular array and is numbered 0;

[0072] Step S12: The pitch angle θ is the angle between the signal incident direction and the XOY plane, and its maximum value, minimum value, and step length are θ max , θ min and θ step ;

[0073] The azimuth angle is the angle between the projection of the signal incident direction on the XOY plane and the X-axis, and its maximum value, minimum value, and step length are respectively and

[0074] The steering vector corresponding to the pitch angle θ and the azimuth angle is:

[0075]

[0076] wherein,

[0077]

[0078] Step S13: According to the pitch angle and azimuth angle observation ranges [θ min , θ max and the step length θ step and and construct a steering vector library for all combinations of pitch angles and azimuth angles.

[0079] Furthermore, the step S2 includes the following steps:

[0080] Step S21: The flag information includes at least the MAC address for identifying and distinguishing the terminal and the feature identification code for identifying the sine wave;

[0081] Step S22: The sine wave signal s(t) is generated by modulating the direction finding information code, and the frequency is f sin , that is, s(t) = exp{j2πf sin t}.

[0082] Furthermore, the step S3 includes the following steps:

[0083] Step S31: The RF switch selects and gates the communication antenna to receive the space radio signal;

[0084] Step S32: When detecting the feature identification code for identifying the sine wave, the base station controls the RF switch to sequentially select and gate the direction finding antenna and the communication antenna to receive the sine wave signal in a time-sharing manner;

[0085] Step S33: The preset element gating sequence is to alternately gate the communication antenna elements, the direction-finding antenna elements, the communication antenna elements, and the direction-finding antenna elements. Optionally, after cycling through the gating sequence several times, the communication antenna elements are finally gated;

[0086] Step S34: The gating duration T sw , and 2f sin T sw is an integer;

[0087] Step S35: When the gated element receives a sine wave signal s(t) with a wavelength of λ in the direction of the elevation angle θ and azimuth of the antenna array, there is s(t - 2T ) = exp{j(2πft - 2π·2f sw t - 2π·2f sin t - 2π·2f sin T sw )} = exp{j2πft} = s(t); sin t} = s(t);

[0088] When the communication antenna is gated, that is, when i = 0, n = 0, 2,..., 2N - 2,

[0089] y i (t) = s(t - nT sw )exp{j2πΔf(t - nT sw )},

[0090] When the direction-finding antenna is gated, that is, when i = 1,..., N, n = 1, 3,..., 2N - 1,

[0091]

[0092] where Δf is the frequency difference caused by the transceiver carrier frequency mismatch;

[0093] Step S36: The transceiver carrier frequency mismatch is caused by the combined action of the Doppler frequency shift introduced by the relative motion between the terminal and the base station and the transceiver local oscillator mismatch.

[0094] Furthermore, step S4 in the above includes the following steps:

[0095] Step S41: Compensate for the phase difference of the RF channels. The phase difference is calibrated by a stationary signal source in the normal direction of the far field of the antenna array. Since there is no phase difference introduced by the incident angle in the received signals of each antenna at this time, the analyzed phase difference is caused by the RF channels, components, and transceiver carrier frequency mismatch;

[0096] Step S42: Compensate for the phase difference caused by the transceiver carrier frequency mismatch and construct the multi-channel received signal r i (t), i = 1, 2,..., N, satisfying:

[0097]

[0098] Among them, exp{jγ} is a constant, and we get:

[0099]

[0100] Furthermore, the step S5 includes the following steps:

[0101] Step S51: Adopt an M-level two-dimensional hierarchical search. According to the principle of minimizing the total number of searches, determine the range lengths, number of segments, and segment lengths of the pitch angles and azimuth angles at each level.

[0102] Step S52: Starting from the first level, according to the steering vectors A corresponding to the pitch angle and azimuth angle combinations in each segment during the searches at each level, calculate all combinations S = A H R and its energy P = ∑s i 2 , s i being the i-th element in the data vector S, select the segment where the pitch angle and azimuth angle corresponding to the maximum energy are located as the search range for the next level until the M-th level.

[0103] Step S53: Take the pitch angle and azimuth angle corresponding to the maximum energy at the M-th level as the arrival angle estimation value.

[0104] Preferably, in the step S51, the determination of minimizing the total number of searches adopts an M-level two-dimensional hierarchical search;

[0105] The range length of the pitch angle at the first level The number of segments The segment length

[0106] The range length of the azimuth angle at the first level The number of segments The segment length

[0107] The number of combinations of the pitch angle and azimuth angle at the first level is

[0108] The range length of the pitch angle at the m-th level The number of segments The segment length

[0109] The range length of the azimuth angle at the m-th level The number of segments The segment length

[0110] The number of combinations of the pitch angle and azimuth angle at the m-th level is

[0111] The range length of the pitch angle at the M-th level Number of segments Segment length

[0112] Length of the azimuth range of the Mth level Number of segments Segment length

[0113] The number of combinations of the elevation angle and azimuth angle of the Mth level is

[0114] Determine the number of segments of the elevation angle and azimuth angle at each level Satisfy:

[0115]

[0116] Example:

[0117] The base station includes an array antenna, which is composed of a communication antenna element and 6 direction-finding antenna elements. The antenna array is as Figure 2 shown. The direction-finding antennas are evenly distributed along a circle with a radius of R = λ / 2. The carrier wavelength is λ = 12.5 cm, and the element interval in radians is ω = π / 3. They are numbered 1, 2,..., 6 in sequence, and element 1 is on the X-axis. The communication antenna element is located at the center of the uniform circular array and is numbered 0;

[0118] The elevation angle θ is the angle between the signal incident direction and the XOY plane. Its maximum value, minimum value, and step length are θ max = π / 2, θ min = 0, and θ step = π / 180;

[0119] Azimuth angle is the angle between the projection of the signal incident direction on the XOY plane and the X-axis. Its maximum value, minimum value, and step length are respectively and

[0120] The elevation angle θ and the azimuth angle corresponding steering vector is:

[0121]

[0122] where

[0123]

[0124] According to the observation ranges [0, π / 2] and [0, 2π] of the elevation angle and azimuth angle, the step lengths θ step and and construct a steering vector library for all combinations of the elevation angle and azimuth angle.

[0125] The terminal broadcasts a data packet signal with flag information using the Bluetooth communication protocol. The data packet signal contains a continuous sine wave signal for direction finding. The data packet contains the following information:

[0126] Byte numbers 7 to 12 represent the MAC address used to identify and distinguish the terminal;

[0127] Byte numbers 15 to 17 represent the characteristic identification code used to identify the sine wave;

[0128] Byte numbers 27 to 43 represent the direction finding information code. For example, when using the CH37 broadcast channel and the signal bandwidth is 1 MHz, the direction finding information code is: 0xCC, 0x27, 0x45, 0x67, 0xF7, 0xDB, 0x34, 0xC4, 0x03, 0x8E, 0x5C, 0x0B, 0xAA, 0x97, 0x30, 0x56, 0xE6. The signal generated after whitening filtering through the CH37 channel and GFSK modulation is a 250 kHz sine wave, that is, f sin = 250 kHz.

[0129] When the characteristic identification code used to identify the sine wave is detected, the base station controls the RF switch to sequentially select and connect the direction finding antenna and the communication antenna to receive the sine wave signal in a time-division manner. The preset array element selection sequence is 0, 1, 0, 2, 0, 3,..., 0, 6, and the selection duration T sw = 2 μs, 2f sin T sw = 1;

[0130] When the selected array element receives the sine wave signal s(t) with a wavelength of λ in the direction of the elevation angle θ and azimuth angle of the antenna array, there is s(t - 2T sw ) = exp{j(2πft - 2π)} = exp{j2πft} = s(t); sin t - 2π)} = exp{j2πf sin t} = s(t);

[0131] When the communication antenna is selected and connected, that is, when i = 0, n = 0, 2,..., 2N - 2,

[0132] y i (t) = s(t - nT sw )exp{j2πΔf(t - nT sw )},

[0133] When the direction finding antenna is selected and connected, that is, when i = 1,..., N, n = 1, 3,..., 2N - 1,

[0134]

[0135] Among them, Δf is the frequency difference caused by the transceiver carrier frequency mismatch.

[0136] Compensate for the phase difference of the RF channel. The phase difference is calibrated by a stationary signal source in the normal direction of the far field of the antenna array. Since there is no phase difference introduced by the incident angle in the received signals of each antenna at this time, the phase difference is caused by the RF channel, components, and transceiver local oscillator mismatch;

[0137] Compensate for the phase difference caused by the transceiver carrier frequency mismatch and construct the multi-channel received signal r i (t), i = 1, 2,..., N, satisfying:

[0138]

[0139] Among them, exp{jγ} is a constant, and we get:

[0140]

[0141] Furthermore, adopt an M-level two-dimensional hierarchical search. According to the principle of minimizing the total search times, determine the length of the elevation angle range, azimuth angle range, number of segments, and segment length at each level;

[0142] Determine to adopt an M-level two-dimensional hierarchical search;

[0143] The length of the elevation angle range at the first level The number of segments The segment length

[0144] The length of the azimuth angle range at the first level The number of segments The segment length

[0145] The combination number of the elevation angle and azimuth angle at the first level is

[0146] The length of the elevation angle range at the mth level The number of segments The segment length

[0147] The length of the azimuth angle range at the mth level The number of segments The segment length

[0148] The combination number of the elevation angle and azimuth angle at the mth level is

[0149] The length of the elevation angle range at the Mth level The number of segments The segment length

[0150] Length of azimuth range at the M-th level Number of segments Length of each segment

[0151] The number of combinations of pitch angle and azimuth angle at the M-th level is

[0152] Determine the number of segments of pitch angle and azimuth angle at each level Meet

[0153]

[0154] Starting from the first level, according to the steering vector A corresponding to each combination of pitch angle and azimuth angle in the search at each level, calculate all combinations S = A H R and its energy P = ∑|s i | 2 s i , where s

[0155] Take the segment where the pitch angle and azimuth angle corresponding to the maximum energy at the M-th level are located as the search range for the next level until the M-th level;

[0156] As mentioned above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A direction-finding method of an interferometer related to a direction-finding and positioning system, characterized in that, Including the following steps: Step S1: According to the base station arrival angle observation range, angle observation step length, direction-finding antenna array manifold, and carrier wavelength information, establish the mapping relationship between the incident angle and the steering vector, and construct a steering vector library; Step S2: The terminal broadcasts a data packet signal with flag information, and the data packet signal contains a continuous sine wave signal for direction finding; Step S3: After the central communication antenna of the base station receives and recognizes the flag information, the base station controls the RF switch to time-divisionally select and connect the direction-finding antenna and the communication antenna in a preset order to receive the sine wave signal in the data packet signal; Step S4: Preprocess the received signal to eliminate the phase difference caused by the RF channel phase difference and the transceiver carrier frequency mismatch, and construct a multi-channel received signal R; Step S5: Based on the two-dimensional hierarchical search algorithm, combine with the steering vector library to obtain the steering vector A, construct the vector S, where vector S = A H R, calculate the energy of the vector S, and take the angle with the strongest energy as the estimated value.

2. The method for interferometer direction finding related to a direction finding and positioning system according to claim 1, wherein The step S1 includes the following steps: Step S11: The base station includes an array antenna, which is composed of a communication antenna element and N direction-finding antenna elements. The direction-finding antennas are evenly distributed along a circle with a radius of R = λ / 2, where λ is the carrier wavelength. The element interval in radians is ω = 2π / N, and they are numbered 1, 2,..., N in sequence. And element 1 is on the X-axis, and the communication antenna element is located at the center of the uniform circular array and is numbered 0; Step S12: The pitch angle θ is the angle between the signal incident direction and the XOY plane, and its maximum value, minimum value, and step length are θ max , θ min and θ step ; Azimuth angle is the angle between the projection of the signal incident direction on the XOY plane and the X-axis, and its maximum value, minimum value and step length are respectively and Pitch angle θ and azimuth angle The corresponding steering vector is as follows: Among them, Step S13: According to the pitch angle and azimuth angle observation ranges [θ min , θ max , and the step length θ step and as well as construct a steering vector library for all combinations of pitch angles and azimuth angles.

3. The method for direction finding by an interferometer related to a direction finding and positioning system according to claim 1, characterized in that The step S2 includes the following steps: Step S21: The flag information at least includes the MAC address for identifying and distinguishing the terminal and the characteristic identification code for identifying the sine wave; Step S22: The sine wave signal s(t) is generated by modulating the direction finding information code, with a frequency of f sin , that is, s(t) = exp{j2πf sin t}.

4. The method for interferometric direction finding of a direction finding and positioning system according to claim 1, characterized in that The step S3 includes the following steps: Step S31: The RF switch selects and connects the communication antenna to receive the space radio signal; Step S32: When detecting the characteristic identification code for identifying the sine wave, the base station controls the RF switch to time-divisionally select and connect the direction-finding antenna and the communication antenna in a preset order to receive the sine wave signal; The preset element selection order is to alternately select and connect the communication antenna element, the direction-finding antenna element, the communication antenna element, and the direction-finding antenna element, and cycle through the selection order several times, and finally select and connect the communication antenna element; Step S34: Gating duration T sw , and 2f sin T sw is an integer; Step S35: The receiving wavelength of the selected array element is λ, which is determined by the antenna array elevation angle θ and azimuth angle When the sine wave signal s(t) is in the direction, there exists s(t-2T sw )=exp{j(2πf sin t-2π·2f sin T sw )}=exp{j2πf sin t}=s(t); When the communication antenna is selected and connected, that is, when i = 0, n = 0, 2,..., 2N - 2, y i (t) = s(t - nT sw ) exp{j2πΔf(t - nT sw )}, When the direction-finding antenna is selected and connected, that is, when i = 1,..., N, n = 1, 3,..., 2N - 1, Among them, Δf is the frequency difference caused by the transceiver carrier frequency mismatch; The transceiver carrier frequency mismatch is generated by the combined action of the Doppler frequency shift introduced by the relative motion between the terminal and the base station and the transceiver local oscillator mismatch.

5. A direction finding method of an interferometer related to a direction finding and positioning system according to claim 1, characterized in that, The step S4 includes the following steps: Step S41: Compensate the RF channel phase difference, and the phase difference is calibrated by a stationary signal source in the normal direction of the far field of the antenna array; Step S42: Compensate the phase difference caused by the transceiver carrier frequency mismatch and construct the multi-channel received signal r i (t), i = 1, 2,..., N, satisfying: Among them, exp{jγ} is a constant, and we get:

6. The method for interferometer direction finding related to a direction finding and positioning system according to claim 1, characterized in that The step S5 includes the following steps: Step S51: Adopt M two - level two - dimensional hierarchical search. According to the principle of minimizing the total number of searches, determine the range lengths, number of segments, and segment lengths of the pitch angles and azimuth angles at each level. Step S52: Starting from the first level, calculate all combinations S = A according to the steering vectors A corresponding to the pitch angle and azimuth angle combinations in each segment during the search at each level. H R and its energy P = ∑|s i | 2 , where s i is the i-th element in the data vector S. Select the segment where the pitch angle and azimuth angle corresponding to the maximum energy are located as the search range for the next level until the M last level. Step S53: Use the pitch angle and azimuth angle corresponding to the maximum energy at the M th level as the arrival angle estimation value.

7. The direction finding method of an interferometer related to a direction finding and positioning system according to claim 6, characterized in that, In the step S51, the determination of minimizing the total number of searches adopts M two-level two-dimensional hierarchical search; Length of the first - level pitch - angle range Number of segments Length of each segment Length of the first-level azimuth range Number of segments Segment length The combination number of the first-level pitch angle and azimuth angle is Length of the pitch angle range of the m-th level Number of segments Length of each segment Length of the azimuth range of the m-th level Number of segments Length of each segment The number of combinations of pitch angle and azimuth angle at the m-th level is Level M Pitch Angle Range Length Number of Segments Segment Length No. M Length of azimuth range at the Number of segments Length of segment Level M The combined number of pitch angles and azimuth angles is Determine the number of segments of pitch angles and azimuth angles at each level Satisfy:

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