Residual frequency offset estimation method based on multichannel along-track interference

Abstract

The invention discloses a residual frequency offset estimation method based on multichannel along-track interference, and belongs to the field of radio reconnaissance, and the method comprises the steps: arranging a plurality of detection antennas front and back along the flight direction, passively receiving a signal transmitted by a radiation source target through the detection antennas, processing the received signal, and calculating the residual frequency offset of the radiation source target; due to the fact that the multiple antennas are subjected to interference processing after passing through the same slant distance process and compensating for phases caused by time delay, the interference phase between channels is zero under the ideal condition, and the interference phase between the channels is the phase generated under the combined action of the time delay and the residual frequency offset under the condition that the residual frequency offset exists. The residual frequency offset can be estimated according to the corresponding relation between the residual frequency offset and the interference phase. According to the invention, under the condition of non-cooperative reception, accurate estimation of the residual frequency offset can be realized, and the influence of the residual frequency offset on subsequent signal processing can be eliminated.

Description

Technical Field

[0001] The invention belongs to the technical field of radio reconnaissance, and in particular relates to a residual frequency deviation estimation method based on multi-channel along-track interference. Background Art

[0002] In non-cooperative reception, such as radio spectrum monitoring, the received signal still contains residual frequency offset after down-conversion, which is called residual frequency offset. Residual frequency offset can cause signal distortion, error accumulation, and affect the accuracy and reliability of the system. Effective frequency offset estimation and compensation are the key to ensuring system performance. Summary of the invention

[0003] The present invention aims to solve the technical problems existing in the background technology and to provide a residual frequency offset estimation method based on multi-channel along-track interference, so as to realize the residual frequency offset estimation between transceivers in the case of non-cooperative reception.

[0004] In order to solve the technical problem, the technical solution of the present invention is:

[0005] A residual frequency offset estimation method based on multi-channel along-track interference, the method comprising:

[0006] S1: Down-convert and de-modulate the received signals of multiple channels respectively to obtain corresponding Doppler signals;

[0007] S2: Calculate the time delay between channels through the same slant range according to the platform flight speed and antenna baseline;

[0008] S3: Perform phase compensation on Doppler signals of different channels according to the calculated time delay to eliminate the phase deviation caused by the distance difference between antennas;

[0009] S4: Perform interference processing on signals from different channels and obtain the interference phase through conjugate multiplication; preliminarily estimate the short baseline and long baseline frequency deviation values ​​based on the relationship between the interference phase and the residual frequency deviation; defuzzify the long baseline estimation result based on the short baseline estimation result to obtain the final estimation result.

[0010] Further, the step S1 specifically includes:

[0011] Three-channel along-track interferometry is used, and three detection antennas are arranged front and back along the flight direction. Antenna 1 and antenna 2 form a short baseline, and antenna 1 and antenna 3 form a long baseline. The signals emitted by the radiation source target are passively received, and the received signals are down-converted to obtain baseband signals; the baseband signals are demodulated to obtain the corresponding Doppler signals;

[0012] Assume that the instantaneous distances between the three-channel antenna of the aircraft and the radiation source target are R1, R2 and R3 respectively, and the distance between the radiation source target and the flight path of the aircraft is R0. The relationship between R1, R2 and R3 and R0 is shown in formula (1) (2).

[0013]

[0014] Where: the aircraft flying speed is v, the baseline length between antenna 1 and antenna 2 is d 12 , the baseline length between antenna 1 and antenna 3 is d 13 , the zero Doppler moment, i.e. the azimuth time, is t p ;

[0015] The Doppler signals r1(t), r2(t) and r3(t) obtained after baseband demodulation processing of antennas 1, 2 and 3 are expressed as:

[0016]

[0017] Among them, f0 is the carrier frequency of the radiation source, c is the speed of light, and f1 is the residual frequency deviation.

[0018] Further, the step S2 specifically includes:

[0019] Using Taylor's formula, the instantaneous distances between the aircraft's three-channel antenna and the radiation source target are R1, R2, and R3 at t = t p , and Expanding to the quadratic term, we have:

[0020]

[0021] in, is the time delay between the baseline length of antenna 1 and antenna 2 and the aircraft speed, is the time delay between the baseline length of antenna 1 and antenna 3 and the aircraft speed.

[0022] Further, the short baseline compensation in step S3 specifically includes:

[0023] The delay is calculated based on the aircraft flight speed and the baseline length between antenna 1 and antenna 2, and phase compensation is performed on r1(t). The compensated signal is expressed as:

[0024]

[0025] Further, the step S4 specifically includes:

[0026] Short baseline interference processing: multiply the compensated signal r′1(t) by the conjugate of the signal r2(t) from antenna 2 to calculate the interference result I 12 , and extract the interference phase

[0027] Short baseline frequency offset estimation: using interferometric phase and t 12 The relationship between the short baseline frequency offset f′1 is estimated, and its unambiguous range is:

[0028] Long baseline compensation: Perform long baseline compensation on the signal of antenna 1 to obtain r1″(t);

[0029] Long baseline interference processing: multiply the compensated signal r1″(t) by the conjugate of the signal r3(t) from antenna 3 to calculate the interference result I 13 , and extract the interference phase

[0030] Long baseline frequency offset estimation: using interferometric phase and t 13 The relationship between the long baseline frequency offset f1″ is estimated, and its unambiguous range is:

[0031] Frequency offset deambiguation: The long baseline result f1″ is deambiguated using the short baseline result f′ to obtain the final residual frequency offset estimate.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] The present invention discloses a method for measuring residual frequency deviation by using multiple antennas along-track interference, which can accurately estimate the residual frequency deviation in the case of non-cooperative reception. The residual frequency deviation in the signal is accurately estimated at the receiving end, and compensation is performed according to the estimated result, thereby reducing or eliminating the influence of the frequency deviation on the system performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 , a flow chart of a residual frequency offset estimation method based on multi-channel along-track interference disclosed in the present invention;

[0035] Figure 2 , Geometric model diagram of the residual frequency offset estimation method based on multi-channel along-track interference. DETAILED DESCRIPTION

[0036] The specific implementation mode of the present invention is described below in conjunction with embodiments:

[0037] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0038] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0039] Embodiment 1:

[0040] The objective of the present invention is achieved through the following technical solutions:

[0041] A residual frequency offset estimation method based on multi-channel along-track interferometry: multiple detection antennas are arranged in front and behind the flight direction to passively receive the signals emitted by the radiation source target, and the received signals are processed. Since multiple antennas pass through the same slant range course one after another, interference processing is performed after compensating for the phase caused by the time delay.

[0042] Ideally, the inter-channel interference phase is 0. In the presence of residual frequency offset, the inter-channel interference phase is the phase produced by the combined effect of time delay and residual frequency offset. The residual frequency offset can be estimated from the corresponding relationship between the residual frequency offset and the interference phase.

[0043] Since the interference phase range is (-π,π), the frequency offset estimation value is obtained by performing the corresponding deambiguation process through the interference phase of multiple channels.

[0044] Specifically, the steps include:

[0045] Step 1: Taking three-channel down-track interferometry as an example, three detection antennas are arranged front and back along the flight direction. Antenna 1 and antenna 2 form a short baseline, and antenna 1 and antenna 3 form a long baseline. The signal emitted by the radiation source target is passively received, and the received signal is down-converted to obtain a baseband signal; the baseband signal is demodulated to obtain the corresponding Doppler signal;

[0046] Assume that the instantaneous distances between the three-channel antenna of the aircraft and the radiation source target are R1, R2 and R3 respectively, and the distance between the radiation source target and the flight path of the aircraft is R0. The relationship between R1, R2 and R3 and R0 is shown in formula (1) (2).

[0047]

[0048] Where: the aircraft flying speed is v, the baseline length between antenna 1 and antenna 2 is d 12 , the baseline length between antenna 1 and antenna 3 is d 13 , the zero Doppler moment, i.e. the azimuth time, is t p ;

[0049] The Doppler signals r1(t), r2(t) and r3(t) obtained after baseband demodulation of antennas 1, 2 and 3 in step 1 are expressed as:

[0050]

[0051] Where f0 is the carrier frequency of the radiation source, c is the speed of light, and f1 is the residual frequency deviation;

[0052] Using Taylor's formula, R1, R2 and R3 are respectively p , and Expanding to the quadratic term, we have

[0053]

[0054] in, is the time delay between the baseline length of antenna 1 and antenna 2 and the aircraft speed, is the time delay between the baseline length of antenna 1 and antenna 3 and the aircraft speed.

[0055] Step 2: Calculate the delay based on the aircraft flight speed and the baseline length of antenna 1 and antenna 2, and perform phase compensation on r1(t). The compensated signal is expressed as

[0056]

[0057] Step 3: Conjugate multiply the compensated signal r′1(t) of channel 1 with the Doppler signal r2(t) of channel 2 to obtain the interference processing result:

[0058]

[0059] Step 4: As shown in formula (12), the corresponding relationship between the residual frequency offset and the interference phase is:

[0060]

[0061] in, is the interference phase between channel 1 and channel 2 after phase compensation.

[0062] Since the range of the interference phase is (-π,π), the unambiguous range of the frequency deviation measurement in step 4 is

[0063] Step 5: Calculate the delay based on the aircraft flight speed and the baseline lengths of antenna 1 and antenna 3, and perform phase compensation on r1(t). The compensated signal is expressed as

[0064]

[0065] Step 6: Conjugate multiply the compensated signal r1″(t) of channel 1 with the Doppler signal r3(t) of channel 3 to obtain the interference processing result:

[0066]

[0067] Step 7: As shown in formula (15), the corresponding relationship between the residual frequency deviation and the interference phase is:

[0068]

[0069] in, is the interference phase between channel 1 and channel 3 after phase compensation.

[0070] Since the range of the interference phase is (-π,π), the unambiguous range of the frequency deviation measurement in step 4 is

[0071] Step 8: Deambiguate the long baseline measurement result f1″ according to the short baseline measurement result f′1 to obtain a frequency offset estimation result.

[0072] Embodiment 2:

[0073] like Figure 1 As shown, the present embodiment discloses a residual frequency offset estimation method based on multi-channel along-track interference, and the specific implementation steps are as follows:

[0074] Assume that the drone flies in a straight line at a constant speed, the flight speed v is 15m / s, and the flight altitude is 500 meters. The carrier frequency f0 of the radiation source is 5GHz, and the distance R0 from the radiation source to the drone route is 10km. Taking three-channel along-track interferometry as an example, three detection antennas are arranged in front and behind along the flight direction. Antenna A1 and antenna A2 form a short baseline with a baseline length d 12 is 0.05m, antenna A1 and antenna A3 form a long baseline, the baseline length is d 13 is 0.3m, the residual frequency deviation is set to 218.64Hz, and the geometric model is as follows Figure 2 shown.

[0075] Step 1: The three antennas passively receive the signal emitted by the radiation source target, down-convert the received signal to obtain a baseband signal; de-modulate the baseband signal to obtain a corresponding Doppler signal;

[0076] Assume that the instantaneous distances between the three-channel antenna of the aircraft and the radiation source target are R1, R2 and R3 respectively, and the distance between the radiation source target and the flight path of the aircraft is R0. The relationship between R1, R2 and R3 and R0 is shown in formula (1) (2).

[0077]

[0078] Where: the aircraft flying speed is v, the baseline length between antenna 1 and antenna 2 is d 12 , the baseline length between antenna 1 and antenna 3 is d 13 , the zero Doppler moment, i.e. the azimuth time, is t p ;

[0079] The Doppler signals r1(t), r2(t) and r3(t) obtained after baseband demodulation of antennas 1, 2 and 3 in step 1 are expressed as:

[0080]

[0081]

[0082] Where f0 is the carrier frequency of the radiation source, c is the speed of light, and f1 is the residual frequency deviation;

[0083] Using Taylor's formula, R1, R2 and R3 are respectively p , and Expanding to the quadratic term, we have

[0084]

[0085] in, is the time delay between the baseline length of antenna 1 and antenna 2 and the aircraft speed, is the time delay between the baseline length of antenna 1 and antenna 3 and the aircraft speed.

[0086] Step 2: Calculate the delay based on the aircraft flight speed and the baseline length of antenna 1 and antenna 2, and perform phase compensation on r1(t). The compensated signal is expressed as

[0087]

[0088] Step 3: Conjugate multiply the compensated signal r′1(t) of channel 1 with the Doppler signal r2(t) of channel 2 to obtain the interference processing result:

[0089]

[0090] Step 4: As shown in formula (12), the corresponding relationship between the residual frequency offset and the interference phase is:

[0091]

[0092] in, is the interference phase between channel 1 and channel 2 after phase compensation.

[0093] Since the range of the interference phase is (-π,π), the unambiguous range of the frequency offset measurement in step 4 is In this embodiment, the time delay t of antenna A1 and antenna A2 through the same slant distance process is 12 The unambiguous range of frequency deviation measurement is (-250, 250) Hz. The mean value is -2.6504rad. According to formula (12), the residual frequency offset estimation result f′1 is 210.9134Hz.

[0094] Step 5: Calculate the delay based on the aircraft flight speed and the baseline lengths of antenna 1 and antenna 3, and perform phase compensation on r1(t). The compensated signal is expressed as

[0095]

[0096] Step 6: Conjugate multiply the compensated signal r1″(t) of channel 1 with the Doppler signal r3(t) of channel 3 to obtain the interference processing result:

[0097]

[0098] Step 7: As shown in formula (12), the corresponding relationship between the residual frequency deviation and the interference phase is:

[0099]

[0100] in, is the interference phase between channel 1 and channel 3 after phase compensation.

[0101] Since the range of the interference phase is (-π,π), the unambiguous range of the frequency offset measurement in step 4 is In this embodiment, the time delay t of antenna A1 and antenna A3 through the same slant distance process is 13 The unambiguous range of frequency deviation measurement is (-41.6667, 41.6667) Hz. The mean value is 2.3604 rad. According to formula (12), the residual frequency offset estimation result f1″ is -31.3052 Hz.

[0102] Step 8: Defuzzify the long baseline measurement result f1″ according to the short baseline measurement result f′1 to obtain a frequency offset estimation result. In this embodiment, the fuzzy number is 6, and the final estimation result is 218.6948 Hz.

[0103] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0104] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0105] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0106] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0107] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

[0108] Many other changes and modifications may be made without departing from the concept and scope of the present invention.It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A residual frequency offset estimation method based on multi-channel along-track interference, characterized in that: The method comprises: S1: Down-convert and de-modulate the received signals of multiple channels respectively to obtain corresponding Doppler signals; S2: Calculate the time delay between channels through the same slant range according to the platform flight speed and antenna baseline; S3: Perform phase compensation on Doppler signals of different channels according to the calculated time delay to eliminate the phase deviation caused by the distance difference between antennas; S4: Perform interference processing on signals from different channels and obtain the interference phase through conjugate multiplication; preliminarily estimate the short baseline and long baseline frequency deviation values ​​based on the relationship between the interference phase and the residual frequency deviation; defuzzify the long baseline estimation result based on the short baseline estimation result to obtain the final estimation result.

2. The residual frequency offset estimation method based on multi-channel along-track interference according to claim 1 is characterized in that: The step S1 specifically includes: Three-channel along-track interferometry is used, and three detection antennas are arranged front and back along the flight direction. Antenna 1 and antenna 2 form a short baseline, and antenna 1 and antenna 3 form a long baseline. The signals emitted by the radiation source target are passively received, and the received signals are down-converted to obtain baseband signals; the baseband signals are demodulated to obtain the corresponding Doppler signals; Assume that the instantaneous distances between the three-channel antenna of the aircraft and the radiation source target are R1, R2 and R3 respectively, and the distance between the radiation source target and the flight path of the aircraft is R0. The relationship between R1, R2 and R3 and R0 is shown in formula (1) (2). Where: the aircraft flying speed is v, the baseline length between antenna 1 and antenna 2 is d 12 , the baseline length between antenna 1 and antenna 3 is d 13 , the zero Doppler moment, i.e. the azimuth time, is t p ; The Doppler signals r1(t), r2(t) and r3(t) obtained after baseband demodulation processing of antennas 1, 2 and 3 are expressed as: Among them, f0 is the carrier frequency of the radiation source, c is the speed of light, and f1 is the residual frequency deviation.

3. The residual frequency offset estimation method based on multi-channel along-track interference according to claim 1 is characterized in that: The step S2 specifically includes: Using Taylor's formula, the instantaneous distances between the aircraft's three-channel antenna and the radiation source target are R1, R2, and R3 at t = t p , and Expanding to the quadratic term, we have: in, is the time delay between the baseline length of antenna 1 and antenna 2 and the aircraft speed, is the time delay between the baseline length of antenna 1 and antenna 3 and the aircraft speed.

4. The residual frequency offset estimation method based on multi-channel along-track interference according to claim 1 is characterized in that: The short baseline compensation step S3 specifically includes: The delay is calculated based on the aircraft flight speed and the baseline length between antenna 1 and antenna 2, and phase compensation is performed on r1(t). The compensated signal is expressed as:

5. The residual frequency offset estimation method based on multi-channel along-track interference according to claim 4 is characterized in that: The step S4 specifically includes: Short baseline interference processing: multiply the compensated signal r′1(t) by the conjugate of the signal r2(t) from antenna 2 to calculate the interference result I 12 , and extract the interference phase Short baseline frequency offset estimation: using interferometric phase and t 12 The relationship between the short baseline frequency offset f′1 is estimated, and its unambiguous range is: Long baseline compensation: Perform long baseline compensation on the signal of antenna 1 to obtain r″1(t); Long baseline interference processing: multiply the compensated signal r″1(t) by the conjugate of the signal r3(t) from antenna 3 to calculate the interference result I 13 , and extract the interference phase Long baseline frequency offset estimation: using interferometric phase and t 13 The relationship between the long baseline frequency offset f″1 is estimated, and its unambiguous range is: Frequency offset deambiguation: The long baseline result f″1 is deambiguated using the short baseline result f′1 to obtain the final residual frequency offset estimate.

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