CN107561357B - High-precision instantaneous frequency measurement method and device based on channelization - Google Patents
High-precision instantaneous frequency measurement method and device based on channelization Download PDFInfo
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Abstract
The invention provides a high-precision instantaneous frequency measurement method and a device based on channelization, which comprises the following steps: the digital channelizing processing is carried out on the input radar signals, and comprises the following steps: extracting and filtering the input radar signals by adopting a multiphase band-pass filter group, performing Fourier transform (FFT), and outputting sample points of a plurality of channels to realize digital channelization; respectively adopting a phase difference method and an interpolation method to carry out instantaneous frequency measurement on the multi-channel signals after the digital channelization; and performing deblurring processing on the frequency obtained by the phase difference method according to the frequency obtained by the interpolation method so as to correct the originally blurred frequency back to the correct frequency. The invention still has higher frequency measurement precision when the digital channelization is not over-sampled.
Description
Technical Field
The invention relates to the technical field of radar signal reconnaissance and interference in electronic reconnaissance, in particular to a high-precision instantaneous frequency measurement method and device based on channelization.
Background
Modern electronic warfare needs to intercept the electromagnetic spectrum information of enemies, wherein the most important thing is to measure the frequency parameter of the enemy electromagnetic signal, and according to the frequency parameter, important indexes such as the frequency agility range and the spectrum width of the frequency agility radar can be obtained, and the frequency agility range and the spectrum width can reflect the functions and the purposes of the radar. In order to implement effective interference in modern complex electromagnetic environments, signals must be sorted and threat identified first, and frequency information of radar is an important basis for sorting and threat identification.
The more common frequency measurement methods include pure channelization frequency measurement and phase comparison instantaneous frequency measurement. Pure channelized frequency measurement has the advantage of high sensitivity, but is limited by the number of channels which cannot be too many, and the frequency measurement precision is low; compared with the instantaneous frequency measurement of a phase method, the method has high frequency measurement accuracy, but has high requirement on signal to noise ratio of signals and poor sensitivity. The method combining the two can improve the signal detection sensitivity and the frequency measurement precision. That is, the digital channelization is used to perform channelization division on the signal, and then the phase difference method is used to measure the instantaneous frequency of the signal.
However, when the digital channelization is not adopted, the phase difference instantaneous frequency measurement has the problem of phase measurement ambiguity under the influence of noise, and the frequency measurement precision is greatly influenced.
Disclosure of Invention
The object of the present invention is to solve at least one of the technical drawbacks mentioned.
Therefore, the invention aims to provide a high-precision instantaneous frequency measurement method and device based on channelization.
In order to achieve the above object, an embodiment of an aspect of the present invention provides a high-precision instantaneous frequency measurement method based on channelization, including the following steps:
step S1, performing digital channelization on the input radar signal, including: extracting and filtering the input radar signals by adopting a multiphase band-pass filter group, performing Fourier transform (FFT), and outputting sample points of a plurality of channels to realize digital channelization;
step S2, respectively adopting a phase difference method and an interpolation method to carry out instantaneous frequency measurement on the multi-channel signals after the digital channelization processing in the step S1;
in step S3, the frequency obtained by the phase difference method is deblurred according to the frequency obtained by the interpolation method, so that the frequency in which the blur originally exists is corrected back to the correct frequency.
Further, in step S1, the digital channelization process is implemented by using an even-order and critically-decimated polyphase bandpass filter bank.
Further, in the step S2,
assuming that the signal after the digital channelization in step S1 is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
the calculation steps for measuring the instantaneous frequency by adopting the phase difference method are as follows:
step 1: conjugate multiplication is carried out on two adjacent sampling points xi (n) and xi (n-1) of the ith channel after digital channelization:
yi(n)＝xi(n)·conj(xi(n-1))＝Ii(n)+jQi(n)
step 2: obtaining phase angle phi by using the relationship between orthogonal signals Ii (n) and Qi (n)i(n) that is
And step 3: the instantaneous frequency of the corresponding signal in each channel is obtained through the conversion operation between the phase and the frequency:
where Δ t is a sampling interval, i.e. a time interval between two sampling points of the current channel, and fi (n) is a signal frequency obtained by the ith channel phase difference method.
Further, in the step S2,
assuming that the signal after the digital channelization in step S1 is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
the calculation steps for instantaneous frequency measurement using the interpolation method are as follows:
step 1: calculating the signal amplitudes of the ith channel, the (i-1) th channel and the (i + 1) th channel:
where Ii (n) and Qi (n) are orthogonal signals at the nth point of the ith channel, and ai (n) is the signal amplitude at the nth point of the ith channel;
step 2: calculating the ith channel signal frequency from the signal amplitude using interpolation:
where Ai (n) is the ith channel signal amplitude, Aneighbour (n) is the larger of Ai-1(n) and Ai +1(n), and Δ t is the sampling interval. When Ai-1(n) is greater than Ai +1(n), λ ═ 1; when Ai-1(n) is less than Ai +1(n), λ is 1.
Further, in the step S3,
assuming that the frequency obtained by the phase difference method is f1(n), the frequency obtained by the interpolation method is f2(n), and the frequency after final deblurring is f (n), the deblurring process is as follows:
if it is not
Then
If it is not
Then
If it is not
Then f (n) ═ f1(n)，
Wherein alpha is more than or equal to 0 and less than or equal to 1, and the more suitable value of alpha is 0.75.
The embodiment of the invention also provides a high-precision instantaneous frequency measurement device based on channelization, which comprises: a digital channelization module, an instantaneous frequency measurement module, and a frequency disambiguation module, wherein,
the digital channelizing module is used for carrying out digital channelizing processing on an input radar signal, and comprises the following steps: extracting and filtering the input radar signals by adopting a multiphase band-pass filter group, performing Fourier transform (FFT), and outputting sample points of a plurality of channels to realize digital channelization;
the instantaneous frequency measurement module is used for respectively adopting a phase difference method and an interpolation method to carry out instantaneous frequency measurement on the multi-channel signals subjected to the digital channelization processing in the step S1;
and the frequency ambiguity resolution module is used for performing ambiguity resolution on the frequency obtained by the phase difference method according to the frequency obtained by the interpolation method so as to correct the original frequency with ambiguity back to the correct frequency.
Further, the digital channelizing module adopts a multi-phase band-pass filter bank with even arrangement and critical extraction to realize digital channelizing processing.
Further, assume that the signal after digital channelization is a baseband single frequency signal, and its expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
the instantaneous frequency measurement module adopts a phase difference method to measure the instantaneous frequency, and the calculation steps are as follows:
step 1: conjugate multiplication is carried out on two adjacent sampling points xi (n) and xi (n-1) of the ith channel after digital channelization:
yi(n)＝xi(n)·conj(xi(n-1))＝Ii(n)+jQi(n)
step 2: obtaining phase angle phi by using the relationship between orthogonal signals Ii (n) and Qi (n)i(n) that is
And step 3: the instantaneous frequency of the corresponding signal in each channel is obtained through the conversion operation between the phase and the frequency:
where Δ t is a sampling interval, i.e. a time interval between two sampling points of the current channel, and fi (n) is a signal frequency obtained by the ith channel phase difference method.
Further, assume that the signal after digital channelization is a baseband single frequency signal, and its expression is:
wherein the content of the first and second substances,
is a true signal, A is the signal amplitude, φ is the initial phase, f is the signal frequency, Δ t is the sampling timeInterval, ω (n) is zero-mean white gaussian noise;
the instantaneous frequency measurement module adopts the interpolation method to carry out instantaneous frequency measurement, and the calculation steps are as follows:
step 1: calculating the signal amplitudes of the ith channel, the (i-1) th channel and the (i + 1) th channel:
where Ii (n) and Qi (n) are orthogonal signals at the nth point of the ith channel, and ai (n) is the signal amplitude at the nth point of the ith channel;
step 2: calculating the ith channel signal frequency from the signal amplitude using interpolation:
where Ai (n) is the ith channel signal amplitude, Aneighbour (n) is the larger of Ai-1(n) and Ai +1(n), and Δ t is the sampling interval. When Ai-1(n) is greater than Ai +1(n), λ ═ 1; when Ai-1(n) is less than Ai +1(n), λ is 1.
Further, the frequency ambiguity resolution module assumes that the frequency obtained by the phase difference method is f1(n), the frequency obtained by the interpolation method is f2(n), and the frequency after final ambiguity resolution is f (n), and the ambiguity resolution process is as follows:
if it is not
Then
If it is not
Then
If it is not
Then
Wherein alpha is more than or equal to 0 and less than or equal to 1, and the more suitable value of alpha is 0.75.
The invention discloses a high-precision instantaneous frequency measurement method and device based on channelization, and aims to achieve high frequency measurement precision when digital channelization is not adopted excessively. The invention carries out channelization processing on the received external signal, can filter out-of-band noise, improves the signal-to-noise ratio, and improves the signal detection sensitivity and the frequency measurement precision; the instantaneous frequency measurement based on the phase difference and the interpolation method is carried out on the channelized signal, so that the frequency information of the signal can be accurately obtained; by frequency deblurring processing, namely, deblurring is carried out on the frequency measured by the phase difference method according to the frequency obtained by the interpolation method, the signal frequency without ambiguity can be ensured to be obtained, and the measurement accuracy of the signal frequency is greatly improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a flow chart of a channelized-based high-precision instantaneous frequency measurement method according to an embodiment of the present invention;
FIG. 2 is a block diagram of a channelized based high precision instantaneous frequency measurement device according to an embodiment of the present invention;
FIG. 3 is a diagram of a digital channelization scheme based on a polyphase filter structure according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of instantaneous frequency measurement by phase difference method according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating an example of frequency disambiguation according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
As shown in fig. 1, the channelized-based high-precision instantaneous frequency measurement method of the embodiment of the present invention includes the following steps:
step S1, performing digital channelization on the input radar signal, including: a multiphase band-pass filter group is adopted to extract and filter the input radar signals, and sample points of a plurality of channels are output after Fourier FFT (fast Fourier transform) conversion is carried out, so that digital channelization processing is realized, and noise outside the channels is filtered.
Specifically, a polyphase phase band-pass filter bank with even arrangement and critical extraction is adopted to realize digital channelization processing. And a group of band-pass filter banks with the same performance are used for the input radar signals, and the original full-band signals are divided into a plurality of sub-band signals. Digital channelization has an efficient implementation, namely a channelization structure based on a polyphase filter bank.
As shown in fig. 3, the diagram shows an even arrangement and critical decimation polyphase filtering structure of complex signals, and the main process is to perform D-fold decimation on input signals, then filter the decimated signals, and finally output sample points of D channels through D-point FFT. In the embodiment, the digital channelization is realized by adopting a polyphase filter structure with even arrangement and critical extraction.
And step S2, respectively adopting a phase difference method and an interpolation method to carry out instantaneous frequency measurement on the multi-channel signals after the digital channelization processing in the step S1.
(1) Phase difference method
Assume that the signal after the digital channelization in step S1 is a baseband single frequency signal, and its expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
as shown in fig. 4, the calculation steps for instantaneous frequency measurement by the phase difference method are as follows:
step 1: conjugate multiplication is carried out on two adjacent sampling points xi (n) and xi (n-1) of the ith channel after digital channelization:
yi(n)＝xi(n)·conj(xi(n-1))＝Ii(n)+jQi(n)
step 2: obtaining phase angle phi by using the relationship between orthogonal signals Ii (n) and Qi (n)i(n) that is
And step 3: the instantaneous frequency of the corresponding signal in each channel is obtained through the conversion operation between the phase and the frequency:
where Δ t is a sampling interval, i.e. a time interval between two sampling points of the current channel, and fi (n) is a signal frequency obtained by the ith channel phase difference method.
(2) Interpolation method
Assume that the signal after the digital channelization in step S1 is a baseband single frequency signal, and its expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
the calculation steps for instantaneous frequency measurement by interpolation are as follows:
step 1: calculating the signal amplitudes of the ith channel, the (i-1) th channel and the (i + 1) th channel:
where Ii (n) and Qi (n) are orthogonal signals at the nth point of the ith channel, and ai (n) is the signal amplitude at the nth point of the ith channel;
step 2: calculating the ith channel signal frequency from the signal amplitude using interpolation:
where Ai (n) is the ith channel signal amplitude, Aneighbour (n) is the larger of Ai-1(n) and Ai +1(n), and Δ t is the sampling interval. When Ai-1(n) is greater than Ai +1(n), λ ═ 1; when Ai-1(n) is less than Ai +1(n), λ is 1.
The frequency precision obtained by instantaneous frequency measurement by the phase difference method is higher, but the phase ambiguity phenomenon exists, so that the frequency measurement is ambiguous; the frequency precision obtained by frequency measurement by the interpolation method is low, but the frequency measurement blurring phenomenon cannot exist.
And step S3, performing deblurring processing on the frequency obtained by the phase difference method according to the frequency obtained by the interpolation method so as to correct the original frequency with the blur back to the correct frequency and ensure the accuracy of frequency measurement.
Specifically, assuming that the frequency obtained by the phase difference method is f1(n), the frequency obtained by the interpolation method is f2(n), and the frequency after final deblurring is f (n), the deblurring process is as follows:
if it is not
Then
If it is not
Then
If it is not
Then f (n) ═ f1(n)，
Wherein alpha is more than or equal to 0 and less than or equal to 1, and the more suitable value of alpha is 0.75.
After the deblurring process, the frequencies where the original blur may exist are all corrected back to the correct frequencies, thus making the measured frequencies more accurate. Fig. 5 shows the frequency measurement effect before and after the frequency deblurring algorithm is adopted. In fig. 5, the channel bandwidth is 18.75MHz, i.e., the frequency range is between-9.375 MHz and +9.375 MHz.
When the phase difference method is adopted for instantaneous frequency measurement, the frequency measurement blurring phenomenon is serious, namely, the frequency near-9 MHz is measured into the frequency around +9MHz, and after the blurring treatment, the frequency near +9MHz is corrected back to the correct frequency.
As shown in fig. 2, an embodiment of the present invention further provides a high-precision instantaneous frequency measuring device based on channelization, including: a digital channelization module 100, an instantaneous frequency measurement module 200, and a frequency disambiguation module 300.
Specifically, the digital channelization module 100 is configured to perform digital channelization on an input radar signal, and includes: and extracting and filtering the input radar signals by adopting a multiphase band-pass filter group, performing Fourier FFT (fast Fourier transform) and outputting sample points of a plurality of channels so as to realize digital channelization processing.
In one embodiment of the present invention, the digital channelization module 100 implements a digital channelization process using an even-order, critically-decimated polyphase bandpass filter bank. And a group of band-pass filter banks with the same performance are used for the input radar signals, and the original full-band signals are divided into a plurality of sub-band signals. Digital channelization has an efficient implementation, namely a channelization structure based on a polyphase filter bank.
As shown in fig. 3, the diagram shows an even arrangement and critical decimation polyphase filtering structure of complex signals, and the main process is to perform D-fold decimation on input signals, then filter the decimated signals, and finally output sample points of D channels through D-point FFT. In the embodiment, the digital channelization is realized by adopting a polyphase filter structure with even arrangement and critical extraction.
The instantaneous frequency measurement module 200 is configured to perform instantaneous frequency measurement on the multi-channel signal after the digital channelization processing in step S1 by using a phase difference method and an interpolation method, respectively.
(1) Phase difference method
Assuming that the signal after digital channelization is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
the instantaneous frequency measurement module 200 adopts the phase difference method to perform instantaneous frequency measurement, and the calculation steps are as follows:
step 1: conjugate multiplication is carried out on two adjacent sampling points xi (n) and xi (n-1) of the ith channel after digital channelization:
yi(n)＝xi(n)·conj(xi(n-1))＝Ii(n)+jQi(n)
step 2: obtaining phase angle phi by using the relationship between orthogonal signals Ii (n) and Qi (n)i(n) that is
And step 3: the instantaneous frequency of the corresponding signal in each channel is obtained through the conversion operation between the phase and the frequency:
where Δ t is a sampling interval, i.e. a time interval between two sampling points of the current channel, and fi (n) is a signal frequency obtained by the ith channel phase difference method.
(2) Interpolation method
Assuming that the signal after digital channelization is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude, phi is the initial phase, f is the signal frequency, Δ t is the sampling time interval, and ω (n) is zero-mean gaussian white noise;
the instantaneous frequency measurement module 200 performs instantaneous frequency measurement by interpolation as follows:
step 1: calculating the signal amplitudes of the ith channel, the (i-1) th channel and the (i + 1) th channel:
where Ii (n) and Qi (n) are orthogonal signals at the nth point of the ith channel, and ai (n) is the signal amplitude at the nth point of the ith channel;
step 2: calculating the ith channel signal frequency from the signal amplitude using interpolation:
where Ai (n) is the ith channel signal amplitude, Aneighbour (n) is the larger of Ai-1(n) and Ai +1(n), and Δ t is the sampling interval. When Ai-1(n) is greater than Ai +1(n), λ ═ 1; when Ai-1(n) is less than Ai +1(n), λ is 1.
The frequency deblurring module 300 is configured to deblur the frequency obtained by the phase difference method according to the frequency obtained by the interpolation method, so as to correct the originally blurred frequency back to the correct frequency, thereby ensuring the accuracy of frequency measurement.
Specifically, the frequency deblurring module 300 assumes that the frequency obtained by the phase difference method is f1(n), the frequency obtained by the interpolation method is f2(n), and the frequency after final deblurring is f (n), and the deblurring process is as follows:
if it is not
Then
If it is not
Then
If it is not
Then f (n) ═ f1(n)，
Wherein alpha is more than or equal to 0 and less than or equal to 1, and the more suitable value of alpha is 0.75.
After the deblurring process, the frequencies where the original blur may exist are all corrected back to the correct frequencies, thus making the measured frequencies more accurate. Fig. 5 shows the frequency measurement effect before and after the frequency deblurring algorithm is adopted. In fig. 5, the channel bandwidth is 18.75MHz, i.e., the frequency range is between-9.375 MHz and +9.375 MHz.
When the phase difference method is adopted for instantaneous frequency measurement, the frequency measurement blurring phenomenon is serious, namely, the frequency near-9 MHz is measured into the frequency around +9MHz, and after the blurring treatment, the frequency near +9MHz is corrected back to the correct frequency.
The invention discloses a high-precision instantaneous frequency measurement method and device based on channelization, and aims to achieve high frequency measurement precision when digital channelization is not adopted excessively. The invention carries out channelization processing on the received external signal, can filter out-of-band noise, improves the signal-to-noise ratio, and improves the signal detection sensitivity and the frequency measurement precision; the instantaneous frequency measurement based on the phase difference and the interpolation method is carried out on the channelized signal, so that the frequency information of the signal can be accurately obtained; by frequency deblurring processing, namely, deblurring is carried out on the frequency measured by the phase difference method according to the frequency obtained by the interpolation method, the signal frequency without ambiguity can be ensured to be obtained, and the measurement accuracy of the signal frequency is greatly improved.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (6)
1. A high-precision instantaneous frequency measurement method based on channelization is characterized by comprising the following steps:
step S1, performing digital channelization on the input radar signal, including: extracting and filtering the input radar signals by adopting a multiphase band-pass filter group, performing Fourier transform (FFT), and outputting sample points of a plurality of channels to realize digital channelization;
step S2, respectively adopting a phase difference method and an interpolation method to carry out instantaneous frequency measurement on the multi-channel signals after the digital channelization processing in the step S1; assuming that the signal after the digital channelization in step S1 is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude,
is the initial phase, f is the signal frequency, Δ t is the sampling time interval, ω (n) is zeroMean white gaussian noise;
the calculation steps for instantaneous frequency measurement using the interpolation method are as follows:
step 1: calculating the signal amplitudes of the ith channel, the (i-1) th channel and the (i + 1) th channel:
wherein, Ii(n) and Qi(n) is the quadrature signal at the nth point of the ith channel, Ai(n) is the signal amplitude at the nth point of the ith channel;
step 2: calculating the ith channel signal frequency from the signal amplitude using interpolation:
wherein A isi(n) is the ith channel signal amplitude, Aneighbour(n) is Ai-1(n) and Ai+1(n) greater signal amplitude, Δ t is the sampling interval, when Ai-1(n) is greater than Ai+1When (n), λ ═ 1; when A isi-1(n) is less than Ai+1When (n) is greater than 1, λ is 1;
step S3, the frequency obtained by the phase difference method is processed by deblurring according to the frequency obtained by the interpolation method, so as to correct the original frequency with blurring back to the correct frequency; assuming a frequency f obtained by the phase difference method1(n) frequency f obtained by interpolation2(n), the frequency after final deblurring is f (n), and the deblurring process is as follows:
if it is not
Then
If it is not
Then
If it is not
Then f (n) ═ f1(n)，
Wherein alpha is more than or equal to 0 and less than or equal to 1, and the value of alpha is 0.75.
2. The channelized high-precision instantaneous frequency measurement method according to claim 1, characterized in that in said step S1, the digital channelizing process is implemented by using an even-order critically-decimated polyphase bandpass filter bank.
3. The channelized high precision instantaneous frequency measuring method according to claim 1, characterized in that in said step S2,
assuming that the signal after the digital channelization in step S1 is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude,
is the initial phase, f is the signal frequency, Δt is the sampling time interval, ω (n) is zero-mean gaussian white noise;
the calculation steps for measuring the instantaneous frequency by adopting the phase difference method are as follows:
step 1: two adjacent sampling points x of ith channel after digital channelizationi(n) and xi(n-1) conjugate multiplication:
yi(n)＝xi(n)·conj(xi(n-1))＝Ii(n)+jQi(n)
step 2: using orthogonal signals Ii(n) and Qi(n) the relationship yields a phase angle phii(n) that is
And step 3: the instantaneous frequency of the corresponding signal in each channel is obtained through the conversion operation between the phase and the frequency:
where Δ t is the sampling interval, i.e. the time interval between two sampling points of the current channel, fi(n) is a signal frequency obtained by the ith channel phase difference method.
4. A channelized-based high-precision instantaneous frequency measurement device, comprising: a digital channelization module, an instantaneous frequency measurement module, and a frequency disambiguation module, wherein,
the digital channelizing module is used for carrying out digital channelizing processing on an input radar signal, and comprises the following steps: extracting and filtering the input radar signals by adopting a multiphase band-pass filter group, performing Fourier transform (FFT), and outputting sample points of a plurality of channels to realize digital channelization;
the instantaneous frequency measurement module is used for respectively adopting a phase difference method and an interpolation method to carry out instantaneous frequency measurement on the multi-channel signals subjected to the digital channelization processing in the step S1; wherein, assuming that the signal after digital channelization is a baseband single frequency signal, its expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude,
is the initial phase, f is the signal frequency, Δ t is the sampling time interval, ω (n) is zero mean gaussian white noise;
the instantaneous frequency measurement module adopts the interpolation method to carry out instantaneous frequency measurement, and the calculation steps are as follows:
step 1: calculating the signal amplitudes of the ith channel, the (i-1) th channel and the (i + 1) th channel:
wherein, Ii(n) and Qi(n) is the quadrature signal at the nth point of the ith channel, Ai(n) is the signal amplitude at the nth point of the ith channel;
step 2: calculating the ith channel signal frequency from the signal amplitude using interpolation:
wherein A isi(n) is the ith channel signalAmplitude, Aneighbour(n) is Ai-1(n) and Ai+1(n) greater signal amplitude, Δ t is the sampling interval, when Ai-1(n) is greater than Ai+1When (n), λ ═ 1; when A isi-1(n) is less than Ai+1When (n) is greater than 1, λ is 1;
the frequency ambiguity resolution module is used for performing ambiguity resolution on the frequency obtained by the phase difference method according to the frequency obtained by the interpolation method so as to correct the original frequency with ambiguity back to the correct frequency; the frequency ambiguity resolution module assumes that the frequency obtained by the phase difference method is f1(n) frequency f obtained by interpolation2(n), the frequency after final deblurring is f (n), and the deblurring process is as follows:
if it is not
Then
If it is not
Then
If it is not
Then f (n) ═ f1(n)，
Wherein alpha is more than or equal to 0 and less than or equal to 1, and the value of alpha is 0.75.
5. The channelized high precision instantaneous frequency measurement device of claim 4, wherein said digital channelizing module uses an even-order critically-decimated polyphase bandpass filter bank to implement digital channelizing processing.
6. The channelized based high precision instantaneous frequency measuring device of claim 4,
assuming that the signal after digital channelization is a baseband single frequency signal, the expression is:
wherein the content of the first and second substances,
is a true signal, a is the signal amplitude,
is the initial phase, f is the signal frequency, Δ t is the sampling time interval, ω (n) is zero mean gaussian white noise;
the instantaneous frequency measurement module adopts a phase difference method to measure the instantaneous frequency, and the calculation steps are as follows:
step 1: two adjacent sampling points x of ith channel after digital channelizationi(n) and xi(n-1) conjugate multiplication:
yi(n)＝xi(n)·conj(xi(n-1))＝Ii(n)+jQi(n)
step 2: using orthogonal signals Ii(n) and Qi(n) the relationship yields a phase angle phii(n) that is
And step 3: the instantaneous frequency of the corresponding signal in each channel is obtained through the conversion operation between the phase and the frequency:
where Δ t is the sampling interval, i.e. the time interval between two sampling points of the current channel, fi(n) is a signal frequency obtained by the ith channel phase difference method.
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| CN109387813B (en) * | 2018-08-31 | 2023-04-11 | 中国电子科技集团公司第二十九研究所 | High-precision frequency measurement method based on broadband radar signal reception |
| CN109270344B (en) * | 2018-10-07 | 2021-01-08 | 扬州大学 | Coherent pulse signal frequency estimation method under pulse loss |
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| CN113219424A (en) * | 2021-04-29 | 2021-08-06 | 中国船舶重工集团公司第七二三研究所 | Parallel output multi-channel instantaneous frequency measurement system |
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