Ultra-wideband instantaneous frequency measurement method and circuit

Abstract

The invention provides an ultra-wideband instantaneous frequency measurement method and circuit, and the method comprises the steps: obtaining a radio frequency signal, carrying out the signal folding of the radio frequency signal at a certain moment based on a local oscillator signal, and obtaining a target sampling signal; performing signal type conversion on the target sampling signal in the preset signal processing frequency band to obtain a digital signal; according to the method, the digital signal is firstly demodulated, and then the frequency is measured according to the demodulated signal, so that the instantaneous frequency before the radio frequency signal is folded is restored, the analog processing of the digital signal is completed, and additional analog frequency conversion processing is not needed. According to the ultra-wideband instantaneous frequency measurement method provided by the invention, the limitation of the Nyquist sampling theorem is broken through, the radio-frequency signal is folded to obtain a related signal conforming to the signal processing of the analog-to-digital converter, and the ultra-wideband radio-frequency signal can be received and processed by directly adopting the single analog-to-digital converter; and the instantaneous frequency value of the related radio frequency signal is restored without other analog processing circuits.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency circuits, and in particular to an ultra-wideband instantaneous frequency measurement method and circuit. Background Art

[0002] Receivers are used in the field of communications to receive various radio signals and convert them into corresponding audio, video or digital signals. With the continuous updating of technology, fully digital receivers are the current development direction. They can directly perform analog-to-digital conversion on the signals sent by the antenna, and do not require additional analog frequency conversion devices. However, due to the limitation of the sampling frequency of the analog-to-digital converter, the analog-to-digital conversion cannot synchronously process the signals of the entire frequency band. In the related art, the signal receiving system is limited by the analog-to-digital converter, and the signal bandwidth needs to be less than the first Nyquist zone of the analog-to-digital converter, that is, fs / 2. When the signal bandwidth is greater than the first Nyquist zone: on the one hand, the entire measured bandwidth can be traversed by frequency sweeping with each step of fs / 2, but this method cannot receive or cannot completely receive the instantaneously generated signal, and the signal reception speed is relatively slow; on the other hand, the entire frequency domain is segmented based on the fs / 2 frequency, and the signal is acquired in segments. At least 2BW / fs channels are required to achieve full frequency band coverage, but this method is not only complex in design structure, but also high in cost, which is not conducive to large-scale application.

[0003] Therefore, how to provide a technical solution for real-time reception and measurement of the instantaneous frequency of ultra-wideband is a technical problem that urgently needs to be solved. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a technical solution for ultra-wideband instantaneous frequency measurement to solve at least one of the above-mentioned technical problems.

[0005] In order to achieve the above-mentioned purpose and other related purposes, the technical solution provided by this application is as follows.

[0006] According to a first aspect of an embodiment of the present application, there is provided an ultra-wideband instantaneous frequency measurement method, comprising:

[0007] Acquire radio frequency signals;

[0008] Performing signal folding on the radio frequency signal at a certain moment based on the local oscillator signal to obtain a target sampling signal, wherein the target sampling signal is within a preset signal processing frequency band, and the local oscillator signal corresponds to a signal modulation bandwidth of a baseband signal;

[0009] Performing signal conversion on the target sampling signal to obtain a digital signal;

[0010] The digital signal is demodulated, and frequency measurement is performed based on the demodulated signal to obtain an instantaneous frequency, wherein the instantaneous frequency is consistent with the frequency of the radio frequency signal before being folded.

[0011] In one embodiment of the present application, signal folding is performed on the RF signal at a certain moment based on the local oscillator signal to obtain a target sampling signal, including: performing multiple signal folding on the RF signal based on the local oscillator signal to obtain multiple folded signals; filtering the multiple folded signals according to a preset filtering cutoff frequency to obtain a target sampling signal.

[0012] In one embodiment of the present application, the radio frequency signal is folded multiple times based on the local oscillator signal to obtain multiple folded signals, including: folding the radio frequency signal according to the center frequency of the local oscillator signal to determine the center frequency of each of the folded signals; and determining the signal modulation bandwidth of the folded signal based on the signal modulation bandwidth of the local oscillator signal and the number of folding times.

[0013] In one embodiment of the present application, the digital signal is demodulated, and a frequency measurement is performed based on the demodulated signal to obtain an instantaneous frequency, including: demodulating the digital signal to obtain the target sampling signal; determining the Nyquist zone of the RF signal based on the signal modulation bandwidth of the target sampling signal and the signal modulation bandwidth of the local oscillator signal; and measuring the instantaneous frequency based on the Nyquist zone, the center frequency of the target sampling signal, and the center frequency of the local oscillator signal.

[0014] In one embodiment of the present application, the center frequency determination expression of the folded signal is as follows:

[0015] f2=f1-nf C

[0016] In the above expression, f2 is the center frequency of the folded signal, f1 is the RF signal, n is the number of folding times, and f c is the center frequency of the local oscillator signal.

[0017] According to a second aspect of an embodiment of the present application, an ultra-wideband instantaneous frequency measurement circuit is provided, comprising:

[0018] A signal folding module is connected to a local oscillator signal and a radio frequency signal, and performs multiple signal folding on the radio frequency signal at a certain moment according to the local oscillator signal to obtain multiple folded signals, wherein there is a signal within a preset signal processing frequency band among the multiple folded signals, and the local oscillator signal corresponds to the signal modulation bandwidth of the baseband signal;

[0019] A signal processing module, connected to the signal folding module, performs signal conversion on the folded signal in the preset signal processing frequency band to obtain a digital signal;

[0020] The frequency determination module is connected to the signal processing module, performs signal demodulation on the digital signal, and performs frequency measurement based on the demodulated signal to obtain the instantaneous frequency of the radio frequency signal before being folded.

[0021] In one embodiment of the present application, the signal folding module includes: a signal generating unit, used to provide the baseband signal and migrate the frequency of the baseband signal to a preset frequency threshold to generate the local oscillator signal; a signal folding unit, used to fold the radio frequency signal according to the center frequency of the local oscillator signal to obtain a plurality of folded signals.

[0022] In one embodiment of the present application, the signal processing module includes: a filtering unit, used to filter the multiple folded signals according to a preset filtering cutoff frequency to obtain a target sampling signal; an analog-to-digital conversion unit, used to perform analog-to-digital signal conversion on the target sampling signal to obtain the digital signal.

[0023] In one embodiment of the present application, the frequency determination module includes: a signal demodulation unit, used to demodulate the digital signal to obtain the target sampling signal; a frequency measurement unit, used to determine the Nyquist zone of the radio frequency signal according to the signal modulation bandwidth of the target sampling signal and the signal modulation bandwidth of the local oscillator signal, and determine the instantaneous frequency according to the Nyquist zone of the radio frequency signal.

[0024] The present application provides an ultra-wideband instantaneous frequency measurement method and circuit, the method comprising: acquiring a radio frequency signal, performing signal folding on the radio frequency signal at a certain moment based on a local oscillator signal to obtain a target sampling signal; performing signal type conversion on the target sampling signal in a preset signal processing frequency band to obtain a digital signal; first performing signal demodulation on the digital signal, and then measuring the frequency according to the demodulated signal, thereby restoring the instantaneous frequency of the radio frequency signal before being folded, and completing the analog processing of the digital signal without the need for additional analog frequency conversion processing. The ultra-wideband instantaneous frequency measurement method provided by the present application breaks through the limitations of the Nyquist sampling theorem, first folds the radio frequency signal to obtain a related signal that complies with the signal processing of an analog-to-digital converter, and can directly use a single analog-to-digital converter to receive and process ultra-wideband radio frequency signals, and restore the instantaneous frequency value of the related radio frequency signal, without the need for other analog processing circuits.

[0025] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present invention, and together with the specification, are used to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0027] Figure 1 is a flow chart of an ultra-wideband instantaneous frequency measurement method shown in an exemplary embodiment of the present invention;

[0028] Figure 2 is a block diagram of an ultra-wideband instantaneous frequency measurement circuit shown in an exemplary embodiment of the present invention;

[0029] Figure 3 It is a specific structural diagram of an ultra-wideband instantaneous frequency measurement circuit shown in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0031] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0032] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0033] The Nyquist sampling theorem, also known as the Shannon sampling theorem, explains the relationship between the sampling frequency and the signal spectrum. It is the basic basis for the discretization of continuous signals. Specifically, in order to restore the analog signal without distortion, the sampling frequency fs should be greater than or equal to twice the highest frequency fmax in the analog signal spectrum, that is, fs ≥ 2fmax.

[0034] Receivers are used in the field of communications to receive various radio signals and convert them into corresponding audio, video or digital signals. With the continuous updating of technology, fully digital receivers are the current development direction. They can directly convert the signals sent by the antenna into analog-to-digital signals, and do not require additional analog frequency conversion devices. However, due to the sampling frequency limitation of the analog-to-digital converter, the analog-to-digital conversion cannot synchronously process signals of the entire frequency band. The signal receiving system is limited by the sampling input frequency range of the analog-to-digital converter, and the highest frequency of the signal to be sampled must be less than the first Nyquist zone of the analog-to-digital converter, that is, fs / 2.

[0035] Generally, when the signal bandwidth is greater than the first Nyquist zone: On the one hand, the entire measured bandwidth can be traversed by frequency sweeping with each step of fs / 2, but this method cannot receive or cannot completely receive instantaneous signals, and the signal reception speed is relatively slow. On the other hand, the entire frequency domain is segmented based on the fs / 2 frequency, and the signal is acquired in segments. At least 2BW / fs channels are required to achieve full frequency coverage; for example, the frequency of the signal to be sampled is 20GHZ, and the maximum sampling rate of the analog-to-digital converter is 4GHZ, and the number of channels required is:

[0036]

[0037] It can be seen that sampling signals by designing channels not only has a complex design structure but also has high costs, which is not conducive to large-scale applications.

[0038] To solve the above problems, the present application provides an ultra-wideband instantaneous frequency measurement method, comprising:

[0039] S110, obtaining a radio frequency signal;

[0040] S120, performing signal folding on a radio frequency signal at a certain moment based on a local oscillator signal to obtain a target sampling signal, wherein the target sampling signal is within a preset signal processing frequency band, and the local oscillator signal corresponds to a signal modulation bandwidth of the baseband signal;

[0041] S130, performing signal conversion on the target sampling signal to obtain a digital signal;

[0042] S140, demodulating the digital signal, and performing frequency measurement based on the demodulated signal to obtain an instantaneous frequency, wherein the instantaneous frequency is consistent with the frequency of the radio frequency signal before being folded.

[0043] In detail, the step of acquiring the local oscillator signal includes: acquiring a baseband signal, and shifting the frequency of the baseband signal to obtain a local oscillator signal. Specifically, a baseband signal can be generated by a digital-to-analog converter, and the baseband signal can be frequency-shifted to obtain a local oscillator signal; for example, if the baseband signal generated by the analog-to-digital converter is 500MHz±5MHz, the signal is subjected to microwave mixing processing, the center frequency of the baseband signal is converted to 4GHz, and the local oscillator signal is obtained, and the local oscillator signal is 4GHz±5MHz.

[0044] In detail, signal folding is performed on a radio frequency signal at a certain moment based on a local oscillator signal to obtain a target sampling signal, including: performing multiple signal folding on the radio frequency signal based on the local oscillator signal to obtain multiple folded signals; filtering the multiple folded signals according to a preset filter cutoff frequency to obtain the target sampling signal. Specifically, the radio frequency signal is folded multiple times based on the local oscillator signal, and a folded signal is obtained each time the signal is folded, thereby obtaining multiple folded signals, but not every folded signal meets the preset signal processing frequency band of the analog-to-digital converter. Therefore, the multiple folded signals can be filtered through a filter to obtain a target sampling signal that meets the preset signal processing frequency band of the analog-to-digital converter.

[0045] In detail, the radio frequency signal is folded multiple times based on the local oscillator signal to obtain multiple folded signals, including: folding the radio frequency signal according to the center frequency of the local oscillator signal to determine the center frequency of each folded signal; determining the signal modulation bandwidth of the folded signal based on the signal modulation bandwidth of the local oscillator signal and the number of folding times. Specifically, if the radio frequency signal is 17GHz, the radio frequency signal is folded twice based on the center frequency of the local oscillator signal of 4GHz to obtain a first folded signal with a center frequency of (17-2*4)=9GHz. According to the signal modulation bandwidth of the local oscillator signal of 5MHz and the number of folding times (2 times), the signal modulation bandwidth of the first folded signal is calculated to be 10MHz, so the first folded signal is (9G±10M)Hz. Similarly, the radio frequency signal is folded three times to obtain a second folded signal of (5G±15M)Hz; the radio frequency signal is folded four times to obtain a third folded signal of (1G±20M)Hz.

[0046] In more detail, the expression for determining the center frequency of the folded signal is as follows:

[0047] f2=f1-nf C (1)

[0048] In expression (1), f2 is the center frequency of the folded signal, f1 is the RF signal, n is the number of folding times, and f c is the center frequency of the local oscillator signal.

[0049] It should be noted that performing signal conversion on the target sampling signal to obtain a digital signal includes: inputting the target sampling signal into an analog-to-digital converter, performing signal sampling conversion from the analog signal to the digital signal, and obtaining a digital signal. For example, a low-pass filter can be used to retain only signals within 2 GHz, and the obtained target sampling signal is (1G±20M) Hz, and then performing analog-to-digital conversion to obtain a digital signal.

[0050] In detail, the digital signal is demodulated, and the frequency is measured based on the demodulated signal to obtain the instantaneous frequency, including: demodulating the digital signal to obtain the target sampling signal; determining the Nyquist area of ​​the RF signal according to the signal modulation bandwidth of the target sampling signal and the signal modulation bandwidth of the local oscillator signal; measuring the instantaneous frequency according to the Nyquist area, the center frequency of the target sampling signal and the center frequency of the local oscillator signal. Specifically, the digital signal is first demodulated, that is, the digital signal is restored to an analog signal to obtain the target sampling signal (1G±20MHz), and the Nyquist area of ​​the RF signal is calculated according to the signal modulation bandwidth of the target sampling signal (20MHz) and the signal modulation bandwidth of the local oscillator signal (5MHz), for example:

[0051] 20MHz / 5MHz=4(NZ) (2)

[0052] In expression (2), 20 MHz is the signal modulation bandwidth of the target sampling signal, 5 MHz is the signal modulation bandwidth of the local oscillator signal, and 4(NZ) represents the 4th Nyquist zone.

[0053] The instantaneous frequency of the RF signal is calculated based on the Nyquist zone, the center frequency of the target sampling signal and the center frequency of the local oscillator signal.

[0054] 1GHz+4(NZ)×4GHz=17GHz (3)

[0055] From expression (3), it can be seen that 1 GHz is the center frequency of the target sampling signal, 4(NZ) represents the 4th Nyquist zone, and 4 GHz is the center frequency of the local oscillator signal.

[0056] It should be noted that the ultra-wideband instantaneous frequency measurement method provided in the present application is not only applicable to the instantaneous frequency measurement of a single RF signal, but also to the instantaneous frequency measurement of multiple ultra-wideband RF signals. The processing method of multiple RF signals is the same as that of a single RF signal, except that after signal folding, the target sampling signals obtained are different. The multiple target sampling signals corresponding to the multiple RF signals all meet the sampling frequency of the analog-to-digital converter.

[0057] From the above description, it can be seen that this method breaks through the limitation of Nyquist sampling theorem and can use a lower-speed analog-to-digital converter to obtain a larger bandwidth signal.

[0058] Second, as Figure 2 As shown, the present application also provides an ultra-wideband instantaneous frequency measurement circuit, comprising:

[0059] A signal folding module receives a local oscillator signal and a radio frequency signal, performs multiple signal folding on the radio frequency signal at a certain moment according to the local oscillator signal, and obtains multiple folded signals, wherein there is a signal within a preset signal processing frequency band among the multiple folded signals, and the local oscillator signal corresponds to the signal modulation bandwidth of the baseband signal;

[0060] The signal processing module is connected to the signal folding module, and performs signal conversion on the folded signal in the preset signal processing frequency band to obtain a digital signal;

[0061] The frequency determination module is connected to the signal processing module, demodulates the digital signal, and performs frequency measurement based on the demodulated signal to obtain the instantaneous frequency of the radio frequency signal before being folded.

[0062] Specifically, the signal folding module includes: a signal generating unit, which is used to provide a baseband signal and migrate the frequency of the baseband signal to a preset frequency threshold to generate a local oscillator signal; a signal folding unit, which is used to fold the radio frequency signal according to the center frequency of the local oscillator signal to obtain multiple folded signals. Figure 3 As shown, the signal generating unit provides a baseband signal through a digital-to-analog converter, and performs frequency mixing and migration on the baseband signal through a mixer to obtain a local oscillator signal; the signal folding unit folds the RF signal according to the local oscillator signal to obtain multiple folded signals.

[0063] In more detail, the signal processing module includes: a filtering unit, which is used to filter the multiple folded signals according to a preset filter cutoff frequency to obtain a target sampling signal; an analog-to-digital conversion unit, which is used to perform analog-to-digital signal conversion on the target sampling signal to obtain a digital signal. Specifically, Figure 3 As shown, the filtering unit filters multiple folded signals through a low-pass filter to obtain a target sampling signal that meets the preset signal processing frequency band of the analog-to-digital converter, inputs the target sampling signal into the analog-to-digital converter ADC, samples the analog signal to a digital signal, and obtains a digital signal.

[0064] In more detail, Figure 3 As shown, the frequency determination module includes: a signal demodulation unit for demodulating the digital signal to obtain a target sampling signal; a frequency measurement unit for determining the Nyquist area of ​​the RF signal according to the signal modulation bandwidth of the target sampling signal and the signal modulation bandwidth of the local oscillator signal, and finally calculating the instantaneous frequency of the RF signal before being folded according to the Nyquist area of ​​the RF signal.

[0065] The present application provides an ultra-wideband instantaneous frequency measurement method and circuit, the method comprising: acquiring a radio frequency signal, folding the radio frequency signal multiple times based on a local oscillator signal to obtain multiple folded signals, so that a target sampling signal within a preset signal processing frequency band exists in the multiple folded signals; performing signal type conversion on the target sampling signal to obtain a digital signal; first demodulating the digital signal, and then measuring the frequency according to the demodulated signal, thereby restoring the instantaneous frequency of the radio frequency signal, and completing the analog processing of the digital signal without the need for additional analog frequency conversion processing. The ultra-wideband instantaneous frequency measurement method of the present application breaks through the limitations of the Nyquist sampling theorem, first folds the radio frequency signal, and then selects the relevant signal that complies with the signal processing of the analog-to-digital converter from the folded multiple signals, and can directly use a single analog-to-digital converter to receive and process the ultra-wideband radio frequency signal, and can restore the frequency value of the relevant input signal, without the need for other analog processing circuits.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An ultra-wideband instantaneous frequency measurement method, characterized in that: include: Acquire radio frequency signals; Performing signal folding on the radio frequency signal at a certain moment based on the local oscillator signal to obtain a target sampling signal, wherein the target sampling signal is within a preset signal processing frequency band, and the local oscillator signal corresponds to a signal modulation bandwidth of a baseband signal; Performing signal conversion on the target sampling signal to obtain a digital signal; The digital signal is demodulated, and frequency measurement is performed based on the demodulated signal to obtain an instantaneous frequency, wherein the instantaneous frequency is consistent with the frequency of the radio frequency signal before being folded.

2. The ultra-wideband instantaneous frequency measurement method according to claim 1, characterized in that: Performing signal folding on the radio frequency signal at a certain moment based on the local oscillator signal to obtain a target sampling signal includes: Performing multiple signal folding on the radio frequency signal based on the local oscillator signal to obtain multiple folded signals; The plurality of folded signals are filtered according to a preset filter cutoff frequency to obtain a target sampling signal.

3. The ultra-wideband instantaneous frequency measurement method according to claim 2, characterized in that: The radio frequency signal is folded multiple times based on the local oscillator signal to obtain multiple folded signals, including: Folding the radio frequency signal according to the center frequency of the local oscillator signal to determine the center frequency of each folded signal; The signal modulation bandwidth of the folding signal is determined based on the signal modulation bandwidth of the local oscillator signal and the number of folding times.

4. The ultra-wideband instantaneous frequency measurement method according to claim 3, characterized in that: The digital signal is demodulated, and frequency measurement is performed based on the demodulated signal to obtain an instantaneous frequency, including: Performing signal demodulation on the digital signal to obtain the target sampling signal; Determine the Nyquist zone of the radio frequency signal according to the signal modulation bandwidth of the target sampling signal and the signal modulation bandwidth of the local oscillator signal; The instantaneous frequency is measured according to the Nyquist zone, the center frequency of the target sampling signal and the center frequency of the local oscillator signal.

5. The ultra-wideband instantaneous frequency measurement method according to claim 3, characterized in that: The center frequency determination expression of the folded signal is as follows: <h2 style=";text-align:left;direction:ltr">f2=f1-nf<h2 style=";text-align:left;direction:ltr"> C In the above expression, f2 is the center frequency of the folded signal, f1 is the RF signal, n is the number of folding times, and f c is the center frequency of the local oscillator signal.

6. An ultra-wideband instantaneous frequency measurement circuit, characterized in that: include: A signal folding module is connected to a local oscillator signal and a radio frequency signal, and performs multiple signal folding on the radio frequency signal at a certain moment according to the local oscillator signal to obtain multiple folded signals, wherein there is a signal within a preset signal processing frequency band among the multiple folded signals, and the local oscillator signal corresponds to the signal modulation bandwidth of the baseband signal; A signal processing module, connected to the signal folding module, performs signal conversion on the folded signal in the preset signal processing frequency band to obtain a digital signal; The frequency determination module is connected to the signal processing module, performs signal demodulation on the digital signal, and performs frequency measurement based on the demodulated signal to obtain the instantaneous frequency of the radio frequency signal before being folded.

7. The ultra-wideband instantaneous frequency measurement circuit according to claim 6, characterized in that: The signal folding module comprises: A signal generating unit, configured to provide the baseband signal and migrate the frequency of the baseband signal to a preset frequency threshold to generate the local oscillator signal; A signal folding unit is used to fold the radio frequency signal according to the center frequency of the local oscillator signal to obtain a plurality of folded signals.

8. The ultra-wideband instantaneous frequency measurement circuit according to claim 6, characterized in that: The signal processing module comprises: A filtering unit, used for filtering the plurality of folded signals according to a preset filtering cutoff frequency to obtain a target sampling signal; The analog-to-digital conversion unit is used to perform analog-to-digital signal conversion on the target sampling signal to obtain the digital signal.

9. The ultra-wideband instantaneous frequency measurement circuit according to claim 8, characterized in that: The frequency determination module comprises: A signal demodulation unit, used for performing signal demodulation on the digital signal to obtain the target sampling signal; A frequency measurement unit is used to determine the Nyquist zone of the radio frequency signal according to the signal modulation bandwidth of the target sampling signal and the signal modulation bandwidth of the local oscillator signal, and determine the instantaneous frequency according to the Nyquist zone of the radio frequency signal.

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