Microwave signal multi-frequency measuring device and method based on electric domain amplitude equalization and optical domain linearity correction

Abstract

The invention discloses a microwave signal multi-frequency measuring device and method based on electric domain amplitude equalization and optical domain linearity correction, and belongs to the technical field of microwave photons.The microwave signal multi-frequency measuring device comprises a broadband matched filtering unit, a signal processing unit and a signal processing unit, generating narrow pulses which are related to the frequency of the signal to be measured and appear at different moments; the electric domain amplitude equalization unit is used for receiving the control signal and carrying out amplitude equalization on the received microwave signal to be measured; the optical domain linearity correction unit is used for receiving the control signal and correcting the linearity of system frequency-time mapping; and the acquisition processing and control unit is used for sampling and quantifying the matched and filtered pulse to obtain and output control signals of the electric domain amplitude equalization unit and the optical domain linearity correction unit. According to the invention, not only can real-time multi-frequency measurement be realized, but also the characteristic of uniform response to different frequencies is realized.

Description

Technical Field

[0001] The present invention relates to the field of microwave photon technology, and more specifically, to a microwave signal multi-frequency measurement device and method based on electrical domain amplitude equalization and optical domain linearity correction. Background Art

[0002] Frequency parameters are intrinsic parameters of microwave electromagnetic waves. Measuring microwave frequency is an important means of identifying signal types in information technology fields such as radar and communication. The traditional means of microwave frequency measurement is electronic means. The basic method is to sample and quantize the intercepted signal and perform Fourier transform and other operations in the digital domain. However, limited by the electronic bottleneck, the electronic microwave frequency measurement method faces bottleneck problems such as limited instantaneous bandwidth, slow measurement speed, and electromagnetic interference. Thanks to its inherent advantages, the photonic microwave frequency measurement method naturally has the characteristics of large instantaneous bandwidth, parallel processing, and resistance to electromagnetic interference. Therefore, it is widely used in the field of microwave frequency measurement. Microwave frequency measurement based on photonics can be divided into frequency-power mapping type, frequency-channel mapping type, and frequency-time mapping type.

[0003] The basic idea of ​​the frequency-power mapping type microwave photon frequency measurement method is to establish a one-to-one mapping relationship between the frequency of the microwave signal to be measured and the output signal power, map the frequency information of the microwave signal to be measured into power information that is easy to measure, and infer the frequency of the microwave signal to be measured based on the frequency-power mapping relationship. Its core is a microwave photon filter whose passband response varies with frequency, which can be achieved through programmable optical filters, microring resonators, fiber Bragg gratings, Mach-Zehnder interferometers, etc.

[0004] The basic idea of ​​the frequency-channel mapping type microwave photon frequency measurement method is to divide the broadband microwave signal into different channels, and then recover the spectrum information of the microwave signal to be measured by parallel measurement in each channel. Its core is the channelizer, which can be realized by a spatial domain channelizer such as a diffraction grating, or by a wavelength domain channelizer such as a wavelength division multiplexer and a chirped Bragg grating array.

[0005] The basic idea of ​​the frequency-time mapping type microwave photon frequency measurement method is to introduce a device with a time-frequency correspondence and perform frequency sweep reception on the broadband microwave signal, so that the frequency information of the microwave signal to be measured can be mapped into the peak pulses output by the system at different times. The core of the method is a device with a time-frequency correspondence, such as a swept filter, which can be realized by means of a swept Fabry–Perot etalon, an electrically controlled FBG, a swept stimulated Brillouin scattering, etc.

[0006] Among the above microwave photon frequency measurement methods, the frequency-power mapping technology cannot measure multi-frequency signals due to the superposition of power. The frequency-channel mapping technology has a huge amount of resources when facing multi-frequency signal measurement scenarios. The frequency-time type technology cannot measure multi-frequency burst pulse signals. At the same time, since the modulator and the detector are both frequency-related devices, the system has different sensitivities in measuring multi-frequency signals; due to the existence of mapping nonlinearity, the mapping slopes of different frequencies to other parameters are different, resulting in uneven frequency errors in the system's measurement of multi-frequency signals. Therefore, the existing technology cannot achieve multi-frequency signal frequency measurement with uniform response characteristics. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a microwave signal multi-frequency measurement device and method based on electrical domain amplitude equalization and optical domain linearity correction, which can not only realize real-time multi-frequency measurement but also have the characteristic of uniform response to different frequencies.

[0008] The object of the present invention is achieved through the following solutions:

[0009] A microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction, comprising:

[0010] A broadband matched filter unit is used to implement electro-optical modulation and matched filtering of the microwave signal to be measured, and to generate narrow pulses that appear at different times and are related to the frequency of the signal to be measured;

[0011] The electrical domain amplitude equalization unit is used to receive the control signal and perform amplitude equalization on the received microwave signal to be tested. By introducing electrical domain amplitude equalization, the frequency-related amplitude jitter introduced by the frequency-related components in the system link is eliminated, so that when signals with the same power but different frequencies are input, the system has pulse outputs with the same peak amplitude.

[0012] The optical domain linearity correction unit is used to receive the control signal and correct the linearity of the system frequency-time mapping so that different frequencies of the measured signals have the same mapping slope when they are mapped to pulses appearing at different times;

[0013] The acquisition processing and control unit is used to sample and quantize the pulses after matched filtering, calculate the signal frequency according to the pulse peak moment, and obtain and output the control signals of the electrical domain amplitude equalization unit and the optical domain linearity correction unit according to the input signal frequency amplitude information and the output signal frequency amplitude information.

[0014] Furthermore, the broadband matched filtering unit includes a frequency sweeping optical unit for generating an optical carrier required for broadband matched filtering.

[0015] Furthermore, the broadband matched filter unit includes an electro-optical modulation unit for modulating the microwave signal to be measured onto a frequency-sweeping optical carrier by electro-optical modulation.

[0016] Furthermore, the broadband matched filtering unit includes a matched filtering unit for performing matched filtering and pulse compression on the swept frequency optical carrier modulated with the microwave signal to be measured.

[0017] Furthermore, the electrical domain amplitude equalization unit is specifically implemented by a broadband microwave equalizer.

[0018] Furthermore, the optical domain linearity correction unit is specifically implemented by a dispersion management optical fiber, or by an adjustable dispersion compensation module.

[0019] Furthermore, the broadband matched filter unit is specifically implemented by a frequency-sweeping laser driven by a time-varying current, or by a frequency-shifting loop, or by a combination of a mode-locked laser and a dispersive optical fiber.

[0020] Furthermore, the broadband matched filter unit implements double sideband modulation, carrier suppressed double sideband modulation through a common Mach-Zehnder modulator, or implements complex modulation such as single sideband through a dual parallel Mach-Zehnder modulator.

[0021] Furthermore, the broadband matched filter unit is implemented by a dispersive optical fiber, or by a chirped fiber grating or an integrated chirped Bragg optical waveguide.

[0022] A microwave signal multi-frequency measurement method based on electrical domain amplitude equalization and optical domain linearity correction comprises the following steps:

[0023] First, a frequency-sweeping optical signal is generated, and the microwave signal to be measured is modulated onto the frequency-sweeping optical signal by electro-optical modulation. The frequency-sweeping optical signal that has passed through the microwave signal to be measured is subjected to broadband matched filtering, and the frequency information of the microwave signal to be measured is converted into peak pulses that appear at different times. The real-time frequency measurement of multi-frequency signals is achieved by measuring and calculating the pulse peak time.

[0024] Then, based on broadband matched filtering, electrical domain amplitude equalization is introduced before electro-optical modulation to eliminate the frequency-related amplitude jitter introduced by frequency-related devices in the system link, so that the system has pulse outputs with the same peak amplitude when signals of the same power but different frequencies are input, so that the sensitivity characteristics of the system remain uniform when measuring multi-frequency signals;

[0025] Furthermore, on the basis of broadband matched filtering, optical domain linearity correction is introduced after matched filtering to eliminate the frequency-time mapping nonlinearity introduced by nonlinear devices in the system link, ensuring that different frequency test signals have the same mapping slope when mapped to pulses appearing at different times, so that the frequency error characteristics of the system remain uniform when measuring multi-frequency signals.

[0026] The beneficial effects of the present invention include:

[0027] The present invention provides a method and device for realizing multi-frequency signal frequency measurement by using broadband matched filtering, electric domain amplitude equalization, and optical domain linearity correction. Compared with the traditional method, the present invention can not only realize real-time multi-frequency measurement, but also has the characteristic of uniform response to different frequencies. Specifically, the present invention realizes multi-frequency signal frequency measurement with uniform response characteristics by means of broadband matched filtering, combined with electric domain amplitude equalization and optical domain linearity correction methods. By matching filtering the swept frequency light source modulated by the microwave signal to be measured, the microwave signal to be measured is converted into spike pulses appearing at different times in real time, realizing the frequency-time mapping of the microwave signal, and realizing the frequency measurement of multi-frequency signals on this basis; by using electric domain amplitude equalization, the amplitude response related to the frequency in the system link is eliminated, so that the sensitivity characteristics of the system when measuring multi-frequency signals remain uniform; by using optical domain linearity correction, the slope of the signal to be measured is guaranteed to be the same when it is mapped to the time parameter, so that the frequency error characteristics of the system when measuring multi-frequency signals remain uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 A schematic diagram of the system principle structure of an embodiment of the present invention;

[0030] Figure 2 The structure and schematic diagram of a broadband matched filtering system based on a frequency-sweeping laser and a dispersive optical fiber according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0032] The specific implementation process of the present invention is as follows:

[0033] The principle structure and schematic diagram of the present invention are as follows Figure 1 As shown, the system is divided into four parts:

[0034] Broadband matched filter part: includes frequency sweep optical unit, electro-optic modulation unit and matched filter unit, which realize electro-optic modulation and matched filtering of the microwave signal to be measured, and generate narrow pulses that appear at different times and are related to the frequency of the signal to be measured.

[0035] Electrical domain amplitude equalization part: receives the control signal, introduces electrical domain amplitude equalization, eliminates the frequency-related amplitude jitter introduced by frequency-related devices such as modulators and detectors in the system link, so that when signals of the same power but different frequencies are input, the system has pulse outputs with the same peak amplitude.

[0036] Optical domain linearity correction part: receives the control signal and introduces optical domain linearity correction after matched filtering, thereby eliminating the frequency-time mapping nonlinearity introduced by nonlinear devices such as frequency sweep nonlinearity and matched filter nonlinearity in the system link, so that different frequency signals to be tested have the same mapping slope when mapped to pulses appearing at different times.

[0037] Acquisition, processing and control part: Sample and quantize the pulses after matched filtering, calculate the signal frequency according to the pulse peak moment, and obtain and output the control signals of the electrical domain amplitude equalization unit and the optical domain linearity correction unit based on the input signal frequency amplitude information and the output signal frequency amplitude information.

[0038] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail in combination with a broadband matched filter system based on a swept laser and a dispersion fiber. The specific implementation examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] In this embodiment, if Figure 2As shown, the swept light generated by the swept light unit has a spectrum width of 1nm, a duration of 10ns and a repetition period of 10ns. The electro-optical modulation unit uses a dual-drive Mach-Zehnder modulator to achieve single-sideband modulation. The matching filter uses a dispersive fiber with a dispersion of 10ns / nm to match the swept light. When there is no modulation of the microwave signal to be measured, the dispersive fiber performs matched filtering on the swept light. Different frequency components of the swept light are introduced into different delays after passing through the dispersive fiber. The delay difference between the starting frequency component and the ending frequency component is 10ns / nm×1nm=10ns. Therefore, after matching filtering, an ultra-narrow pulse will be output. When there is modulation of the signal to be measured, the electro-optical modulation will generate a carrier part and a first-order sideband part, with a spectrum width of 1nm, a duration of 10ns, and a repetition period of 10ns. The frequency difference between the carrier part and the first-order sideband part is the frequency of the signal to be measured. This frequency difference will be converted into the peak time difference of the ultra-narrow pulse generated after matching filtering. Therefore, by detecting and calculating the pulse peak time difference, the frequency information of the signal to be measured can be inferred.

[0040] Specifically, this implementation example is divided into the following steps:

[0041] Step 1, injecting driving current into the laser to generate a frequency sweeping optical signal with a spectrum width of 1 nm, a duration of 10 ns, and a repetition period of 10 ns;

[0042] Step 2: The microwave signal to be tested is the superposition of three single-frequency signals, with frequencies of 25 GHz, 50 GHz, and 75 GHz respectively. The microwave signal to be tested modulates the swept frequency optical signal using a dual-drive Mach-Zehnder modulator, and the modulation format is single-sideband modulation.

[0043] Step 3: The modulated frequency-sweep optical signal is sent to the dispersive optical fiber. The output of the dispersive optical fiber in a single 10 ns cycle can be expressed as

[0044]

[0045] Wherein, s0(t) is the optical pulse formed by the original frequency-sweeping optical signal after the dispersion fiber matched filtering, a1, a2, a3 represent the different amplitude attenuation factors introduced by the frequency-related amplitude jitter introduced by the frequency-related devices such as the modulator and the detector in the system link to the pulses formed by the different frequency components of the microwave signal to be measured, Δt1, Δt2, Δt3 represent the different time deviation factors introduced by the frequency-time mapping nonlinearity introduced by the nonlinear devices such as the frequency-sweeping nonlinearity and the nonlinearity of the matched filter in the system link to the pulses formed by the different frequency components of the microwave signal to be measured.

[0046] Step 4: When the electric domain amplitude equalization unit and the optical domain linearity correction unit are in the initial state, the acquisition processing and control unit acquires and processes the signal after matched filtering to obtain the amplitude and peak moment of the pulse, and calculates the frequency information of the microwave signal to be measured. The actual parameter information is compared with the measured parameter information to obtain and output the control parameters of the electric domain amplitude equalization unit and the optical domain linearity correction unit.

[0047] Step 5: After the electrical domain amplitude equalization unit and the optical domain linearity correction unit are set according to the control parameters, the output signal of the system can be expressed as

[0048]

[0049] It can be seen that after electrical domain amplitude equalization, the frequency-dependent amplitude response in the system link is eliminated, and the sensitivity characteristics of the system can remain uniform when measuring multi-frequency signals; after optical domain linearity correction, the slope is the same when the frequency of the signal to be measured is mapped to the time parameter, and the frequency error characteristics of the system can remain uniform when measuring multi-frequency signals.

[0050] It should be noted that within the scope of protection defined in the claims of the present invention, the following embodiments can be combined and / or expanded or replaced in any logical way from the above specific implementation methods, such as disclosed technical principles, disclosed technical features or implicitly disclosed technical features.

[0051] Example 1

[0052] A microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction, comprising:

[0053] A broadband matched filter unit is used to implement electro-optical modulation and matched filtering of the microwave signal to be measured, and to generate narrow pulses that appear at different times and are related to the frequency of the signal to be measured;

[0054] The electrical domain amplitude equalization unit is used to receive the control signal and perform amplitude equalization on the received microwave signal to be tested. By introducing electrical domain amplitude equalization, the frequency-related amplitude jitter introduced by the frequency-related components in the system link is eliminated, so that when signals with the same power but different frequencies are input, the system has pulse outputs with the same peak amplitude.

[0055] The optical domain linearity correction unit is used to receive the control signal and correct the linearity of the system frequency-time mapping so that different frequencies of the measured signals have the same mapping slope when they are mapped to pulses appearing at different times;

[0056] The acquisition processing and control unit is used to sample and quantize the pulses after matched filtering, calculate the signal frequency according to the pulse peak moment, and obtain and output the control signals of the electrical domain amplitude equalization unit and the optical domain linearity correction unit according to the input signal frequency amplitude information and the output signal frequency amplitude information.

[0057] Example 2

[0058] On the basis of Embodiment 1, the broadband matched filtering unit includes a frequency sweeping optical unit, which is used to generate an optical carrier required for broadband matched filtering.

[0059] Example 3

[0060] On the basis of Embodiment 1, the broadband matched filter unit includes an electro-optical modulation unit, which is used to modulate the microwave signal to be measured onto a swept frequency optical carrier by electro-optical modulation.

[0061] Example 4

[0062] On the basis of Example 1, the broadband matched filtering unit includes a matched filtering unit for performing matched filtering and pulse compression on the swept frequency optical carrier modulated with the microwave signal to be measured.

[0063] Example 5

[0064] Based on Example 1, the electrical domain amplitude equalization unit is specifically implemented by a broadband microwave equalizer.

[0065] Example 6

[0066] Based on Example 1, the optical domain linearity correction unit is specifically implemented by a dispersion management optical fiber, or by an adjustable dispersion compensation module.

[0067] Example 7

[0068] On the basis of Example 2, the broadband matched filter unit is specifically implemented by a frequency-sweeping laser driven by a time-varying current, or by a frequency-shifting loop, or by a combination of a mode-locked laser and a dispersive optical fiber.

[0069] Example 8

[0070] On the basis of Example 3, the broadband matched filter unit specifically implements double sideband modulation, carrier suppressed double sideband modulation through an ordinary Mach-Zehnder modulator, or implements complex modulation such as single sideband through dual parallel Mach-Zehnder modulators.

[0071] Example 9

[0072] On the basis of Example 4, the broadband matched filter unit is implemented by a dispersive optical fiber, or by a chirped fiber grating or an integrated chirped Bragg optical waveguide.

[0073] Example 10

[0074] A microwave signal multi-frequency measurement method based on electrical domain amplitude equalization and optical domain linearity correction comprises the following steps:

[0075] First, a frequency-sweeping optical signal is generated, and the microwave signal to be measured is modulated onto the frequency-sweeping optical signal by electro-optical modulation. The frequency-sweeping optical signal that has passed through the microwave signal to be measured is subjected to broadband matched filtering, and the frequency information of the microwave signal to be measured is converted into peak pulses that appear at different times. The real-time frequency measurement of multi-frequency signals is achieved by measuring and calculating the pulse peak time.

[0076] Secondly, on the basis of broadband matched filtering, electrical domain amplitude equalization is introduced before electro-optical modulation to eliminate the frequency-related amplitude jitter introduced by frequency-related devices in the system link, so that the system has the same peak amplitude pulse output when signals of the same power but different frequencies are input, so that the sensitivity characteristics of the system remain uniform when measuring multi-frequency signals;

[0077] Furthermore, on the basis of broadband matched filtering, optical domain linearity correction is introduced after matched filtering to eliminate the frequency-time mapping nonlinearity introduced by nonlinear devices in the system link, ensuring that different frequency test signals have the same mapping slope when mapped to pulses appearing at different times, so that the frequency error characteristics of the system remain uniform when measuring multi-frequency signals.

[0078] The units involved in the embodiments of the present invention may be implemented by software or hardware, and the units described may also be arranged in a processor. The names of these units do not, in some cases, limit the units themselves.

[0079] According to one aspect of an embodiment of the present invention, a computer program product or a computer program is provided, the computer program product or the computer program includes a computer instruction, and the computer instruction is stored in a computer-readable storage medium. A processor of a computer device reads the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes the method provided in the above various optional implementations.

[0080] As another aspect, an embodiment of the present invention further provides a computer-readable medium, which may be included in the electronic device described in the above embodiment; or may exist independently without being assembled into the electronic device. The above computer-readable medium carries one or more programs, and when the above one or more programs are executed by an electronic device, the electronic device implements the method described in the above embodiment.

Claims

1. A microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction, characterized in that: include: A broadband matched filter unit is used to implement electro-optical modulation and matched filtering of the microwave signal to be measured, and to generate narrow pulses that appear at different times and are related to the frequency of the signal to be measured; The electric domain amplitude equalization unit is used to receive the control signal and perform amplitude equalization on the received microwave signal to be tested; By introducing electrical domain amplitude equalization, the frequency-related amplitude jitter introduced by frequency-related devices in the system link is eliminated, so that when signals with the same power but different frequencies are input, the system has pulse outputs with the same peak amplitude; The optical domain linearity correction unit is used to receive the control signal and correct the linearity of the system frequency-time mapping so that different frequencies of the measured signals have the same mapping slope when they are mapped to pulses appearing at different times; The acquisition processing and control unit is used to sample and quantize the pulses after matched filtering, calculate the signal frequency according to the pulse peak moment, and obtain and output the control signals of the electrical domain amplitude equalization unit and the optical domain linearity correction unit according to the input signal frequency amplitude information and the output signal frequency amplitude information.

2. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 1 is characterized in that: The broadband matched filtering unit comprises a frequency sweeping optical unit, which is used to generate an optical carrier required for broadband matched filtering.

3. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 1, characterized in that: The broadband matched filter unit comprises an electro-optical modulation unit, which is used to modulate the microwave signal to be measured onto a frequency-sweeping optical carrier by means of electro-optical modulation.

4. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 1, characterized in that: The broadband matched filtering unit comprises a matched filtering unit, which is used for performing matched filtering and pulse compression on the swept frequency optical carrier modulated with the microwave signal to be measured.

5. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 1, characterized in that: The electric domain amplitude equalization unit is specifically implemented by a broadband microwave equalizer.

6. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 1, characterized in that: The optical domain linearity correction unit is specifically implemented by a dispersion management optical fiber, or by an adjustable dispersion compensation module.

7. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 2, characterized in that: The broadband matched filter unit is specifically implemented by a frequency-sweeping laser driven by a time-varying current, or by a frequency-shifting loop, or by a combination of a mode-locked laser and a dispersive optical fiber.

8. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 3, characterized in that: The broadband matched filter unit specifically implements double sideband modulation, carrier suppressed double sideband modulation through a common Mach-Zehnder modulator, or implements complex modulation such as single sideband through a dual parallel Mach-Zehnder modulator.

9. The microwave signal multi-frequency measurement device based on electrical domain amplitude equalization and optical domain linearity correction according to claim 4, characterized in that: The broadband matched filter unit is realized by a dispersive optical fiber, or by a chirped optical fiber grating or an integrated chirped Bragg optical waveguide.

10. A microwave signal multi-frequency measurement method based on electrical domain amplitude equalization and optical domain linearity correction, characterized in that: The following steps are involved: First, a frequency-sweeping optical signal is generated, and the microwave signal to be measured is modulated onto the frequency-sweeping optical signal by electro-optical modulation. The frequency-sweeping optical signal that has passed through the microwave signal to be measured is subjected to broadband matched filtering, and the frequency information of the microwave signal to be measured is converted into peak pulses that appear at different times. The real-time frequency measurement of multi-frequency signals is achieved by measuring and calculating the pulse peak time. Then, based on broadband matched filtering, electrical domain amplitude equalization is introduced before electro-optical modulation to eliminate the frequency-related amplitude jitter introduced by frequency-related devices in the system link, so that the system has pulse outputs with the same peak amplitude when signals of the same power but different frequencies are input, so that the sensitivity characteristics of the system remain uniform when measuring multi-frequency signals; Furthermore, on the basis of broadband matched filtering, optical domain linearity correction is introduced after matched filtering to eliminate the frequency-time mapping nonlinearity introduced by nonlinear devices in the system link, ensuring that different frequency test signals have the same mapping slope when mapped to pulses appearing at different times, so that the frequency error characteristics of the system remain uniform when measuring multi-frequency signals.

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