A method and device for measuring the spectral line phase-frequency characteristics of a comb generator

Abstract

The application provides a comb wave generator spectrum line phase frequency characteristic measurement method and device, relates to the electronic information technical field, and utilizes a phase continuous frequency synthesizer to provide an excitation signal for the comb wave generator, so that the comb wave generator generates a measured comb wave; the frequency synthesizer is set to adopt a step sweep frequency working mode, and the phase difference of each spectrum line of the measured comb wave is measured in turn at each step frequency point; an ideal comb wave is defined, the phase deviation of the synthesizer output signal and the corresponding spectrum line of the ideal comb wave is calculated according to the frequency interval of the adjacent spectrum lines of the comb wave signal and the synthesizer frequency step time; the measured phase difference is corrected according to the phase deviation; and the phase-frequency graph is drawn in turn based on the relative difference of each corrected spectrum line, so that the phase frequency characteristic of the measured comb wave is obtained.

Description

Technical Field

[0001] This invention belongs to the field of electronic information technology, and in particular relates to a method and device for measuring the phase frequency characteristics of a comb wave generator spectral lines. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Comb wave generators are an important type of radio frequency microwave electronic device that can generate radio frequency microwave signals with long-sequence frequency domain equally spaced spectral lines, i.e., comb waves. Their performance is mainly characterized by the amplitude-frequency characteristics and phase-frequency characteristics of each spectral line. The amplitude-frequency characteristics can be easily obtained by sweeping the frequency using a vector network analyzer or a spectrum analyzer, but the phase-frequency characteristics are very difficult to measure.

[0004] From a scientific perspective, high-speed time-domain sampling of comb wave signals allows for the acquisition of complex spectra through Fourier transform, thus simultaneously obtaining amplitude-frequency and phase-frequency characteristics. However, for radio frequency microwave comb wave signals, due to their high frequency and large bandwidth, it is difficult for either digitizers or storage oscilloscopes to meet the Nyquist frequency sampling speed and transformation accuracy word length requirements of Fourier transform, from a technical implementation standpoint. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method and apparatus for measuring the phase frequency characteristics of a comb wave generator spectral lines. The method calculates the phase deviation between the output signal of the phase-continuously stepping frequency synthesizer and the ideal comb wave reference signal, corrects the phase of the output signal of the frequency synthesizer based on the phase difference, and forms an equivalent ideal reference comb wave signal with the same frequency structure as the comb wave signal under test. The phase difference of each spectral line is compared to obtain the phase frequency characteristics of the signal under test.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0007] The first aspect of the present invention provides a method for measuring the phase frequency characteristics of a comb wave generator spectral lines.

[0008] A method for measuring the phase frequency characteristics of a comb wave generator spectral lines includes:

[0009] Using a frequency synthesizer with continuous phase stepping frequency sweep function, reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test are provided sequentially, and the phase difference between each spectral line of the comb wave and the reference signal is compared and measured.

[0010] Based on the frequency interval between adjacent spectral lines of the comb wave and the step sweep time of the frequency synthesizer, the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal is calculated. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and having zero phase at a certain moment for each spectral line.

[0011] By correcting the phase difference using the phase deviation, the phase difference between the comb wave signal and the ideal comb wave signal is obtained, thereby obtaining the phase frequency characteristics of the spectrum of the comb wave generator under test.

[0012] Furthermore, the step-sweep frequency refers to controlling the frequency synthesizer to sequentially output frequencies corresponding to each spectral line of the comb wave generator under test, specifically as follows:

[0013] The frequency synthesizer changes its output frequency by an equal amount every time interval ΔT, also known as the frequency sustaining time or switching time. The spectral lines of the comb generator are numbered according to their harmonic orders, and the cumulative phase change of the signal corresponding to the nth spectral line within the time interval ΔT is denoted as Δθ. n =2πf n ΔT=ω n ΔT, f n It is the frequency of the n-spectral line, ω n That is the corresponding angular frequency.

[0014] Furthermore, the phase continuous step sweep frequency means that the frequency synthesizer can sequentially output signals corresponding to the spectral frequencies of the output signal of the comb wave generator under test according to a specified time interval ΔT, and the phase change of the signal is continuous when the frequency synthesizer changes the frequency.

[0015] Furthermore, the frequency synthesizer employs direct digital synthesis (DDS) or fractional frequency division (FN) techniques to achieve a high-resolution, precisely controllable output signal with continuous phase when the output frequency changes.

[0016] Furthermore, the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral line of the ideal comb wave signal is specifically as follows:

[0017] (1) The frequency interval between spectral lines is Δf = f n+1 -f n The time interval for each frequency step switching of the synthesizer is ΔT = t m+1 -t m Then, for each frequency step between adjacent spectral lines, the phase difference increases by ΔΦ = 2πΔfΔT = ΔωΔT; where f n f n+1 t represents the frequencies corresponding to adjacent spectral lines. m t m+1Δf represents the time point corresponding to adjacent frequency step changes, Δω represents the frequency difference between adjacent spectral lines, and Δω represents the corresponding angular frequency difference.

[0018] (2) For any sweep frequency starting frequency, let t be the end of the m-th step time period of the sweep frequency. m Then the step time point t m The phase deviation is in, It is the phase of the spectral line corresponding to the ideal comb wave signal. It is the actual cumulative phase of the phase continuous step sweep frequency, that is, the phase of the synthesizer output signal.

[0019] Furthermore, the modifications include software methods, hardware methods, and speed-specific methods:

[0020] (1) Based on software, utilizing the phase deviation ΔΦ m The phase values ​​of the comb wave spectral lines obtained by comparison with the output signal of the frequency synthesizer are numerically compensated according to the spectral line number of the m-index to obtain the phase-frequency characteristics of the measured comb wave signal relative to the ideal comb wave.

[0021] (2) Based on hardware, referring to the phase deviation ΔΦ m One approach is to directly control and adjust the initial phase of the frequency synthesizer output signal to make it equivalent to the phase of an ideal comb wave signal; or to divide the time interval ΔT of the frequency synthesizer into two segments, one for phase difference measurement and the other for adjusting the phase through a specific frequency setting, so that the phase of the measurement time segment is equivalent to the phase of an ideal comb wave signal.

[0022] (3) Achieve natural correction based on a specific velocity: according to the phase deviation ΔΦ m The characteristics of this method are as follows: for the frequency interval Δf of the comb wave spectral line under test, a specific time interval ΔT is selected such that ΔfΔT=M, where M is a natural number. Then the phase deviation between the phase of the frequency synthesizer output signal and the phase of the corresponding spectral line of the ideal comb wave signal is equivalent to 0. The phase frequency characteristics of the spectral line of the comb wave generator under test can be obtained by direct comparison and measurement.

[0023] Furthermore, the direct control and adjustment of the initial phase of the frequency synthesizer output signal specifically involves:

[0024] For a frequency synthesizer with initial phase control capability, the phase deviation ΔΦ m As an additional phase offset, the initial phase is controlled and corrected to eliminate the phase deviation between the output signal of the frequency synthesizer and the ideal comb wave signal, thereby enabling direct comparison and measurement of the spectral phase frequency characteristics of the comb wave generator.

[0025] Furthermore, the time interval ΔT of the frequency synthesizer is divided into two segments, with correction performed in the latter half, specifically as follows:

[0026] The step interval ΔT is divided into two halves: ΔT(N-1) / N and ΔT / N, where N is a rational number greater than 1. In the first half, the normal frequency f is used. n Set the synthesizer frequency and measure the corresponding comb spectral line phase difference; then, in the latter half of the time, control the synthesizer frequency to increase by NΔf in a phase-continuous manner, i.e., make the synthesizer operate at frequency f. n +NΔf, and at the end of this ΔT time period, change the synthesizer frequency to f in a phase-continuous manner. n +Δf=f n+1 That is, the synthesizer frequency corresponding to the next comb wave spectral line is measured at the beginning of the next ΔT time period.

[0027] Furthermore, the time interval ΔT of the frequency synthesizer is divided into two segments, with correction performed in the first half, specifically as follows:

[0028] The time interval ΔT is divided into two halves, ΔT / N and ΔT(N-1) / N. Starting from the second ΔT time interval, the synthesizer frequency is set to f in the first half in a phase-continuous manner. n +NΔf, set the synthesizer frequency to f in the second half. n Then the synthesizer phase is equivalent to the phase of the ideal comb wave signal in the second half of each ΔT, realizing direct comparison and measurement of the spectral phase frequency characteristics of the comb wave generator.

[0029] A second aspect of the present invention provides a device for measuring the phase frequency characteristics of a comb wave generator spectral lines.

[0030] A device for measuring the phase frequency characteristics of a comb wave generator spectrum includes a phase difference measurement unit, a phase deviation calculation unit, and a phase frequency characteristic calculation unit.

[0031] The phase difference measurement unit is configured to: use a frequency synthesizer with a phase continuous step sweep frequency function to sequentially provide reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test, and compare and measure the phase difference between each spectral line of the comb wave and the reference signal;

[0032] The phase deviation calculation unit is configured to: calculate the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal based on the frequency interval between adjacent spectral lines of the comb wave and the step sweep time of the frequency synthesizer. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and having zero phase at a certain moment for each spectral line.

[0033] The phase frequency characteristic calculation unit is configured to: correct the phase difference using the phase deviation, obtain the phase difference between the comb wave signal and the ideal comb wave signal, and thus obtain the phase frequency characteristic of the spectrum of the comb wave generator under test.

[0034] The above one or more technical solutions have the following beneficial effects:

[0035] This invention calculates the phase deviation between a frequency synthesizer with continuous phase step sweep and an ideal comb wave signal. Based on the phase difference, the synthesized phase is corrected to obtain an equivalent ideal comb wave reference signal with the same frequency structure as the comb wave signal under test. By comparing the phase difference of each spectral line, the phase frequency characteristics of the signal under test can be obtained. This invention solves the problem of insufficient sampling speed or dynamic range when measuring the phase frequency characteristics of RF microwave comb wave signals using a digitizer or digital storage oscilloscope, and also solves the problem of lack of coherent phase reference when measuring the phase frequency characteristics of microwave comb wave signals using a traditional vector network analyzer.

[0036] Advantages of additional aspects 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. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0038] Figure 1 This is a flowchart of the method in the first embodiment.

[0039] Figure 2 The phase-time diagram is for the ideal comb wave signal in the first embodiment.

[0040] Figure 3 The phase-frequency diagram of the ideal comb wave signal in the first embodiment is shown.

[0041] Figure 4 This is a phase-time schematic diagram of the initial phase signal shift of the comb wave signal spectral line in the first embodiment.

[0042] Figure 5 This is a phase-frequency diagram illustrating the initial phase shift of the comb wave signal spectral line in the first embodiment.

[0043] Figure 6 This is a schematic diagram illustrating the principle of comb wave signal phase measurement in the first embodiment.

[0044] Figure 7 This is a schematic diagram illustrating the phase deviation between the phase-continuously-stepped sweep frequency signal and the ideal comb wave signal in the first embodiment.

[0045] Figure 8 This is a schematic diagram of the interleaved step sweep frequency mode 1 of the first embodiment.

[0046] Figure 9 This is a schematic diagram of the interleaved step sweep frequency mode 2 of the first embodiment.

[0047] Figure 10 Device structure of the second embodiment Figure 1 .

[0048] Figure 11 Device structure of the second embodiment Figure 2 . Detailed Implementation

[0049] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0050] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0051] This invention provides a method and apparatus for measuring the phase-frequency characteristics of a comb wave generator spectral lines. It utilizes a frequency synthesizer with continuous phase-stepping sweep function to sequentially provide reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test. The phase difference between each spectral line of the comb wave and the reference signal is compared and measured. Based on the frequency interval between adjacent spectral lines of the comb wave and the sweep time of the frequency synthesizer, the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal is calculated. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and all spectral lines simultaneously having zero phase at a certain moment. The phase difference is corrected using the phase deviation to obtain the phase difference between the comb wave signal and the ideal comb wave signal, thereby obtaining the phase-frequency characteristics of the comb wave generator spectral lines under test.

[0052] The essence of this invention is as follows: at the physical level, the phase frequency characteristics of the comb wave generator are compared and measured by using the signal output by the "synthesizer" as a reference, i.e., the "phase difference"; at the mathematical level, the "phase deviation" between the synthesizer and the defined ideal signal is calculated; at the practical level, the "phase difference" is corrected based on the "phase deviation" to obtain the difference in phase frequency characteristics between the measured comb wave and the ideal signal.

[0053] Example 1

[0054] In one or more embodiments, a method for measuring the phase frequency characteristics of a comb wave generator spectral lines is disclosed, such as... Figure 1 As shown, it includes the following steps:

[0055] Step S1: The comb wave generator is provided with an excitation signal through a frequency synthesizer with continuous phase stepping frequency sweep function, so that the comb wave generator generates the comb wave to be measured.

[0056] Step S2: Using a frequency synthesizer, provide reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test in sequence, and compare the phase difference between each spectral line of the comb wave and the reference signal.

[0057] Step S3: Based on the frequency interval between adjacent spectral lines of the comb wave and the frequency synthesizer step sweep time, calculate the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and having zero phase at a certain moment for each spectral line.

[0058] Step S4: Correct the phase difference using the phase deviation to obtain the phase difference between the comb wave signal and the ideal comb wave signal;

[0059] Step S5: Based on the phase difference between the corrected comb wave signal and the ideal comb wave signal, plot the "phase-frequency" diagram in sequence to obtain the phase-frequency characteristics of the spectral lines of the comb wave generator under test.

[0060] The implementation process of a method for measuring the phase frequency characteristics of a comb wave generator spectrum line in this embodiment will be described in detail below.

[0061] First, let's explain the phase frequency characteristics of the comb wave.

[0062] In the frequency domain, a comb wave appears as a series of spectral lines with equal frequency intervals. Each spectral line represents a sinusoidal signal component. That is, a comb wave is composed of a set of sinusoidal signals, in which each sinusoidal signal component has equal frequency intervals but may have different amplitudes and different instantaneous phases at different times.

[0063] Due to the equal frequency spacing of comb-shaped spectral lines, the relative phase between their sinusoidal signal components changes with time in a fixed relationship: Let the frequency difference between adjacent spectral lines be Δf, then the angular frequency difference is Δω = 2πΔf. This angular frequency difference is also the rate of change of the phase difference between adjacent spectral lines. Let the instantaneous phase difference between adjacent spectral lines at a certain time t be... have

[0064] As a benchmark for measuring the phase-frequency characteristics of the spectral lines of a comb wave generator, this embodiment defines an ideal comb wave signal that has the same zero phase at a certain moment. Using this as the origin, the phase-time diagrams of each sinusoidal component are plotted, which are represented as a family of intersecting straight lines of different frequencies, such as... Figure 2 As shown, the slanted solid lines represent the phase variation of each spectral line over time, with the horizontal axis representing time and the vertical axis representing phase, denoted by f. n The frequencies corresponding to the sinusoidal spectral lines are identified, where the subscripts are the sequential numbers of the comb-shaped spectral lines, and the slope difference between adjacent lines is Δω. Without loss of generality, assuming the phase and time at the origin are zero, the phase of the nth spectral line at time t is... Obviously, at the same time t m Each adjacent spectral line (sine wave component) has the same phase difference. The phase difference is different at different times, but the amount of change of the phase difference over time is constant: This is called "phase coherence".

[0065] Will Figure 2 The phase-time diagram is converted into a phase-frequency diagram, such as... Figure 3 As shown, it will be represented as a family of intersecting straight lines at different measurement times.

[0066] It can be seen that for an ideal comb wave with the same phase starting point, due to the phase coherence relationship, it can exhibit a linear "phase-frequency" relationship, that is, a linear phase-frequency characteristic. The linearity is the result of the "common phase starting point" and "phase coherence".

[0067] For comb wave generators with inconsistent initial phases of spectral lines, the linearity of the phase frequency characteristics will be disrupted. Measuring the phase frequency characteristics of a comb wave generator means determining the relationship between the phase difference between its output comb wave signal and the ideal comb wave signal as a function of the spectral line frequency; using f... n+1 Taking the initial phase offset δ of this signal component as an example, Figure 2 The corresponding line in the equation will be translated by δ, such as... Figure 4 As shown; and as Figure 5 As shown, f n+1 The phase value corresponding to the frequency signal will shift by δ from the linear value, thus disrupting the phase-frequency linear relationship; however, due to It is evident that different initial phases of spectral lines do not disrupt the phase coherence relationship between them. Therefore, the phase coherence relationship between comb-wave spectral lines can be used to characterize the relative phase characteristics between them by measuring the phase-frequency relationship.

[0068] Based on the phase coherence and phase frequency characteristics of comb waves, the basic principle of relative phase measurement of comb waves is explained.

[0069] like Figure 6 As shown, if an ideal comb wave signal with the same frequency structure as the comb wave signal being measured can be found as a phase reference, the phase difference of each spectral line can be compared to obtain the phase frequency characteristics of the measured signal. That is, the phase frequency characteristics of the measured comb wave are the relationship between the phase difference between its output comb wave signal and the ideal comb wave signal and the spectral line frequency.

[0070] Figure 6 The family of thick solid lines represents the phase-time diagram of the comb wave under test, while the family of thin solid lines represents the phase-time diagram of the ideal comb wave signal used as a phase measurement reference. Considering the phase coherence characteristics of the comb wave signal analyzed above, without loss of generality, only the typical case where spectral lines have a common zero phase is used as an example in the diagram. If the initial phase of a spectral line of the measured signal deviates from the "common zero phase," it will be reflected as the phase deviation of the thick solid lines at the corresponding frequencies, such as... Figure 5 As shown. The ideal comb wave signal, which serves as the reference signal, must have a common zero-phase moment, denoted as T, which lags behind the common zero-phase moment of the measured signal.

[0071] Figure 6 Double subscript symbol This represents the phase difference between corresponding spectral lines of the measured and reference comb wave signals. The subscript before the colon indicates the phase comparison measurement time, and the subscript after the colon indicates the spectral line number being compared. It can be seen that, with an ideal comb wave reference, the measurement results are independent of the measurement time; they are all equivalent to the instantaneous phases of each spectral line of the measured comb wave signal at the zero-phase moment of the reference signal. Arranging these instantaneous phase measurements in spectral order yields the spectral phase-frequency characteristics of the measured comb wave.

[0072] However, obtaining a comb wave reference signal that adapts to any possible frequency interval is difficult as a measurement method and device design. This invention is based on a frequency synthesizer using direct digital synthesis (DDS) or fractional-N (FN) technology. Under the condition of precise and controllable phase continuous step sweep, it provides phase compensation data of the synthesizer output signal relative to the equivalent ideal comb wave signal. The phase frequency characteristics of the comb wave signal can be measured by software correction, using the phase continuous step sweep synthesizer output signal as a reference; or, by referring to the compensation data and through precise control timing design, by hardware correction, the frequency synthesizer output signal has an equivalent ideal comb wave coherent phase when sweeping through the spectral line corresponding to the measured signal, thereby directly realizing the phase frequency characteristics measurement of the comb wave signal; or, based on the characteristics of the compensation data, at a specific sweep speed, the phase frequency characteristics measurement of the comb wave signal can be directly realized without manual compensation. The following is a detailed description.

[0073] Software fix

[0074] Based on software numerical processing, the measurement results can be numerically compensated by using the phase deviation of the synthesizer signal phase relative to the ideal comb wave signal, based on the output signal of the phase continuous frequency synthesizer with step sweep frequency as the phase comparison measurement reference.

[0075] Frequency synthesizers based on direct digital synthesis (DDS) or fractional-N (FN) can output high-resolution, precisely controllable, and phase-continuous frequency signals, which can be used as phase comparison reference signals for comb wave signal measurements. However, unlike comb wave signal generators that output a series of sinusoidal signal lines in parallel, DDS or FN can only output a sinusoidal signal of a specific frequency at a time. Therefore, using DDS or FN-based frequency synthesizers, the phase of each spectral line can only be measured sequentially by setting the corresponding frequencies for different spectral lines in a time-division manner.

[0076] Considering that only equally spaced discrete spectral lines of the comb wave signal need to be measured, the frequency synthesizer can be set to perform a step-sweep, sequentially outputting reference signals for the frequencies corresponding to each spectral line. At each output frequency, the working mechanism of the frequency synthesizer can be equivalent to... That is, under the control of the clock signal, the phase of the synthesizer output signal increases in steps every δt time interval. The output angular frequency is generated through phase accumulation and change. The macroscopic effect. With the clock constant, changing different step phases... This will result in a change in frequency; step sweep frequency refers to changing the step phase once every certain period of time ΔT. And until the change The previous phase accumulation is the initial value for this phase accumulation. It can be seen that frequency synthesizers based on DDS or FN do not possess the phase coherence characteristics of ideal comb-wave signals during stepped frequency sweeps, but they do have the characteristic of phase continuity, such as... Figure 7 As shown.

[0077] Figure 7 In the diagram, the thin solid line represents the phase-time plot of an ideal comb wave. Without loss of generality, the phase changes of the first few spectral lines, starting from the fundamental wave, over time are plotted, each represented by its spectral frequency f. n The labels are spectral line numbers and the first few ΔT step time periods corresponding to the frequency synthesizer's step sweep. The subscripts on the horizontal axis are the numbers of the time periods on the left. The thick solid lines represent the desired phase-time relationship of the frequency synthesizer signal when comparing and measuring the corresponding spectral lines of the comb wave, while the thick dashed lines represent the actual phase-time relationship given by the frequency synthesizer's continuous phase sweep signal. The difference between this and the ideal phase-time relationship is indicated by a thin solid arrow.

[0078] Let the frequency interval between spectral lines be Δf = f n+1 -f n The duration of each frequency step in the frequency synthesizer is ΔT = t. m+1 -t m Then, for each frequency step duration between adjacent spectral lines, the phase difference increases by ΔΦ = 2πΔfΔT = ΔωΔT, resulting in an increasingly larger lag between the phase of continuously frequency-stepped phases and the ideal coherent phase after each step; let t m The phase deviation corresponding to the step time point is ΔΦ m , has ΔΦ m =ΔΦ×m(m-1) / 2; It can be seen that by using a continuously stepped frequency sweep signal as a phase reference to measure the phase of the comb wave spectral line, and then performing phase numerical correction according to the above formula, the phase-frequency characteristics of the comb wave signal generator spectral line relative to the ideal comb wave signal can be obtained. Note that the phase deviation remains constant during the stepped frequency maintenance period, therefore the specific timing requirements for phase relative measurement are not strict, which is very beneficial for the design of the measurement circuit and control timing. However, precise control of the frequency switching time point should be ensured.

[0079] Regarding ΔΦ m Proof: For any sweep starting frequency f0, the sweep frequency is stepped to t m At the end of the time period, the phase of the spectral line corresponding to the ideal comb wave is:

[0080]

[0081] Among them, f m t represents the spectral line frequency of the measured comb wave. m The subscripts indicate the measurement time, and are the sequential numbers of the spectral lines or time periods. Since each frequency step corresponds to a phase measurement of a spectral line during the measurement process, the subscripts are the same for both.

[0082] The actual cumulative phase of the phase-stepped frequency sweep is:

[0083]

[0084] Therefore:

[0085]

[0086] in, It is the phase of the spectral line corresponding to the ideal comb wave. It is the actual cumulative phase of the phase continuous step sweep frequency.

[0087] Hardware correction method

[0088] Based on hardware control, the phase of the frequency synthesizer can be adjusted to eliminate the phase deviation between its output signal and the ideal comb wave, including two methods:

[0089] (1) Directly control the initial phase of the output signal of the frequency synthesizer.

[0090] In a frequency synthesizer with initial phase digital control, the compensation data based on continuous phase step sweep can be directly used to correct the phase of the synthesizer output signal, thereby obtaining a phase reference equivalent to an ideal comb wave signal, and then directly measuring the phase frequency characteristics of the comb wave spectral line.

[0091] Frequency synthesizers based on direct digital synthesis (DDS) or fractional-N (FN) techniques typically feature initial phase control, meaning that while controlling the output frequency of the synthesizer, an offset is simultaneously added to the initial phase. This offset is defined as the phase deviation ΔΦ given above. m =ΔΦ×m(m-1) / 2, while changing the frequency through step sweep, this phase deviation is provided to the frequency synthesizer as a phase offset. This will cause the phase of the output signal of the frequency synthesizer to jump to the phase of the corresponding spectral line of the ideal comb wave signal, while maintaining phase continuity. Figure 7 The phase-time relationship of the continuous phase sweep, indicated by the thick dashed line, is forcibly converted to the ideal phase-time relationship indicated by the thick solid line. In the formula, m is the number of the frequency step time interval, which is also the number of the spectral line of the comb wave signal being measured; ΔΦ=2πΔfΔT is a constant, where Δf is the frequency interval of the synthesizer step sweep, which is also the frequency difference between adjacent spectral lines of the comb wave signal, and ΔT is the frequency step time interval.

[0092] By performing the aforementioned phase correction control, the output signal of the frequency synthesizer at each frequency step is equal in phase with the corresponding spectral line of the ideal comb wave signal. This allows for equivalent phase comparison between the measured comb wave signal and the ideal comb wave signal, thereby directly realizing the measurement of the phase-frequency characteristics of the comb wave signal spectral line.

[0093] (2) Based on the phase deviation law, the initial phase of the output signal of the frequency synthesizer is corrected by frequency interleaving step control.

[0094] For frequency synthesizers that lack or are inconvenient to perform initial phase digital control, the phase of the corresponding spectral lines of an equivalent ideal comb wave signal can also be achieved through digitally controlled interleaved frequency sweeps, such as... Figure 8 and Figure 9 As shown, corrections can be made in the latter half of the ΔT time period or in the first half.

[0095] The second-half correction divides the step interval ΔT into two halves: ΔT(N-1) / N and ΔT / N, where N is a rational number greater than 1. In the first half, the normal frequency f is applied. n Set the synthesizer frequency and measure the corresponding comb spectral line phase difference; then, in the latter half of the time, control the synthesizer frequency to increase by NΔf in a phase-continuous manner, i.e., make the synthesizer operate at frequency f. n +NΔf, and at the end of this ΔT time period, change the synthesizer frequency to f in a phase-continuous manner. n +Δf=f n+1 That is, the synthesizer frequency corresponding to the next comb wave spectral line is set at the beginning of the next ΔT time interval. In the first half of the next ΔT time interval, the synthesizer frequency is equivalent to the phase of the ideal comb wave signal at the next spectral line, allowing direct measurement of the corresponding comb wave spectral line phase difference. The synthesizer frequency can then be set again in a phase-continuous manner in the second half of the time interval. n+1 +NΔf. By continuously controlling the synthesizer frequency steps in this manner, the phase of the synthesizer output signal is equivalent to the phase of an ideal comb wave signal in the first half of each ΔT, thus enabling direct comparison and measurement of the spectral phase-frequency characteristics of the comb wave generator. As a special case, such as... Figure 8 As shown, taking N=2, each ΔT is divided into two ΔT / 2 segments. If the synthesizer frequency of the first half is f... n Then the frequency of the second half is f. n +2Δf=f n+2 Correspondingly, the frequencies of the preceding and following segments in the next ΔT time interval are f and f, respectively. n+1 and f n+1 +2Δf=f n+3 The thin solid line in the figure represents the phase-time diagram of the ideal comb wave signal. The thick solid line represents the time period when the output signal of the frequency synthesizer is in phase with the corresponding spectral line of the ideal comb wave, which can be directly used as an ideal reference for measuring the phase-frequency characteristics of the comb wave. The thick dashed line represents the time period when the phase is corrected using special frequency control. The thin solid arrows in the figure indicate the frequency of the frequency synthesis in each time period. Note that the signal phase change is continuous. The dashed arrows indicate the frequency difference between the synthesizer output frequency and the ideal signal in the corresponding time period during the phase correction time period.

[0096] The first half correction involves dividing the step interval ΔT into two halves, ΔT / N and ΔT(N-1) / N, and starting from the second ΔT time interval, setting the synthesizer frequency f in the first half in a phase-continuous manner. n +NΔf, set the synthesizer frequency to f in the second half. n Then, the synthesizer phase is equivalent to the phase of the ideal comb wave signal in the latter half of each ΔT, enabling direct comparison and measurement of the spectral phase-frequency characteristics of the comb wave generator. As a special case, such as... Figure 9As shown, taking N=2, each ΔT is divided into two ΔT / 2 segments, with the synthesizer frequency of the first segment being f. n +2Δf=f n+2 The frequencies in the latter half are the corresponding f values ​​for comb-shaped spectral lines measured. n Correspondingly, the frequencies of the first and second halves of the next ΔT time interval are f and f, respectively. n+1 +2Δf=f n+3 and f n+1 The thin solid line in the figure represents the phase-time diagram of the ideal comb wave signal. The thick solid line represents the time period when the output signal of the frequency synthesizer is in phase with the corresponding spectral line of the ideal comb wave, which can be directly used as an ideal reference for measuring the phase-frequency characteristics of the comb wave. The thick dashed line represents the time period when the phase is corrected using special frequency control. The thin solid arrows in the figure indicate the frequency of the frequency synthesis in each time period. Note that the signal phase change is continuous. The dashed arrows indicate the frequency difference between the synthesizer output frequency and the ideal signal in the corresponding time period during the phase correction time period.

[0097] Achieving natural correction based on a specific speed.

[0098] Based on a specific speed, during the test, a specific step frequency sweep interval ΔT is selected according to the spectral line spacing of the comb wave generator under test, such that ΔfΔT=M, where M is a natural number. When the synthesizer sweeps the frequency at these specific step speeds determined by ΔT, the deviation between the instantaneous phase of the phase continuous synthesizer and the phase of the ideal comb wave signal is an integer multiple of 2π, which is equivalent to 0 in the phase domain, that is, there is no actual deviation. Therefore, the spectral line phase frequency characteristics of the comb wave generator can be directly compared and measured without the need for software and hardware compensation.

[0099] Example 2

[0100] In one or more embodiments, a comb wave generator spectral line phase frequency characteristic measurement device is disclosed, which can be divided from the perspective of logical function, such as... Figure 10 As shown, it includes a phase difference measurement unit, a phase deviation calculation unit, and a phase frequency characteristic calculation unit:

[0101] The phase difference measurement unit is configured to: use a frequency synthesizer with a phase continuous step sweep frequency function to sequentially provide reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test, and compare and measure the phase difference between each spectral line of the comb wave and the reference signal;

[0102] The phase deviation calculation unit is configured to: calculate the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal based on the frequency interval between adjacent spectral lines of the comb wave and the step sweep time of the frequency synthesizer. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and having zero phase at a certain moment for each spectral line.

[0103] The phase frequency characteristic calculation unit is configured to: correct the phase difference using the phase deviation, obtain the phase difference between the comb wave signal and the ideal comb wave signal, and thus obtain the phase frequency characteristic of the spectrum of the comb wave generator under test.

[0104] This embodiment discloses a comb wave generator spectral line phase frequency characteristic measurement device, which can be divided from the perspective of physical function, such as... Figure 11 As shown, it includes a reference signal generation module, a reference signal correction module, and a phase-frequency response calculation module:

[0105] The reference signal generation module is configured to: provide an excitation signal to the comb wave generator using a frequency synthesizer, and simultaneously adopt a step-sweep frequency operation mode to provide a phase measurement reference signal corresponding to each spectral line of the comb wave under test at each step frequency point.

[0106] The reference signal correction module is configured to: based on the comb wave phase measurement reference signal, calculate the phase deviation between the reference signal provided by the phase continuous synthesizer and the corresponding spectral lines of the ideal comb wave signal according to the frequency interval of adjacent spectral lines of the comb wave signal and the synthesizer frequency step time; and based on the phase deviation, perform initial phase or step mode correction on the frequency synthesizer so that the phase of the synthesizer output signal is equivalent to the phase of the ideal comb wave signal during measurement.

[0107] The phase-frequency characteristic calculation module is configured to: based on the phase deviation between the reference signal provided by the phase continuous synthesizer and the corresponding spectral line of the ideal comb wave signal, and the phase difference obtained by comparing each spectral line of the comb wave signal under test with the corresponding output reference signal of the frequency synthesizer, draw the "phase-frequency" diagram in sequence according to the correction results to obtain the phase-frequency characteristic of the comb wave under test.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring the phase frequency characteristics of a comb wave generator spectral lines, characterized in that, include: Using a frequency synthesizer with continuous phase stepping frequency sweep function, reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test are provided sequentially, and the phase difference between each spectral line of the comb wave and the reference signal is compared and measured. Based on the frequency interval between adjacent spectral lines of the comb wave and the step sweep time of the frequency synthesizer, the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal is calculated. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and having zero phase at a certain moment for each spectral line. The phase difference is corrected by using the phase deviation to obtain the phase difference between the comb wave signal and the ideal comb wave signal, thereby obtaining the phase frequency characteristics of the spectrum of the comb wave generator under test. Specifically, the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral line of the ideal comb wave signal is as follows: (1) The frequency interval between spectral lines is The time interval for each frequency step switching of the synthesizer is Then, the phase difference between adjacent spectral lines increases with each frequency step. ;in, These represent the frequencies corresponding to adjacent spectral lines. This indicates the time points corresponding to adjacent frequency step changes. Indicates the frequency difference between adjacent spectral lines. This represents the corresponding angular frequency difference; (2) For any sweep start frequency, let the step sweep number be denoted as _____. The end of the step time period is Then the step time point The phase deviation is ;in, It is the phase of the spectral line corresponding to the ideal comb wave signal. It is the actual cumulative phase of the phase continuous step sweep frequency, that is, the phase of the synthesizer output signal.

2. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 1, characterized in that, The stepped frequency sweep refers to controlling the frequency synthesizer to sequentially output the frequencies corresponding to each spectral line of the comb wave generator under test, specifically: Frequency synthesizer per interval The output frequency is changed by the same amount once. Also known as frequency sustaining time or switching time, it is used to number the spectral lines of a comb wave generator according to their harmonic orders, and is denoted as... The signal corresponding to the spectral line is The phase change accumulated over time is , yes Spectral line frequencies, That is the corresponding angular frequency.

3. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 1, characterized in that, The phase continuous step sweep frequency refers to the frequency synthesizer being able to perform frequency sweep according to a specified time interval. The signal is output sequentially with the frequency corresponding to the spectral line frequency of the output signal of the comb wave generator under test, and the phase change of the signal is continuous when the frequency synthesizer changes the frequency.

4. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 1, characterized in that, The frequency synthesizer uses direct digital synthesis (DDS) or fractional frequency division (FN) technology to achieve a high-resolution, precisely controllable output signal with continuous phase when the output frequency changes.

5. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 1, characterized in that, The corrections include software methods, hardware methods, and speed-specific methods: (1) Based on software, utilizing the phase deviation The phase values ​​of the comb-shaped spectral lines obtained by comparison and measurement using the output signal of the frequency synthesizer as a reference are, according to... The indexed spectral line numbers are numerically compensated to obtain the phase frequency characteristics of the measured comb wave signal relative to the ideal comb wave; (2) Based on hardware, referring to the phase deviation The initial phase of the frequency synthesizer output signal can be directly controlled and adjusted to make it equivalent to the phase of an ideal comb wave signal; or the time interval of the frequency synthesizer can be adjusted. It is divided into two segments: one segment is used for phase difference measurement, and the other segment adjusts the phase through a specific frequency setting so that the phase of the measurement period is equivalent to the phase of an ideal comb wave signal. (3) Achieve natural correction based on a specific speed: according to the phase deviation The characteristics of the comb-shaped spectral line frequency spacing are targeted at the test. Choose a specific time interval , making ,in, If the value is a natural number, then the phase deviation between the output signal of the frequency synthesizer and the corresponding spectral line of the ideal comb wave signal is equivalent to 0, and the spectral phase frequency characteristics of the comb wave generator under test can be obtained by direct comparison and measurement.

6. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 5, characterized in that, The direct control and adjustment of the initial phase of the frequency synthesizer output signal specifically involves: For a frequency synthesizer with initial phase control capability, the phase deviation will be... As an additional phase offset, the initial phase is controlled and corrected to eliminate the phase deviation between the output signal of the frequency synthesizer and the ideal comb wave signal, thereby enabling direct comparison and measurement of the spectral phase frequency characteristics of the comb wave generator.

7. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 5, characterized in that, The time interval of the frequency synthesizer Divide into two parts, and make corrections in the second half, specifically as follows: Step interval Divided into and The two halves, For rational numbers greater than 1, the first half follows the normal frequency. Set the synthesizer frequency and measure the corresponding comb spectral line phase difference; then, in the latter half of the time, control the synthesizer frequency to increase in a phase-continuous manner. That is, to make the synthesizer operate at a frequency and in this At the end of the time period, the synthesizer frequency is changed in a phase-continuous manner. That is, in the next The start time of the time period is set to the synthesizer frequency corresponding to the next comb wave spectral line measurement.

8. The method for measuring the phase frequency characteristics of a comb wave generator spectral lines as described in claim 5, characterized in that, The time interval of the frequency synthesizer Divide into two parts, and make corrections in the first half, specifically: Time interval Divided into and The two halves, and from the second At the start of the time period, the synthesizer frequency is set to [value] in the first half of the period, using a phase-continuous approach. In the second half, the synthesizer frequency is set to... The synthesizer phase is in each The latter half of the signal is phase-equivalent to that of an ideal comb wave signal, enabling direct comparison and measurement of the spectral phase frequency characteristics of the comb wave generator.

9. A device for measuring the phase frequency characteristics of a comb wave generator spectrum, characterized in that, It includes a phase difference measurement unit, a phase deviation calculation unit, and a phase frequency characteristic calculation unit: The phase difference measurement unit is configured to: use a frequency synthesizer with a phase continuous step sweep frequency function to sequentially provide reference signals corresponding to the frequencies of the comb wave spectral lines generated by the comb wave generator under test, and compare and measure the phase difference between each spectral line of the comb wave and the reference signal; The phase deviation calculation unit is configured to: calculate the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral lines of the ideal comb wave signal based on the frequency interval between adjacent spectral lines of the comb wave and the step sweep time of the frequency synthesizer. The ideal comb wave signal is defined as having the same spectral line frequencies as the comb wave and having zero phase at a certain moment for each spectral line. The phase frequency characteristic calculation unit is configured to: correct the phase difference by using the phase deviation to obtain the phase difference between the comb wave signal and the ideal comb wave signal, thereby obtaining the phase frequency characteristic of the spectrum of the comb wave generator under test; Specifically, the phase deviation between the reference signal output by the frequency synthesizer and the corresponding spectral line of the ideal comb wave signal is as follows: (1) The frequency interval between spectral lines is The time interval for each frequency step switching of the synthesizer is Then, the phase difference between adjacent spectral lines increases with each frequency step. ;in, These represent the frequencies corresponding to adjacent spectral lines. This indicates the time points corresponding to adjacent frequency step changes. Indicates the frequency difference between adjacent spectral lines. This represents the corresponding angular frequency difference; (2) For any sweep start frequency, let the step sweep number be denoted as _____. The end of the step time period is Then the step time point The phase deviation is ;in, It is the phase of the spectral line corresponding to the ideal comb wave signal. It is the actual cumulative phase of the phase continuous step sweep frequency, that is, the phase of the synthesizer output signal.

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