CN112763769B - Signal generator with ultralow harmonic distortion - Google Patents
Signal generator with ultralow harmonic distortion Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
A signal generator with ultra-low harmonic distortion comprises a harmonic compensation unit, a control processing unit, a waveform generation unit and an output conditioning unit, wherein the harmonic compensation unit is configured with harmonic calibration data; the control processing unit is used for generating harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters; the waveform generating unit is used for generating a single-tone signal corresponding to preset parameters and each subharmonic signal corresponding to harmonic compensation data, and obtaining a compensation signal by superposing each subharmonic signal on the single-tone signal; the output conditioning unit is used for carrying out waveform conditioning on the compensation signal to generate an output signal. The technical scheme of the application provides the harmonic compensation mechanism of the signal generator, can effectively avoid the phenomenon that the signal generator has serious signal distortion under the condition of outputting a high-frequency large signal, and effectively overcomes the harmonic distortion problem of the output signal, so that the signal generator has higher practical value.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a signal generator with ultralow harmonic distortion.
Background
A signal generator is a device that can provide electrical signals of various frequencies, waveforms and output levels, and is often used as a signal source or stimulus for testing when measuring amplitude characteristics, frequency characteristics, transmission characteristics and other electrical parameters of various telecommunication systems or equipment, and when measuring characteristics and parameters of a component.
The signal generator of the Direct Digital frequency Synthesis adopts Direct Digital Synthesis (DDS), which can improve the frequency stability and accuracy of the signal generator to the same level as the reference frequency, and can perform fine frequency adjustment in a wide frequency range. The signal source designed by the DDS technology can work in a modulation state, can adjust the output level and can output various waveforms.
Harmonic distortion refers to a signal with integral multiple of the frequency of the original single-tone signal generated after a pure single-tone sine wave passes through a system with nonlinearity, for example, a signal with twice the frequency of the original single-tone sine signal as the second harmonic. Harmonic distortion is a non-linear operating characteristic due to the presence of active devices in the system, such as typically expressed as a percentage in audio applications and typically expressed as dB in communications applications.
Harmonic distortion of an output signal of a signal generator is generally limited by an output amplifying circuit which is arranged inside the signal generator, the output amplifying circuit generally adopts an integrated broadband amplifier, and because the broadband amplifier mainly adopts active devices, a signal amplifying process presents nonlinear working characteristics, harmonic distortion of the output signal can be increased along with the increase of the frequency of the output signal and the amplitude of the output signal, and the harmonic distortion problem is particularly obvious when a high-frequency large signal is output.
Disclosure of Invention
The technical problem that this application mainly solved is how to overcome the output signal harmonic distortion problem that current signal generator exists. To solve the above problems, the present application provides a signal generator with ultra-low harmonic distortion and a calibration method thereof.
According to a first aspect, an embodiment provides a signal generator with ultra-low harmonic distortion, comprising: a harmonic compensation unit configured with harmonic calibration data; the control processing unit is used for generating harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters; the preset parameters comprise frequency parameters and amplitude parameters of the single-tone signals, and the harmonic compensation data comprise phase compensation values and amplitude compensation values of each harmonic; the waveform generating unit is used for generating a single tone signal corresponding to the preset parameter and each subharmonic signal corresponding to the harmonic compensation data, and superposing each subharmonic signal on the single tone signal to obtain a compensation signal; the output conditioning unit is used for carrying out waveform conditioning on the compensation signal to generate an output signal; and each subharmonic signal in the compensation signal is used for offsetting each interference harmonic generated by the output conditioning unit.
The control processing unit generates harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters, and the harmonic compensation data comprises: selecting two adjacent calibration frequency points from the harmonic compensation data according to the frequency parameters of the single tone signals; performing linear interpolation on the phases of the harmonics respectively corresponding to the two calibration frequency points, and obtaining phase compensation values of the harmonics by using interpolation results; calling amplitude curve fitting functions respectively corresponding to the two calibration frequency points according to the amplitude parameters of the single-tone signal, and performing function solving on the amplitude of each subharmonic to obtain an amplitude compensation value of each subharmonic; and obtaining harmonic compensation data of the single-tone signal by using the phase compensation value and the amplitude compensation value of each harmonic.
The output conditioning unit comprises an output attenuation circuit and an output amplification circuit; the output attenuation circuit is connected with the waveform generation unit and is used for carrying out waveform attenuation on the compensation signal to obtain an attenuation signal; the output amplifying circuit is connected with the output attenuating circuit and is used for carrying out waveform amplification on the attenuated signal to obtain the output signal.
The signal generator also comprises an output control unit; the output control unit is connected with the output conditioning unit and used for carrying out output control on the output signal so as to transmit the output signal to external equipment of the signal generator in a coaxial mode.
The signal generator also comprises an input unit and a display unit; the input unit is connected with the control processing unit and is used for configuring preset parameters for generating the single tone signal; the display unit is connected with the control processing unit and used for displaying preset parameters, waveforms and/or harmonic compensation data of the single-tone signal.
According to a second aspect, an embodiment provides a calibration method for a signal generator for outputting output signals of various frequencies and amplitudes, the calibration method comprising the steps of: obtaining amplitudes corresponding to the harmonics of the calibration frequency points in a first output signal output by the signal generator respectively, and obtaining amplitudes corresponding to the harmonics of the calibration frequency points in a second output signal output by the signal generator respectively; the first output signal is a signal generated by waveform conditioning of a single tone signal with a preset frequency and a preset amplitude; the second output signal is a signal generated by waveform conditioning a single-tone signal on which a plurality of calibration harmonics are superimposed, wherein the plurality of calibration harmonics include a plurality of harmonics with different amplitudes and the same phase; calculating amplitude-related calibration data according to the amplitude corresponding to each harmonic of the calibration frequency point in the first output signal, calculating phases corresponding to each harmonic of the calibration frequency point according to the amplitude corresponding to each harmonic of the calibration frequency point in the second output signal, and generating phase-related calibration data; harmonic calibration data is formed using the calibration data for amplitude and the calibration data for phase and configured to the signal generator.
The step of calculating the amplitude-related calibration data according to the amplitudes corresponding to the harmonics of the calibration frequency points in the first output signal includes: and performing curve fitting on the preset amplitude of the single tone signal and the amplitude corresponding to each subharmonic of the calibration frequency point in the first output signal, and using an amplitude curve fitting function obtained by fitting as calibration data about the amplitude.
The calculating, according to the amplitudes corresponding to the harmonics of the calibration frequency points in the second output signal, the phases corresponding to the harmonics of the calibration frequency points, respectively, and generating calibration data about the phases includes: if the amplitudes of the calibration harmonics are set to bea 12~a 1n，a 12Representing amplitudea 1The 2 nd harmonic of the time (x),a 1nrepresenting amplitudea 1The amplitude of each harmonic of the calibration frequency point in the second output signal is respectively corresponding to n harmonics of timea´12~a´1n(ii) a Respectively corresponding amplitudes of each harmonic of the calibration frequency pointa 12~a 1n Anda´12~a´1ninput to the phase calculation formula
So as to calculate and obtain the phase corresponding to each harmonic of the calibration frequency point; wherein the subscriptiThe value range of (a) is 2 to n,
the same phase for the plurality of calibration harmonics; and adding the phases corresponding to the harmonics of the calibration frequency points by 180 degrees to obtain calibration data about the phases.
The calibration method further comprises the following steps: and setting the preset frequency and the preset amplitude of the single tone signal for multiple times, and correspondingly generating calibration data about the amplitude and calibration data about the phase after each setting.
According to a third aspect, an embodiment provides a computer-readable storage medium comprising a program executable by a processor to implement the calibration method described in the second aspect above.
The invention has the beneficial effects that:
according to the embodiment, the signal generator with ultralow harmonic distortion comprises a harmonic compensation unit, a control processing unit, a waveform generation unit and an output conditioning unit, wherein the harmonic compensation unit is configured with harmonic calibration data; the control processing unit is used for generating harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters; the waveform generating unit is used for generating a single-tone signal corresponding to preset parameters and each subharmonic signal corresponding to harmonic compensation data, and obtaining a compensation signal by superposing each subharmonic signal on the single-tone signal; the output conditioning unit is used for carrying out waveform conditioning on the compensation signal to generate an output signal. On the first hand, because the harmonic compensation unit is added in the signal generator, the control processing unit can generate the harmonic compensation data of the single-tone signal by utilizing the harmonic calibration data, and the realization possibility is provided for the harmonic compensation of the single-tone signal; in the second aspect, because the waveform generating unit superimposes each harmonic signal on the single-tone signal to obtain the compensation signal, each harmonic signal in the compensation signal can be used to cancel each interference harmonic generated by the output conditioning unit, so that harmonic distortion or ultralow harmonic distortion can be eliminated in the output signal as much as possible; in a third aspect, the technical scheme of the application provides a harmonic compensation mechanism of the signal generator, which can effectively avoid the phenomenon that the signal generator has serious signal distortion when outputting a high-frequency large signal, and effectively overcome the harmonic distortion problem of the output signal, so that the signal generator has higher practical value.
Drawings
FIG. 1 is a schematic diagram of a signal generator;
FIG. 2 is another schematic diagram of the signal generator;
FIG. 3 is a schematic diagram of a calibration system for a signal generator;
FIG. 4 is a flow chart of a calibration method for a signal generator;
FIG. 5 is another flow chart of a calibration method;
fig. 6 is a schematic structural diagram of the calibration control device.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. Wherein like elements in different embodiments are numbered with like associated elements. In the following description, numerous details are set forth in order to provide a better understanding of the present application. However, those skilled in the art will readily recognize that some of the features may be omitted or replaced with other elements, materials, methods in different instances. In some instances, certain operations related to the present application have not been shown or described in detail in order to avoid obscuring the core of the present application from excessive description, and it is not necessary for those skilled in the art to describe these operations in detail, so that they may be fully understood from the description in the specification and the general knowledge in the art.
Furthermore, the features, operations, or characteristics described in the specification may be combined in any suitable manner to form various embodiments. Also, the various steps or actions in the method descriptions may be transposed or transposed in order, as will be apparent to one of ordinary skill in the art. Thus, the various sequences in the specification and drawings are for the purpose of describing certain embodiments only and are not intended to imply a required sequence unless otherwise indicated where such sequence must be followed.
The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings).
The first embodiment,
Referring to fig. 1, in the present embodiment, a signal generator with ultra-low harmonic distortion is disclosed, and the signal generator 1 includes a harmonic compensation unit 12, a control processing unit 11, a waveform generation unit 13, and an output conditioning unit 14, which are respectively described below.
The harmonic compensation unit 12 is configured with harmonic calibration data for implementing compensation of harmonics of the output signal of the signal generator such that the output waveform has ultra-low harmonic distortion. How to configure the formation of the harmonic calibration data will be specifically described in example two below.
The control processing unit 11 has a data processing capability, is connected to the harmonic compensation unit 12, and is mainly configured to generate harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters in the harmonic compensation unit 12. The preset parameters include frequency parameters and amplitude parameters of the single-tone signal, and the harmonic compensation data includes phase compensation values and amplitude compensation values of the respective harmonics.
It should be noted that the single-tone signal refers to a signal form of a single frequency, such as a pure sinusoidal signal of a single frequency. If the user desires the signal generator to output a frequency offThe amplitude of the sine wave signal is a, the frequency parameter and the amplitude parameter of the single-tone signal can be set to be respectivelyf、aThereby forming preset parameters of the monophonic signal.
The waveform generating unit 13 is connected to the control processing unit 11, and is configured to generate a single-tone signal corresponding to a preset parameter and each subharmonic signal corresponding to the harmonic compensation data, and obtain a compensation signal by superimposing each subharmonic signal on the single-tone signal.
Since the waveform generating unit 13 needs to generate a single tone signal using preset parameters and generate each subharmonic signal using harmonic compensation data, the generation of the single tone signal and the harmonic signal can be realized by means of a direct digital frequency synthesis (DDS) technique. Direct digital frequency synthesis (DDS) is a new frequency synthesis technique and signal generation method, has ultra-high frequency conversion time, extremely high frequency resolution and low phase noise, and can maintain phase continuity during frequency change and modulation, thereby easily realizing frequency, phase and amplitude modulation. In addition, the DDS technology is mostly based on digital circuit technology, and has the outstanding advantage of programmable control. Therefore, the signal generation technology is more and more widely applied, and a DDS (direct digital synthesizer) special chip (such as an AD9850 chip) is produced by a plurality of manufacturers, and the device becomes the preferred device of the current electronic system.
It will be appreciated that the waveform generation unit 13 has, in addition to the waveform generation, the conversion of the signal from the digital domain to the analogue domain, and the compensation signal formed by the superposition is then in the form of an analogue signal.
The output conditioning unit 14 is connected to the waveform generating unit 13, and then the output conditioning unit 14 is configured to perform waveform conditioning on the compensation signal to generate an output signal. Because the output conditioning unit 14 has active devices such as a broadband amplifier, the output conditioning unit exhibits a nonlinear operating characteristic, and then each harmonic signal in the compensation signal is used for canceling each interference harmonic generated by the output conditioning unit 14.
It will be appreciated that the output conditioning unit 14 should have analog conditioning functions for the analog signal, such as filtering, signal attenuation, signal amplification, amplitude adjustment, etc., in order to achieve the waveform conditioning effect.
In this embodiment, the process of generating the harmonic compensation data of a single tone signal by the control processing unit 11 according to the harmonic calibration data and the preset parameters includes the following steps:
(1) the control processing unit 11 selects two adjacent calibration frequency points from the harmonic compensation data according to the frequency parameters of the single-tone signal. For example, if the frequency parameter of the tone signal isfThen the closest calibration frequency point can be selected in the harmonic compensation dataf 1、f 2Which satisfiesf 1<f<f 2。
(2) The control processing unit 11 performs linear interpolation on the phases of the harmonics corresponding to the two calibration frequency points, and obtains the phase compensation value of each harmonic by using the interpolation result. Due to the calibration of frequency pointsf 1Calibrating frequency points corresponding to phases with respective harmonicsf 2Corresponding to the phase of each harmonic, interpolating between the phases of certain harmonic to obtain frequency parameterfThe phase of the harmonic wave is obtained by the same method as the frequency parameterfThe phase of other harmonics to obtain frequency parametersfThe phase of the next harmonic.
(3) The control processing unit 11 calls the amplitude curve fitting functions respectively corresponding to the two calibration frequency points according to the amplitude parameters of the single-tone signal, and obtains the amplitude compensation value of each subharmonic by performing function solution on the amplitude of each subharmonic. Because the amplitude curve fitting function represents the nonlinear fitting relation between the amplitude of the output signal and the amplitude of each harmonic wave at a certain calibration frequency point, the amplitude parameter of the single-tone signal is obtainedaIn this case, the amplitude of each harmonic can be easily obtained by functional calculation, and an amplitude compensation value for each harmonic can be formed.
(4) The control processing unit 11 obtains the harmonic compensation data of the monophonic signal using the phase compensation value and the amplitude compensation value of each harmonic. Frequency parameter configuration in single-tone signal configurationfAmplitude parameteraIn the case of (1), a phase compensation value and an amplitude compensation value of each harmonic are obtained, so that it is easy to construct harmonic compensation data to perform phase compensation and amplitude compensation on the single-tone signal, thereby canceling each interference harmonic generated by the output conditioning unit 14.
For example, when the signal generator 1 outputs a frequency offWith a magnitude ofaIs not only a sheetWhen a sinusoidal wave is generated, the control processing unit 11 searches two calibration frequency points adjacent to the harmonic wave calibration data stored in the harmonic wave compensation unit 12 according to the set frequency parameters, obtains the phase of each harmonic wave by calibrating the two adjacent calibration frequency points and performs linear interpolation, and thus the phase of the output signal at the frequency can be obtainedfThe phase compensation value of each subharmonic. Further, the control processing unit 11 controls the amplitude of the output signalaAnd calling curves of the harmonic waves and the amplitudes of two adjacent calibration frequency points, calculating the amplitude compensation value of each subharmonic wave of the two adjacent calibration frequency points under the amplitude, and then performing linear interpolation to obtain the amplitude compensation value of each subharmonic wave of the output signal. Then, according to the compensation values of the amplitude and phase of each harmonic, the waveform generating unit 13 superimposes the corresponding harmonic on the original single-tone sine wave to cancel each interference harmonic generated by the output conditioning unit 14, so that the output signal has ultra-low harmonic distortion.
In one embodiment, referring to fig. 2, the output conditioning unit 14 includes an output attenuation circuit 141 and an output amplification circuit 142, each described below.
The output attenuation circuit 141 is connected to the waveform generating unit 13, and is configured to perform waveform attenuation on the compensation signal output by the waveform generating unit 13 to obtain an attenuated signal. It will be appreciated that the waveform attenuation process may include filtering, reducing the amplitude level, etc., such as using a high precision resistor to achieve waveform attenuation.
The output amplifying circuit 142 is connected to the output attenuating circuit 141, and is configured to perform waveform amplification on the attenuated signal output by the output attenuating circuit 141 to obtain an output signal. It is understood that the waveform amplification process may include increasing the amplitude level, etc., such as using a bandwidth amplifier or a triode amplifier circuit to achieve waveform amplification.
Further, referring to fig. 2, the signal generator further includes an output control unit 15, where the output control unit 15 is connected to the output conditioning unit 14 (i.e. connected to the output amplifying circuit 142 in the output conditioning unit 14), and then the output control unit 15 is configured to perform output control on the output signal output by the output amplifying circuit 142, so as to be coaxially transmitted to an external device of the signal generator. It will be appreciated that the processing of the output control may include turning the output on/off, detecting the output signal amplitude, etc.
Further, referring to fig. 2, the signal generation further includes an input unit 16 and a display unit 17. Then, the input unit 16 is connected to the control processing unit 11 for configuring preset parameters for generating a monophonic signal, and it is understood that the input unit 16 may be a keyboard, a knob, a touch screen, a mouse, or the like, and can freely set frequency parameters in the preset parametersfAmplitude parametera. In addition, the display unit 17 is connected to the control processing unit 11 for displaying preset parameters, waveforms and/or harmonic compensation data of the monophonic signal for the user to view.
Further, referring to fig. 2, the signal generator further includes a storage unit 18, where the storage unit 18 is connected to the control processing unit 11, and is configured to store some preset parameters and some process parameters, such as some configuration parameters related to the harmonic compensation unit 12, the waveform generation unit 13, the output attenuation circuit 141, the output amplification circuit 142, and the output control unit 15, so as to facilitate the control processing unit 11 to respectively control and monitor the working processes of the harmonic compensation unit 12, the waveform generation unit 13, the output attenuation circuit 141, the output amplification circuit 142, and the output control unit 15, and ensure the normal working performance of each component.
It should be noted that, referring to fig. 2, the control processing unit 11 and the storage unit 18 may cooperate as a main control unit of the entire signal generator to implement the functions of configuring and monitoring other units. The waveform generating unit 13 mainly implements the generation and superposition of single-tone signals and individual harmonics, and the conversion of signals from the digital domain to the analog domain. The output attenuation circuit 141, the output amplification circuit 142 and the output control unit 15 mainly implement the conditioning functions of the analog signal, including filtering, amplitude control and the like. The input unit 16 and the display unit 17 constitute a man-machine part of the signal generator. In addition, the harmonic compensation data configured by the harmonic compensation unit 12 is used to realize the compensation of the harmonic of the output signal, so that the output waveform has ultra-low harmonic distortion.
When the signal generator outputs the mono-tone sine wave, the output waveform includes the mono-tone sine wave generated by the waveform generation unit 13, the harmonics of the mono-tone sine wave generated by the output amplification circuit 142, and the harmonic compensation data acquired by the control processing unit 11 from the harmonic compensation unit 12, and the harmonics generated by the waveform generation unit 13. When the amplitude of each harmonic generated by the waveform generating unit 13 is the same as the amplitude of each harmonic generated by the single-tone sine wave through the output amplifying circuit 142 and the phase is deviated by 180 °, harmonic cancellation is generated, that is, the vector sum of the harmonic generated by the output amplifying circuit 142 and the harmonic generated by the waveform generating unit 13 at the output terminal is equal to 0, so that the output signal has ultra-low harmonic distortion.
It should be noted that the harmonic generated by the output amplifying circuit 142 when outputting the signal is related to the amplitude and frequency of the output signal, and accordingly, the harmonic compensating unit 12 needs to store data of each harmonic at different amplitudes and frequencies of the output signal. Then, the data stored in the harmonic compensation unit 12 needs to be obtained by the calibration method in the second embodiment, the amplitude and the phase of each subharmonic of the output signal at each amplitude and each frequency are obtained by the calibration method, and then the corresponding compensation value is calculated and stored in the harmonic compensation unit.
It can be understood by those skilled in the art that in the present embodiment, a harmonic compensation unit is added in the signal generator, so that the control processing unit can generate harmonic compensation data of the single-tone signal by using the harmonic calibration data, and implementation possibility is provided for harmonic compensation of the single-tone signal. In addition, because the waveform generating unit superposes each harmonic signal on the single-tone signal to obtain the compensation signal, each harmonic signal in the compensation signal can be used for offsetting each interference harmonic generated by the output conditioning unit, so that harmonic distortion or ultralow harmonic distortion can be eliminated in the output signal as much as possible. In addition, this application technical scheme provides signal generator's harmonic compensation mechanism, can effectively avoid signal generator serious phenomenon of signal distortion under the big signal of output high frequency, has effectively overcome output signal's harmonic distortion problem for signal generator has higher practical value.
Example II,
Referring to fig. 3, the present embodiment provides a calibration system for a signal generator, and the calibration system 2 includes a signal generator 21, a signal analyzer 22 and a calibration control device 23.
The signal generator 21 is used for outputting output signals of various frequencies and amplitudes, and the structure and specific functions can refer to the signal generator 1 in the first embodiment.
The signal analyzer 22 is in signal connection with the signal generator 21 through a coaxial cable, and is configured to perform signal analysis on the coaxial signal output by the signal generator to obtain the amplitude of the single signal and the amplitude of each subharmonic in the coaxial signal. The signal analyzer 22 may be a spectrum analyzer or the like, and may measure the power (amplitude), frequency, bandwidth, etc. of the signal, or may even perform various modulation/demodulation analyses on the signal.
The calibration control device 23 is in communication connection with the signal generator 21 and the signal analyzer 22, and is configured to control the signal generator 21 to generate an output signal at a preset frequency and a preset amplitude, obtain measured amplitude data from the signal analyzer 22, generate harmonic calibration data according to the amplitude data, and send the harmonic calibration data to the signal generator 21. For example, the calibration control device 23 may be a computer, a workstation, a microcontroller, a mobile electronic terminal, or the like.
It is understood that in the field of test measurements, signal generators (including arbitrary waveform generators, radio frequency signal sources, vector signal generators, etc.) are used to generate signals of various frequencies and various waveform shapes, often including an analog signal channel and a digital signal channel, the analog signal channel is provided with a large number of analog devices, such as amplifiers, filters, mixers, etc., the amplitude-frequency response curve (referred to as amplitude-frequency response) of the analog circuit formed by these analog devices is generally uneven, and may be changed with the change of the environment (temperature, humidity, etc.), it is necessary to acquire harmonic compensation data at each frequency point in advance, therefore, parameters such as amplitude, phase and the like of the input signal or the output signal are compensated correspondingly, so as to achieve the purpose of accurately generating the signal, and the process can be called as a calibration process of the signal generator.
To assist the skilled person in better understanding the working principle of the calibration system 2 in fig. 3, the present embodiment also discloses a calibration method for a signal generator, which is mainly applied to the calibration control device 23 in fig. 3.
Referring to fig. 4, the claimed calibration method includes steps S310-S330, which are described below.
Step S310, obtaining the amplitudes corresponding to the harmonics of the calibration frequency point in the first output signal output by the signal generator 21, and obtaining the amplitudes corresponding to the harmonics of the calibration frequency point in the second output signal output by the signal generator 21.
In this embodiment, the first output signal is a signal generated by waveform-conditioning a single-tone signal with a preset frequency and a preset amplitude; the second output signal is a signal generated by waveform-conditioning a single-tone signal on which a plurality of calibration harmonics are superimposed, where the plurality of calibration harmonics include a plurality of harmonics having different amplitudes and the same phase. In addition, the signal generator 21 can configure a plurality of different calibration frequency points, and each calibration frequency point corresponds to a plurality of harmonics (i.e. each harmonic). It is also noted that the individual harmonics of the calibration frequency points may be used as a plurality of calibration harmonics for superposition on the single-tone signal.
It can be understood that if the preset frequency of the single tone signal is set to befA predetermined amplitude ofaThe first output signal includes the waveform of the tone signal and also includes the waveform of the interference harmonic generated after the tone signal passes through the output conditioning unit 14 in fig. 1; the second output signal includes the waveform of the single-tone signal and also includes the waveform of the interference harmonic generated after the single-tone signal passes through the output conditioning unit 14 in fig. 1 and the waveform of the calibration harmonic vector.
Step S320, calculating a calibration data related to the amplitude according to the amplitude corresponding to each harmonic of the calibration frequency point in the first output signal, calculating a phase corresponding to each harmonic of the calibration frequency point according to the amplitude corresponding to each harmonic of the calibration frequency point in the second output signal, and generating the calibration data related to the phase.
It will be appreciated that, referring to fig. 3, the amplitude of each harmonic of the output signal of the signal generator 21 can be measured directly by the signal analyzer 22 (e.g. a spectrum analyzer), but the phase of each harmonic cannot be measured directly, but needs to be scaled by indirect measurement. At step S330, harmonic calibration data is formed using the calibration data on the amplitude and the calibration data on the phase and configured to the signal generator. Specifically, the calibration control device 23 in fig. 2 issues the formed harmonic calibration data to the signal generator 21, and stores the harmonic calibration data in a harmonic compensation unit (such as the harmonic compensation unit 12 in fig. 1) in the signal generator 21.
In an embodiment, in the step S320, the calculating, according to the amplitudes corresponding to the harmonics of the calibration frequency point in the first output signal, calibration data about the amplitudes is obtained, and the method includes:
and performing curve fitting on the preset amplitude of the single-tone signal and the amplitude corresponding to each subharmonic of the calibration frequency point in the first output signal respectively, and using an amplitude curve fitting function obtained by fitting as calibration data about the amplitude.
It should be noted that the calibration control device 23 in fig. 2 may further select several amplitudes within the output amplitude range to perform calibration of the amplitudes of the subharmonics according to the original amplitudes of the output signal. At a frequency of the output signal off 1In the case of (1), since the amplitude of the output signal and the amplitude data corresponding to each subharmonic are obtained, the amplitude of the output signal is taken as the X axis, the amplitude of each subharmonic is taken as the Y axis, a curve of the amplitude of the output signal and the amplitude of each subharmonic is drawn, a polynomial equation is fitted according to the curve, the polynomial equation of the amplitude of the output signal and the amplitude of each subharmonic is obtained, and thus an amplitude curve fitting function is generated, and the relation between the input quantity and the output quantity in the amplitude curve fitting function is the calibration data about the amplitude. For example, as shown in fig. 3, when the signal generator 21 is used as the signal source to be calibrated, if the output signal of the signal generator 21 is set to be the frequencyf 1Amplitude of the vibrationa 1The single-tone sine wave of (a) is,the output signal is measured by the signal analyzer 22 to obtain the amplitude of each harmonic in the output signal asa 12~a 1nWhere n denotes the number of harmonics, e.g.a 12Representing amplitudea 1The 2 nd harmonic of the time (x),a 1nrepresenting amplitudea 1The nth harmonic of time. The calibration control means 23 then obtain the preset frequency of the output signalf 1Preset amplitudea 1The amplitude of each harmonic in the output signal isa 12~a 1nChanging the predetermined amplitude toa nObtaining the amplitude of each corresponding harmonica n2~a nnTo a predetermined amplitude
Corresponding second harmonic
And performing curve fitting to obtain a polynomial equation serving as a second harmonic amplitude curve fitting function. Similarly, for the preset amplitude
And n harmonics
And performing curve fitting to obtain a polynomial equation serving as an n-th harmonic amplitude curve fitting function.
In an embodiment, in the step S320, calculating phases corresponding to the harmonics of the calibration frequency point according to the amplitudes corresponding to the harmonics of the calibration frequency point in the second output signal, and generating calibration data about the phases includes:
(1) if the amplitudes of the plurality of calibration harmonics are set to bea 12~a 1n，a 12Representing amplitudea 1The 2 nd harmonic of the time (x),a 1nrepresenting amplitudea 1The nth harmonic of time, measured by the signal analyzer 22The amplitudes corresponding to the harmonics of the calibration frequency point in the second output signal area´12~a´1n。
(2) Respectively corresponding amplitudes of each harmonic of the calibration frequency pointa´12~a´1nInput to the phase calculation formula
So as to calculate the phase corresponding to each harmonic of the calibration frequency point, which can be expressed as
. Wherein the subscriptiThe value range of (a) is 2 to n,
the same phase is used for multiple calibration harmonics.
(3) And adding the phases corresponding to the harmonics of the calibration frequency points by 180 degrees to obtain calibration data about the phases.
Note that, in order to obtain the phase of the harmonic wave, the phase of the harmonic wave is calculated
Firstly, the amplitude of the harmonic wave is measured by a spectrum analyzeraThen, the original single-tone signal is superimposed with an amplitude ofaIs shifted in phase by
Harmonics, and then measuring the amplitudes of the harmonics at that timea´. The harmonic at this time is a vector sum of a harmonic generated by the nonlinear operating characteristic of the output amplifier circuit and a harmonic generated by the waveform generating unit, and is expressed by a formula
Thus, the method can obtain the product,
further solving to obtain
It should also be noted that the above solution results in two mirror images
Selecting
As the final harmonic phase.
Of course, it is also possible to generate an amplitude QUOTE by means of a DAC
In phase QUOTE
Repeating the calibration process to obtain
At this time, the unique can be solved
. Then, the phase of the harmonic to be compensated is 180 +
。
For example, as shown in fig. 3, the calibration control means 23 is arranged to superimpose the amplitude of the original mono sine wave on the original mono sine wave by the waveform generating unit in the signal generator 21
In a phase of
Then the amplitude of the harmonic at that time is measured by the signal analyzer 22 as
To calculate the corresponding harmonic phase
. At this time, the calibration control device 23 can be utilized
And
determination of final by comparison
。
Further, referring to fig. 5, the claimed calibration method further includes a step S340 after the step S330, which is explained as follows.
Step S340, differently setting the preset frequency and the preset amplitude of the monophonic signal for a plurality of times, and correspondingly generating calibration data about the amplitude and calibration data about the phase after each setting.
The output frequency is as follows due to the completion of steps S310-S330f 1And (3) calibrating the amplitude and the phase of each subharmonic, if the amplitude and the phase of each subharmonic under other output frequencies need to be calibrated, selecting a plurality of frequencies in the frequency range of the output signals according to the frequency range of the output signals to repeat the calibration steps, thereby obtaining the newly set calibration data of the amplitude and the phase of each subharmonic under each output frequency.
Example III,
On the basis of the calibration method for a signal generator disclosed in the second embodiment, a calibration control device is disclosed in the present embodiment.
Referring to fig. 6, the calibration control device 4 mainly includes a memory 41 and a processor 42. The memory 41 serves as a computer-readable storage medium for storing a program, which is a program code corresponding to the calibration methods S100 to S300 for the signal generator in the second embodiment.
The processor 42 is connected to the memory 41 for executing the program stored in the memory 41 to implement the calibration method for the signal generator. The functions performed by the processor 42 can refer to the calibration control device 23 in the second embodiment, and will not be described in detail here.
Those skilled in the art can understand that the technical solution in this embodiment superimposes the corresponding harmonics on the single-tone sinusoidal signal generated by the signal generator through the calibration of the amplitude and phase of the harmonics of the output signal, so that the output signal has ultra-low harmonic distortion. And the derivation and calculation of the harmonic phase are realized by measuring the harmonic amplitude after the harmonic waves with different phases are superposed. In addition, the amplitude of the output signal and the corresponding curve of each subharmonic are fitted into a polynomial equation, and a equation coefficient is used as calibration data to be stored, so that the data volume of the harmonic calibration data is greatly reduced.
Those skilled in the art will appreciate that all or part of the functions of the various methods in the above embodiments may be implemented by hardware, or may be implemented by computer programs. When all or part of the functions of the above embodiments are implemented by a computer program, the program may be stored in a computer-readable storage medium, and the storage medium may include: a read only memory, a random access memory, a magnetic disk, an optical disk, a hard disk, etc., and the program is executed by a computer to realize the above functions. For example, the program may be stored in a memory of the device, and when the program in the memory is executed by the processor, all or part of the functions described above may be implemented. In addition, when all or part of the functions in the above embodiments are implemented by a computer program, the program may be stored in a storage medium such as a server, another computer, a magnetic disk, an optical disk, a flash disk, or a removable hard disk, and may be downloaded or copied to a memory of a local device, or may be version-updated in a system of the local device, and when the program in the memory is executed by a processor, all or part of the functions in the above embodiments may be implemented.
The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.
Claims (4)
1. A signal generator having ultra-low harmonic distortion, comprising:
a harmonic compensation unit configured with harmonic calibration data;
the control processing unit is used for generating harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters; the preset parameters comprise frequency parameters and amplitude parameters of the single-tone signals, and the harmonic compensation data comprise phase compensation values and amplitude compensation values of each harmonic; the control processing unit generates harmonic compensation data of a single tone signal according to the harmonic calibration data and preset parameters, and the harmonic compensation data comprises: selecting two adjacent calibration frequency points before and after the frequency parameter from the harmonic compensation data according to the frequency parameter of the single-tone signal; performing linear interpolation on the phases of the harmonics respectively corresponding to the two calibration frequency points, and obtaining phase compensation values of the harmonics by using interpolation results; calling amplitude curve fitting functions respectively corresponding to the two calibration frequency points according to the amplitude parameters of the single-tone signal, and performing function solving on the amplitude of each subharmonic to obtain an amplitude compensation value of each subharmonic; obtaining harmonic compensation data of the single-tone signal by using the phase compensation value and the amplitude compensation value of each harmonic;
the waveform generating unit is used for generating a single tone signal corresponding to the preset parameter and each subharmonic signal corresponding to the harmonic compensation data, and superposing each subharmonic signal on the single tone signal to obtain a compensation signal;
the output conditioning unit is used for carrying out waveform conditioning on the compensation signal to generate an output signal; and each subharmonic signal in the compensation signal is used for offsetting each interference harmonic generated by the output conditioning unit.
2. The signal generator of claim 1, wherein the output conditioning unit includes an output attenuation circuit and an output amplification circuit;
the output attenuation circuit is connected with the waveform generation unit and is used for carrying out waveform attenuation on the compensation signal to obtain an attenuation signal;
the output amplifying circuit is connected with the output attenuating circuit and is used for carrying out waveform amplification on the attenuated signal to obtain the output signal.
3. The signal generator of claim 2, further comprising an output control unit;
the output control unit is connected with the output conditioning unit and used for carrying out output control on the output signal so as to transmit the output signal to external equipment of the signal generator in a coaxial mode.
4. The signal generator of any one of claims 1-3, further comprising an input unit and a display unit;
the input unit is connected with the control processing unit and is used for configuring preset parameters for generating the single tone signal;
the display unit is connected with the control processing unit and used for displaying preset parameters, waveforms and/or harmonic compensation data of the single-tone signal.
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| CN112763769A (en) | 2021-05-07 |
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