Background technology
Along with science and technology development, systems such as communication, radar and high speed data transfer need the signal of high stable as the base-band information carrier wave.The base-band information carrier wave is normally sinusoidal wave, and sinusoidal wave three elements comprise amplitude, frequency and phase place.Generally, the stability indicator of phase place represents that with phase noise phase noise is an important parameter of gauge signal stability.At present, information transmission is modulated on the carrier phase more or follows on the relevant frequency of phase place, and the phase noise index of baseband signal is the bottom line of total system.Raising along with electronic product performance requires also improves signal source and frequency source performance demands thereupon, and phase noise is drawn attention more widely.The application scenario of phase noise mainly contains: the reference signal in electronic device, the instrument, the carrier signal in the microwave communication, electromagnetic wave positioning distance measuring, temporal frequency counting and data transmission baseband signal or the like.
Contemporary electronic systems and equipment all be unable to do without the requirement of phase noise test, because the local oscillator phase noise affects the final signal to noise ratio (S/N ratio) of frequency modulation, phase modulating system, worsen the performance of some amplitude-modulation detector; The minimum bit-error rate of restriction frequency shift keying (FSK) and phase-shift keying (PSK) (PSK); Influence maximum noise power of frequency division multiple access receiving system or the like.In a lot of advanced electronic system and equipment, a low phase noise frequency source is often arranged in the core technology.As seen phase noise is characterized, tests and how to reduce phase noise be in the contemporary electronic systems avoidance not problem.Traditional phase noise detection method mainly contains following several:
1, direct frequency spectrograph method
Unmodulated high frequency or microwave CF signal directly are added on the high frequency or microwave spectrometer that frequency range and performance be fit to, demonstrate the frequency spectrum of this signal, thereby detect the phase noise of this measured signal.Analyser commonly used at present mainly is divided into spectrum analyzer and waveform analyzer.Spectrum analyzer allows input signal to have very wide frequency range, and possesses moderate analysis bandwidth, for example the operating frequency range of HP8568A is 100Hz~1.5GHz, the minimum bandwidth of analyzing is generally operational in lower frequency range for the 10Hz waveform analyzer, and has very high frequency resolution, for example the operating frequency range of HP 3582A is 0.02Hz~25.599Hz, and frequency resolution is 0.02Hz.The relatively more suitable less and relative higher signal of the phase noise source of drift of measuring of this method.
2, frequency-discrimination method
Frequency-discrimination method also claims single source method, is that the frequency fluctuation Δ f with the measured signal source becomes voltage fluctuation Δ V by certain microwave discriminator, detects with the baseband frequency spectrum instrument, directly draws S Δ f (f), and then obtains phase noise.A kind of frequency-discrimination method principle of work commonly used is: divide two-way with the measured source signal through power splitter, the one tunnel through broadband lag line time delay τ
d, so that enter phase detector after frequency fluctuation become phase fluctuation Δ j; Another road signal enters phase detector and carries out the quadrature phase demodulation after the phase shift of variable bandwidth phase shifter, by phase detector phase noise is converted to voltage noise, after signal Processing such as A/D conversion, Fast Fourier Transform (FFT) and power Spectral Estimation, detect the phase noise power spectrum Sj (f) and relative one-sided power spectrum Lp (f) that obtain measured signal.
3, phase demodulation method
The phase demodulation method also claims the phase detector method, be with measured signal with together frequently the reference source of high stable carry out the quadrature phase demodulation, adopt the heterodyne mode that the measured source signal is reduced to intermediate frequency, purify with crystal filter and phase-locked loop that contains VCXO or phaselocked loop at intermediate frequency, to obtain the continuous carrier signal of measured signal, this signal after phase shift with the measured signal phase detector in the quadrature phase demodulation, extract the phase noise of measured signal.
But all there is defective in above-mentioned three kinds of phase noise detection methods: directly the frequency spectrograph method can not be differentiated AM noise and phase noise, and the signal source serious to AM noise can not directly record phase noise; Frequency-discrimination method is low in nearly carrier frequency place system sensitivity, and broadband lag line, broad-band phase shifter are made difficulty; The phase demodulation method is purified at carrier wave, and the development of phase shifter is difficulty, and phase-shifter, crystal filter characteristic, phase demodulation gain etc. are subjected to all multifactor influences such as temperature and noise size and change, and is difficult for realizing automatic measurement.In addition, above-mentioned phase noise detection method need rely on the hardware system support of complicated costliness, and detection speed is slow, and popularization and application is restricted.
Summary of the invention
Be difficult to detect in order to solve phase noise, and accuracy of detection is not high and problem such as difficult realization robotization, the invention provides a kind of phase noise detection method, described method comprises:
According to the frequency and the measurement frequency band range in measured signal source, select corresponding phase-locked loop circuit;
Described phase-locked loop circuit carries out phase locked track to described measured signal source;
Check whether described phase locked track is finished, if do not have the losing lock signal in the phase noise signal of described phase-locked loop circuit output, then described phase locked track is finished, and gathers the phase noise signal of described phase-locked loop circuit output; Otherwise, whether the spectrum component of checking the phase noise signal of described phase-locked loop circuit output is in phase-locked stabilized zone, if not, then described phase-locked loop circuit increases the band bandwidth to described measured signal source, and whether the spectrum component that reexamines described phase noise signal is in phase-locked stabilized zone; If described phase-locked loop circuit as narrow-band bandwidth, carries out described phase locked track with the band bandwidth in described measured signal source again;
With described phase noise conversion of signals is frequency-region signal, described frequency-region signal is carried out logarithm handle and calibrate and handle, and according to described logarithm result and calibration result, draw out the phase noise curve map.
The step that described phase-locked loop circuit carries out phase locked track to described measured signal source is specially: it is phase-locked that described phase-locked loop circuit carries out band bandwidth to described measured signal source, and reducing the band bandwidth in the measured signal source after phase-locked gradually, the band bandwidth up to the measured signal source reaches the minimum value of the measurement frequency band range that sets in advance.
The step of the phase noise signal of the described phase-locked loop circuit output of described collection specifically comprises:
High frequency phase noise signal to phase-locked loop circuit output carries out preposition amplification;
High frequency phase noise signal after the preposition amplification is carried out high-pass filtering;
High frequency phase noise signal after the high-pass filtering is carried out high frequency single-ended transfer difference and the program control amplification of high frequency;
High frequency phase noise signal after high frequency single-ended transfer difference and the program control amplification of high frequency is carried out the high frequency low-pass filtering, the high frequency phase noise signal after the output high frequency low-pass filtering;
High frequency phase noise signal after the high frequency low-pass filtering is carried out the A/D analog-to-digital conversion process.
The step of the phase noise signal of the described phase-locked loop circuit output of described collection specifically comprises:
Low frequency phase noise signal to phase-locked loop circuit output is carried out preposition amplification;
Low frequency phase noise signal after the preposition amplification is carried out high-pass filtering;
Low frequency phase noise signal after the high-pass filtering is carried out low frequency single-ended transfer difference and the program control amplification of low frequency;
Low frequency phase noise signal after low frequency single-ended transfer difference and the program control amplification of low frequency is carried out the low frequency low-pass filtering, the phase noise signal after the output low frequency low-pass filtering;
Low frequency phase noise signal after the low frequency low-pass filtering is carried out the A/D analog-to-digital conversion process.
The described step that is frequency-region signal with described phase noise conversion of signals specifically comprises:
Described phase noise signal is carried out digital filtering and adds the time domain window function;
To carry out Fast Fourier Transform (FFT) through digital filtering and the phase noise signal that adds behind the time domain window function.
The present invention also provides a kind of phase noise detection system, and described system comprises:
Select module, be used for frequency and measurement frequency band range, select corresponding phase-locked loop circuit according to the measured signal source;
Phase-locked module is used for phase locked track is carried out in described measured signal source, and the output phase noise signal;
Check acquisition module, be used for whether finishing, if then gather and send the phase noise signal that described phase-locked module is exported according to the phase locked track of the described phase-locked module of described phase noise signal check;
Processing module, be used to receive the phase noise signal of described inspection acquisition module output, and be frequency-region signal with described phase noise conversion of signals, described frequency-region signal is carried out logarithm to be handled and calibrates and handle, according to described logarithm result and calibration result, draw out the phase noise curve map.
Described inspection acquisition module comprises:
Inspection unit is used to receive the phase noise signal of described phase-locked module output, and checks in the described phase noise signal whether lose lock signal, sends check result;
First collecting unit, be used to receive the check result that does not have the losing lock signal that described inspection unit sends, and the high frequency phase noise signal that described phase-locked module is exported carries out preposition amplification, high frequency phase noise signal after the preposition amplification is carried out high-pass filtering, high frequency phase noise signal after the high-pass filtering is carried out high frequency single-ended transfer difference and the program control amplification of high frequency, high frequency phase noise signal after high frequency single-ended transfer difference and the program control amplification of high frequency is carried out the high frequency low-pass filtering, high frequency phase noise signal after the output high frequency low-pass filtering carries out the A/D analog-to-digital conversion process with the high frequency phase noise signal after the high frequency low-pass filtering.
Described inspection acquisition module also comprises:
Second collecting unit, be used to receive the check result that does not have the losing lock signal that described inspection unit sends, and the low frequency phase noise signal of described phase-locked module output carried out preposition amplification, low frequency phase noise signal after the preposition amplification is carried out high-pass filtering, low frequency phase noise signal after the high-pass filtering is carried out low frequency single-ended transfer difference and the program control amplification of low frequency, low frequency phase noise signal after low frequency single-ended transfer difference and the program control amplification of low frequency is carried out the low frequency low-pass filtering, phase noise signal after the output low frequency low-pass filtering carries out the A/D analog-to-digital conversion process with the low frequency phase noise signal after the low frequency low-pass filtering.
Described processing module comprises:
Receive converting unit, be used to receive the phase noise signal of described inspection acquisition module output, and be frequency-region signal, send described frequency-region signal described phase noise conversion of signals;
Logarithm calibration unit is used to receive described frequency-region signal, and described frequency-region signal is carried out logarithm handle and calibrate and handle, and sends logarithm and calibration result;
Drawing unit is used to receive described logarithm and calibration result, and according to described logarithm and calibration result, draws out the phase noise curve map.
Beneficial effect: the present invention amplifies by phase locked track, high frequency low noise broadband and low frequency low noise broadband is amplified, realized the test request of wideband phase noise signal has greatly been satisfied in the detection of frequency from 0.01Hz to 100MHz phase noise signal; In addition, phase noise detection method provided by the invention realizes that the hardware system of support is simple, is convenient to popularization and application easily.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, embodiment of the present invention is described further in detail below in conjunction with accompanying drawing.
Referring to Fig. 1, the embodiment of the invention provides a kind of phase noise detection method, may further comprise the steps:
Step 101: input test information, and the amplification coefficient of detected parameters, filter parameter and operational amplifier is set;
Detecting information comprises the model and the frequency in measured signal source; Detected parameters comprises measures frequency band range and level and smooth selectance; Filter parameter comprises Hi-pass filter parameter and low-pass filter parameter; Operational amplifier comprises high-frequency operational amplifier and low frequency operational amplifier; In actual applications, measure frequency band range and can be set to 0~1MHz, 0~101MHz, 0~501MHz or 0~1001MHz, can also require to be provided with different measurement frequency band ranges according to actual measurement; Level and smooth selectance is divided into height, neutralization is low;
Step 102:, select corresponding phase-locked loop circuit according to the frequency and the measurement frequency band range in measured signal source;
Phase-locked loop circuit comprises a plurality of low-pass filter units, local oscillation signal source, DC voltage regulon, signal amplification unit and bandwidth selection filter unit; In actual applications,, change the output bandwidth of phase-locked loop circuit, can detect the signal source of different frequency and the phase noise signal of different measuring frequency band range like this by changing the bandwidth of low-pass filter unit;
Step 103: phase-locked loop circuit carries out phase locked track to the measured signal source to be handled;
Phase-locked loop circuit carries out phase locked track to the measured signal source to be handled and specifically to comprise: it is phase-locked that phase-locked loop circuit carries out band bandwidth to the measured signal source, and reducing the band bandwidth in the measured signal source after phase-locked gradually, the band bandwidth up to the measured signal source reaches the minimum value of the measurement frequency band range that sets in advance;
In actual applications, can accelerate phase-locked process by adjusting the parameter of the low-pass filter unit in the phase-locked loop circuit to the measured signal source; On the basis that ensures the phase locked track process stabilization, reduce the band bandwidth of phase-locked loop circuit gradually, can detect the phase noise signal of low-frequency range like this;
Step 104: whether the phase noise signal of checking phase-locked loop circuit output loses lock signal, if then execution in step 105, otherwise execution in step 108;
Whether the losing lock signal is used to detect phase-locked loop circuit finishes the phase-locked process of phase noise signal; When phase-locked loop circuit was not finished phase-locked process to the phase noise signal, the losing lock signal can be detected, and has this moment low frequency signal to occur in the phase noise signal; The losing lock signal difference frequency signal that is otherwise known as usually, the power of difference frequency signal represents that with the difference frequency amplitude difference frequency amplitude can be used as judges the foundation that whether contains the losing lock signal in the phase noise signal, can also be as the discriminator sensitivity parameter of phase noise signal;
Step 105: whether the spectrum component that detects the phase noise signal of phase-locked loop circuit output is in phase-locked stabilized zone, if then execution in step 107, otherwise execution in step 106;
Step 106: phase-locked loop circuit increases the band bandwidth to the measured signal source, execution in step 105;
Step 107: phase-locked loop circuit with the band bandwidth in measured signal source as narrow-band bandwidth, execution in step 103;
Step 108: data acquisition circuit carries out high-speed data acquisition and low speed data collection to the phase noise signal;
1) high-speed data acquisition
Data acquisition circuit carries out preposition amplification to the high frequency phase noise signal of phase-locked loop circuit output, high frequency phase noise signal after the preposition amplification is carried out high-pass filtering, high frequency phase noise signal after the high-pass filtering is carried out high frequency single-ended transfer difference and the program control amplification of high frequency, high frequency phase noise signal after high frequency single-ended transfer difference and the program control amplification of high frequency is carried out the high frequency low-pass filtering, high frequency phase noise signal after the output high frequency low-pass filtering carries out the A/D analog-to-digital conversion process with the high frequency phase noise signal after the high frequency low-pass filtering;
2) low speed data collection
Data acquisition circuit carries out preposition amplification to the low frequency phase noise signal of phase-locked loop circuit output, low frequency phase noise signal after the preposition amplification is carried out high-pass filtering, low frequency phase noise signal after the high-pass filtering is carried out low frequency single-ended transfer difference and the program control amplification of low frequency, low frequency phase noise signal after low frequency single-ended transfer difference and the program control amplification of low frequency is carried out the low frequency low-pass filtering, phase noise signal after the output low frequency low-pass filtering carries out the A/D analog-to-digital conversion process with the low frequency phase noise signal after the low frequency low-pass filtering;
Generate in the practice concrete, data acquisition circuit carries out high-speed data acquisition earlier, carries out the low speed data collection again; High-speed data acquisition and low speed data collection are all carried out respectively at twice, promptly gather two segment datas, and each image data realizes by changing the collection clock frequency; In actual applications, the high frequency prime amplifier that can set in advance by adjustment and the amplification coefficient of low-frequency preamplifier, the maximal value that guarantees the phase noise signal that high-speed data acquisition and low speed data are gathered is corresponding with the maximal value of A/D analog to digital converter input, can obtain the ultimate resolution of phase noise signal like this; Generally, the phase noise signal is non-stabilization signal, in order to make the high frequency prime amplifier that sets in advance and the amplification coefficient of low-frequency preamplifier, the maximal value of maximal value and A/D analog to digital converter input of phase noise signal that can satisfy collection is corresponding, can sample to one section phase noise signal of phase-locked loop circuit output, and the maximal value MS of definite this section phase noise signal, the maximal value MS of this section phase noise signal and the maximal value MAD of A/D analog to digital converter input are compared, if satisfy following formula
Then can determine the input value coupling of phase noise signal and A/D analog to digital converter, be that the phase noise signal meets the requirement of A/D analog to digital converter to the input value scope, and then the amplification coefficient of high frequency prime amplifier that sets in advance and low-frequency preamplifier meet the requirement of analog to digital converter to the input value scope; If the maximal value MS of phase noise signal does not satisfy above-mentioned formula, then need to reset the amplification coefficient of high frequency prime amplifier and low-frequency preamplifier, till the maximal value MS of phase noise signal satisfies above-mentioned formula; In actual applications, the span of phase noise signal maximum can be determined according to the input value of A/D digital to analog converter, except the span that can be arranged to above-mentioned expression formula, can also be arranged to (MAD/101, MAD/9) span, the embodiment of the invention does not limit the choosing method of the input value scope of A/D digital to analog converter, and the amplification coefficient of high frequency prime amplifier and low-frequency preamplifier can be provided with according to the input value scope of A/D digital to analog converter;
Step 109: data processing circuit carries out pre-service with the phase noise signal of gathering;
Data processing circuit carries out pre-service with the phase noise signal and is specially: the phase noise signal of gathering is carried out digital filtering and adds the time domain window function; In actual applications, the phase noise signal is carried out digital filtering handle, the radio-frequency component in can filtering phase noise signal if the phase noise signal is not carried out digital filtering, then can produce phase noise signal aliasing effect; In addition, the phase noise signal is added the time domain window function handle, can analyze the concentration of energy distribution situation of the phase noise signal in the different frequency bands bandwidth range;
Step 110: data processing circuit is a frequency-region signal with pretreated phase noise conversion of signals;
Data processing circuit is a frequency-region signal with pretreated phase noise conversion of signals, can realize by the phase noise signal is carried out Fast Fourier Transform (FFT);
Step 111: data processing circuit carries out logarithm with frequency-region signal to be handled and calibrates and handle, and according to logarithm result and calibration result, draws out the phase noise curve map;
In actual applications, the phase noise signal is linear through the frequency-region signal that obtains after the Fourier transform; In order to draw out the phase noise curve map more exactly, usually to carry out logarithm operation to frequency-region signal, for example can carry out with e frequency-region signal is the logarithm operation at the end, is the common logarithm computing at the end with 10 perhaps, and present embodiment does not limit the truth of a matter of logarithm operation; When frequency-region signal is carried out logarithm operation, on horizontal ordinate direction and ordinate direction, frequency-region signal is carried out logarithm operation respectively, wherein horizontal ordinate is frequency (dividing with logarithm), ordinate is noise voltage density (unit is dB); Frequency-region signal is calibrated processing, is according to the discriminator sensitivity parameter of phase noise and the amplification coefficient of the amplifier that sets in advance, and frequency-region signal is demarcated, and then obtained phase noise curve exactly; In concrete production practices, can use a computer and draw out the phase noise curve.
Referring to Fig. 2, the embodiment of the invention also provides a kind of phase noise detection system, and this system comprises:
Select module, be used for frequency and measurement frequency band range, select corresponding phase-locked loop circuit according to the measured signal source;
Phase-locked module is used for phase locked track is carried out in the measured signal source, and the output phase noise signal;
Check acquisition module, be used for whether finishing, if then gather and send the phase noise signal that phase-locked module is exported according to the phase locked track of the phase-locked module of phase noise signal check;
Processing module, the phase noise signal that is used for receiving check acquisition module output, and be frequency-region signal with the phase noise conversion of signals carries out to frequency-region signal that logarithm is handled and calibration is handled, according to logarithm result and calibration result, draw out the phase noise curve map.
Phase-locked module comprises:
Phase locking unit, it is phase-locked to be used for that band bandwidth is carried out in the measured signal source, and sends phase-locked result;
Reduce the unit, be used to receive phase-locked result, and reduce the band bandwidth in the measured signal source after phase-locked gradually according to phase-locked result, the band bandwidth up to the measured signal source reaches the minimum value of the measurement frequency band range that sets in advance.
The inspection acquisition module comprises:
Inspection unit is used to receive the phase noise signal of phase-locked module output, and checks in the phase noise signal whether lose lock signal, sends check result;
First collecting unit, be used for the check result that does not have the losing lock signal that the receiving check unit sends, and the high frequency phase noise signal that phase-locked module is exported carries out preposition amplification, high frequency phase noise signal after the preposition amplification is carried out high-pass filtering, high frequency phase noise signal after the high-pass filtering is carried out high frequency single-ended transfer difference and the program control amplification of high frequency, high frequency phase noise signal after high frequency single-ended transfer difference and the program control amplification of high frequency is carried out the high frequency low-pass filtering, high frequency phase noise signal after the output high frequency low-pass filtering carries out the A/D analog-to-digital conversion process with the high frequency phase noise signal after the high frequency low-pass filtering.
Check that acquisition module also comprises:
Second collecting unit, be used for the check result that does not have the losing lock signal that the receiving check unit sends, and the low frequency phase noise signal of phase-locked module output carried out preposition amplification, low frequency phase noise signal after the preposition amplification is carried out high-pass filtering, low frequency phase noise signal after the high-pass filtering is carried out low frequency single-ended transfer difference and the program control amplification of low frequency, low frequency phase noise signal after low frequency single-ended transfer difference and the program control amplification of low frequency is carried out the low frequency low-pass filtering, phase noise signal after the output low frequency low-pass filtering carries out the A/D analog-to-digital conversion process with the low frequency phase noise signal after the low frequency low-pass filtering.
Processing module comprises:
Receive converting unit, be used for the phase noise signal of receiving check acquisition module output, and be frequency-region signal, send frequency-region signal the phase noise conversion of signals;
Logarithm calibration unit is used to receive frequency-region signal, and frequency-region signal is carried out logarithm handle and calibrate and handle, and sends logarithm and calibration result;
Drawing unit is used to receive logarithm and calibration result, and according to logarithm and calibration result, draws out the phase noise curve map.
The embodiment of the invention is amplified by phase locked track, high frequency low noise broadband and low frequency low noise broadband is amplified, and has realized the test request of wideband phase noise signal has greatly been satisfied in the detection of frequency from 0.01Hz to 100MHz phase noise signal; In addition, phase noise detection method provided by the invention realizes that the hardware system of support is simple, is convenient to popularization and application easily.
The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.