CN1182402C - Homosequence specific phase frequency measurement method and high accuracy frequency meter - Google Patents

Abstract

The present invention relates to a homo-sequence phase comparison frequency measuring method. The present invention is characterized in that a phase comparison circuit can generate phase accordant pulse detecting signals of f#-[x] and f#-[0] to control a counter gate to be opened or closed by using natural phase change rules after the present invention performs homo-sequence processes on signals to be measured f#-[x] and standard frequency signals f#-[0]; strict multiple periodic values N#-[x] and N#-[0] of f#-[x] and f#-[0] can be recorded within the opening time of the counter gate so as to figure out: f#-[x]=(N#-[x]/N#-[0]) f#-[0]. A frequency meter with high precision, which is designed according to the measuring method, is composed of a homo-sequence circuit, the phase comparison circuit, a signal conditioning circuit, a frequency multiplier circuit, a frequency synthesizing circuit, the counter, a time base forming circuit and a single chip computer. By performing the homo-sequence processes on f#-[x] and f#-[0], the present invention can always keep output f#-[x] and f#-[0] in a determinate time sequence relationship when the counter gate is opened in advance; homo-sequence f#-[x] and f#-[0] can control the gate to be opened or closed by using a next phase accordant detection pulse which is generated by the phase comparison circuit; the defect of imperfect consistency of phase accordant signals as opening and closing the gate can be avoided, and the present invention can be adapted to wide frequency ranges to improve frequency measuring resolution.

Description

With preface than phase frequency measuring method and high precision frequency meter

Technical field:

The present invention relates to electronics and frequency measurement technical field, be specifically related to a kind of measuring method of frequency and utilize the designed frequency meter of this method.

Background technology:

Because universal electronic counter is intrinsic ± and the 1Hz error that counts, make the frequency-measurement accuracy of conventional frequency meter be severely limited, be generally 10 ^-7～10 ^-8Magnitude.Although adopt some technical skill: as the multicycle simultaneous techniques, interpositioning, the time-interval averaging technology, digital vernier technology etc., measuring accuracy also can only reach 10 ^-10Magnitude.Simultaneously, these test philosophies and test circuit are comparatively complicated, and very high to the requirement of components and parts performance index, cost also rises significantly.Adopt the error doubling technology, then not only increase noise, increase equipment, and can only measure some certain criteria Frequency point, very inconvenient, be not " the universal frequency meter " on the ordinary meaning.The disclosed patent of Patent Office of the People's Republic of China " etc. the full-automatic frequency meter of precision " (patent No. 96224444.9) and " a kind of frequency, periodic measurement methods and device " (patent No.: 00133654.1) in two kinds of frequency measurement methods introducing respectively, although can measure many doubling times number N of measured signal _x, but owing to can not accurately measure counter T gate time, according to formula: frequency $f=\frac{N_X}{T}$ These two kinds of methods are difficult to accurately survey frequency precision as can be known.And the disclosed patent of Patent Office of the People's Republic of China " examining broadband frequency measuring method and high precision the frequency meter mutually " (patent No.: 90103664.1) be the multi-period synchronous measurement that adopts based on phase-detection, its measuring accuracy only is relevant to the accuracy of detection of phase-detection circuit, comparable common multi-period synchronous measurement method improves thousands of times of measuring accuracy, has obtained major progress in the high accuracy frequency measurement field.But, in broadband frequency measurement technique relative inspection, owing to 1. there is the randomness of measured signal and standard signal phase-detection sequential, the phase place of 2. opening the door meets consistance that signal and the phase place of closing the door meet signal and reason such as gets well inadequately, cause counter records to the phase-detection error, measuring accuracy is descended.

Summary of the invention:

Technical matters to be solved by this invention is how to overcome in the broadband frequency measurement technique relative inspection because the adverse effect that exists the phase-detection error to bring further improves frequency measurement accuracy.

The present invention adopts following technical scheme to solve the problems of the technologies described above, and it is characterized in that it is with measured signal f _xWith standard-frequency signal f ₀By carry out making the f of its output with the preface circuit with the preface processing _xAnd f ₀When the counter gate is opened in advance, always keep the sequential relationship determined, utilize measured signal f then with preface _xWith standard-frequency signal f ₀The phase change rule of nature is by producing f than circuitry phase _xAnd f ₀Phase place coincidence impulse detection signal, the unlatching of control counter gate or close, record measured signal f in the counter gate opening time _xWith standard-frequency signal f ₀Many doubling times value N _xAnd N ₀, and then calculate: $f_x=\frac{N_x}{N_0}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="C0213978500102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0.$ The present invention also has been equipped with frequency multiplier circuit and frequency comprehensive circuit before with the preface circuit, by frequency multiplication f _xWith adjust standard frequency f by frequency comprehensive circuit ₀, control frequency difference Δ f size and f ₀, then according to expression formula Δ f/f ₀ ²T calculated rate resolution, its middle frequency difference Δ f=f _x-f ₀, T is the gate opening time.The present invention has designed the high precision frequency meter according to the said determination method, it is characterized in that it by with the preface circuit, than circuitry phase, signal conditioning circuit, frequency multiplier circuit, frequency comprehensive circuit, counter, the time base form circuit, single-chip microcomputer is formed, described being interconnected by square wave rising edge spike pulse formation circuit, spike pulse phase place coincidence detection circuitry, delay circuit and counter gate prewired circuit with the preface circuit forms measured signal f _xForming the gate prewired circuit in the pre-unlatching moment of circuit, spike pulse phase place coincidence detection circuitry and may command gate by the spike pulse of square wave rising edge respectively is connected with time base circuit with the main shutter circuit, simultaneously by delay circuit be connected standard-frequency signal f than circuitry phase ₀Respectively by the spike pulse of square wave rising edge form circuit, spike pulse phase place coincidence detection circuitry is connected with time base circuit with the main shutter circuit with the gate prewired circuit, the while be connected than circuitry phase; Interconnect by square wave rising edge spike pulse formation circuit and spike pulse phase place coincidence detection circuitry than circuitry phase and to form.Can carry out the frequency multiplier circuit of process of frequency multiplication and the synthetic circuit of adjusting frequency to the lower frequency measured signal with also establishing before the preface circuit, frequency multiplier circuit with join with the preface circuit input end, frequency comprehensive circuit with join with another input end of preface circuit.Described spike pulse phase place coincidence circuit adopts NAND gate circuit with the preface circuit with than square wave rising edge spike pulse formation circuit employing gate circuit narrow pulse forming circuit in the circuitry phase, and delay circuit adopts two not circuits, gate prewired circuit employing d type flip flop.

The present invention passes through measured signal f _xWith standard-frequency signal f ₀Carry out with the preface processing feasible f with the output of preface circuit _xAnd f ₀When opening in advance, the counter gate always keeps the sequential relationship determined, with the f of preface _xAnd f ₀Producing the pulse of next phase place coincidence detection through phase-comparison circuit goes the unlatching of control gate or closes, so just avoided the phase place of opening the door in the prior art to meet signal and met the imperfect defective of consistance of signal with the phase place of closing the door, can adapt to wide frequency ranges, improve frequency measurement resolution, thereby have higher frequency measurement accuracy.The high resolution frequency meter frequency measurement accuracy of design can reach 10 according to the present invention ^-12Magnitude (one second gate time), its device line is simple, and is cheap, can be applicable to fields such as communication, metering, fundamental research, has excellent popularization and is worth.

Description of drawings:

Fig. 1 is a frequency measurement theory diagram of the present invention;

Fig. 2 is the measured signal f of counter records among the present invention _xWith standard-frequency signal f ₀Oscillogram;

Fig. 3 is that the present invention is with the preface circuit block diagram;

Fig. 4 is that the present invention is with preface circuit embodiments schematic diagram;

Fig. 5 is the oscillogram of the present invention with each point in the preface circuit embodiments;

Fig. 6 is a high precision frequency meter panel synoptic diagram of the present invention.

Embodiment:

The present invention improves broadband frequency measurement technique relative inspection.The applicant finds in using broadband frequency measurement technique relative inspection because its measured signal has randomness with standard signal phase-detection sequential, the phase place that causes opening the door meet signal and the phase place of closing the door to meet signal conformance bad, thereby influence its frequency-measurement accuracy.The present invention is directed to above-mentioned defective and improve, it is characterized in that its frequency measuring method is: f at first to measured signal _xWith standard-frequency signal f ₀By carry out making the f of its output with the preface circuit with the preface processing _xAnd f ₀When opening in advance, the counter gate always keeps the sequential relationship determined.Then, under the cooperation of single-chip microcomputer time base circuit (or hardware time base circuit), utilize measured signal f with preface _xWith standard-frequency signal f ₀The phase change rule of nature produces f by phase comparator _xAnd f ₀The opening and closing of removing the control counter gate of phase place coincidence impulse detection signal.Because the process that control gate is opened and control gate cuts out is identical, while f _xWith f ₀Sequential relationship determine, then gate opening and when closing the phase place coincidence detection error delta of phase comparator offset fully.So just can in the counter gate opening time, write down measured signal f _xWith standard-frequency signal f ₀Many doubling times value N _xAnd N ₀, and then calculate: $f_x=\frac{N_x}{N_0}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="C0213978500102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0.$

Frequency measurement principle of the present invention as shown in Figure 1, it mainly by with the preface circuit, than circuitry phase, signal conditioning circuit, frequency multiplier, counter, the time base form circuit, frequency synthesizer, Single Chip Microcomputer (SCM) system etc. and form.As shown in Figure 3, Figure 4, described being interconnected by square wave rising edge spike pulse formation circuit 1, spike pulse phase place coincidence detection circuitry 2, delay circuit 4 and counter gate prewired circuit 3 with the preface circuit forms measured signal f _xBe connected with time base circuit with the main shutter circuit with gate prewired circuit 3 by square wave rising edge spike pulse formation circuit 1, spike pulse phase place coincidence detection circuitry 2 respectively, pass through delay circuit 4 simultaneously and be connected standard-frequency signal f than circuitry phase ₀Respectively by the spike pulse of square wave rising edge form circuit 1, spike pulse phase place coincidence detection circuitry 2 is connected with time base circuit with the main shutter circuit with gate prewired circuit 3, the while be connected than circuitry phase.It is at first respectively to f _xAnd f ₀Form rising edge spike pulse signal, find out this two moment that rising edge spike pulse signal phase meets with Sheffer stroke gate again, then to f _xDo delay process and the initialize switch that opens the sluices; So just guaranteed f _xWith f ₀When the counter gate is opened in advance, definite sequential relationship is arranged, with the f after the preface _xAnd f ₀Be sent to than circuitry phase, wherein f _xHysteresis f ₀Time be τ, Fig. 5 has showed the oscillogram with each key point in the preface circuit.

The present invention also is made up of square wave rising edge spike pulse formation circuit and spike pulse phase place coincidence detection circuitry than circuitry phase, and its effect is to produce f _xWith f ₀Two rising edge spike pulse signals are also judged this two moment that signal phase meets, so that the unlatching of control counter gate or close.For f with preface _xAnd f ₀, suppose f _x＞f ₀, and f _xHysteresis f ₀Time be that τ (works as f _x＜f ₀Can be illustrated similarly), f then _xRising edge spike pulse signal will pull up to f step by step ₀Rising edge spike pulse signal, through simple analysis as can be known, the phase place of catching up with is 2 π Δ f/f the phase weekly ₀(abbreviate step-length as, frequency difference Δ f=f _x-f ₀), the time that its correspondence is caught up with is T Δ f/f ₀(T ₀Be f ₀Cycle), and produce the unlatching of the phase place coincidence detection signal of these two spike pulse signals and control gate thereupon or close.Exist the phase-detection error delta when as shown in Figure 2, these two spike pulse signals meet comparison; But counter opens the door and f at closing time _xWith respect to f ₀To catch up with direction identical, the step-length of catching up with is identical, the control procedure that produces gate opening and closing gate is identical, phase-detection error when phase-detection error during gate opening and closing gate also is identical, and the identical phase-detection error of this character can be offset in the record of counter fully; So just record measured signal f _xWith standard-frequency signal f ₀Many doubling times value N _xAnd N ₀, promptly overcome the phase-detection error that exists in the broadband frequency measurement technique relative inspection.Signal conditioning circuit is used for signal is carried out as processing such as amplification, shaping, time-delays.Frequency multiplier is used for the signal of lower frequency (as tens K or hundreds of K) is handled, so that improve its measuring accuracy.Dominant frequency mark f ₀After be connected with to form and become certain difference frequency signal f with it ₀₁Frequency synthesizer.Work as f _xWith f ₀Frequency values become strict mark, (such f when multiple concern _xWith f ₀The position do not change mutually or change too greatly, phase comparator can not be worked), automatic transfer switch K then ₂, by the mark frequency signal f of frequency synthesizer generation ₀₁Replace f ₀, working properly to guarantee phase comparator, measurement can be proceeded down.According to frequency resolution expression formula Δ f/f ₀ ²T, the present invention are provided with frequency multiplier circuit and frequency comprehensive circuit, f before with the preface circuit _xBy the frequency multiplier circuit that can handle low frequency signals with join with the preface circuit input end; f ₀By frequency comprehensive circuit with join with another input end of preface circuit.By frequency multiplication f _xWith adjustment standard frequency f ₀, the suitable and enough big f of control frequency difference Δ f size ₀, can obtain high frequency measurement resolution, adapt to the needs of high precision frequency measurement in the wide frequency ranges.The present invention is in the prior art field circuit commonly used than circuitry phase, signal conditioning circuit, frequency multiplier circuit, frequency comprehensive circuit, counter, time base circuit, and Single Chip Microcomputer (SCM) system is used to control demonstration, frequency multiplier, frequency synthesizer, time base circuit, keyboard, interface circuit and according to formula $f_x=\frac{N_x}{N_0}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="C0213978500102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0$ The calculated rate value.

With preface processing f _xWith f ₀Be one of core content of the present invention, further specify it below for improving a series of technical improvement that frequency-measurement accuracy brings:

1.. for f with preface _xAnd f ₀, suppose f _x＞f ₀, and f _xHysteresis f ₀Time be that τ (works as f _x＜f ₀Can be illustrated similarly), f then _xRising edge spike pulse signal will pull up to f step by step ₀Rising edge spike pulse signal, and produce the unlatching of the phase place coincidence detection signal of these two spike pulse signals and control gate thereupon or close; Because counter opens the door and f at closing time _xAnd f ₀To catch up with direction identical, the step-length of catching up with is identical, then counter opens the door and phase place coincidence detection error delta is at closing time offset fully, Fig. 2 has showed the f that counter records arrives _xAnd f ₀Oscillogram.So just can guarantee in the counter gate opening time, to record f _xAnd f ₀Many doubling times value N _xAnd N ₀, and then calculate: $f_x=\frac{N_x}{N_0}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="C0213978500102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0.$

2. .f _xWith f ₀The relative variation of phase place in one-period of two signals is 2 π Δ f/f ₀(abbreviation step-length) is as two signal f _xWith f ₀Frequency difference Δ f very little, and tested frequency f _xWhen higher, step-length 2 π Δ f/f ₀It is very little amount.Step-length 2 π Δ f/f ₀Be exactly the minimum phase that phase comparator can be differentiated, that is the present invention's's (with preface than phase measuring method) measuring error.Its corresponding frequency measurement resolution is: Δ f/f ₀ ²T, its middle frequency difference Δ f=f _x-f ₀, T is the gate opening time.Measured signal with common 10MHz is an example, if frequency difference is 5Hz, then the frequency-measurement accuracy of one second gate time is: 5 * 10 ^-14, this is that general frequency measurement technology is not accomplished.For the signal of 100MHz, if frequency difference is 5Hz, then the frequency-measurement accuracy of one second gate time is: 5 * 10 ^-16Consider the influence of the factors such as repeatability of the intrinsic noise of background noise, circuit of phase comparator and device itself, actual frequency-measurement accuracy can decrease, but according to the high precision frequency meter of the inventive method design, even adopt middlebrow TTL device, frequency-measurement accuracy still reaches 10 ^-12Magnitude (one second gate time).

3.. with preface processing f _xWith f ₀, in the time of can avoiding the basic at that time signal of appearance to arrive, phase comparator also just in time produces the rough sledding of phase place coincidence detection pulse signal.Under this disadvantageous situation, because phase comparator can not be differentiated f _xWith f ₀Sequential, might cause counter to open the door and at closing time phase place coincidence detection error delta is not to offset, but bigger counting error appears in the relation of addition.In the broadband frequency measurement technique relative inspection just this rough sledding may appear.

4.. as shown in Figure 5, the f through handling with preface _xApproximately than f ₀Fall behind a delay time τ, subsequently, f _xTo pass through The time interval and f ₀Produce next phase place coincidence detection pulse signal and (suppose f here _x＞f ₀Work as f _x＜f ₀Can be illustrated similarly).Because the process of gate opening and closing gate is an all fours, with the f after the preface _xAnd f ₀Will be with the time interval much at one

Produce next phase place coincidence detection pulse signal and go the unlatching of control counter gate or close, the phase place coincidence detection pulse signal that opens the door that phase comparator will be produced is better with the consistance of the phase place coincidence detection pulse signal of closing the door.Because measuring accuracy is directly relevant with the consistance of the phase place coincidence detection pulse signal of phase comparator generation, so, do like this and help improving frequency-measurement accuracy.

The principle of work and the course of work of the high precision frequency meter of the present invention's design: measured signal f _xWith standard-frequency signal f ₀After modulate circuit is shaped to square-wave signal, deliver to the preface circuit and carry out at first judging f with the preface circuit with the preface processing _xWith f ₀The rising edge spike pulse phase place of two signals meets constantly, then a certain signal is wherein done delay process, opens counter gate initialize switch simultaneously, so just can guarantee f _xWith f ₀Definite sequential relationship when opening in advance, the counter gate is always arranged.Then by than circuitry phase to f _xAnd f ₀Rising edge spike pulse signal compare, produce next phase place coincidence detection signal.The time-base signal that this detection signal produces at time base circuit (10ms, 100ms, 1s, under cooperation 10s), the unlatching of control counter gate or close.Two counters gate opening in the time respectively to f _xWith f ₀Counting.Because the process that control gate is opened and control gate cuts out is identical, f _xWith f ₀Sequential relationship determine that again then the phase place coincidence detection error delta that phase comparator exists when gate opening and closing gate is offset fully in counter.So just can guarantee that meter is recorded measured signal f in the counter gate opening time _xWith standard-frequency signal f ₀Many doubling times value N _xAnd N ₀, and then calculate by single-chip microcomputer: $f_x=\frac{N_x}{N_0}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="C0213978500102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0.$ The measuring accuracy of the multi-period synchronous measurement method that the result is more common improves a lot.The high precision frequency meter frequency measurement accuracy of design reaches 10 according to the present invention ^-12Magnitude (1 second gate time), computing counter (as the HP5360A) precision of external import is high more than 100 times, adopts the high precision frequency meter frequency-measurement accuracy of broadband frequency measurement technique relative inspection to improve about 10 times.In order to obtain higher frequency-measurement accuracy and to adapt to wider frequency measurement scope, from expression formula Δ f/f ₀ ²T is as seen: for low frequency signal, can make process of frequency multiplication with frequency multiplier to measured signal at front end, can produce f with frequency synthesis technique simultaneously ₀₁, make it and f _xFrequency difference suitable.Can also avoid occurring f like this _xWith f ₀Frequency values identical or become strict mark, multiple relation (f like this _xWith f ₀The position do not change mutually or change too greatly, phase comparator can not be worked), working properly to guarantee phase comparator.From expression formula $f_x=\frac{N_x}{N_0}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="C0213978500102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0$ As can be seen, as long as with standard frequency value f ₀By keyboard input single-chip microcomputer, measuring measured signal f _xFrequency values the time, can use the standard frequency source of optional frequency value.This is very useful advantage under many occasions.The frequency meter of the present invention's design can adopt the arbitrary standards frequency source of 1MHz～15MHz.

Claims (6)

1, a kind of with preface than phase frequency measuring method, it is characterized in that it is with measured signal (f _x) and standard-frequency signal (f ₀) by carry out making (the f of its output with the preface circuit with the preface processing _x) and (f ₀) when opening in advance, the counter gate always keeps the sequential relationship determined, utilize measured signal (f then with preface _x) and standard-frequency signal (f ₀) natural phase change rule, by producing (f than circuitry phase _x) and (f ₀) phase place coincidence impulse detection signal, measured signal (f is write down in the unlatching of control counter gate or close in the counter gate opening time _x) and standard-frequency signal (f ₀) many doubling times value (N _x) and (N ₀), and then calculate: $f_x=\frac{N_x}{N_0}{f}_0.$

2, according to claim 1 with preface than phase frequency measuring method, it is characterized in that before with the preface circuit, being equipped with frequency multiplier circuit and frequency comprehensive circuit, by frequency multiplication (f _x) and by frequency comprehensive circuit adjustment standard frequency (f ₀), control frequency difference (Δ f) size and (f ₀), then according to expression formula Δ f/f ₀ ²T calculated rate resolution, its middle frequency difference Δ f=f _x-f ₀, (T) be the gate opening time.

3, according to claim 1 with preface than phase frequency measuring method, it is characterized in that measuring measured signal (f _x) during frequency values, adopt the standard frequency source of optional frequency.

4, a kind of high precision frequency meter that designs according to claim 1, it is characterized in that it by with the preface circuit, than circuitry phase, signal conditioning circuit, frequency multiplier circuit, frequency comprehensive circuit, counter, the time base form circuit, single-chip microcomputer is formed, described being interconnected by square wave rising edge spike pulse formation circuit, spike pulse phase place coincidence detection circuitry, delay circuit and counter gate prewired circuit with the preface circuit forms measured signal (f _x) the pre-gate prewired circuit constantly of opening that forms circuit, spike pulse phase place coincidence detection circuitry and may command gate by the spike pulse of square wave rising edge respectively is connected with time base circuit with the main shutter circuit, simultaneously by delay circuit be connected standard-frequency signal (f than circuitry phase ₀) respectively by the spike pulse of square wave rising edge form circuit, spike pulse phase place coincidence detection circuitry is connected with time base circuit with the main shutter circuit with the gate prewired circuit, the while be connected than circuitry phase; Interconnect by square wave rising edge spike pulse formation circuit and spike pulse phase place coincidence detection circuitry than circuitry phase and to form.

5, high precision frequency meter according to claim 4, it is characterized in that to carry out the frequency multiplier circuit of process of frequency multiplication and the synthetic circuit of adjusting frequency to the lower frequency measured signal with establishing before the preface circuit, frequency multiplier circuit with join with the preface circuit input end, frequency comprehensive circuit with join with another input end of preface circuit.

6, according to claim 4 or 5 described high precision frequency meters, it is characterized in that with the preface circuit and form circuit adopting the gate circuit narrow pulse forming circuit than square wave rising edge spike pulse in the circuitry phase, spike pulse phase place coincidence circuit adopts NAND gate circuit, delay circuit adopts two not circuits, and the gate prewired circuit adopts d type flip flop.

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