CN114878910B - High-precision frequency measurement method, device and system based on beat sampling - Google Patents
High-precision frequency measurement method, device and system based on beat sampling Download PDFInfo
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Abstract
The invention discloses a high-precision frequency measurement method, a device and a system based on beat sampling, wherein the method comprises the following steps: generating a sampling signal by taking a high-precision clock source as a reference clock, wherein the frequency of the sampling signal is equal to the frequency estimated value of the signal to be measured minus the estimated beat frequency; carrying out beat sampling on a signal to be detected by using the generated sampling signal to obtain a beat signal; and calculating pulse counting on the beat signal to obtain the frequency of the beat signal, and summing the frequency of the beat signal and the frequency of the sampling signal to obtain the frequency of the signal to be measured. According to the method, the signal spectrum period at the high frequency is extended to the low frequency, the high frequency measurement is converted into the low frequency measurement, and the measurement precision of the frequency is further improved.
Description
Technical Field
The invention relates to the field of signal processing, in particular to a high-precision frequency measurement method, device and system.
Background
With the progress of time-frequency technology, the precision and stability of the frequency source are higher and higher, and therefore the index requirements on the measurement system are higher and higher. In some applications, the communication system needs to obtain high-precision frequency value feedback in a short time to perform self-calibration.
The beat method frequency measurement is one of the main means of the current precision frequency measurement, the main flow is to mix the frequency of the signal to be measured and the estimated frequency signal, the beat signal is obtained by a low pass filter, the frequency of the beat signal is the difference value of the frequency to be measured and the estimated frequency, the beat frequency signal forms a square wave after filtering, amplifying and shaping, and the frequency of the measured signal is obtained by measuring the frequency of the square wave by a counter. The beat method frequency measurement converts high frequency measurement into low frequency measurement, so that the measurement precision is improved by a beat factor.
However, the existing beat circuit has a complex structure, and is easy to introduce new noise into each stage of circuit, so as to limit the measurement precision of frequency, and cannot be applied to measurement in different frequency ranges through flexible configuration, resulting in higher construction cost of a measurement system, and certain limitations.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a high-precision frequency measurement method, a high-precision frequency measurement device and a high-precision frequency measurement system based on beat sampling, which can improve the measurement precision and further solve the technical problems in the prior art.
The purpose of the invention is realized by the following technical scheme:
the embodiment of the invention provides a high-precision frequency measurement method based on beat sampling, which comprises the following steps:
generating a sampling signal by taking a high-precision clock source as a reference clock, wherein the frequency of the sampling signal is equal to the frequency estimated value of the signal to be measured minus the estimated beat frequency;
carrying out beat sampling on a signal to be detected by using the generated sampling signal to obtain a beat signal;
and calculating the pulse count of the beat signal to obtain the frequency of the beat signal, and summing the frequency of the beat signal and the frequency of the sampling signal to obtain the frequency of the signal to be detected.
The embodiment of the invention also provides a high-precision frequency measuring device based on beat sampling, which comprises:
a clock module, a comparator and a frequency measurement processor; wherein, the first and the second end of the pipe are connected with each other,
the clock module is respectively connected with the high-precision clock source and the frequency measurement processor, can generate a sampling signal as a sampling clock of the frequency measurement processor by taking the high-precision clock source as a reference clock, and the frequency of the sampling signal is equal to the frequency estimated value of a signal to be measured minus the estimated beat frequency;
the comparator is respectively provided with a signal input end and a digital level signal output end, the signal input end is used for being connected with a signal source to be measured, the digital level signal output end is connected with the frequency measurement processor, and the comparator can condition the signal to be measured received by the signal input end into a digital level signal and then send the digital level signal to the frequency measurement processor through the digital level signal output end;
the frequency measurement processor is respectively connected with the clock module and the comparator, and can perform beat sampling on a digital level signal which is output by the comparator and corresponds to a signal to be detected according to a sampling signal provided by the clock module to obtain a beat signal; and carrying out pulse counting on the beat signals obtained by sampling, calculating the beat signal frequency through pulse counting, and adding the beat signal frequency and the sampling signal frequency to obtain the frequency of the signal to be detected.
The embodiment of the invention also provides a high-precision frequency measurement system based on beat sampling, which comprises:
the high-precision clock source and the high-precision frequency measuring device based on beat sampling are provided by the invention; wherein the content of the first and second substances,
the clock module of the high-precision frequency measuring device based on beat sampling is connected with the high-precision clock source and can receive a reference clock signal of the high-precision clock source.
Compared with the prior art, the high-precision frequency measurement method, device and system based on beat sampling provided by the invention have the beneficial effects that:
the high-precision clock source is used as a reference clock, a sampling signal with the frequency close to that of the signal to be measured and smaller than that of the signal to be measured is generated, the sampling signal is used for beat sampling of the signal to be measured to obtain a beat signal, the frequency spectrum of the signal to be measured is extended from a high-frequency position period to a low-frequency position, high-frequency measurement is converted into low-frequency measurement, the counting clock period of the beat signal is far smaller than the low-frequency signal period, relative errors caused by counting are lower, and the measurement precision is improved by a beat factor, namely the ratio of the frequency of the signal to be measured to the frequency of the beat signal, so that the measurement precision of the frequency is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a high-precision frequency measurement method based on beat sampling according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of beat sampling of the high-precision frequency measurement method based on beat sampling according to the embodiment of the present invention.
Fig. 3 is a processing flow chart of a counting module of the high-precision frequency measurement method based on beat sampling according to the embodiment of the present invention.
Fig. 4 is another processing flow chart of the counting module of the high-precision frequency measurement method based on beat sampling according to the embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a high-precision frequency measurement device based on beat sampling according to an embodiment of the present invention.
Detailed Description
The technical scheme in the embodiment of the invention is clearly and completely described below by combining the specific content of the invention; it should be understood that the described embodiments are only some of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The terms that may be used herein are first described as follows:
the term "and/or" means that either or both can be achieved, for example, X and/or Y means that both cases include "X" or "Y" as well as three cases including "X and Y".
The terms "comprising," "including," "containing," "having," or other similar terms in describing these terms are to be construed as non-exclusive inclusions. For example: including a feature (e.g., material, component, ingredient, carrier, formulation, material, dimension, part, component, mechanism, device, step, process, method, reaction condition, processing condition, parameter, algorithm, signal, data, product, or article, etc.) that is not specifically recited, should be interpreted to include not only the specifically recited feature but also other features not specifically recited and known in the art.
The term "consisting of … …" is meant to exclude any technical feature elements not explicitly listed. If used in a claim, the term shall render the claim closed except for the inclusion of the technical features that are expressly listed except for the conventional impurities associated therewith. If the term occurs in only one clause of the claims, it is defined only to the elements explicitly recited in that clause, and elements recited in other clauses are not excluded from the overall claims.
Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "secured," etc., are to be construed broadly, as for example: can be fixedly connected, can also be detachably connected or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms herein can be understood by those of ordinary skill in the art as appropriate.
The terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in an orientation or positional relationship that is indicated based on the orientation or positional relationship shown in the drawings for ease of description and simplicity of description only, and are not intended to imply or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting herein.
The high-precision frequency measurement method and device based on beat sampling provided by the invention are described in detail below. Details which are not described in detail in the embodiments of the invention belong to the prior art which is known to the person skilled in the art. Those not specifically mentioned in the examples of the present invention were carried out according to the conventional conditions in the art or conditions suggested by the manufacturer. The reagents or instruments used in the examples of the present invention are not specified by manufacturers, and are all conventional products available by commercial purchase.
As shown in fig. 1, an embodiment of the present invention provides a high-precision frequency measurement method based on beat sampling, including:
generating a sampling signal by taking a high-precision clock source as a reference clock, wherein the frequency of the sampling signal is equal to the frequency estimated value of the signal to be measured minus the estimated beat frequency;
carrying out beat sampling on a signal to be detected by using the generated sampling signal to obtain a beat signal; the sampling interval of the beat signal is the reciprocal of the frequency of the sampling signal, and the frequency of the beat signal obtained after sampling is equal to the difference between the frequency of the signal to be detected and the frequency of the sampling signal;
and calculating the pulse count of the beat signal to obtain the frequency of the beat signal, and summing the frequency of the beat signal and the frequency of the sampling signal to obtain the frequency of the signal to be detected.
The estimated beat frequency is 0.01% -10% of the estimated value of the frequency of the signal to be measured. The estimated beat frequency can also be set according to actual needs, as long as the sampling signal frequency calculated by the estimated beat frequency is close to the frequency of the signal to be detected and is less than the frequency of the signal to be detected.
In the method, the beat sampling is performed on the signal to be measured by using the sampling signal which has a frequency close to that of the signal to be measured and is smaller than that of the signal to be measured, so that the frequency spectrum of the signal is periodically extended from a high frequency position to a low frequency position (see fig. 2, a horizontal axis f in fig. 2 represents the signal frequency, and a vertical axis s (f) represents the energy of the signal frequency, namely the power spectral density of the signal frequency), and further, the high frequency measurement is converted into the low frequency measurement, and the measurement accuracy of the frequency is improved.
In the measuring method, the reference clock of the high-precision clock source is received by the phase-locked loop frequency synthesizer to generate the sampling signal.
The phase-locked loop frequency synthesizer can generate sampling signals with corresponding frequencies according to measurement requirements, so that the measurement requirements of signals to be measured with different frequencies are met, a new measurement system does not need to be reconstructed, and the cost of the frequency measurement system is reduced.
In the measuring method, after the signal to be measured is conditioned into the digital level signal by the comparator, the signal to be measured is subjected to beat sampling by the generated sampling signal to obtain a beat signal, the beat signal is subjected to pulse counting to obtain a beat signal frequency by the pulse counting, and the beat signal frequency and the sampling signal frequency are summed to obtain the signal frequency to be measured.
In the above measurement method, the frequency measurement processor uses the sampling signal as a sampling clock;
carrying out beat sampling on a signal to be detected by using the sampling signal generated by cascading a plurality of shift registers in the frequency measurement processor to the digital level signal to obtain a beat signal;
the counting module in the frequency measurement processor is used for carrying out pulse counting on the beat signals obtained by sampling so as to obtain the frequency of the beat signals through pulse counting calculation, and the frequency of the beat signals and the frequency of the sampling signals are added to obtain the frequency of the signals to be measured.
The cascaded registers can reduce the probability of appearance of a metastable state to a negligible degree, and the circuit overall structure formed by the quantization of the comparator and the sampling of the registers is simpler than that of a traditional mixing circuit, so that the introduction of noise can be reduced as much as possible, and the precision of a beat signal obtained by sampling is ensured.
In the measuring method, the number of the plurality of cascaded shift registers in the frequency measuring processor is not less than 2;
as shown in fig. 3 and 4, the pulse counting of the sampled beat signals by the counting module inside the frequency measurement processor includes:
pulse counting is carried out on the rising edge of the beat signal obtained by sampling through a pulse counter of a counting module;
when the pulse count value of the pulse counter is 1, starting counting by a clock counter of the counting module, and when the pulse count value of the pulse counter reaches a pulse counting preset end value, ending clock counting of the clock counter and outputting the clock count value at the moment;
the length of the measuring time is controlled by adjusting the size of the pulse counting preset end value. The pulse counting preset end value can be adjusted, so that different measurement requirements can be met conveniently.
In the above measurement method, the frequency of the signal to be measured is obtained by adding the frequency of the beat signal and the frequency of the sampling signal according to the following formula:
wherein the content of the first and second substances,f x is the frequency of the signal to be measured;f s is the sampling signal frequency;f y is the beat signal frequency; Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;Nthe clock count value is output by the counting module;Xpresetting an end value for pulse counting of the counting module;
when the measurement time is 1s, the measurement error is determined by the following formulaf x ：
Wherein, Δf x Measuring error of the frequency of the signal to be measured; Δf y Is the measurement error of the beat signal frequency; Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;f y is the beat signal frequency.
Preferably, the frequency measurement processor in the measurement method is implemented by an FPGA.
As shown in fig. 5, an embodiment of the present invention further provides a high-precision frequency measurement apparatus based on beat sampling, for implementing the measurement method described above, including:
a clock module, a comparator and a frequency measurement processor; wherein the content of the first and second substances,
the clock module is respectively connected with the high-precision clock source and the frequency measurement processor, can use the high-precision clock source as a reference clock to generate a sampling signal as a sampling clock of the frequency measurement processor, and the frequency of the sampling signal is equal to the frequency estimated value of the signal to be measured minus the estimated beat frequency;
the comparator is respectively provided with a signal input end and a digital level signal output end, the signal input end is used for being connected with a signal source to be measured, the digital level signal output end is connected with the frequency measurement processor, and the comparator can condition the signal to be measured received by the signal input end into a digital level signal and then send the digital level signal to the frequency measurement processor through the digital level signal output end;
the frequency measurement processor is respectively connected with the clock module and the comparator, and can perform beat sampling on a digital level signal which is output by the comparator and corresponds to a signal to be detected according to a sampling signal provided by the clock module to obtain a beat signal; and carrying out pulse counting on the beat signals obtained by sampling, calculating the beat signal frequency through pulse counting, and adding the beat signal frequency and the sampling signal frequency to obtain the frequency of the signal to be detected.
In the above-described measuring device, the frequency measurement processor includes: the device comprises a counting module, a calculating module and a plurality of cascaded shift registers; wherein, the first and the second end of the pipe are connected with each other,
the cascaded shift registers are respectively connected with the clock module, the comparator and the counting module, and can perform beat sampling on a digital level signal which is output by the comparator and corresponds to a signal to be detected according to a sampling signal given by the clock module to obtain a beat signal;
the counting module is connected with the calculating module, and is used for carrying out pulse counting on beat signals obtained by sampling of a plurality of cascaded shift registers and calculating the frequency of the beat signals through the pulse counting;
and the computing module is connected with the clock module and is used for adding the beat signal frequency output by the counting module and the sampling signal frequency output by the clock module to obtain the frequency of the signal to be detected.
Preferably, the calculation module is implemented by a floating-point adder.
The counting module comprises:
a pulse counter and a clock counter; wherein, the first and the second end of the pipe are connected with each other,
the pulse counter is connected with the plurality of cascaded shift registers and can count the pulse of the rising edge of the beat signal sampled by the plurality of cascaded shift registers;
the clock counter is connected with the pulse counter and can start counting when the pulse count value of the pulse counter is 1, finish clock counting and output the clock count value at the moment when the pulse count value of the pulse counter reaches a pulse counting preset finish value, and the pulse counting preset finish value is a value capable of adjusting the size; the pulse counting preset ending value X is adjustable in size, so that different measurement requirements can be met conveniently.
In the measuring device, the clock module adopts a phase-locked loop frequency synthesizer;
the comparator adopts a high-speed comparator;
the cascaded shift registers, the counting module and the calculating module are all packaged in an FPGA and are realized through programming of the FPGA.
In the measuring device, the calculation module adds the beat signal frequency and the sampling signal frequency according to the following formula to obtain the frequency of the signal to be measured, and the frequency is as follows:
wherein the content of the first and second substances,f x is the frequency of the signal to be measured;f s is the sampling signal frequency;f y is the beat signal frequency; Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;Nthe clock count value is output by the counting module;Xpresetting an end value for pulse counting of the counting module;
when the measurement time is 1s, the measurement is determined by the following formulaMargin errorf x ：
Wherein, Δf x Measuring error of the frequency of the signal to be measured; Δf y Is the measurement error of the beat signal frequency; Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;f y is the beat signal frequency.
The embodiment of the invention also provides a high-precision frequency measurement system based on beat sampling, which comprises:
a high-precision clock source and the high-precision frequency measuring device based on beat sampling; wherein the content of the first and second substances,
and a clock module of the high-precision frequency measuring device based on beat sampling is connected with the high-precision clock source and can receive a reference clock signal of the high-precision clock source.
Further, the above system further comprises: and a computer, namely a PC in figure 5, which is connected with the high-precision frequency measuring device based on the beat sampling in a communication way and is used for receiving and recording the frequency value measured by the high-precision frequency measuring device based on the beat sampling.
In summary, in the measurement method and the measurement device of the embodiment of the invention, the sampling signal with the frequency similar to that of the signal to be measured and lower than that of the signal to be measured is introduced for beat sampling, so that the frequency spectrum period of the signal to be measured at the high frequency is extended to the low frequency, the high frequency measurement is converted into the low frequency measurement, and the measurement precision of the frequency is improved; because the comparator and the shift register combined measuring circuit are realized by the FPGA, compared with the traditional beat mixing circuit, the device has simpler structure, lower construction cost and fewer approaches for introducing noise, and can meet the measuring requirements of different frequencies through flexible configuration.
In order to more clearly show the technical solutions and the technical effects provided by the present invention, the high-precision frequency measurement method and apparatus based on beat sampling provided by the embodiments of the present invention are described in detail below with specific embodiments.
Example 1
As shown in fig. 5, an embodiment of the present invention provides a high-precision frequency measurement apparatus based on beat sampling, including: a clock module, a comparator and a frequency measurement processor; wherein:
the clock module adopts a phase-locked loop (PLL) frequency synthesizer to receive a reference clock from a high-precision clock source to generate a sampling signal, the frequency of the sampling signal is equal to a predicted value of the frequency of a signal to be measured minus an estimated beat frequency, the estimated beat frequency is 0.01% -10% of the frequency of the signal to be measured, the frequency of the generated sampling signal is close to the frequency of the signal to be measured and is smaller than the frequency of the signal to be measured, and the sampling signal is used as the sampling clock of a frequency measurement processor; the high-precision clock source is an external device and is used for providing a high-precision and high-stability reference clock for the clock module, and the measuring device is combined with the high-precision clock source to form a high-precision frequency measuring system;
the comparator is used for conditioning the signal to be measured into a digital level signal and inputting the digital level signal into the frequency measurement processor;
the frequency measurement processor comprises: the device comprises a counting module, a calculating module and a plurality of cascaded shift registers; the cascade-connected shift registers receive digital level signals corresponding to the signals to be detected and output by the comparator, and perform beat sampling according to sampling signals provided by the clock module and used as sampling clocks, and the metastable state in the sampling process can be eliminated by performing beat sampling through the cascade-connected shift registers;
the counting module performs pulse counting on beat signals obtained by sampling a plurality of cascaded shift registers, and calculates the beat signal frequency according to the pulse counting;
and the calculating module is used for adding the beat signal frequency obtained by the counting module and the sampling signal frequency given by the clock module to obtain the frequency of the signal to be detected.
Example 2
Referring to fig. 1, an embodiment of the present invention further provides a high-precision frequency measurement method based on beat sampling, where the measurement apparatus may be used, and the method includes:
receiving a reference clock from a high-precision clock source by using a phase-locked loop frequency synthesizer, and generating a sampling signal with high precision and high stability as a sampling clock of a frequency measurement processor, wherein the frequency of the sampling signal is similar to that of a signal to be measured and is less than that of the signal to be measured;
conditioning a signal to be measured into a digital level signal by using a comparator and inputting the digital level signal into a frequency measurement processor;
beating and sampling the digital level signal from the comparator through a plurality of cascaded shift registers in the frequency measurement processor, and eliminating a metastable state in the sampling process through cascading;
pulse counting is carried out on the beat signal obtained by sampling the shift register through a counting module in the frequency measurement processor, and the frequency of the beat signal is obtained through calculation;
and adding the beat signal frequency and the sampling signal frequency by a calculation module in the frequency measurement processor to obtain the frequency of the signal to be measured.
Assuming that the frequency of the signal to be measured isf x = f 0 +∆f，f 0 For estimating the frequency of the signal to be measuredf isThe error between the actual frequency of the signal to be measured and the estimated frequency of the signal to be measured, and the measurement error between the frequency of the signal to be measuredf x In the same way, the internal clock module of the frequency measurement processor receives the reference clock and multiplies it tof 0 -f b As a result of the sampling signal, the signal,f b for estimating beat frequency, frequency estimation of signal to be measuredf 0 And the estimated beat frequencyf b The difference is the sampling signal frequency, and finally the beat signal is obtained by beating and sampling the signal to be detected with the sampling signal, namely the frequency isf y =f b +∆fFor counting the beat signal for multiple cycles when the sampling time reachesAnd when the frequency is close to 1s, outputting the counting of the pulse and the counting of the sampling clock, obtaining the frequency of the beat signal through calculation, and adding the frequency of the beat signal and the frequency of the sampling signal to obtain the frequency of the signal to be detected.
Suppose thatf x If it counts directly, the measurement error is Δ if it is 1sf x =1Hz; if the measurement error measured by the method of the invention is as follows:
wherein, Δ τ =10ns is the sampling interval, and the signal frequency is in errorf y When not less than 20kHz, the measurement errorf x =0.2mHz, the accuracy is increased compared to a direct measurementf x /f y Doubling; in the actual measurement process, the measurement error may increase to about 10mHz due to the influence of noise.
The measuring device can realize frequency measurement in the range of 1-500MHz, and can flexibly configure the sampling signal frequency output by the PLL through the FPGA so as to meet the measurement requirements of different frequency sources. The measurement range of the device is mainly limited by the bandwidth of the high-speed comparator and the IO data rate of the FPGA.
Example 3
In this embodiment, the measurement system in embodiment 1 is used to perform measurement, a sinusoidal signal with a frequency of 100.02MHz is input to the high-speed comparator as a signal to be measured, the threshold of the high-speed comparator is the same as the bias voltage of the input signal, and the input analog signal is quantized into a digital level signal by the high-speed comparator.
As shown in fig. 1, the high-precision clock source provides a reference clock to input into the PLL, and generates a sampling signal having a frequency similar to but less than a frequency to be measured as a sampling clock, where the frequency of the sampling signal is set in this embodimentf s The frequency is set to be 100MHz, an upper computer can be used for issuing an instruction in the practical application process, and the sampling signal frequency output by the PLL can be modified in real time so as to meet different measurement requirements.
The frequency measurement processor receives a clock from the PLL as a sampling clock, inputs a digital level signal from the high-speed comparator into the shift register to realize single-bit sampling, and can eliminate a metastable state in the sampling process through the cascade connection of the shift register.
Inputting beat signals sampled by single bits into a counting module, wherein the counting module mainly comprises a pulse counter and a clock counter; as shown in fig. 3, every time a signal rising edge is detected, the pulse counter is incremented by 1, and is cleared until the value of the pulse counter is equal to X, where X =20000 in this embodiment; as shown in fig. 4, when the value of the pulse counter is equal to 1, the clock counter starts counting until the value of the pulse counter is equal to X, and the value N of the clock counter at that time is output.
The frequency of the signal to be measured can be calculated according to the output of the counting module by the following formulaf x Comprises the following steps:
wherein the content of the first and second substances,f s is the sampling signal frequency;f y is the beat signal frequency; Δ τ is the sampling interval.
The measurement is carried out for a plurality of times according to the steps, the variance of the measurement result is about 10mHz, and the whole measurement system has higher precision and stability.
Those of ordinary skill in the art will understand that: all or part of the processes of the methods for implementing the embodiments may be implemented by a program, which may be stored in a computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods as described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.
Claims (7)
1. A high-precision frequency measurement method based on beat sampling is characterized by comprising the following steps:
generating a sampling signal by taking a high-precision clock source as a reference clock, wherein the frequency of the sampling signal is equal to the frequency estimated value of the signal to be measured minus the estimated beat frequency;
carrying out beat sampling on a signal to be detected by using the generated sampling signal to obtain a beat signal;
calculating the pulse count of the beat signal to obtain the frequency of the beat signal, and summing the frequency of the beat signal and the frequency of the sampling signal to obtain the frequency of the signal to be detected;
after a signal to be detected is conditioned into a digital level signal through a high-speed comparator, the digital level signal is subjected to beat sampling through the generated sampling signal through a frequency measurement processor to obtain a beat signal, the beat signal is subjected to pulse counting to obtain a beat signal frequency through pulse counting calculation, and the beat signal frequency and the sampling signal frequency are summed to obtain the frequency of the signal to be detected; the frequency measurement processor takes the sampling signal as a sampling clock; carrying out beat sampling on the digital level signal by a sampling clock through a plurality of cascaded shift registers in the frequency measurement processor to obtain a beat signal; pulse counting is carried out on the beat signals obtained by sampling through a counting module in the frequency measurement processor, so that the frequency of the beat signals is obtained through pulse counting calculation; and adding the beat signal frequency and the sampling signal frequency by a computing module in the frequency measurement processor to obtain the frequency of the signal to be measured.
2. The beat sampling-based high-precision frequency measurement method according to claim 1, wherein a high-precision clock source is received by a phase-locked loop frequency synthesizer as a reference clock to generate a sampling signal;
the estimated beat frequency is 0.01% -10% of the estimated value of the frequency of the signal to be measured.
3. The beat sampling-based high-precision frequency measurement method according to claim 1, wherein the number of the plurality of shift registers cascaded inside the frequency measurement processor is not less than 2;
the pulse counting of the sampled beat signals is carried out by a counting module in the frequency measurement processor according to the following modes:
pulse counting is carried out on the rising edge of the beat signal obtained by sampling through a pulse counter of a counting module;
when the pulse count value of the pulse counter is 1, starting counting by a clock counter of the counting module, and when the pulse count value of the pulse counter reaches a preset pulse count finishing value, finishing clock counting of the clock counter and outputting a clock count value N at the moment;
the length of the measuring time is controlled by adjusting the size of the pulse counting preset end value.
4. A method for measuring a frequency with high precision based on beat sampling according to any one of claims 1 to 3, wherein the frequency of the signal to be measured is calculated by adding the frequency of the beat signal and the frequency of the sampling signal according to the following formula:
wherein the content of the first and second substances,f x is the frequency of the signal to be measured;f s is the sampling signal frequency;f y is the beat signal frequency; Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;Nthe clock count value is output by the counting module;Xis a counting moduleThe pulse count of (1) is preset to an end value;
when the measurement time is 1s, the measurement error is determined by the following formulaf x ：
Wherein, the winef x Measuring error of the frequency of the signal to be measured; Δf y Is the measurement error of the beat signal frequency; the Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;f y is the beat signal frequency.
5. A high-precision frequency measuring device based on beat sampling, which is used for realizing the measuring method of any one of claims 1 to 4, and comprises the following steps:
a clock module, a comparator and a frequency measurement processor; wherein the content of the first and second substances,
the clock module is respectively connected with the high-precision clock source and the frequency measurement processor, can use the high-precision clock source as a reference clock to generate a sampling signal as a sampling clock of the frequency measurement processor, and the frequency of the sampling signal is equal to the frequency estimated value of the signal to be measured minus the estimated beat frequency;
the comparator is respectively provided with a signal input end and a digital level signal output end, the signal input end is used for connecting a signal source to be measured, the digital level signal output end is connected with the frequency measurement processor, and the comparator can condition the signal to be measured received by the signal input end into a digital level signal and then send the digital level signal to the frequency measurement processor through the digital level signal output end;
the frequency measurement processor is respectively connected with the clock module and the comparator, and can perform beat sampling on a digital level signal which is output by the comparator and corresponds to a signal to be measured according to a sampling signal provided by the clock module to obtain a beat signal; carrying out pulse counting on the beat signals obtained by sampling, calculating the beat signal frequency through pulse counting, and adding the beat signal frequency and the sampling signal frequency to obtain the frequency of the signal to be detected;
the frequency measurement processor includes: the device comprises a counting module, a calculating module and a plurality of cascaded shift registers; wherein the content of the first and second substances,
the cascaded shift registers are respectively connected with the clock module, the comparator and the counting module, and can perform beat sampling on a digital level signal which is output by the comparator and corresponds to a signal to be detected according to a sampling signal given by the clock module to obtain a beat signal;
the counting module is connected with the calculating module, performs pulse counting on the beat signals sampled by the plurality of cascaded shift registers, and calculates the beat signal frequency through pulse counting;
and the computing module is connected with the clock module and is used for adding the beat signal frequency output by the counting module and the sampling signal frequency output by the clock module to obtain the frequency of the signal to be detected.
6. The beat sampling based high precision frequency measurement device according to claim 5, wherein the counting module comprises:
a pulse counter and a clock counter; wherein the content of the first and second substances,
the pulse counter is connected with the plurality of cascaded shift registers and can count the pulse of the rising edge of the beat signal sampled by the plurality of cascaded shift registers;
the clock counter is connected with the pulse counter and can start counting when the pulse count value of the pulse counter is 1, finish clock counting and output the clock count value at the moment when the pulse count value of the pulse counter reaches a pulse counting preset finish value, and the pulse counting preset finish value is a value capable of adjusting the size;
the clock module adopts a phase-locked loop frequency synthesizer;
the comparator adopts a high-speed comparator;
the calculation module adds the beat signal frequency and the sampling signal frequency to calculate the frequency of the signal to be measured by the following formula:
wherein the content of the first and second substances,f x is the frequency of the signal to be measured;f s is the sampling signal frequency;f y is the beat signal frequency; the Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;Nthe clock count value is output by the counting module;Xpresetting an end value for pulse counting of a counting module;
when the measurement time is 1s, the measurement error is determined by the following formulaf x ：
Wherein, Δf x Measuring error of the frequency of the signal to be measured; Δf y Is the measurement error of the beat signal frequency; Δ τ is the sampling interval, which is the reciprocal of the sampling signal frequency;f y is the beat signal frequency.
7. A high accuracy frequency measurement system based on beat sampling, comprising:
a high-precision clock source and a high-precision frequency measurement device based on beat sampling according to any one of claims 5 to 6; wherein, the first and the second end of the pipe are connected with each other,
the clock module of the high-precision frequency measuring device based on beat sampling is connected with the high-precision clock source and can receive a reference clock signal of the high-precision clock source.
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| GB1089372A (en) * | 1964-04-17 | 1967-11-01 | Gen Electric Co Ltd | Improvements in or relating to frequency measuring apparatus |
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| CN101706516B (en) * | 2009-10-30 | 2011-07-20 | 中国科学院武汉物理与数学研究所 | Frequency offset method based on beat method |
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