CN106841776B - A kind of method of frequency measurement machine and measuring signal frequency - Google Patents
A kind of method of frequency measurement machine and measuring signal frequency Download PDFInfo
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Abstract
The invention discloses a kind of frequency measurement machine and the methods of measuring signal frequency, wherein, the frequency measurement machine carries out scaling down processing to the radiofrequency signal of input by the frequency divider of setting, to obtain the lower fractional frequency signal of frequency, so that the modulus acquisition module can be acquired the fractional frequency signal, so that the frequency measurement machine can be applied to the frequency measurement of the radiofrequency signal of upper frequency；In addition, further digital detection has been carried out to the complex signal by the digital detection unit in the frequency computing module and shaping filter is handled, so that the edge of a pulse for obtaining rectified signal is steeper, convenient for the identification and processing for taking dot element for each effective impulse, the frequency-measurement accuracy of the frequency measurement machine is increased.
Description
Technical Field
The invention relates to the technical field of signal frequency measurement, in particular to a frequency measuring machine and a method for measuring signal frequency.
Background
The signal frequency measurement (frequency measurement) is one of the most basic measurements in electronic measurement, and the common frequency measurement technology in the prior art mainly comprises a multichannel frequency measurement technology, a frequency discrimination frequency measurement technology, an interferometer phase comparison frequency measurement technology and a digital calculation method frequency measurement technology, wherein the digital calculation method frequency measurement technology becomes a frequency measurement method which is widely applied in the frequency measurement field due to the problems that the frequency measurement precision of the multichannel frequency measurement technology and the frequency discrimination frequency measurement technology is low, the volume of an instrument used by the interferometer phase comparison method is large, and the like.
The frequency measuring machine based on the digital calculation method frequency measuring technology firstly performs analog-to-digital conversion and acquisition on an input radio frequency signal to obtain a signal to be calculated, and then calculates the signal to be calculated by using a frequency measuring algorithm to obtain the frequency of the input radio frequency signal. But is limited by the limit of the sampling rate of the signal acquisition equipment, so that the frequency measurement machine realized based on the frequency measurement technology of the digital calculation method cannot realize the frequency measurement of the radio frequency signal with higher frequency.
Disclosure of Invention
In order to solve the technical problems, the invention provides a frequency measuring machine and a signal frequency measuring method, so as to achieve the purpose of realizing the frequency measurement of a radio frequency signal with higher frequency based on a digital computing method frequency measuring technology.
In order to achieve the technical purpose, the embodiment of the invention provides the following technical scheme:
a frequency measuring machine comprising: the frequency division module, the analog-digital acquisition module and the frequency calculation module; wherein,
the frequency division coefficient of the frequency division module is a preset value and is used for performing frequency division processing on an input radio frequency signal to obtain a frequency division signal and transmitting the frequency division signal to the analog-digital acquisition module;
the analog-digital acquisition module is used for sampling the frequency division signal at a preset sampling rate to obtain a sampling signal and transmitting the sampling signal to the frequency calculation module;
the frequency calculation module includes: the device comprises a digital down-conversion unit, a digital detection unit, a point taking unit and a calculation unit; wherein,
the digital down-conversion unit is used for performing digital down-conversion on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal;
the digital detection unit is used for carrying out digital detection and shaping filtering processing on the complex signal to obtain a detection signal;
the point taking unit is used for carrying out point taking for at least one time on each pulse of the detection signal, obtaining a group of signals to be processed each time, wherein each group of signals to be processed comprises a preset number of signals to be processed, and carrying out averaging calculation on a normal phase signal and an orthogonal signal of each signal to be processed in each group of signals to be processed to obtain at least one group of signals to be calculated;
the calculating unit is used for calculating and obtaining at least one frequency measuring code of each pulse of the radio frequency signal by using all signals to be calculated of each pulse of the radio frequency signal according to a digital instantaneous frequency measuring method, and multiplying each frequency measuring code by the preset value to obtain at least one measuring frequency of the radio frequency signal.
Optionally, when the radio frequency signal is a point pulse signal, the point taking unit performs at least one point taking on each pulse of the detection signal, specifically, performs one point taking after a preset distance of a rising edge of each pulse of the detection signal.
Optionally, when the radio frequency signal is a broadband pulse signal, the point taking unit performs at least one time of point taking on each pulse of the detection signal, specifically, performs the first time of point taking after a preset distance of a rising edge of each pulse of the detection signal, and performs the second time of point taking before the preset distance of a falling edge of each pulse of the detection signal.
Optionally, the computing unit includes:
the delay conjugation unit is used for calculating the delay conjugation correlation of each signal to be calculated in each group of signals to be calculated of each pulse of the radio frequency signal and expressing the delay conjugation correlation of each signal to be calculated in the form of a first preset formula;
the accumulation unit is used for respectively accumulating and averaging the real parts and the imaginary parts of all the signals to be calculated in each group of signals to be calculated to obtain the average real part and the average imaginary part of each group of signals to be calculated;
the frequency code unit is used for substituting the average real part and the average imaginary part of each group of signals to be calculated into a second preset formula to calculate and obtain at least one frequency measuring code of each pulse of the radio frequency signals;
the frequency unit is used for multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal;
the first preset formula is as follows: m ═ x + jy, where x denotes the real part and y denotes the imaginary part;
the second preset formula is as follows:wherein f is0Representing said frequency measurement code, fsRepresenting the sampling rate of the digital down-conversion unit.
Optionally, the digital down-conversion unit performs digital down-conversion on the sampling signal to obtain a complex signal including an in-phase signal and a quadrature signal, and specifically performs down-mixing and filtering extraction on the sampling signal to obtain a complex signal including an in-phase signal and a quadrature signal.
A method of measuring a signal frequency, comprising:
performing frequency division processing on an input radio frequency signal by taking a preset value as a frequency division coefficient to obtain a frequency division signal;
sampling the frequency division signal at a preset sampling rate to obtain a sampling signal;
carrying out digital down-conversion on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal;
carrying out digital detection and shaping filtering processing on the complex signal to obtain a detection signal;
performing point acquisition on each pulse of the detection signal at least once, wherein each point acquisition obtains a group of signals to be processed, and each group of signals to be processed comprises a preset number of signals to be processed;
averaging the normal phase signal and the orthogonal signal of each signal to be processed in each group of signals to be processed to obtain at least one group of signals to be calculated;
according to a digital instantaneous frequency measurement method, calculating all signals to be calculated of each pulse by using the radio frequency signals to obtain at least one frequency measurement code of each pulse of the radio frequency signals, and multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signals.
Optionally, when the radio frequency signal is a point pulse signal, the performing at least one point extraction on each pulse of the detection signal includes:
and carrying out point acquisition once after the preset distance of the rising edge of each pulse of the detection signal.
Optionally, when the radio frequency signal is a broadband pulse signal, the performing at least one point fetch on each pulse of the detection signal includes:
and performing first point taking after the preset distance of the rising edge of each pulse of the detection signal, and performing second point taking before the preset distance of the falling edge of each pulse of the detection signal.
Optionally, the obtaining, according to a digital instantaneous frequency measurement method, at least one frequency measurement code of each pulse of the radio frequency signal by calculating all signals to be calculated of each pulse using the radio frequency signal, and obtaining at least one measurement frequency of the radio frequency signal by multiplying each frequency measurement code by the preset value includes:
calculating the delay conjugate correlation of each signal to be calculated in each group of signals to be calculated of each pulse of the radio frequency signal, and expressing the delay conjugate correlation of each signal to be calculated in the form of a first preset formula;
respectively accumulating the real parts and the imaginary parts of all the signals to be calculated in each group of signals to be calculated and calculating the average to obtain the average real part and the average imaginary part of each group of signals to be calculated;
substituting the average real part and the average imaginary part of each group of signals to be calculated into a second preset formula to calculate and obtain at least one frequency measurement code of each pulse of the radio frequency signals;
multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal;
the first preset formula is as follows: m ═ x + jy, where x denotes the real part and y denotes the imaginary part;
the second preset formula is as follows:wherein f is0Representing said frequency measurement code, fsRepresenting the sampling rate of the digital down-conversion unit.
Optionally, the performing digital down-conversion on the sampling signal to obtain a complex signal including an in-phase signal and a quadrature signal includes:
and performing down-mixing and filtering extraction on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal.
It can be seen from the foregoing technical solutions that the embodiments of the present invention provide a frequency measuring machine and a signal frequency measuring method, wherein the frequency measuring machine performs frequency division processing on an input radio frequency signal through a set frequency divider to obtain a frequency division signal with a lower frequency, so that the analog-to-digital acquisition module can acquire the frequency division signal, and the frequency measuring machine can be applied to frequency measurement of a radio frequency signal with a higher frequency; in addition, the digital detection unit performs further digital detection and shaping filtering processing on the complex signal in the frequency calculation module, so that the pulse edge of the obtained detection signal is steeper, the point taking unit is convenient to identify and process each effective pulse, and the frequency measurement precision of the frequency measurement machine is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a frequency measuring machine according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a frequency measuring machine according to another embodiment of the present invention;
FIG. 3 is a schematic diagram of digital down conversion;
fig. 4 is a flowchart illustrating a method for measuring a signal frequency according to an embodiment of the present invention;
FIG. 5 is a flowchart illustrating a method for measuring a signal frequency according to another embodiment of the present invention;
FIG. 6 is a flow chart illustrating a method for measuring signal frequency according to another embodiment of the present invention;
fig. 7 is a flowchart illustrating a method for measuring a signal frequency according to a preferred embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
An embodiment of the present invention provides a frequency measuring machine, as shown in fig. 1, including: the frequency division module 100, the analog-digital acquisition module 200 and the frequency calculation module 300; wherein,
the frequency division coefficient of the frequency division module 100 is a preset value, and is configured to perform frequency division processing on an input radio frequency signal to obtain a frequency division signal, and transmit the frequency division signal to the analog-to-digital acquisition module 200;
the analog-to-digital acquisition module 200 is configured to sample the frequency division signal at a preset sampling rate, obtain a sampling signal, and transmit the sampling signal to the frequency calculation module 300;
the frequency calculation module 300 includes: digital down-conversion section 310, digital detection section 320, point-taking section 330, and calculation section 340; wherein,
the digital down-conversion unit 310 is configured to perform digital down-conversion on the sampled signal to obtain a complex signal including an in-phase signal and a quadrature signal;
the digital detection unit 320 is configured to perform digital detection and shaping filtering processing on the complex signal to obtain a detection signal;
the point taking unit 330 is configured to perform point taking for each pulse of the detection signal at least once, obtain a set of signals to be processed each time, where each set of signals to be processed includes a preset number of signals to be processed, and perform averaging calculation on a normal phase signal and a quadrature signal of each signal to be processed in each set of signals to be processed to obtain at least one set of signals to be calculated;
the calculating unit 340 is configured to calculate and obtain at least one frequency measurement code of each pulse of the radio frequency signal according to a digital instantaneous frequency measurement method by using all signals to be calculated of each pulse of the radio frequency signal, and multiply each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal.
It should be noted that, the frequency measurement range that the frequency measurement machine can implement is related to the frequency division coefficient and the preset sampling rate, when the frequency division coefficient is 16 and the preset sampling rate is 2.5GHz, the frequency measurement machine can measure the frequency of the radio frequency signal with the frequency range of 6-18GHz, after the radio frequency signal in the frequency range is subjected to frequency division by 16, the frequency of the radio frequency signal is compressed to 375MHz-1.125GHz, and the radio frequency signal can be collected by the analog-to-digital collection module 200 with the preset sampling rate of 2.5 GHz; when the frequency division coefficient is changed to 8, if the preset sampling rate is kept unchanged, the frequency measuring machine can realize frequency measurement of 10GHz radio frequency signals at most, and if the frequency measurement of 18GHz radio frequency signals is realized on the premise that the frequency division coefficient is 8, the preset sampling rate needs to be changed to 5 GHz. In other embodiments of the present invention, the frequency division coefficient may also be 12 or 10, and the preset sampling rate may also be 10GHz or 7.5GHz, and specific values of the frequency division coefficient and the preset sampling rate are not limited in the present invention, which is determined specifically according to actual situations.
It should be noted that the frequency division factor is not suitably too high, since the frequency measurement accuracy of the frequency measuring machine is related to the frequency division factor. Taking the frequency division coefficient of 16 as an example, the frequency measurement precision of the frequency calculation module 300 is 0.5MHz, and then the frequency measurement precision of the frequency measurement machine is (16 × 0.5 MHz) ═ 8MHz, and this frequency measurement precision can meet the requirement of broadband frequency measurement and the engineering application of various receiver items.
In addition, through the test of the frequency measuring machine, it is found that when the number of the sampling points of the sampling point unit 330 is 8 or more each time, a more reasonable output result can be ensured. The accuracy of the measurement frequency output by the frequency measuring machine is higher as the number of points taken each time is increased, but the increase of the number of points taken increases the time consumption of calculation. For the engineering application with lower requirement on precision, the number of the points taken by the point taking unit 330 may be preferably set to 8, so as to ensure the purpose of improving the efficiency of the frequency measuring machine as much as possible on the premise that the output measuring frequency is available.
In the frequency calculation module 300, the digital detection of the complex signal is specifically to obtain a corresponding relationship of signal amplitude by squaring a modulus value of the complex signal. The shaping and filtering process of the complex signal is specifically to perform amplitude square operation on the current complex signal, wherein the amplitude square operation is the sum of squares of a real part and an imaginary part of the complex signal. And performing amplitude square accumulation, namely averaging to obtain a group of data representing the amplitude of the signal, setting a threshold value, wherein the data exceeding the threshold value is 1, and otherwise, the data is 0, namely a discontinuous pulse capable of basically representing the existence of the signal. Then filtering burrs appearing at the front end of the signal, judging whether the signal is an effective signal or not by counting the number of the filtered burrs in a counting mode, and considering the signal as a burr if the continuous counting number is very small; by judging the pulse width of the signal before and after, the discontinuity in the signal is reasonably compensated by counting.
It should be further noted that the frequency measuring machine performs frequency division processing on the input radio frequency signal through the set frequency divider to obtain a frequency division signal with a lower frequency, so that the analog-to-digital acquisition module 200 can acquire the frequency division signal, and the frequency measuring machine can be applied to frequency measurement of the radio frequency signal with the higher frequency; in addition, in the frequency calculation module 300, the digital detection unit 320 performs further digital detection and shaping filtering processing on the complex signal, so that the pulse edge of the obtained detected signal is steeper, which is convenient for the point taking unit 330 to identify and process each effective pulse, and increases the frequency measurement accuracy of the frequency measurement machine.
Furthermore, because the internal processing process of the frequency measuring machine can be completely completed through digital equipment, the frequency measuring machine can be realized based on a high-performance acquisition and processing platform, so that the functions can be expanded on the basis of realizing the functions, the function of digitally processing the input radio-frequency signal is added, for example, an anti-interference algorithm can be added, and the frequency measuring machine has a certain anti-interference effect and the like.
On the basis of the above embodiment, in an embodiment of the present invention, when the rf signal is a point pulse signal, the point taking unit 330 performs at least one point taking for each pulse of the detection signal, specifically, performs one point taking after a preset distance of a rising edge of each pulse of the detection signal.
It should be noted that, when the radio frequency signal is a point pulse signal, the width of each pulse is small, and only a leading edge frequency measurement mode needs to be adopted, but because the signal quality of a plurality of points after the rising edge and the rising edge of each pulse is poor, in this embodiment, it is preferable to perform a point taking operation after a preset distance after the rising edge of each pulse, so as to ensure that the data quality of the point taking operation is good, and improve the frequency measurement accuracy of the frequency measuring machine. The specific value of the preset distance is different according to the type of the radio frequency signal, and the specific value of the preset distance is not limited by the invention and is determined according to the actual situation.
On the basis of the above embodiment, in another embodiment of the present invention, when the rf signal is a wideband pulse signal, the point-taking unit 330 performs at least one point-taking for each pulse of the detection signal, specifically, performs a first point-taking after a preset distance of a rising edge of each pulse of the detection signal, and performs a second point-taking before the preset distance of a falling edge of each pulse of the detection signal.
It should be noted that, when the radio-frequency signal is a broadband pulse signal, the width of each pulse is large, and the frequencies of the rising edge and the falling edge of the pulse may have a non-negligible difference, so that the leading edge frequency and the trailing edge frequency need to be measured simultaneously. Similarly, because the signal quality of each pulse within the preset distance range from the rising edge to the falling edge is poor, in this embodiment, it is preferable to perform the first time of point acquisition after the preset distance from the rising edge of each pulse, and perform the second time of point acquisition before the preset distance from the falling edge, so as to ensure that the data quality of the point acquisition is good, and improve the frequency measurement accuracy of the frequency measurement machine. The specific value of the preset distance is different according to the type of the radio frequency signal, and the specific value of the preset distance is not limited by the invention and is determined according to the actual situation.
On the basis of the above embodiment, in another embodiment of the present invention, as shown in fig. 2, the calculating unit 340 includes:
a delay conjugation unit 341, configured to calculate a delay conjugation correlation of each to-be-calculated signal in each group of to-be-calculated signals of each pulse of the radio frequency signal, and express the delay conjugation correlation of each to-be-calculated signal in a form of a first preset formula;
the accumulation unit 342 is configured to perform accumulation and averaging calculation on the real parts and the imaginary parts of all the signals to be calculated in each group of signals to be calculated, so as to obtain an average real part and an average imaginary part of each group of signals to be calculated;
a frequency code unit 343, configured to substitute the average real part and the average imaginary part of each group of signals to be calculated into a second preset formula to calculate at least one frequency measurement code of each pulse of the radio frequency signal;
a frequency unit 344, configured to multiply each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal;
the first preset formula is as follows: m ═ x + jy, where x denotes the real part and y denotes the imaginary part;
the second preset formula is as follows:wherein f is0Representing said frequency measurement code, fsRepresenting the sample rate of the digital down-conversion unit 310.
It should be noted that the expression for each signal to be calculated can be written as: s (n) exp (2 pi f)0n+φ0) Wherein phi is0Representing the phase of the signal to be calculated.
Taking the correlation of the signal to be computed and its delayed conjugate, one obtains:
M＝s(n)s*(n-Δn)＝exp(j2πf0n+φ0)exp(j2πf0(n-Δn)+jφ0)＝exp(j2πf0Δn)；
expressing M by a first preset formula, thenTo obtain
GetThen it can be obtained
Where Δ n represents the sampling interval.
On the basis of the foregoing embodiment, in a preferred embodiment of the present invention, the digital down-conversion unit 310 performs digital down-conversion on the sampled signal to obtain a complex signal including an in-phase signal and a quadrature signal, and is specifically configured to perform down-mixing and filtering decimation on the sampled signal to obtain a complex signal including an in-phase signal and a quadrature signal.
Referring to fig. 3, fig. 3 is a schematic diagram of the digital down-conversion;
the digital down-conversion of the sampled signal includes two steps of down-mixing and filtering the sampled signal, which are described below:
a. frequency conversion without multiplication:
in reality, the input rf signal is a real narrow-band signal, which can be expressed as:
after analog-to-digital (AD) sampling, it becomes a digital signal:
the digital signal is divided into two paths which are respectively connected with cos (w) by a frequency mixing technologyon) and-sin (w)on) to obtain the quadrature variation of the signal, and the digital signal quadrature mixing can be expressed as:
the frequency conversion is a common digital signal processing algorithm, and for 1/4 signal sampling rate frequency conversion, a simple implementation method is provided
Here, the sampling rate fs2.5GHz, local oscillator frequency fc625MHz, satisfies fc＝fsThe relationship of/4 can be realized by adopting the following efficient mode;
b. and (3) polyphase filtering:
after quadrature mixing, the signal is passed through a low-pass Filter (FIR) to filter out unwanted frequencies. And performing low-pass filtering and extraction (↓ D). Here, filtering and decimation may be performed simultaneously. For a causal FIR system, its equations can be simplified as:
where M is the filter coefficient length. If multi-path parallel processing is adopted and N is the number of paths of FIR filtering parallel processing, then
In this embodiment, the sampling signal is decimated after low-pass filtering, so as to reduce the sampling rate and reduce the data amount of subsequent processing. In other embodiments of the present invention, the sampled signal is decimated by a multiple ofSelecting 2 times, taking the preset sampling rate as 2.5GHz as an example, and after performing double decimation on the sampling signal, the sampling rate (f) of the digital down-conversion unit 310s) Namely 1.25 GHz.
Correspondingly, an embodiment of the present invention further provides a method for measuring a signal frequency, as shown in fig. 4, including:
s101: performing frequency division processing on an input radio frequency signal by taking a preset value as a frequency division coefficient to obtain a frequency division signal;
s102: sampling the frequency division signal at a preset sampling rate to obtain a sampling signal;
s103: carrying out digital down-conversion on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal;
s104: carrying out digital detection and shaping filtering processing on the complex signal to obtain a detection signal;
s105: performing point acquisition on each pulse of the detection signal at least once, wherein each point acquisition obtains a group of signals to be processed, and each group of signals to be processed comprises a preset number of signals to be processed;
s106: averaging the normal phase signal and the orthogonal signal of each signal to be processed in each group of signals to be processed to obtain at least one group of signals to be calculated;
s107: according to a digital instantaneous frequency measurement method, calculating all signals to be calculated of each pulse by using the radio frequency signals to obtain at least one frequency measurement code of each pulse of the radio frequency signals, and multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signals.
It should be noted that the frequency measurement range which can be realized by the method is related to the frequency division coefficient and the preset sampling rate, when the frequency division coefficient is 16 and the preset sampling rate is 2.5GHz, the method can perform frequency measurement on the radio frequency signal with the frequency range of 6-18GHz, and after the radio frequency signal in the frequency range is subjected to frequency division by 16, the frequency of the radio frequency signal is compressed to 375MHz-1.125GHz and can be acquired by the analog-digital acquisition module with the preset sampling rate of 2.5 GHz; when the frequency division coefficient is changed to 8, if the preset sampling rate is kept unchanged, the method can realize frequency measurement of a radio frequency signal of 10GHz at most, and if the frequency measurement of the radio frequency signal of 18GHz is realized on the premise that the frequency division coefficient is 8, the preset sampling rate needs to be changed to 5 GHz. In other embodiments of the present invention, the frequency division coefficient may also be 12 or 10, and the preset sampling rate may also be 10GHz or 7.5GHz, and specific values of the frequency division coefficient and the preset sampling rate are not limited in the present invention, which is determined specifically according to actual situations.
It should be noted, however, that the frequency division factor is not suitably too high, since the frequency measurement accuracy of this method is related to the frequency division factor. Taking the frequency division coefficient of 16 as an example, the frequency measurement precision of the frequency calculation module is 0.5MHz, and then the frequency measurement precision of the method is (16 × 0.5 MHz) ═ 8MHz, and this frequency measurement precision can meet the requirement of broadband frequency measurement and the engineering application of various receiver items.
In addition, tests of the method find that when the number of the point taking units for taking the points each time is 8 or more, a reasonable output result can be ensured. The accuracy of the measurement frequency output by the method is higher as the number of the points taken each time is increased, but the increase of the number of the points taken increases the time consumption of calculation. In the engineering application with lower precision requirement, the number of the points taken by the point taking unit each time can be preferably set to be 8, so as to ensure the aim of improving the efficiency of the method as much as possible on the premise that the output measurement frequency is available.
In the method, the digital detection of the complex signal is specifically to obtain the corresponding relation of the signal amplitude by squaring the modulus value of the complex signal. Performing shaping filtering processing on the complex signal, specifically performing amplitude square operation on the current complex signal, performing amplitude square accumulation, namely obtaining an averaging effect, filtering out burrs appearing at the front end of the signal, and judging whether the signal is an effective signal or not through counting by the size of a counting value in a counting mode; by judging the pulse width of the front and the rear signals, the interruption in the middle of the signals is reasonably compensated.
It should be further noted that, the method performs frequency division processing on the input radio frequency signal to obtain a frequency-divided signal with a lower frequency, so that the method can be applied to frequency measurement of the radio frequency signal with a higher frequency; in addition, the method further performs digital detection and shaping filtering processing on the complex signal, so that the pulse edge of the obtained detection signal is steeper, the point taking unit is convenient to identify and process each effective pulse, and the frequency measurement precision of the method is improved.
Furthermore, because the processing process of the method can be completely completed by digital equipment, the method can be realized based on a high-performance acquisition and processing platform, so that the functions can be expanded on the basis of realizing the functions, the function of digitally processing the input radio-frequency signal is added, for example, an anti-interference algorithm can be added, and the method has a certain anti-interference effect and the like.
On the basis of the foregoing embodiment, in an embodiment of the present invention, as shown in fig. 5, when the radio frequency signal is a point pulse signal, the performing at least one point extraction on each pulse of the detected signal includes:
s1051: and carrying out point acquisition once after the preset distance of the rising edge of each pulse of the detection signal.
It should be noted that, when the radio frequency signal is a point pulse signal, the width of each pulse is small, and only a leading edge frequency measurement mode needs to be adopted, but because the signal quality of a plurality of points after the rising edge and the rising edge of each pulse is poor, in this embodiment, it is preferable to perform a point taking operation after a preset distance after the rising edge of each pulse, so as to ensure that the data quality of the point taking operation is good, and improve the frequency measurement accuracy of the frequency measuring machine. The specific value of the preset distance is different according to the type of the radio frequency signal, and the specific value of the preset distance is not limited by the invention and is determined according to the actual situation.
On the basis of the above embodiment, in another embodiment of the present invention, as shown in fig. 6, when the radio frequency signal is a wideband pulse signal, the performing at least one point extraction on each pulse of the detected signal includes:
s1052: and performing first point taking after the preset distance of the rising edge of each pulse of the detection signal, and performing second point taking before the preset distance of the falling edge of each pulse of the detection signal.
It should be noted that, when the radio-frequency signal is a broadband pulse signal, the width of each pulse is large, and the frequencies of the rising edge and the falling edge of the pulse may have a non-negligible difference, so that the leading edge frequency and the trailing edge frequency need to be measured simultaneously. Similarly, because the signal quality of each pulse within the preset distance range from the rising edge to the falling edge is poor, in this embodiment, it is preferable to perform the first time of point acquisition after the preset distance from the rising edge of each pulse, and perform the second time of point acquisition before the preset distance from the falling edge, so as to ensure that the data quality of the point acquisition is good, and improve the frequency measurement accuracy of the frequency measurement machine. The specific value of the preset distance is different according to the type of the radio frequency signal, and the specific value of the preset distance is not limited by the invention and is determined according to the actual situation.
On the basis of the above embodiment, in another embodiment of the present invention, the obtaining at least one frequency measurement code for each pulse of the radio frequency signal by calculating all signals to be calculated for each pulse using the radio frequency signal according to a digital instantaneous frequency measurement method, and multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal includes:
calculating the delay conjugate correlation of each signal to be calculated in each group of signals to be calculated of each pulse of the radio frequency signal, and expressing the delay conjugate correlation of each signal to be calculated in the form of a first preset formula;
respectively accumulating the real parts and the imaginary parts of all the signals to be calculated in each group of signals to be calculated and calculating the average to obtain the average real part and the average imaginary part of each group of signals to be calculated;
substituting the average real part and the average imaginary part of each group of signals to be calculated into a second preset formula to calculate and obtain at least one frequency measurement code of each pulse of the radio frequency signals;
multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal;
the first preset formula is as follows: m ═ x + jy, where x denotes the real part and y denotes the imaginary part;
the second preset formula is as follows:wherein f is0Representing said frequency measurement code, fsRepresenting the sampling rate of the digital down-conversion unit.
It should be noted that the expression for each signal to be calculated can be written as: s (n) exp (2 pi f)0n+φ0) Wherein phi is0Representing the phase of the signal to be calculated.
Taking the correlation of the signal to be computed and its delayed conjugate, one obtains:
M＝s(n)s*(n-Δn)＝exp(j2πf0n+φ0)exp(j2πf0(n-Δn)+jφ0)＝exp(j2πf0Δn)；
expressing M by a first preset formula, thenTo obtain
GetThen it can be obtained
Where Δ n represents the sampling interval.
On the basis of the foregoing embodiment, in a preferred embodiment of the present invention, as shown in fig. 7, the performing digital down-conversion on the sampling signal to obtain a complex signal including an in-phase signal and a quadrature signal includes:
s1031: and performing down-mixing and filtering extraction on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal.
Referring to fig. 3, fig. 3 is a schematic diagram of the digital down-conversion;
the digital down-conversion of the sampled signal includes two steps of down-mixing and filtering the sampled signal, which are described below:
a. frequency conversion without multiplication:
in reality, the input rf signal is a real narrow-band signal, which can be expressed as:
after analog-to-digital (AD) sampling, it becomes a digital signal:
the digital signal is divided into two paths which are respectively connected with cos (w) by a frequency mixing technologyon) and (-sin (w)on)) to obtain the quadrature variation of the signal, and the digital signal quadrature mixing can be expressed as:
the frequency conversion is a common digital signal processing algorithm, and for 1/4 signal sampling rate frequency conversion, a simple implementation method is provided
Here, the sampling rate fs2.5GHz, local oscillator frequency fc625MHz, satisfies fc＝fsThe relationship of/4 can be realized by adopting the following efficient mode;
b. and (3) polyphase filtering:
after quadrature mixing, the signal is passed through a low-pass Filter (FIR) to filter out unwanted frequencies. And performing low-pass filtering and extraction (↓ D). Here, filtering and decimation may be performed simultaneously. For a causal FIR system, its equations can be simplified as:
where M is the filter coefficient length. If multi-path parallel processing is adopted and N is the number of paths of FIR filtering parallel processing, then
In this embodiment, the sampling signal is decimated after low-pass filtering, so as to reduce the sampling rate and reduce the data amount of subsequent processing. In other embodiments of the present invention, the multiple of the sampling signal is 2 times, and the sampling rate (f) in step S1031 is the sampling rate (f) after the sampling signal is twice extracted, for example, the preset sampling rate is 2.5GHzs) Namely 1.25 GHz.
In summary, the embodiments of the present invention provide a frequency measuring machine and a signal frequency measuring method, wherein the frequency measuring machine performs frequency division processing on an input radio frequency signal through a set frequency divider to obtain a frequency divided signal with a lower frequency, so that the analog-to-digital acquisition module can acquire the frequency divided signal, and the frequency measuring machine can be applied to frequency measurement of a radio frequency signal with a higher frequency; in addition, the digital detection unit performs further digital detection and shaping filtering processing on the complex signal in the frequency calculation module, so that the pulse edge of the obtained detection signal is steeper, the point taking unit is convenient to identify and process each effective pulse, and the frequency measurement precision of the frequency measurement machine is improved.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. A frequency measuring machine, comprising: the frequency division module, the analog-digital acquisition module and the frequency calculation module; wherein,
the frequency division coefficient of the frequency division module is a preset value and is used for performing frequency division processing on an input radio frequency signal to obtain a frequency division signal and transmitting the frequency division signal to the analog-digital acquisition module;
the analog-digital acquisition module is used for sampling the frequency division signal at a preset sampling rate to obtain a sampling signal and transmitting the sampling signal to the frequency calculation module;
the frequency calculation module includes: the device comprises a digital down-conversion unit, a digital detection unit, a point taking unit and a calculation unit; wherein,
the digital down-conversion unit is used for performing digital down-conversion on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal;
the digital detection unit is used for carrying out digital detection and shaping filtering processing on the complex signal to obtain a detection signal;
the point taking unit is used for carrying out point taking for at least one time on each pulse of the detection signal, obtaining a group of signals to be processed each time, wherein each group of signals to be processed comprises a preset number of signals to be processed, and carrying out averaging calculation on a normal phase signal and an orthogonal signal of each signal to be processed in each group of signals to be processed to obtain at least one group of signals to be calculated;
the calculating unit is used for calculating and obtaining at least one frequency measuring code of each pulse of the radio frequency signal by utilizing all signals to be calculated of each pulse of the radio frequency signal according to a digital instantaneous frequency measuring method, and multiplying each frequency measuring code by the preset value to obtain at least one measuring frequency of the radio frequency signal;
the calculation unit includes:
the delay conjugation unit is used for calculating the delay conjugation correlation of each signal to be calculated in each group of signals to be calculated of each pulse of the radio frequency signal and expressing the delay conjugation correlation of each signal to be calculated in the form of a first preset formula;
the accumulation unit is used for respectively accumulating and averaging the real parts and the imaginary parts of all the signals to be calculated in each group of signals to be calculated to obtain the average real part and the average imaginary part of each group of signals to be calculated;
the frequency code unit is used for substituting the average real part and the average imaginary part of each group of signals to be calculated into a second preset formula to calculate and obtain at least one frequency measuring code of each pulse of the radio frequency signals;
the frequency unit is used for multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal;
the first preset formula is as follows: m ═ x + jy, where x denotes the real part and y denotes the imaginary part;
the second preset formula is as follows:wherein f is0Representing said frequency measurement code, fsRepresenting the sampling rate of the digital down-conversion unit.
2. The frequency measuring machine according to claim 1, wherein said point-taking unit takes at least one point-taking for each pulse of said detected signal when said radio frequency signal is a point pulse signal, and is specifically configured to take one point-taking after a predetermined distance of a rising edge of each pulse of said detected signal.
3. The frequency measuring machine according to claim 1, wherein when the rf signal is a wideband pulse signal, the point-taking unit performs at least one point-taking for each pulse of the detection signal, specifically, performs a first point-taking after a preset distance of a rising edge of each pulse of the detection signal, and performs a second point-taking before the preset distance of a falling edge of each pulse of the detection signal.
4. The frequency measuring machine according to claim 1, wherein the digital down-conversion unit performs digital down-conversion on the sampled signal to obtain a complex signal comprising an in-phase signal and a quadrature signal, and is specifically configured to perform down-mixing and filtering decimation on the sampled signal to obtain a complex signal comprising an in-phase signal and a quadrature signal.
5. A method of measuring a frequency of a signal, comprising:
performing frequency division processing on an input radio frequency signal by taking a preset value as a frequency division coefficient to obtain a frequency division signal;
sampling the frequency division signal at a preset sampling rate to obtain a sampling signal;
carrying out digital down-conversion on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal;
carrying out digital detection and shaping filtering processing on the complex signal to obtain a detection signal;
performing point acquisition on each pulse of the detection signal at least once, wherein each point acquisition obtains a group of signals to be processed, and each group of signals to be processed comprises a preset number of signals to be processed;
averaging the normal phase signal and the orthogonal signal of each signal to be processed in each group of signals to be processed to obtain at least one group of signals to be calculated;
according to a digital instantaneous frequency measurement method, calculating all signals to be calculated of each pulse by using the radio frequency signals to obtain at least one frequency measurement code of each pulse of the radio frequency signals, and multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signals;
the obtaining of at least one frequency measurement code of each pulse of the radio frequency signal by calculating all signals to be calculated of each pulse by using the radio frequency signal according to a digital instantaneous frequency measurement method, and the obtaining of at least one measurement frequency of the radio frequency signal by multiplying each frequency measurement code by the preset value comprises:
calculating the delay conjugate correlation of each signal to be calculated in each group of signals to be calculated of each pulse of the radio frequency signal, and expressing the delay conjugate correlation of each signal to be calculated in the form of a first preset formula;
respectively accumulating the real parts and the imaginary parts of all the signals to be calculated in each group of signals to be calculated and calculating the average to obtain the average real part and the average imaginary part of each group of signals to be calculated;
substituting the average real part and the average imaginary part of each group of signals to be calculated into a second preset formula to calculate and obtain at least one frequency measurement code of each pulse of the radio frequency signals;
multiplying each frequency measurement code by the preset value to obtain at least one measurement frequency of the radio frequency signal;
the first preset formula is as follows: m ═ x + jy, where x denotes the real part and y denotes the imaginary part;
the second preset formula is as follows:wherein f is0Representing said frequency measurement code, fsRepresenting the sampling rate of the digital down-conversion unit.
6. The method of claim 5, wherein when the radio frequency signal is a point pulse signal, the taking the point at least once for each pulse of the detected signal comprises:
and carrying out point acquisition once after the preset distance of the rising edge of each pulse of the detection signal.
7. The method of claim 6, wherein when the radio frequency signal is a wideband pulse signal, the taking the point at least once per pulse of the detected signal comprises:
and performing first point taking after the preset distance of the rising edge of each pulse of the detection signal, and performing second point taking before the preset distance of the falling edge of each pulse of the detection signal.
8. The method of claim 5, wherein digitally downconverting the sampled signal to obtain a complex signal comprising an in-phase signal and a quadrature signal comprises:
and performing down-mixing and filtering extraction on the sampling signal to obtain a complex signal comprising an in-phase signal and a quadrature signal.
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