JP6954765B2 - Frequency measuring device, frequency measuring method, and program - Google Patents

Description

The present invention relates to a frequency measuring device, a frequency measuring method, and a program.

Frequency measuring devices can be broadly divided into a method that realizes frequency measurement by an analog circuit (hereinafter, analog method) and a method that realizes frequency measurement by FFT processing after digitally converting microwaves (hereinafter, FFT method). There are two types. Here, FFT is a Fast Fourier Transform, that is, a Fast Fourier Transform.

FIG. 6 shows an example of an analog frequency measuring device. In addition, Patent Document 1 also cites an example of the analog method.

In the analog frequency measuring device shown in FIG. 6, since the phase difference is proportional to the frequency (θ = 2πfτ), the frequency is measured by measuring the phase difference. Here, θ is the phase difference, f is the frequency, τ is the delay amount, and π is the pi.

By using such a circuit, the microwave reception signal (RF) is divided into two, and the signal delayed by the delay time τ is orthogonal to the phase component of the signal before the delay and the phase of the signal before the delay. It can be decomposed into components. The signals decomposed into orthogonal components appear in A and B in the figure.

Then, by using the following equation, the angle of the phase difference between the delayed signal and the undelayed signal can be obtained. In the following equation, A and B represent the amplitudes of the signals A and B. Also, atan represents the inverse tangent of trigonometric functions.

θ = atan (B / A)
As can be seen from this equation, if τ is set larger than the value obtained by multiplying the maximum frequency to be measured by (2π), the phase angle exceeds 2π, and the frequency measurement is erroneous. Therefore, τ can be set only below the value obtained by multiplying the maximum frequency by (2π).

Further, in order to increase the phase sensitivity with respect to the frequency, it is necessary to increase τ.

On the other hand, in the FFT method also shown in Patent Document 2, when measuring a short pulse-modulated signal, the signal is cut out every short time and then measured by FFT processing.

JP-A-59-85964 Japanese Patent No. 5777102

However, in the analog frequency measuring device, if the maximum frequency that can be theoretically measured by the delay τ is set to the upper limit of the frequency to be actually measured, sufficient accuracy cannot be obtained. Therefore, it is necessary to increase τ to provide a plurality of systems having increased phase sensitivity with respect to the frequency to improve the frequency discrimination accuracy.

Furthermore, when the delay circuit is composed of a transmission line, a sufficient amount of delay cannot be obtained for the frequency to be measured, and it is difficult to measure the frequency with stable accuracy. Therefore, a crystal oscillator or SAW (surface acoustic wave) is used. ) A device that uses elements, etc. is essential. When these devices are used in a delay circuit, there is a problem that the linearity of phase vs. frequency largely depends on the measurement accuracy. The stability of these devices against temperature fluctuations is also an issue.

Therefore, there is a problem that it is necessary to select a device according to the application of the frequency measuring device and limit the frequency measured by the frequency measuring device, the installation environment, and the like.

On the other hand, in the FFT type frequency measuring device, the accuracy of the frequency by the FFT processing depends on the signal cutting time, the cutting timing, the length of the FFT processing, the applicable window function, and the like. Therefore, it is necessary to make each setting after assuming a short pulse-modulated microwave to be measured, and there is a problem that it takes time to adjust the setting.

An object of the present invention is to provide a frequency measuring device, a frequency measuring method, and a program for measuring the frequency of a short pulse-modulated microwave with stable accuracy in a short time in view of the above-mentioned problems.

In order to achieve the above object, the frequency measuring device of the present invention includes a phase detection circuit that separates a short pulse modulated signal sampled in the first period into two orthogonal phase components, and a pulse of the short pulse modulated signal. The phase angle was calculated from the pulse detection circuit for detecting the above and the orthogonal phase component, and the first phase angle at the first time when the pulse rises and the first period were added to the first time. The second cycle is calculated from the second phase angle of the second time and the first cycle, and the quotient obtained by dividing the second cycle by the first cycle is multiplied by the first cycle. If the third time obtained by adding the first time and the second time is after the fourth time when the pulse falls, the third phase angle and the second phase at the third time The third period is calculated from the angle and the first time, and if the fourth time is before the third time, the fourth phase angle and the second phase angle at the fourth time are calculated. And a control unit that calculates a third cycle from the first time and calculates the inverse of the third cycle as a frequency.

In order to achieve the above object, the frequency measurement method of the present invention separates the short pulse modulated signal sampled in the first period into two orthogonal phase components, detects the pulse of the short pulse modulated signal, and detects the pulse of the short pulse modulated signal. The phase angle is calculated from the orthogonal phase component, and the first phase angle at the first time when the pulse rises and the second phase at the second time obtained by adding the first period to the first time. The second period is calculated from the phase angle and the first period, and the quotient obtained by dividing the second period by the first period is multiplied by the first period to obtain the first time and the first period. If the third time obtained by adding the two times is after the fourth time when the pulse falls, the third phase angle at the third time, the second phase angle, and the first time The third period is calculated, and if the fourth time is before the third time, the fourth phase angle at the fourth time, the second phase angle, and the first time are used. The period of 3 is calculated, and the inverse of the third period is calculated as the frequency.

In order to achieve the above object, the program of the present invention calculates the phase angle from the orthogonal phase component of the short pulse modulated signal separated into two orthogonal phase components after being sampled in the first period. The phase angle at the first time when the pulse of the short pulse modulated signal rises, the phase angle at the second time obtained by adding the first period to the first time, and the first period. The second time is calculated from the above, and the quotient obtained by dividing the second cycle by the first cycle is multiplied by the first cycle, and the first time and the second time are added to the third time. However, if it is after the fourth time when the pulse falls, the third period is calculated from the third phase angle at the third time, the second phase angle, and the first time, and the third period is calculated. If the time 4 is before the third time, the third period is calculated from the fourth phase angle, the second phase angle, and the first time at the fourth time, and the third period is calculated. Have the computer perform the calculation of the inverse of the period of.

According to the present invention, a frequency measuring device, a frequency measuring method, and a program enable measurement of a short pulse-modulated microwave frequency with stable accuracy and in a short time.

It is a figure which shows the structural example of the 1st Embodiment. It is a figure which shows the structural example of the 2nd Embodiment. It is a figure explaining the operation of the 2nd Embodiment. It is a figure explaining the operation of the 2nd Embodiment. It is a figure explaining the operation of the 2nd Embodiment. It is a figure explaining the operation of the 2nd Embodiment. It is a figure which shows the structural example of the related technology.

[First Embodiment]
The frequency measuring device 10 of the present embodiment includes a phase detection circuit 11, a pulse detection circuit 12, and a control unit 13.

The phase detection circuit 11 separates the short pulse modulation signal sampled in the first period into two quadrature phase components.

The pulse detection circuit 12 detects the pulse of the short pulse modulation signal.

Further, the control unit 13 calculates the phase angle from the quadrature phase component, adds the first phase angle at the first time when the pulse rises, and the first period added to the first time. The second period is calculated from the second phase angle at the time of 2 and the first period. Further, the control unit 13 sets the quotient obtained by dividing the second cycle by the first cycle as the third time obtained by multiplying the quotient by the first cycle and adding the second time to the first time. .. Then, the control unit 13 sets the third phase angle, the second phase angle, and the first to third cycles at the third time after the fourth time when the pulse falls. calculate. Further, if the fourth time is before the third time, the control unit 13 may use the fourth phase angle at the fourth time, the second phase angle, and the first to third times. Is calculated, and the reciprocal of the third cycle is calculated as the frequency.

The frequency measuring device 10 of the present embodiment does not need to be provided with a plurality of systems in order to improve the frequency discrimination accuracy as in the analog type frequency measuring device described above.

Further, unlike the above-mentioned FFT type frequency measuring device, it is not necessary to set the FFT process on the assumption of the short pulse-modulated microwave to be measured, and the time required for the setting is also unnecessary.

By doing so, the frequency measuring device 10 of the present embodiment can measure the frequency of the short pulse-modulated microwave with stable accuracy in a short time.
[Second Embodiment]
Next, an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.
[Description of configuration]
FIG. 2 shows a configuration example of the second embodiment.

The frequency measuring device 20 is composed of an A / D conversion unit 21, a clock 22, a phase detection circuit 23, a 1 cp delay circuit 24, an ncp delay circuit 25, a pulse fall detection circuit 26, an output unit 27, and a control unit 28. It is composed.

The A / D conversion unit 21 includes a conversion circuit that converts a pulse of an analog signal into a digital signal. The clock 22 is a time measuring means realized by using a crystal oscillator or the like that generates a signal in the sampling period of the A / D converter 21. According to Nyquist's theorem, one cycle of the clock, that is, one clock pulse, is set to a value smaller than one-fourth of the period of the waveform to be measured to be measured by the frequency measuring device 20.

The phase detection circuit 23 is a commonly used phase detection circuit for decomposing an input signal into an in-phase signal (I) and a quadrature signal (Q) and outputting the signal. It is also shown in the literature, Japanese Patent Application Laid-Open No. 8-237313, and the like.

The 1cp delay circuit 24 is a delay circuit that delays and outputs an input waveform for one cycle of the clock, that is, a time corresponding to one clock pulse when instructed by the control unit 28. The ncp delay circuit 25 is a delay circuit that delays and outputs an input waveform for a time corresponding to an n clock pulse when instructed by the control unit 28. Here, n is a natural number instructed by the control unit 28. Further, the 1 cp delay circuit 24 and the ncp delay circuit 25 are generally used delay circuits, and are also shown in Patent Documents, Japanese Patent Application Laid-Open No. 2017-73746 and the like.

The 1 cp delay circuit 24 may be referred to as a first delay circuit. Further, the ncp delay circuit 25 may be referred to as a second delay circuit.

The pulse fall detection circuit 26 includes a detection circuit for the output waveform of the A / D conversion unit 16, and transmits a signal for detecting the fall time of the pulse waveform and notifying the control unit 28.

The output unit 27 is a means for outputting the frequency of the waveform to be measured measured by the control unit 28, may be a means for displaying the frequency by a liquid crystal display, and is a means for transmitting a signal for notifying the frequency to another device. It may be.

The control unit 28 includes a CPU (Central Processing Unit), controls the hardware of the frequency measuring device 20, and performs software processing.
[Explanation of operation]
Next, the operation of this embodiment will be described with reference to FIGS. 3 to 6.

FIG. 3 (1) represents the waveform to be measured that the frequency measuring device 20 of the present embodiment intends to measure, the horizontal axis is the time axis, and the right direction is the passage of time. The period of the waveform to be measured is T, and the frequency measuring device 20 aims to measure the value of T.

Further, the clock waveform shown in FIG. 3 is a waveform of a signal generated by the clock 22, and the period tc of the clock waveform coincides with the sampling period of the A / D conversion unit 21. As described above, tk is set to 1/4 or less of the period T of the waveform to be measured according to Nyquist's theorem.

Further, tc may be referred to as a first cycle.

Next, the operation of the frequency measuring device 20 will be described with reference to FIG.

First, the control unit 28 detects the voltages of It0 and Qt0, which are the outputs of the phase detection circuit 23, at time t = t0 (S101).

The time t0 may be referred to as the first time.

At the same time as step S101, the control unit 28 transmits a signal instructing the 1 cp delay circuit 24 to output a waveform delayed by a time tk.

The 1cp delay circuit 24 delays the input waveform by time ct with respect to t = t0 (S102).

The control unit 28 calculates the phase angle θt0 according to the following equation based on It0 and Qt0 detected in step S101 (S103).

θt0 = atan (Qt0 / It0)
Here, atan represents the inverse tangent of trigonometric functions.

FIG. 4 shows a state in which the phase of the waveform rotates in the direction of a thick arrow about the origin, with the horizontal axis as the in-phase component I and the vertical axis as the orthogonal component Q.

θ0 may be referred to as a first phase angle.

In step S104, the control unit 28 detects the voltages of Itc and Qtc at the time when the output is started from the 1 cp delay circuit 24 (S104). The time t at this time is t = (t0 + tk).

The time t = (t0 + tc) may be referred to as the second time.

The control unit 28 calculates the phase angle θtc according to the following equation based on the Itc and Qtc detected in step S103 (S105).

θtc = atan (Qtc / Itc)
θtc may be referred to as a second phase angle.

Next, the control unit 28 calculates the period T1 according to the following equation based on the θt0 calculated in step S103, the θtc calculated in step S105, and the time ct (S106).

T1 = 2 · π · tc / (θtc-θt0)
The period T1 obtained here is obtained from the phase angle at which the phase of the waveform to be measured rotates during one clock pulse, that is, during the time tc, and has a large error.

T1 may be referred to as a second cycle.

Next, the control unit 28 divides the period T1 calculated in step S106 by the time tc, and sets the quotient value to n.

Further, the control unit 28 instructs the ncp delay circuit 25 to delay the input waveform by n times tc (S107).

Further, the control unit 28 sets n times of tc as tn (tun = tk × n) (S108).

tn may be referred to as the first time.

In step S109, the control unit 28 determines whether or not the pulse fall detection circuit 26 has detected the pulse fall (S109).

The case where the pulse is detected in step S109 is the case where the pulse width Tp of the waveform to be measured (A) is equal to or less than the period T of the carrier wave as shown in FIG.

Further, in step S109, the case where the pulse is not detected is the case where the pulse width Tp of the waveform to be measured (A) is larger than the period T of the carrier wave as shown in FIG.

When the falling edge of the pulse is detected in step S109 (Y in S109), the process proceeds to step S115.

If the fall of the pulse is not detected in step S109 (N in S109), the process proceeds to step S110.

In step S110, the control unit 28 determines whether or not the time has elapsed (S110).

Based on the tn used in the determination in step S110, the time t = (t0 + tc + tun) may be referred to as a third time.

If it is determined in step S110 that the time has elapsed (Y in S110), the process proceeds to step S111.

If it is determined in step S110 that the time has not elapsed (N in S110), the process returns to step S109.

In step S111, the control unit 28 detects the voltages of Itn and Qtn at the time when the output is started from the ncp delay circuit 25 (S111). The time t at this time is t = t0 + tc + tn.

In step S112, the phase angle θtn is calculated according to the following equation based on Itn and Qtn detected in step S111 or step S111 (S112).

θtn = atan (Qtn / Itn)
When step S112 is executed following step S110 and step S111, θtn may be referred to as a third phase angle.

Further, when step S112 is executed following step S116 and step S111, θ t n may be referred to as a fourth phase angle.

Next, the control unit 28 calculates the period T2 and the frequency f according to the following equation based on the θtc calculated in step S105, the θtn calculated in step S113, and the time tun (S113).

T2 = 2 · π · tn / (θtc−θtn)
f = 1 / T2
T2 may be referred to as a third cycle.

Here, θtn is at an angle between θt0 and θtc, making less than one rotation from θtc, approximately one rotation, during the time tun. Expressed as an equation, it becomes the following equation.

(Θt0 + 2 ・ π) <θtn <(θtc + 2 ・ π)
T2 obtained in step S112 is a value obtained by calculating the period of the waveform to be measured from the amount of change in the phase angle in a time of about one cycle of the waveform to be measured. On the other hand, T1 obtained in step S106 is a value obtained by calculating the period of the waveform to be measured from the amount of change in the phase angle in an extremely short time corresponding to one clock pulse.

Therefore, the accuracy of T2 is a more precise value than the accuracy of T1.

If the delay time nt is set to a long time regardless of the period T1, it is not possible to determine how many periods of phase change have occurred during tun, and frequency measurement is erroneous. Further, when tn is set to an integral multiple of twice or more of T1, it becomes unclear how many cycles of phase change θtc−θtn causes, and frequency measurement is erroneous.

Therefore, in the present embodiment, the period T1 is first obtained as a rough measurement from the phase change during a short time tc, and then the precise frequency measurement is realized by the delay of the period T1.

In step S114, the control unit 28 outputs the frequency f to the output unit 27 (S114).

In step S115, the control unit 28 again sets the time at the time when the fall of the pulse is detected in step S109 starting from the time t0 as tf, and the quotient of the result obtained by dividing tf by tc as n. Then, the control unit 28 instructs the ncp delay circuit 25 to delay the input waveform by n times tc (S115).

In addition, tf may be referred to as a fourth time.

In step S116, the control unit 28 sets n times tc as tun (tun = tk × n) (S116).

As described above, the frequency measuring device 20 of the present embodiment does not need to be provided with a plurality of systems in order to improve the frequency discrimination accuracy as in the analog type frequency measuring device described above.

Further, unlike the above-mentioned FFT type frequency measuring device, it is not necessary to set the FFT process on the assumption of the short pulse-modulated microwave to be measured, and the time required for the setting is also unnecessary.

In this way, the frequency measuring device 20 of the present embodiment can measure the frequency of the short pulse-modulated microwave with stable accuracy in a short time.

The present invention is also applicable when the information processing program that realizes the functions of the embodiment is directly or remotely supplied to the system or device.

10 Frequency measurement device 11 Phase detection circuit 12 Pulse detection circuit 13 Control unit 16 Conversion unit 20 Frequency measurement device 21 Conversion unit 22 Clock 23 Phase detection circuit 24 Delay circuit 25 Delay circuit 26 Detection circuit 27 Output unit 28 Control unit

Claims (4)

A phase detection circuit that separates the short pulse modulation signal sampled in the first period into two quadrature phase components,
A pulse detection circuit that detects the pulse of the short pulse modulation signal and
The phase angle is calculated from the orthogonal phase component, and the first phase angle at the first time when the pulse rises and the second phase at the second time obtained by adding the first period to the first time. The second period is calculated from the phase angle and the first period, and the quotient obtained by dividing the second period by the first period is multiplied by the first period to obtain the first time and the first period. If the third time obtained by adding the two times is before the fourth time when the pulse falls, the third phase angle at the third time, the second phase angle, and the first time The third period is calculated from the above, and if the fourth time is before the third time, the fourth phase angle at the fourth time, the second phase angle, and the first time are used. A frequency measuring device including a control unit that calculates a cycle of 3 and calculates the inverse of the third cycle as a frequency. A phase detection circuit that separates the short pulse modulation signal sampled in the first period into two quadrature phase components,
A pulse detection circuit that detects the pulse of the short pulse modulation signal and
A first delay circuit that outputs the output waveform of the phase detection circuit with a delay of the first cycle, and a first delay circuit.
A second delay circuit that delays and outputs the output waveform of the first delay circuit, and
The phase angle is calculated from the orthogonal phase component, the first phase angle at the first time when the pulse rises, and the second phase of the waveform whose output is started at the second time from the first delay circuit. The second cycle is calculated from the angle and the first cycle, and the quotient obtained by dividing the second cycle by the first cycle is multiplied by the first cycle for the second delay circuit. The output is instructed to start at the third time obtained by adding the first time and the second time, and if the third time is before the fourth time when the pulse falls, the third time is described. The third period is calculated from the third phase angle, the second phase angle, and the first time at the time of, and if the fourth time is before the third time, the fourth time. second instructing so as to be output starting from the delay circuit calculates a third period from the fourth phase angle between the second phase angle said first time in the fourth time in the A frequency measuring device including a control unit that calculates the inverse number of the third cycle as a frequency. The short pulse modulation signal sampled in the first period is separated into two quadrature phase components.
The pulse of the short pulse modulation signal is detected,
The phase angle is calculated from the orthogonal phase component, and the first phase angle at the first time when the pulse rises and the second phase at the second time obtained by adding the first period to the first time. The second period is calculated from the phase angle and the first period.
The fourth time at which the pulse falls is the third time obtained by adding the first time obtained by multiplying the quotient obtained by dividing the second cycle by the first cycle by the first cycle and the second time. If it is before the time of, the third period is calculated from the third phase angle at the third time, the second phase angle, and the first time.
If the fourth time is before the third time, the third period is calculated from the fourth phase angle, the second phase angle, and the first time at the fourth time.
A frequency measurement method characterized in that the reciprocal of the third cycle is calculated as a frequency. The phase angle is calculated from the orthogonal phase component of the short pulse modulated signal separated into two orthogonal phase components after being sampled in the first period, and the pulse of the short pulse modulated signal rises at the first time. The second period is calculated from the first phase angle, the second phase angle of the second time obtained by adding the first period to the first time, and the first period.
The fourth time at which the pulse falls is the third time obtained by adding the first time obtained by multiplying the quotient obtained by dividing the second cycle by the first cycle by the first cycle and the second time. If it is before the time of, the third period is calculated from the third phase angle at the third time, the second phase angle, and the first time.
If the fourth time is before the third time, the third period is calculated from the fourth phase angle, the second phase angle, and the first time at the fourth time.
A program that causes a computer to calculate the reciprocal of the third cycle as a frequency.

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