JPS6129674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a counting type frequency measuring device that automatically measures frequencies in a high frequency band and displays the results numerically.

Conventionally, there has been a device shown in FIG. 1 that automatically measures frequencies in a high frequency band.

In this conventional example, the phase synchronized circuits 2 to 5 are
to measure the frequency. That is, the external input signal S is divided into two parts by the distributor 1, and mixed with the oscillation output of the variable local oscillator 5, which is swept by one of the drive waveform generators 6, by the harmonic mixer. The output of the harmonic mixer 2 enters a phase detector 3, where it is phase-compared with the output of a reference oscillator 4, and a variable local oscillator 5
A phase-locked loop is formed at a certain oscillation frequency ₁ . Generally, in this phase-locked loop, if the frequency of the external input signal S _{is x} and the reference frequency of the reference oscillator 4 is _r1 , _x = _n1 ± _r1 is formed, and the nth of the oscillation frequency ₁ of the variable local oscillator 5 There are cases where the harmonic is at a frequency above or below the frequency _x by the reference frequency _r1 . Here, in order to find the harmonic order n, the determining device 7 forms a phase-locked loop only when _n1 is a frequency lower than _x by _r1 . Therefore, when phase synchronization is achieved, the following equation holds true.

_x = n ₁ + _r1 ...(1) On the other hand, by setting the frequencies of the variable local oscillator 5 and the reference oscillator 4 appropriately, for example, to _r2 using another phase synchronization circuit, the determination device 8 , n ₂ forms a phase-locked loop only when the frequency is _r2 lower than _x . Therefore, the following equation holds.

_x = n ₂ + _r2 ...(2) Therefore, from equations (1) and (2), the harmonic order n is found as n = ( _r1 - _r2 )/( ₂ - ₁ ), and ₁ or ₂
By counting n times the harmonic order and adding the reference frequency _r1 or _r2 , _x can be found. When this method is used, since the frequency _x of the external input signal S is added to the phase locked circuit, this _frequency
When FM modulation is heavy or a large amount of noise is included, phase synchronization becomes difficult.

This invention has been made in consideration of the above points, and allows measurement even if the external input signal contains FM modulation or a large amount of noise, and in order to improve measurement accuracy, phase synchronization that is not affected by the external input signal is achieved. The system is configured with a circuit, and a central processing unit performs measurement commands and arithmetic processing.
This invention will be explained below.

FIG. 2 is a block diagram showing an embodiment of the present invention, in which 11 is a mixer, one input of which is applied an external input signal S, and the other input of which is a first variable local oscillator 1.
3 is added to output intermediate frequency _IF1 .
The first variable local oscillator 13 is, for example, a YIG
It consists of a tuned oscillator.

A first counter 12 counts and outputs the intermediate frequency _IF1 output from the mixer 11. 14
is a first driving waveform generator, which is composed of, for example, a DA converter and generates a stepped driving waveform.
The variable local oscillator 13 is driven. A reference oscillator 15 is composed of a crystal oscillator with good frequency stability. 16 is a phase detector which receives the intermediate frequency _IF2 output from the harmonic mixer 17 and the reference frequency of the reference oscillator 15, compares the phases, and feeds back the output of the difference to the first variable local oscillator 13. This creates a phase-locked loop. The harmonic mixer 17 adds the output of the first variable local oscillator 13 to one input, and the second variable local oscillator 1 configured from, for example, a voltage controlled oscillator (VCO) to the other input.
8 _{is added} to output the intermediate frequency f _IF2 . Reference numeral 19 denotes a second driving waveform generator, which is composed of, for example, a DA converter, and generates a stepped driving waveform to drive the second variable local oscillator 18. 20
is a frequency divider, which divides the oscillation frequency output from the second variable local oscillator 18. A second counter 21 counts the frequency output from the frequency divider 20. Reference numeral 22 denotes a central processing unit, for example, a microprocessor, which operates the first drive waveform generator 14 and determines when the intermediate frequency _IF1 output from the mixer 11 falls within a predetermined frequency range. At this time, the output of the first driving waveform generator 14 is fixed, the sweep of the first variable local oscillator 13 is stopped, and at that time,
Intermediate frequency _IF counted by first counter 12
₁ , processing to set the harmonic order n of the oscillation frequency of the second variable local oscillator 18 with respect to the oscillation frequency of the first variable local oscillator 13 at that time, and restarting the sweep and increasing or decreasing the oscillation frequency by a predetermined small frequency;
First variable local oscillator 1 for external input signal S
The harmonic order m of the oscillation frequency of 3 is detected, and the intermediate frequency ' _IF1 outputted from the mixer 11 at that time and the already stored intermediate frequency _IF are detected.
₁ , the first variable local oscillator 1 when the external input signal S has an intermediate frequency of _IF1 .
Processing to determine whether the oscillation frequency is higher or lower than the oscillation frequency of No. 3, and the second driving waveform generator 19
, the first and second variable local oscillators 1
3, 18, reference oscillator 15 and phase detector 16
A process of storing the intermediate frequency _IF1 or ' _IF1 when a phase-locked loop is configured by , and also storing the oscillation frequency of the second variable local oscillator 18, and a process of storing the oscillation frequency of the second variable local oscillator 18 when the harmonic orders m and n are phase-locked. A calculation process is performed to determine the frequency _x of the external input signal S using the intermediate frequency _IF1 obtained by the above calculation, the oscillation frequency _vcp of the second variable local oscillator 18, and the predetermined reference frequency ₀ of the reference oscillator 15. Note that 23 is a display device that displays the determined frequency _x .

Next, the operation will be explained. Central processing unit 22
The first driving waveform generator 14 is operated in response to a command from the controller, and the first variable local oscillator 13 is caused to sweep oscillate, for example, repeatedly for two seconds. By adding the frequency _x of the external input signal S to be measured to one input of the mixer 11 and adding the frequency _L of the first variable local oscillator 13 to the other input, the intermediate frequency _IF1 output from the mixer 11 is determined. , for example from 100MHz
When the frequency falls within the range of 200 MHz, the sweep of the first variable local oscillator 13 is stopped, and the intermediate frequency _IF1 at that time is stored in the central processing unit 22. Also, the first variable local oscillator 1 at that time
The harmonic order n of the oscillation frequency _vcp of the second variable local oscillator 18 with respect to the oscillation frequency _L of No. 3 is set as follows. When controlling the oscillation frequency of the first variable local oscillator 13 by operating the first driving waveform generator 14 according to a command from the central processing unit 22, the first variable local oscillator 13 is set in the central processing unit 22 in advance. By memorizing the relationship between the oscillation frequency _L and the drive voltage in No. 13, the central processing unit 22
The oscillation frequency of the variable local oscillator 13 can be found. Also, the oscillation frequency _vc of the second variable local oscillator 18
_p can be grasped by the central processing unit 22 by operating the frequency divider 20 and the second counter 21. Therefore, operate the second driving waveform generator 19 to control the oscillation frequency of the second variable local oscillator 18 to establish the relationship _L = n _vcp + ₀ (n is the harmonic order). I can do it. _L is 4G
For Hz band, n = 4.6GHz band, n = 6.11G
For the Hz band, n=11 is set by the central processing unit 22. This causes the second variable local oscillator 18
The n-th harmonic of the oscillation frequency _vcp and the oscillation frequency _L of the first variable local oscillator 13 are mixed in the harmonic mixer 17.

Next, the sweep of the first variable local oscillator 13 is restarted in response to a command from the central processing unit 22, and the oscillation frequency _L is further increased or _decreased by, for example, 50 MHz. The harmonic order m of the oscillation frequency _L of the variable part oscillator 13 is detected, and the current intermediate frequency ' _IF1 when m=1 is compared with the already stored intermediate frequency _IF1 to determine the external input signal S. The central processing unit 22 determines whether the frequency _x is larger or smaller than the oscillation frequency _L of the first variable local oscillator 13 when the frequency x is the intermediate frequency _IF1 . For example, if _IF1 = 130MHz and _L = 6070MHz, then _x = m _L ± _IF1
holds true (m is the harmonic order). Now when m=1
When _L is increased by 50MHz to 6120MHz,
If ′ _IF1 = 80MHz, then _IF1 > IF1 _x =
= 6200MHz, and when _L is increased by 50MHz, if _IF1 = 180MHz, then _IF1 < IF1.
_x = 5940MHz. When m2, _IF1 is _IF
1 , increases or decreases by m times 50MHz. In other words, a sudden increase or decrease is detected. In this way, the harmonic order m of the oscillation frequency _L of the first variable local oscillator 13 with respect to the frequency _x of the external input signal S is detected, and for example, m
The above judgment is processed only when =1. after that,
The second driving waveform generator 19 is operated in response to a command from the central processing unit 22, causing the second variable local oscillator 18 to sweep oscillate and apply it to one input of the harmonic mixer 17. Further, the output of the first variable local oscillator 13 is added to the other input of the harmonic mixer 17, and the intermediate frequency output from the harmonic mixer 17 is
_IF2 is applied to one input of phase detector 16.
A reference oscillator 15 is connected to the other input of the phase detector 16.
A reference frequency of ₀ is added thereto, the phases are compared, and the output is fed back to the first variable local oscillator 13 to form a phase locked loop. The intermediate frequency _IF1 or ' _IF1 when the phase is synchronized is stored, and the oscillation frequency _vcp of the second variable local oscillator 18 is divided or directly counted by the second counter 21 and stored in the central processing unit 22. . Therefore, the frequency _x of the external input signal S can be determined by the following equation.

_x = m(n _vcp + ₀ ) ± _IF1 = m _L ± _IF1 That is, _IF1 is counted by the first counter 12, and _vcp is counted by the second counter 21. Furthermore, if ₀ is relatively stable, it may be used when calculating the value of that frequency, and if further accuracy is desired, ₀ may be counted by the second counter 21 each time the calculation is performed. As described above, both m and n harmonic orders are set by the central processing unit 22 during measurement.

FIG. 3 is a block diagram showing another embodiment of the present invention. Its configuration is almost the same as that of the embodiment shown in FIG. The reference frequency of the reference oscillator 15 is counted and stored. In this figure, 24 is a switch, for example, composed of a relay, which connects the second variable local oscillator 1 when phase synchronized.
Reference oscillator 15 before and after counting the oscillation frequency of 8
This is to keep track of the reference frequency.
Note that other symbols indicate the same things as in FIG. 2. Further, since its operation is similar to that of the embodiment shown in FIG. 2, its explanation will be omitted.

As explained above, according to the present invention, the local oscillation frequency and the intermediate frequency are each counted by two counters, and the external input signal is not added to the phase-locked loop. Even when modulation is applied or a large amount of noise is included, the frequency can be measured with high accuracy without affecting phase synchronization.
Furthermore, by having two counters count simultaneously for a predetermined period of time, frequency fluctuations can be canceled out and highly accurate measurements can be performed.

Further, since the signal generator has a configuration in which no phase-locked loop is formed with respect to the reference oscillator, the overall configuration has the advantage of being simple and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the structure of a conventional frequency measuring device, FIG. 2 is a block diagram showing the structure of a frequency measuring device according to an embodiment of the present invention, and FIG. 3 is a block diagram showing the structure of another embodiment of the present invention. FIG. In the figure, 11 is a mixer, 12 is a first counter,
13 is a first variable local oscillator; 14 is a first driving waveform generator; 15 is a reference oscillator; 16 is a phase detector; 17 is a harmonic mixer; 18 is a second variable local oscillator; 2 driving waveform generator, 20
2 is a frequency divider, 21 is a second counter, 22 is a central processing unit, 23 is a display, and 24 is a switch.

Claims (1)

[Claims] 1: a first variable local oscillator; a first driving waveform generator that sweeps and oscillates the oscillation frequency of the first variable local oscillator; and an external input for measuring the output and frequency of the first variable local oscillator. a mixer that receives a signal and outputs an intermediate frequency _IF1 ; a first counter that counts the intermediate frequency _IF1 ;
a second variable local oscillator; a second driving waveform generator that sweeps and oscillates the oscillation frequency of the second variable local oscillator; an output of the first variable local oscillator; a harmonic mixer that receives the output and outputs an intermediate frequency _IF2 ; compares the phase of the intermediate frequency _IF2 and a predetermined reference frequency output from the reference oscillator, and transmits the output to the first variable local section; a phase detector that feeds back to the oscillator and synchronizes the phase;
a second counter that counts the oscillation frequency of the variable local oscillator; when the intermediate frequency _IF1 output from the mixer is within a predetermined frequency range;
A process of stopping the sweep of the variable local oscillator and storing the intermediate frequency _IF1 at that time, and harmonics of the oscillation frequency of the second variable local oscillator with respect to the oscillation frequency of the first variable local oscillator at that time. setting the order n; and restarting the sweep of the first variable local oscillator to increase or decrease its oscillation frequency by a predetermined frequency to harmonize the oscillation frequency of the first variable local oscillator in response to the external input. a process of detecting the wave order m and comparing the intermediate frequency ' _IF1 at that time with the recorded intermediate frequency _IF1 to determine the magnitude of the external input signal with respect to the oscillation frequency of the first variable local oscillator; A process of storing the intermediate frequency _IF1 or ' _IF1 when the second variable local oscillator is swept and phase synchronized, and also storing the oscillation frequency of the second variable local oscillator, and the harmonic orders m, n, central processing that calculates the frequency of an external input signal based on the intermediate frequency _IF1 or ' _IF stored when the phase is synchronized, the oscillation frequency of the second variable local oscillator, and the reference frequency of the reference oscillator; A counting type frequency measuring device comprising: