JPS6287874A - Apparatus for measuring phase - Google Patents

Abstract

PURPOSE:To make it possible to measure the phase of a signal to be measured with high accuracy, by mixing a reference signal with a first oscillation signal in a first frequency mixing circuit while mixing said signal with a second oscillation signal in a second frequency mixing circuit and inputting the signals obtained by this method to third and fourth frequency mixing circuits. CONSTITUTION:At first, a signal (f) to be measured with frequency f0 and a reference signal f0 are respectively inputted to frequency mixing circuit 5, 6 through high frequency amplifiers 3, 4. The signal f0 is added to an oscillation signal f1 through a frequency mixing circuit 7 and an oscillation signal f2 is subtracted from the added signal in a frequency mixing circuit 9 and the resulting signal is inputted to the circuits 5, 6 through a distributor 11 to be subtracted from the signals f, f0 to be converted to a beat signal with low frequency f2-f1 while the phase of the signal (f) to the signal f0 is held. A phase detection circuit 14 detects the phase difference of the signal (f) and the signal f0 from respective signals obtained by converting the beat signal by A/D converters 12, 13 to output the same. Then, AND with the oscillation signal f2 is taken in a pulse train circuit 15 and outputted as a signal showing a phase by a counter circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase measuring device, and particularly to a device for measuring the phase of a high frequency signal with high precision. The device according to the present invention is used, for example, as a network analyzer to measure high-frequency parameters of a network (four-terminal network), such as phase differences between input and output signals.

[Conventional technology]

FIG. 2 shows an example of a conventional phase measuring device. Second
In the figure, numerals 3 and 4 are high-frequency amplifiers, which respectively amplify the measured signal f (frequency is fO) input from terminal 1 and the reference signal fo (frequency is fo) input from terminal 2. do. 21 and 22 are frequency mixing circuits, which include a frequency mixer 21a and a filter 21b, and a frequency mixer 22a and a filter 22b, respectively.
Consisting of The frequency mixers 21a and 22a have independent phase-locked closed loops (P L L
) circuit 23 or a tracking oscillator is connected, and filters 21b and 22b are for removing spurious and unnecessary sideband waves. A phase measuring circuit 24 compares the output signals of the frequency mixing circuits 21 and 22 in an analog or digital manner, and measures the phase of the signal under test f with respect to the reference signal fo based on this comparison.

In the apparatus shown in FIG. 2, the signal under test f and the reference signal fo are first amplified to predetermined levels in the high frequency amplifier 3.
A frequency mixer 21a whose output is a local oscillation signal fc (frequency is fc).

22a, the signals are frequency-converted while maintaining their phases, and filters 21b and 22b remove spurious and unnecessary sidebands, and then input to the phase measuring circuit 24 as, for example, a signal (fo+fc).

[Problem that the invention seeks to solve]

In the conventional phase measuring device described above, when the signal under test is a particularly high-frequency signal, if the frequency of the signal under test changes due to external factors such as temperature, that fluctuation appears in the output as a phase error. Therefore, it is necessary to track the frequency of the local oscillation signal of the PLL circuit with high precision, and there is a problem that the configuration of the PLL circuit for this purpose becomes complicated.

The present invention was created in view of the problems with the conventional type described above, and has a relatively small and simple configuration, and is capable of highly accurate phase measurement without being affected by frequency fluctuations of the signal under test. The purpose is to provide a phase measuring device.

[Means for solving problems]

According to the present invention, a local oscillator outputs a first oscillation signal, a reference signal and the first oscillation signal are mixed, and one of the resulting upper sideband and lower sideband signals is output. A first frequency mixing circuit that outputs a sideband signal, a local oscillator that outputs a second oscillation signal having a frequency different from the frequency of the first oscillation signal, and an output signal of the first frequency mixing circuit. The second oscillation signal is mixed with the second oscillation signal, and among the upper sideband and lower sideband signals obtained thereby, a sideband signal on a sideband side different from the sideband signal outputted by the first frequency mixing circuit is output. a second frequency mixing circuit that mixes the signal under test and the output signal of the second frequency mixing circuit, and outputs the lower sideband signal of the upper and lower sideband signals obtained thereby; a fourth frequency mixing circuit that mixes the reference signal and the output signal of the second frequency mixing circuit, and outputs the lower sideband signal of the upper sideband and lower sideband signals obtained thereby; and a phase measuring circuit that compares the output signals of the third and fourth frequency mixing circuits and measures the phase of the signal under test with respect to the reference signal based on this comparison. is provided.

[For production]

In the phase measuring device of the present invention, the reference signal fo and the first oscillation signal fi (with frequency rl) are mixed in the first frequency mixing circuit to produce (fo + fl).
(or a signal of (fo − fl)), and furthermore, in the frequency mixing circuit of the second subsidy, (fo +
fl) signal (or (fo-fl) signal) and the second
oscillation signal f2 (frequency is f2) and (
fo + fl - f2) signal (or (fo + f
2-fl) signal) is inputted to the third and fourth frequency mixing circuits to obtain a signal (f2-11) (or (fl-f
Since the phase of the signal under test f with respect to the reference signal fo is measured by comparing the signals in 2),
Even if the frequency fo of the signal under test f fluctuates, the effect will not appear on the output side, and therefore highly accurate phase measurement is possible.

Furthermore, the device according to the present invention has a relatively complicated configuration.
Since no LL circuit or tracking oscillator is required, the configuration is relatively simple and the overall scale can be reduced.

〔Example〕

FIG. 1 shows in block form one embodiment of a phase measuring device according to the present invention.

In FIG. 1, reference numerals 3 and 4 are high-frequency amplifiers, each of which has a signal under test f input from terminal 1 (the frequency is
(=160MI(z)), the reference signal fo input from terminal 2 (the frequency is fo (-160M
Hz)) is amplified so that no phase fluctuation occurs. This phase variation is mainly caused by the amplifier gain and electrical wiring length, so when laying out the circuit, make sure that the wiring lengths of the reference signal system and the signal under test are as similar as possible, and that the characteristics It is necessary to select almost identical amplifiers.

5 is a frequency mixing circuit, which combines the frequency fo of the signal under test f inputted through the high frequency amplifier 3 and the output signal frequency (fo + fH-12) of the frequency mixing circuit 9 described later inputted through the distributor 11. and a frequency mixer 5a that mixes the upper sideband and lower sideband signals (fo±(fo+f1−fz)) obtained in the frequency mixer 5a.
), the upper sideband signal (fo +
filter 5 for removing fo + f+ - fz)
b It has a hole.

Similarly, 6 is a frequency mixing circuit, and a high frequency amplifier 4
The frequency f of the reference signal input via.

and the output signal frequency (fo + fx - fz) of the frequency mixing circuit 9, which will be described later, which is inputted through the distributor 11, and the upper sideband and lower sideband signals obtained in the frequency mixer 6a. (fo±(fo
+11-fz)), which is an unnecessary sideband signal (fo+fo+fl-fz).

Similarly, 7 is a frequency mixing circuit, and a high frequency amplifier 4
The frequency f of the reference signal input via.

and the oscillation signal f1 of the local oscillator 8 (frequency fl(=
20 MHz))
and a filter 7b for removing the lower sideband signal (fo-fl) which is an unnecessary sideband among the upper sideband and lower sideband signals (fo±f1) obtained in the frequency mixer 7a. .

Similarly, 9 is a frequency mixing circuit, which combines the output signal frequency (fo +11) of the frequency mixing circuit 7 and the local oscillator 1.
0 oscillation signal f2 (frequency fz (=20.1 MHz
)), and the upper sideband signal (fo + fl + fz).

11 is a divider, which outputs the output signal of the frequency mixing circuit 9 (
fo + fl-fz) to the frequency mixer 5a.

6a.

12 and 13 are analog-to-digital (A/D) converters that pulse the low frequency (fz - fs) beat signals obtained in the frequency mixing circuits 5 and 6, respectively, and a zero cross comparator. It is configured.

14 is a digital phase detection circuit having a sequential logic configuration, which compares the rising or falling positions of the pulse signals output from the A/D converters 12 and 13, and detects the signal under test based on this comparison. The phase difference between r and the reference signal fo is output in the form of a pulse having a width corresponding to the phase difference.

Therefore, since it is not related to the width of the pulses from the A10 converters 12 and 13, highly accurate phase detection can be performed.

15 is a pulse train circuit, and the phase detection circuit 14
The AND of the pulse having a width corresponding to the phase difference output from the local oscillator 10 and the oscillation signal f2 pulse of the local oscillator 10 is calculated.

Therefore, the pulse train circuit 15 outputs a pulse signal having the number of pulses corresponding to the phase difference.

Finally, a counter circuit 16 counts the number of pulses of the pulse signal output from the pulse train circuit 15 and outputs this counted value to a terminal 17. This count value represents the phase of the signal under test f with respect to the reference signal fo. Note that it is also possible to preferably connect a display device or the like to the terminal 17 so that the phase can be directly read.

A/D converters 12 and 13, phase detection circuit 14, pulse train circuit 15 and counter circuit 16 constitute a phase measurement circuit.

Next, the operation of the apparatus shown in FIG. 1 will be explained.

First, a signal under test r having a frequency fo and a reference signal fO are passed through high frequency amplifiers 3 and 4 to frequency mixing circuits 5 and 6, respectively.
is input. On the other hand, the reference signal fO is supplied to the frequency mixing circuit 7
is added to the oscillation signal f1 (fo + fl),
Further, the frequency mixing circuit 9 subtracts the oscillation signal f2 (
fo + fl - f2) and then input to the frequency mixing circuit 5.6 via the distributor 11.

In the frequency mixing circuits 5 and 6, the frequency (f
o + fl-f2) is subtracted from the signal under measurement of frequency fo (2) from the reference signal fo of two frequencies fo, and the signal of low frequency (f2-ft) is converted to a beat signal.

The converted low frequency beat signal is sent to an A/D converter 12,
The signal is pulsed at 13 and input to the phase detection circuit 14. The phase detection circuit 14 detects the signal under measurement f and the reference signal fo.
Detects the phase difference between the two and outputs it in the form of a pulse. This pulse is logically ANDed with the oscillation signal f2 pulse in the pulse train circuit 15, and is input to the counter circuit 16. Counter circuit 16 counts the number of pulses from pulse train circuit 15 and outputs this count value as a signal representing the phase.

In this way, the extremely high frequency fO of the signal under test f
Phase measurements can be made without being affected by

Further, in this embodiment, since the output processing is performed digitally, it is extremely convenient when a computer is connected to the output terminal 17.

In this embodiment, the oscillation signal f of the local oscillator 10 is used as the pulse signal input to the pulse train circuit 15.
2 (20,1MHz), but it is not limited to that, for example, the oscillation signal fx (20Mllz) of the local oscillator 8
, a reference signal fo (160MHz) may be used.

When the reference signal fo is used, the phase measurement accuracy is further improved.

〔Effect of the invention〕

According to the present invention, the scale can be reduced with a relatively simple configuration, and phase measurement can be performed with high accuracy without being affected by frequency fluctuations of the signal under test.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a phase measuring device according to the present invention, and FIG. 2 is a block diagram showing an example of a conventional phase measuring device. 3.4...High frequency amplifier, 5.6,7,9...Frequency mixing circuit, 8.10...
Local oscillator, 12, 13... A/D converter, 14.
...Phase detection circuit, 15...Pulse train circuit, 16...Counter circuit, f...Measurement signal, fO...Reference signal, f
l p f2...Local oscillation signal.

Claims (1)

[Claims] A local oscillator that outputs a first oscillation signal, a reference signal and the first oscillation signal, and one of an upper sideband signal and a lower sideband signal obtained thereby. a first frequency mixing circuit that outputs a sideband signal; and a second frequency mixing circuit that has a frequency different from the frequency of the first oscillation signal.
a local oscillator that outputs an oscillation signal, mixes the output signal of the first frequency mixing circuit and the second oscillation signal, and mixes the first oscillation signal of the upper sideband and lower sideband signals obtained thereby. A second frequency mixing circuit outputs a sideband signal on a sideband side different from the sideband signal outputted by the frequency mixing circuit, and mixes the signal under test with the output signal of the second frequency mixing circuit, thereby A third frequency mixing circuit outputs the lower sideband signal of the obtained upper sideband and lower sideband signals, and mixes the reference signal and the output signal of the second frequency mixing circuit, thereby generating the obtained signal. A fourth frequency mixing circuit that outputs the lower sideband signal of the upper sideband and lower sideband signals to be compared with the output signals of the third and fourth frequency mixing circuits, and based on this comparison, the frequency mixing circuit outputs the lower sideband signal. A phase measuring device comprising a phase measuring circuit that measures the phase of a measurement signal with respect to the reference signal.