JPH05346446A - Phase meter - Google Patents

Abstract

PURPOSE:To obtain a phase meter for measuring phase accurately and stably by automatically selecting an appropriate phase measuring range depending on the phase difference of input signal. CONSTITUTION:The phase meter for measuring the phase difference between two signals to be measured applied on input terminals 10, 20 comprises an exclusive OR circuit 1 for switching two overlapping phase measuring ranges of 0-360 deg. and 180 deg.--l80 deg., a first phase measuring system (10-15, 20-25) having discontinuous point in each phase measuring range, and a second phase measuring system (2-4) including an AND circuit 2 having no discontinuous point in phase-output voltage characteristics. Output from the second phase measuring system is fed back to the exclusive OR circuit 1 and a stably operable phase measuring range is automatically selected among phase measuring ranges of first phase measuring system thus avoiding measurement error or instable operation due to discontinuous point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase measuring apparatus suitable for measuring phase characteristics of audio equipment, transmission circuits, etc., and measuring a phase difference between two signals having the same frequency.

[0002]

2. Description of the Related Art In the field of audio equipment, digitization has advanced, and high fidelity recording / reproduction / transmission has become possible, and a phase measuring device, which is one of the devices for measuring these characteristics, can be operated. It is desired that the property is simple and stable and can be measured accurately.

An example of a conventional phase measuring device is shown in FIG. 4, in which voltage comparators 11 and 21 for converting a signal under measurement applied to two input terminals 10 and 20 into a square wave and respective voltage comparators. vessel
The outputs of 11 and 21 are applied to the respective clock input terminals CK via the inverter circuits 12 and 22, respectively, and the first D flip-flop circuit 13 and the D flip-flop circuits 13 and 23.
Switches 14 and 24 which are opened and closed by the Q output and -Q output (inversion of the Q output) and which connect the positive reference voltage source 15 or the negative reference voltage source 25 to the low frequency reactor wave wave 1.

Each of the D input terminals of the two D flip-flop circuits 13 and 23 has a power supply V _D so that the logic level H is always maintained.
Connected to the first D flip-flop circuit 13
Of the second D flip-flop circuit 23 is connected to the reset terminal -R (negative logic) of the second D flip-flop circuit 23.
The -Q output of the flop circuit 23 is connected to the reset terminal -R of the first D flip-flop circuit 13.

These two D flip-flop circuits 13,
The circuit formed by 23 constitutes a so-called set / reset type flip-flop circuit, and the clock input terminal CK of the first D flip-flop circuit 13 serves as a set terminal, and the circuit of the second D flip-flop circuit 23 The clock input pin CK becomes the reset pin.

Next, the operation of the phase measuring apparatus shown in FIG. 4 will be described with reference to the waveform chart of FIG.

When the signals under test (a1, a2) having the same frequency for which the phase difference is to be measured are applied to the two input terminals 10 and 20, the square wave is generated by the voltage comparators 11 and 21 which operate as a zero-crossing detector. (b1, b2) and inverted by the inverter circuits 12 and 22 that perform the waveform shaping operation.
1, c2) and two D flip-flop circuits 13 and 23
Are applied to the respective clock input terminals CK.

The first D flip-flop circuit 13 is set at the rising edge of the output signal (c1) of the inverter circuit 12, and the second D flip-flop circuit 13 is set at the rising edge of the output signal (c2) of the inverter circuit 22. Of the flip-flop circuit 23
At the falling edge of the Q output, the first D flip-flop circuit 13 is reset.

In this way, the phase difference between the signals under test (a1, a2) applied to the two input terminals 10, 20 is determined by the pulse width of the Q output signal generated from the first D flip-flop circuit 13. Is converted to. The cycle of this Q output signal is 2
It is the same as the cycle of the signals under test (a1, a2) applied to the two input terminals 10 and 20.

The first D flip-flop circuit
It is also possible to obtain a DC output proportional to the pulse width, that is, the phase difference by directly guiding the Q output signal of 13 to the low-pass wave reactor 8 and averaging it, but it is generated from the D flip-flop circuit 13. Since the amplitude of the Q output signal varies and is not constant, in order to improve the measurement accuracy, a positive reference voltage source
15 or a negative reference voltage source 25 is provided, and by the Q output signal and -Q output signal of the first D flip-flop circuit 13,
By opening and closing the two switches 14 and 24 and guiding the positive reference voltage Vr or the negative reference voltage -Vr to the low-range reactor wave device 1 and averaging,
An accurate and stable DC output proportional to the pulse width, that is, the phase difference, can be obtained at the output terminal 9 as shown in FIG.

[0011]

In such a conventional phase measuring apparatus, (1) the phase difference between the two signals under measurement (a1, a2) is infinitely zero.
When it approaches 0 ° or 360 °, it becomes unstable due to noise and jitter of the measurement system, and a stable output voltage cannot be obtained. That is, the output voltage Vr with a phase difference of 360 ° and the output voltage -Vr with a phase difference of 0 ° appear in FIG. 6 and measurement becomes impossible.

(2) When the inverter circuits 12 and 22 are changed to buffer circuits, the characteristics shown in FIG. 6 can be changed to an output voltage Vr having a phase difference of 180 ° and an output voltage -Vr having a phase difference of −180 °. It is possible to stably measure the phase difference near 0 ° or 360 °, but it becomes impossible to measure the phase difference −180 ° or 180 °.

(3) The second inverter circuit 22 is changed to a 2-input exclusive OR circuit, and one input terminal of this exclusive OR circuit is used as a control terminal, and the exclusive OR circuit is used as an inverter or a buffer. When the measurement value is unstable or inaccurate when configured so that it can operate, the problems of (1) and (2) above can be solved by controlling the phase measurement range with the control terminal. Therefore, it is difficult to automatically control in the device.

Therefore, the present invention has been conceived in order to solve such a conventional problem, and an appropriate phase measurement range is automatically selected according to the phase difference of the input signals, so that it is accurate and stable. The purpose is to obtain a device that can perform various phase measurements.

[0015]

[Means for Solving the Problem] The phase measurement range is 0 ° to 3
A first phase measurement system having two phase measurement ranges overlapping 60 ° or −180 ° to 180 ° and having a discontinuity point in this measurement range, and no discontinuity point in the phase difference vs. output voltage characteristic. It comprises a second phase measuring system and means for selectively controlling the phase measuring range of the first phase measuring system based on the output of the second phase measuring system.

[0016]

With this configuration, the phase measurement range of the first phase measurement system can be made into two ranges, and the phase measurement of the first phase measurement system can be performed based on the output of the second phase measurement system. Since the range is automatically selected, stable and accurate measurement can be performed over the entire phase measurement range of 0 ° to 360 ° by utilizing the range in which stable measurement is possible within each range.

[0017]

EXAMPLE As shown in FIG. 1, a voltage comparator 1 for converting a signal under measurement applied to two input terminals 10 and 20 into a square wave.
1, 21 and the output of the first voltage comparator 11 are the inverter circuit 1
The first D applied to the clock input terminal CK via 2
The second D flip-flop circuit 23, in which the output of the flip-flop circuit 13 and the second voltage comparator 21 is applied to the clock input terminal CK via the exclusive OR circuit 1, and the first D flip circuit A switch that is opened / closed by the Q output and -Q output of the flop circuit 13 and connects the positive reference voltage source 15 or the negative reference voltage source 25 to the first low-pass reactor 8
It has 14 and 24.

Each of the D input terminals of the two D flip-flop circuits 13 and 23 has a power supply V _D so that the logic level H is always maintained.
Connected to the first D flip-flop circuit 13
Of the second D flip-flop circuit 23 is connected to the reset terminal -R (negative logic) of the second D flip-flop circuit 23.
The -Q output of the flop circuit 23 is connected to the reset terminal -R of the first D flip-flop circuit 13.

Further, an AND circuit 2 for obtaining the logical product of the outputs of the two voltage comparators 11 and 21 is provided, and the output of this AND circuit 2 is passed through the second low-pass wave reactor 3 to the third voltage The voltage comparator 4 is connected to the comparator 4. The output of the voltage comparator 4 is connected to the measurement range information output terminal 5 and the other input terminal of the exclusive OR circuit 1.

These two D flip-flop circuits 1
The circuit formed by 3 and 23 constitutes a set / reset type flip-flop circuit, and includes a first D flip-flop circuit.
The clock input terminal CK of the flop circuit 13 serves as a set terminal, and the clock input terminal CK of the second D flip-flop circuit 23 serves as a reset terminal.

Next, the operation of the phase measuring apparatus shown in FIG. 1 will be described with reference to the waveform chart of FIG.

When the signals under test (a1, a2) having the same frequency for which the phase difference is to be measured are applied to the two input terminals 10 and 20, the duty ratio is changed by the voltage comparators 11 and 21 which operate as a zero-crossing detector. Two square waves (b
1, b2), and one of the square waves (b1) is inverted by an inverter circuit 12 that performs a waveform shaping operation to generate a square wave (c
1), which is applied to the clock input terminal CK of the first D flip-flop circuit 13.

While the exclusive OR circuit 1 performs the waveform shaping operation, the output of the third voltage comparator 4 is
At the logic level L, it operates as a buffer and outputs the signal (c22) having the same waveform as the output (b2) of the second voltage comparator 21 to the second
Applied to the clock input terminal CK of the D flip-flop circuit 23, and when the output of the third voltage comparator 4 is at the logic level H, the exclusive OR circuit 1 operates as an inverter and the inverted waveform Signal (c21) is applied to the clock input terminal CK of the second D flip-flop circuit 23.

Two D flip-flop circuits 13 and 23
Operates as a set / reset type flip-flop circuit, and therefore, when the output of the third voltage comparator 4 is at the logic level H, the first D flip-flop circuit 13
Is set at the falling edge of the output signal (b1) of the first voltage comparator 11, and the falling edge of the output signal (b2) of the second voltage comparator 21 (the output signal of the exclusive OR circuit 1).
It is reset at the rising edge of (c21) and outputs the signal of waveform (d11).

On the other hand, when the output of the third voltage comparator 4 is at the logic level L, the first D flip-flop circuit
13 is the falling edge of the output signal (b1) of the first voltage comparator 11 (the rising edge of the output signal (c1) of the inverter circuit 12)
The rising edge of the output signal (b2) of the second voltage comparator 21 (the output signal of the exclusive OR circuit 1)
It is reset at the rising edge of (c22) and outputs the signal of waveform (d12).

That is, as shown in the characteristic diagram of the input phase difference vs. the output voltage in FIG. 3A, when one input terminal of the exclusive OR circuit 1 is controlled by the logic level H, the input A discontinuity occurs at the phase difference 0 ° and 360 ° of the signals under measurement (a1, a2) applied to terminals 10 and 20,
The phase difference from 180 ° is converted into the pulse width of the Q output signal generated from the first D flip-flop circuit 13.

On the other hand, when one input terminal of the exclusive OR circuit 1 is controlled by the logic level L, the signal under test (a) applied to the input terminals 10 and 20 is
Phase difference of 1 and a2) -Discontinuity points are generated at -180 ° and 180 °, and the phase difference from 0 ° is converted into the pulse width of the Q output signal generated from the first D flip-flop circuit 13. .. The cycle of the Q output signal generated from the first D flip-flop circuit 13 is the same as the cycle of the signals under test (a1, a2) applied to the two input terminals 10 and 20.

When the AND circuit 2 obtains the logical product of the signals output from the two voltage comparators 11 and 21, it is possible to obtain a signal having a waveform shown in FIG. When the averaging is performed by the reactor wave 3, a signal corresponding to the phase difference of the characteristic shown in FIG. 3B is obtained, and two signals under measurement (a1, a
The output voltage increases as the phase difference in 2) approaches 0 ° or 360 °.

According to the phase difference measuring circuit composed of the AND circuit 2, for example, equal voltages are output at 90 ° and 270 °. Therefore, it is inconvenient as a phase difference measuring device to use this circuit alone, but There is an advantage that a discontinuity does not occur in the output voltage having a phase difference of 0 ° and 360 °.

The output of the second low-pass wave reactor 3 is applied to the third voltage comparator 4, and the phase difference of the signals under test (a1, a2) is about 90.
The third voltage comparator 4 is caused to perform a comparison operation at a level of ° or 270 °. The logic level H is output from the third voltage comparator 4 in the phase difference range of about 90 ° to 270 °,
A comparison operation with hysteresis is performed so as to output the logic level L in the range of about 0 ° to 90 ° and 270 ° to 360 °.

By applying the output of the third voltage comparator 4 to one input terminal of the exclusive OR circuit 1, an unstable operation point near 0 ° and 360 ° in the phase measurement range of 0 ° to 360 °, And -180 ° and 1 in the phase measurement range -180 ° to 180 °
It is possible to operate so that no DC output is generated at an unstable operation point near 80 °, and a stable phase difference measurement output can be obtained at the output terminal 9.

Since the state of the selected phase measurement range is generated at the measurement range information output terminal 5, an accurate phase difference can be obtained from the information of the range state and the output voltage of the output terminal 9.

[0033]

As is apparent from the description based on the above embodiments, according to the phase measuring apparatus of the present invention, (1) 0 ° to 360 ° is provided by providing the exclusive OR circuit 1 which performs the inverter operation or the buffer operation.
It is possible to realize two measurement ranges, in which the measurement ranges overlap with each other, that is, ° and −180 ° to 180 °.

(2) By providing the AND circuit 2 and the low frequency wave reactor 3, it is possible to realize a second phase measuring circuit which is simple and has no discontinuity in the voltage output. The output of the voltage comparator 4 that compares the output of the device 3 with the reference voltage can be used to determine which range is selected.

(3) By returning the output of the voltage comparator 4 to the exclusive OR circuit 1 to control the phase measurement range, automatic range selection becomes possible. Since only the range that operates stably is automatically selected, it is possible to avoid a measurement error or an unstable operation due to the discontinuous point.

(4) Since a relatively inexpensive and simple circuit such as an exclusive OR circuit, an AND avoidance circuit, a low frequency wave reactor, and a voltage comparator is added, the measurement accuracy can be increased without increasing the cost of the entire apparatus. The excellent phase measurement of can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a phase measuring device of the present invention,

FIG. 2 is a waveform diagram for explaining the operation of the device shown in FIG.

3 is a characteristic curve diagram showing the relationship between the phase difference and the output voltage for explaining the operation of the device shown in FIG.

FIG. 4 is a block diagram showing an example of a conventional phase measuring device,

5 is a waveform chart for explaining the operation of the apparatus shown in FIG.

FIG. 6 is a characteristic curve diagram showing the relationship between the phase difference and the output voltage for explaining the operation of the device shown in FIG.

[Explanation of symbols]

 1 Exclusive OR circuit 2 AND circuit 3, 8 Low-pass filter 4 Voltage comparator 5 Measurement range information output terminal 9 Phase difference output terminal 10, 20 Input terminal 11, 21 Voltage comparator 13, 23 D flip-flop circuit 14 ， 24 switch 15,25 Reference voltage source

Claims (1)

[Claims] 1. A first phase measurement system having two phase measurement ranges in which the phase measurement ranges overlap, and a first phase measurement system having a discontinuity point in the measurement ranges, and a first phase measurement system having no discontinuity point in the phase difference vs. output voltage characteristic. A phase measuring apparatus comprising: a second phase measuring system; and means for selectively controlling a phase measuring range of the first phase measuring system based on an output of the second phase measuring system.