JP2595523B2 - Measurement device for transfer characteristics of phase-locked oscillator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring transfer characteristics of a phase locked oscillator, and more particularly to an apparatus for measuring input / output transfer characteristics.

〔Overview〕

The present invention provides an apparatus for measuring transfer characteristics of a phase-locked oscillator, comprising: measuring a control input of a voltage-controlled oscillator that generates an input signal of the phase-locked oscillator; and a control input of a voltage-controlled oscillator in the phase-locked oscillator. It measures the transfer characteristics accurately with a simple configuration.

[Conventional technology]

Conventionally, the measurement of the transfer characteristic of a phase locked oscillator has been performed by the configuration shown in FIG.

First, the phase-locked oscillator 3 includes a phase comparison circuit 4 to which a comparison signal is input, a loop filter circuit 5 to which an output of the phase comparison circuit 4 is input, and a voltage-controlled oscillator using the output of the loop filter circuit 5 as a control input. 6 form a synchronous loop, and the output of the voltage controlled oscillator 6 is taken out as a phase locked output.

To measure the transfer characteristic of the phase-locked oscillator 3, the output of the modulation signal generator 8 is used as the control input of the voltage-controlled oscillator 2, and the output of the voltage-controlled oscillator 2 is given as the comparison signal of the phase-locked oscillator 3. The output of the voltage-controlled oscillator 2 and the output of the voltage-controlled oscillator 6 of the phase-locked oscillator 3 are observed by the waveform observer 9, and how the input phase-modulated signal changes as the output signal of the phase-locked oscillator to be measured. Was measured.

[Problems to be solved by the invention]

However, in the above-described conventional measurement method, the transfer characteristic must be measured in a form modulated to the output frequency of the phase-locked oscillator 3 to be measured, and the measured amount depends on the modulated waveform. Because the observation has only means to read the amount of phase fluctuation on the oscilloscope, the measurement accuracy is poor,
In particular, it was difficult to measure the phase difference.

SUMMARY OF THE INVENTION An object of the present invention is to provide a measuring device that can easily increase the measuring accuracy with a simple measuring system by a novel measuring method.

[Means for solving the problem]

The present invention relates to an apparatus for measuring a transfer characteristic of a phase locked oscillator including a phase comparison circuit, a loop filter circuit, and a first voltage controlled oscillator in a locked loop, wherein an oscillation output is provided to a comparison input of the phase comparison circuit. And a means for measuring the amplitude and phase difference between the control input of the second voltage controlled oscillator and the control input of the first voltage controlled oscillator in the phase locked oscillator. And

[Action]

A control input of a voltage-controlled oscillator that outputs a comparison signal to the phase-locked oscillator and a control input of a voltage-controlled oscillator in the phase-locked oscillator are observed with an amplitude and phase measuring device.

Since the control inputs of the two voltage controlled oscillators are in a proportional relationship with the phase variation amounts θ ₀ and θ _{1 of} the comparison signal and the output signal that determine the transfer characteristics of the phase locked oscillator, the amplitudes of the two voltage controlled inputs and By obtaining the phase ratio, the transfer characteristic H of the phase locked oscillator can be obtained.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the measurement principle of the present invention will be described with reference to FIG.

The transfer characteristics of the phase-locked oscillator include the amount of phase fluctuation at point A, which is the comparison input of the phase-locked loop, and the output B
It is indicated by the ratio of the phase fluctuation amount at the point. That is, if the phase at point A is θ ₁ and the phase at point B is θ ₀ , the transfer characteristic H
Is H = θ ₀ / θ ₁ .

Here, the output of the voltage controlled oscillator 6 is θ ₀ and B ′
Assuming that the control value at the point is V ₀ , the phase is the integral of the frequency, so θ ₀ is proportional to (1 / s) V ₀ . Further, the voltage controlled oscillator 2 is considered before the point A, and its control input A '
When the control value is V _1, likewise theta ₁ is proportional to ₍₁ / s) V 1.

Therefore, the transfer characteristic H can be obtained by measuring V ₀ / V ₁ instead of measuring θ ₀ / θ ₁ .

V ₁ and V ₀ is the signal amplitude of the frequency itself of the transfer characteristic to be measured, because it is a phase amount, easily transfer characteristics can be obtained by measuring this signal directly.

 Next, FIG. 1 shows a configuration diagram of an embodiment of the present invention.

The low frequency oscillator 1 outputs the frequency of the transfer characteristic to be measured, and outputs this output signal to the voltage controlled oscillator 2. The output of the voltage controlled oscillator 2 is input to the comparison input of the phase locked oscillator 3. Phase locked oscillator 3
Constitutes a synchronous loop including a phase comparison circuit 4, a loop filter circuit 5, and a voltage controlled oscillator 6, and extracts an output of the voltage controlled oscillator 6 as a phase locked oscillation output.

The transfer characteristic of the phase locked oscillator 3 is measured by measuring the amplitude of the output of the low frequency oscillator 1, ie, the control input of the voltage controlled oscillator 2, and the output of the loop filter circuit 5 of the phase locked oscillator 3, ie, the control input of the voltage controlled oscillator 6. And input to the phase measuring device 7. An amplitude and phase measuring device 7 measures the transfer characteristic of the phase locked oscillator 3 by measuring the ratio of the control inputs of the two voltage controlled oscillators 2 and 6.

〔The invention's effect〕

As described above, according to the present invention, the transfer characteristic of the phase-locked oscillator can be measured with the signal of the frequency component.
There is an effect that measurement accuracy can be easily increased with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention. FIG. 2 is a block diagram showing the principle of the present invention. FIG. 3 is a diagram showing a configuration of a conventional example. 1 low frequency oscillator, 2, 6 voltage controlled oscillator, 3
... A phase locked oscillator, 4... A phase comparison circuit, 5... A loop filter circuit, 7... An amplitude and phase measuring device, 8... A modulated signal generator, 9.

Claims (1)

(57) [Claims] An apparatus for measuring transfer characteristics of a phase locked oscillator (3) including a phase comparison circuit (4), a loop filter circuit (5), and a first voltage controlled oscillator (6) in a locked loop. A second voltage-controlled oscillator (2) for providing an oscillation output to a comparison input of the phase comparison circuit; a control input of the second voltage-controlled oscillator; and control of the first voltage-controlled oscillator in a phase-locked oscillator Means for measuring an amplitude and a phase difference from an input.