JPS58153420A - Phase locked loop - Google Patents

Abstract

PURPOSE:To lock stably a titled loop even when input frequency is sharply changed by providing a frequency voltage converter having I/O characteristics reverse to that of a voltage controlling oscillator in the phase locked loop. CONSTITUTION:An input signal 20 is inputted to the voltage controlling oscillator 24 through a phase comparator 21, an adder 22 and a compensation filter 23 and an output signal from the oscillator 24 is inputted to the other input of the phase comparator 21 to constitute a feedback loop. The input signal 20 is also inputted to a frequency voltage converter 25 having the I/O characteristics reverse to that of the oscillator 24 and an output signal from the converter 25 is inputted to an adder 22 through a low-pass filter 26. When the input signal 20 is sharply different from the output signal 27 in frequency, the frequency 27 of the voltage controlling oscillator 24 can be brought close to the input signal 20 by the output of the frequency voltage converter 25. Thus the titled loop can be stably locked.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention This invention relates to a phase-locked loop.
Ru.

TECHNICAL BACKGROUND OF THE INVENTION A phase-locked loop is generally a phase feedback circuit consisting of a phase comparator, a compensation filter, and a voltage controlled oscillator, and its configuration is shown in FIG.

The input signal 10 and the output signal 14 of the voltage controlled oscillator 13 are input to the phase comparator 11, and the phase difference between these two input signals passes through the compensation filter 12, and the output signal 14 of the voltage controlled oscillator 13 is input to the phase comparator 11.
1tll, the phase of the output signal 14 is locked to the phase of the input signal 100.

Problems with the Background Art However, if the frequencies of the output signal 14 and the input signal 100 are significantly offset, the output signal 14 may be locked by harmonics or subharmonics of the input signal 10, and furthermore, it may become impossible to lock the input signal 10. There may be oscillations unrelated to signal 10.

ql! - Tsuji 61 This invention was made in consideration of Kami Ayu's point Kli, and its purpose is to provide a phase-locked loop that stably locks even when the input frequency changes greatly.

Summary of the invention That is, the present invention provides a frequency-voltage converter having input/output characteristics opposite to that of a phase-locked loop voltage controlled oscillator, converts an input signal into a voltage corresponding to the frequency, and converts the resulting frequency-voltage converted signal. is added to the phase difference signal between the input signal and the voltage-controlled oscillator output after passing through a low-pass filter, and the added output is supplied to the voltage-controlled oscillator.

Embodiments of the invention will now be described in detail with reference to the drawings. No. 211 shows an embodiment of the present invention. The input signal 20 is subjected to a phase comparison 821 and a voltage conversion a2BK. The output of the phase comparator 21 passes through an adder 22 and a compensation filter 23 and is input to the voltage controlled oscillation 1) 24, and this output signal 27
is another input of the phase comparator 21, and the return li
It forms a loop. On the other hand, the output of the interwave number voltage converter 25 is input to the adder 22 through a low-pass filter 26 . ζ Here, it is assumed that the input/output characteristics of the frequency-voltage converter 25 are reverse to the input/output characteristics of the voltage control generator @924. In other words, when the output of the frequency-voltage converter s25 is input to the voltage-controlled oscillator 24, the frequency-voltage converter 25 establishes a relationship in which the input signal frequency of the frequency-voltage converter 25 and the output signal station frequency of the voltage-controlled oscillator 24 are the same. It is assumed that the voltage controlled oscillator 24 has the following.

Next, a description will be given of an operation in which the phase-locked loop locks when the frequencies of the input signal 20 and the output signal 27 are largely offset.

FIG. 3 shows the output of the phase comparator 821 in the present invention. The input signal 20 is input to a phase comparator 21,
Its output adds up to $22. It is applied to a voltage controlled oscillator 24 through a compensation filter 23.

However, if the frequencies tlLa of the input signal 20 and the output signal 27 are largely offset, the output 28 of the phase comparator 21 reciprocates between positive and negative at a high frequency, as shown in FIG. Therefore, when this output 28 passes through the adder 22 and the compensation filter 23, it becomes a very small signal due to the high kaP wave characteristics of the compensation filter 23, and has almost no influence on the voltage controlled oscillator. On the other hand, the output of the wave number voltage exchanger 25 is applied to the voltage controlled oscillator 24 through the low pass filter 126, the adder 22, and the compensation filter 23, so the output signal station wave number approaches the frequency of the input signal 20, and finally enters the phase-locked-loose capture range and becomes locked.

The low-pass filter 26 filters the high-frequency component of the output of the 1-frequency voltage converter 25 when the phase-locked loop is locked, and eliminates the influence of the frequency-voltage converter 825 on the high-frequency characteristics of the 41# return loop. It is meant not to give.

Effects of the Invention With this 5KL, it becomes possible to stably lock the phase locked/loose from an unlocked state. Furthermore, even if the input signal frequency suddenly changes and the lock is lost, it is possible to stably lock it again in the same way. In the present invention, the same effect can be obtained even if a motor is used in place of the voltage controlled oscillator 24. Since voltage controlled oscillators and motors generally have a linear relationship between input voltage and oscillation frequency, it is also advantageous that a linear frequency-to-voltage converter can be used.

The fourth @ is another embodiment of the present invention. In this example, the compensation filter 23 is located immediately after the phase comparator 21, but the same effect can be obtained in this case as well.

[Brief explanation of the drawing]

Figure 11 shows the configuration of the conventional 7A's locked and loose system.
FIG. 2 is a block diagram of one embodiment of the present invention, FIG. 3 is a waveform of an output signal of a phase comparator in one embodiment of the present invention, and FIG. 4 is another embodiment of the present invention. 10... Input signal, 11... Phase comparator, 12...
・Voltage controlled oscillator, 14... Output signal, 20... Input signal, 21... Phase comparator, 22... X adder, 2
3... Compensation filter, 24... Voltage controlled oscillator, 2
5... Frequency voltage converter, 26... Low pass filter. Agent: Patent attorney: Yu Chika Maro (and 1 other person) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a phase-locked loop, the phases of an input signal and an output signal of a voltage-controlled oscillator are compared and the obtained phase difference signal is supplied to a voltage-controlled oscillator via a compensation filter. A frequency-to-voltage converter with opposite input/output characteristics is provided to convert the input signal into nine voltages corresponding to the frequency, and the resulting nine-frequency voltage conversion signal is passed through a low-pass filter and then added to the phase difference signal. 7 A's Locked Loop.