JPH0344214A - Circuit for preventing indefinite phase at momentary interrupt of input reference signal in phase synchronizing oscillation circuit - Google Patents

Abstract

PURPOSE:To prevent a phase of a reference signal in its own station from being deviated early by using a signal from a closed loop circuit of a phase synchronizing oscillation circuit in place of an input reference signal for the time being at the momentary interrupt of the input reference signal of a transmission line. CONSTITUTION:When a reference signal is momentarily interrupted due to the disturbance of a transmission line, it is detected by an input momentary restoration detection control circuit 5 to allow a selection circuit 2 to select an output from an inverting circuit 4 and a reset circuit 6 resets a counter of an input frequency division circuit 1 for the preparation of restoration. A signal extracted from a phase synchronizing oscillation circuit 3 is inverted by the inversion circuit 4, its output signal is given to the phase synchronizing oscillation circuit 3 via the selection circuit 2 to allow the signal to act like an input reference signal IN of a master station tentatively. Thus, when the phase synchronizing oscillation circuit 3 is available for self-running, because of the presence of the signal from the inverting circuit 4, a comparatively longer time is required for the occurrence of a phase shift.

Description

[Detailed Description of the Invention] [Summary] A circuit for preventing phase instability during instantaneous interruption of an input reference signal in a phase synchronized oscillator circuit used to synchronize the reference signal of its own station with the input reference signal sent via a transmission line. Regarding the frequency of the reference input signal, the purpose is to prevent the phase of the output of the phase synchronized oscillator circuit from significantly deviating from the phase before the momentary interruption even if a momentary interruption of the input reference signal occurs in the transmission path. an input frequency divider circuit that converts the reference hexagonal signal into a desired frequency; a selection circuit that switches the circuit upon momentary interruption or restoration of the reference hexagonal signal; and a reference signal output from the input frequency divider circuit that is manually inputted via the selection circuit; a phase-locked oscillation circuit that generates a reference signal in synchronization with the reference signal frequency; an inversion circuit that inverts the output of the closed-loop circuit of the phase-locked oscillation circuit and inputs the output signal to the selection circuit; and the reference input signal. Detects instantaneous interruption or restoration of
and an input instantaneous interruption/recovery detection control circuit that controls the reset of the input frequency divider circuit and the switching of the selection circuit.

[Industrial application field]

The present invention relates to a circuit for preventing phase instability during instantaneous interruption of an input reference signal in a phase synchronized oscillator circuit used to synchronize a reference signal of its own station with an input reference signal sent via a transmission path.

[Conventional technology]

A conventional phase synchronized oscillation circuit will be explained with reference to FIG.

In the figure, reference numeral 11 denotes an input frequency dividing circuit that divides the frequency of the input reference signal IN sent from the mask station via the transmission line in order to synchronize the reference signal within the own station. Then, a phase comparison circuit 13, a low-pass filter 14, a voltage controlled oscillator 1
5 and the frequency divider circuit 16 to form a phase-locked oscillator (PLO) 1.
7.

Therefore, the human reference signal IN, for example, a 6J12MHz or 1.544Hz signal, sent from the mask station via the transmission line is converted to 1.
The frequency is divided by /789 or 1/193 and converted to 8KHz. This 8 KHz reference signal is compared in the phase comparison circuit 13 with a signal obtained by dividing the output of the voltage controlled oscillator 15 by a frequency dividing circuit 16 and half a period earlier.

The phase difference between the signals compared by the phase comparison circuit 13 is:
It is converted to a voltage level by a low pass filter 14. Then, the oscillation frequency of the voltage controlled oscillator 15 is controlled by this voltage level to generate a reference signal within the local station that is synchronized with the input reference signal IN sent from the mask station.

In this manner, the phase synchronized oscillation circuit 17 can always generate a reference signal within its own station that is synchronized with the human-powered reference signal IN of the mask station.

[Problem to be solved by the invention]

However, if there is some kind of disturbance in the transmission path,
The human reference signal may be momentarily interrupted. In such a case,
Since the phase-locked oscillator circuit runs free, it gradually becomes out of synchronization with the input reference signal IN of the mask station as time passes.

An object of the present invention is to prevent the phase of the output of a phase synchronized oscillation circuit from significantly shifting from the phase before the instantaneous interruption even when a momentary interruption of a human input reference signal occurs in a transmission path.

[Means to solve the problem]

FIG. 1 is a block diagram of the principle of the present invention.

In FIG. 1, an input frequency divider circuit 1 converts the frequency of an input reference signal IN input via a transmission line to a desired frequency. The selection circuit 2 switches the circuit when the input reference signal is momentarily interrupted or restored. The signal output from the input frequency divider circuit 1 is input to the phase synchronized oscillation circuit 3 via the selection circuit 2, and the phase synchronized oscillation circuit 3 generates a reference signal phase-synchronized with the input reference signal IN. The inversion circuit 4 inverts the output of the phase synchronized oscillation circuit 3 and inputs the output signal to the selection circuit 2.

The input instantaneous interruption/recovery detection control circuit 5 includes a reset circuit 6 that detects an instantaneous interruption or restoration of the input reference signal and resets the input frequency dividing circuit 1, and an output signal of the input frequency dividing circuit 1 and an inverting circuit. 4 and the selection circuit 2 which switches between the four output signals.

[For production]

The operation of the present invention will be explained with reference to the principle block diagram shown in FIG.

The input reference signal transmitted from the mask station is frequency-divided to 8KHz by the input frequency divider circuit 1, and when there is no momentary interruption in the input reference signal on the transmission path, the input reference signal is divided by the input frequency division circuit 1.
The output from puts the selection circuit 2 in its normal position. Therefore, the frequency-divided 8 KHz reference signal passes through the selection circuit 2 as it is and is input to the phase synchronized oscillation circuit 3. This phase synchronized oscillation circuit 3 generates a reference signal within its own station that is phase synchronized with the human reference signal IN of the mask station.

When the input reference signal is momentarily interrupted due to a disturbance in the transmission path, this is detected by the input momentary interruption/recovery detection control circuit 5, and the selection circuit 2 selects the output from the inverting circuit 4. The reset circuit 6 resets the counter of the input frequency divider circuit 1 in preparation for recovery.

The signal taken out from the phase-locked oscillator circuit 3 is inverted by an inverter 4, and the output signal is given to the phase-locked oscillator circuit 3 via the selection circuit 2, and -temporally serves as the input reference signal IN of the mask station. fulfill. For this reason, even if the phase synchronized oscillation circuit 3 is allowed to run freely, it will take a relatively long time until a phase shift occurs because of the presence of the signal from the inversion circuit 4.

When the disturbance in the transmission path disappears and the transmission path is restored, the instantaneous input interruption/recovery detection control circuit 5 detects this and returns the selection circuit 2 to its original normal state.

As described above, when the input reference signal is momentarily interrupted, the phase synchronized oscillation circuit 3 operates by temporarily regarding the output of the inversion circuit 4 as the input reference signal IN.

〔Example〕

FIG. 2 shows an embodiment of a circuit for preventing phase instability at the time of instantaneous interruption of an input reference signal in a phase synchronized oscillation circuit according to the present invention.

In FIG. 2, numerals 11, 13 to 17 correspond to those in FIG. 3, so their explanation will be omitted.

The selection circuit 12 switches the circuit depending on whether there is a momentary interruption of the input reference signal in the transmission line or when the input reference signal is restored.

The inversion circuit 18 inverts the closed loop signal of the phase synchronized oscillation circuit 17 by 180°, and the inverted output signal is input to the selection circuit 12.

The differentiating circuit 19 detects the rising edge of the output signal of the inverting circuit 18, differentiates the rising edge, and converts this pulse into A.
Output to the ND circuit 20. The input instantaneous interruption/recovery detection control circuit 21 detects an instantaneous interruption or restoration of the input reference signal in the transmission path, and selects the output of the inversion circuit 18 at momentary interruption of the input reference signal to be input to the phase synchronized oscillation circuit 17. circuit 12
Select. Thereafter, when the transmission path is restored, this is detected and the selection circuit 12 is switched to its original position.

Furthermore, when the input reference signal is momentarily interrupted, this is detected and input to the AND circuit 20. Along with the output of the differentiating circuit 19, A
The output from the ND circuit 20 is input to the input frequency divider circuit 11, and the counter of the input frequency divider circuit 11 is reset.

The operation will be explained below.

The input reference signal transmitted from the mask station is frequency-divided to 8 KHz by the input frequency divider circuit 11 and input to the selection circuit 12.

When there is no instantaneous interruption in the input reference signal IN on the transmission path, the selection circuit 12 is activated by the input instantaneous interruption/recovery detection control circuit 21.
to its normal position. For this reason, the manual frequency dividing circuit 11
The 8 KHz reference signal frequency-divided by 2 passes through the selection circuit 12 as it is and is input to the phase synchronized oscillation circuit 17. This phase-locked oscillator circuit 17 is well-known, and the voltage-controlled oscillator 1
A frequency dividing circuit 16 divides the frequency of the signal oscillated at 5, and a phase comparison circuit 13 compares this frequency-divided signal with the input reference signal generated at the mask station. The phase difference between the two signals is converted into a voltage level by a low-pass filter 14, and based on this voltage level, the oscillation frequency of the voltage controlled oscillator 15 is synchronized so as to be drawn into the frequency of the input reference signal of the mask station. to generate the own station white reference signal.

When the input reference signal is momentarily interrupted due to disturbance in the transmission path, the input momentary interruption/recovery detection control circuit 21 detects this and
The selection circuit 12 controls to select the output of the inversion circuit 18, and at the same time, the circuit from the input frequency divider circuit 11 is disconnected. Therefore, a signal obtained by inverting the output of the circuit forming the closed loop of the phase-locked oscillator circuit 17 is input to the phase comparator circuit 13 just like the input reference signal IN and is compared with the output of the frequency divider circuit 16. Ru. Further, at this time, the rising edge change point of the output signal of the inverting circuit 18 is differentiated by the differentiating circuit 19 and input to the AND circuit 20 .

On the other hand, when the human input reference signal is restored, the input instantaneous interruption/recovery detection control circuit 21 detects this and outputs it to the AND circuit 20. The AND circuit 20 receives the signal detecting the restoration of the input reference signal and the output signal of the differentiating circuit 19,
A counter (not shown) of the input frequency divider circuit 11 is reset in preparation for recovery of the input reference signal. At the same time, the input instantaneous interruption/recovery detection control circuit 21 returns the selection circuit 12 to its original normal state.

〔Effect of the invention〕

According to the present invention, when the input reference signal in the transmission line is momentarily interrupted, the signal from the closed loop circuit of the phase synchronized oscillation circuit can temporarily replace the input reference signal.

Therefore, there is no possibility that the input reference signal on the transmission line is disconnected and the phase of the reference signal within the own station shifts early.

[Brief explanation of drawings]

FIG. 1 is a basic block diagram of the present invention, FIG. 2 is an explanatory diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional example. 1... Input frequency divider circuit 2... Selection circuit 3... Phase synchronized oscillation circuit 4... Inversion circuit 5... Input instantaneous interruption/recovery detection control circuit 6... Reset circuit

Claims (1)

[Claims] In a phase-locked oscillator circuit that compares the phases of a reference signal and an output signal of a voltage-controlled oscillator and draws them into the phase of the input reference signal, an input component that converts the frequency of the reference input signal to a desired frequency is provided. a frequency circuit 1; a selection circuit 2 that switches the circuit upon momentary interruption or recovery of the reference input signal; and a reference signal output from the input frequency divider circuit 1 is inputted via the selection circuit 2, and the frequency of the reference signal is A phase-locked oscillation circuit 3 that synchronously generates a reference signal, an inversion circuit 4 that inputs an output signal obtained by inverting the output of the phase-locked oscillation circuit 3 to the selection circuit 2, and a momentary interruption or restoration of the reference input signal. is detected, and the input frequency dividing circuit 1
A circuit for preventing phase instability of an input reference signal at momentary interruption in a phase synchronized oscillator circuit, comprising: an input instantaneous interruption/recovery detection control circuit 5 for controlling reset of the input signal and switching of the selection circuit 2.