JPS5821967B2 - phase synchronizer - Google Patents

Description

Detailed Description of the Invention This invention compares the phase of a reference frequency signal and the output of a voltage controlled oscillator or its frequency conversion output using a phase comparator, and passes the comparison output through a DC amplifier and further through a low-frequency wave generator. In the phase synchronization device that supplies the above-mentioned voltage-controlled oscillator as a control signal, a switch is inserted between the DC amplifier and the low-frequency F-wave generator, and the voltage-controlled oscillator is controlled when the output of the DC amplifier is cut off. The present invention relates to a device having a function of holding voltage.

In a normal phase locking device, if the locking loop opens for some reason, the control voltage for the voltage controlled oscillator may be required to maintain the state before the loop was opened. The holding function was achieved simply by using a switch.

FIG. 1 shows a conventional phase synchronization device. In a normal state, input signals of frequencies F and N input from an input terminal 11 and a signal of an output frequency Fv of a voltage controlled oscillator 12 are converted to a frequency by a frequency converter 13. A part of the output of the converted frequencies F and F is taken out to the output terminal 20 by the directional coupler 14, and the other part is sent to the phase comparator 15 as a signal of the reference frequency FR from the terminal 16. The phase is compared with

The error voltage from the phase comparator 15 is amplified by a DC amplifier 17, and the amplified output is sent to the voltage controlled oscillator 12 through a switch 18 and a low-frequency wave filter 19 that determines the loop characteristics.
is applied to the voltage control terminal of FR
, F, and F have the same frequency with a certain phase difference remaining.

At this time, the input frequency from the terminal 11 includes one or more frequencies in addition to FtN, and these frequencies are input to the oscillator 12.
Considering the case where the signal is supplied to other circuits through the directional coupler 14 after frequency conversion with the oscillation frequency FV, for example, when the input signal of FtN is cut off for some reason, the phase synchronization device becomes open loop. Since the voltage controlled oscillator 12 is in an uncontrolled state, the frequencies supplied to the other circuits are also in an uncontrolled state and become unusable.

In order to eliminate such drawbacks, a switch 18 is inserted as shown in Fig. 1, which forcibly disconnects the circuit at the same time as it becomes an open loop, and prevents the condenser in the low-frequency P wave generator 19 from discharging. The control voltage of the voltage controlled oscillator 12 is held for a certain period of time.

However, in this conventional device, when the FtN input signal is restored and the device is returned to the normal state by the switch 18, it is often difficult to re-engage the device depending on the initial conditions.

This situation will be explained with reference to FIG.

Assuming that the output side of the DC amplifier 17 is point A, and the output side of the low-frequency wave generator 19 is point B, both points A and B are at the same voltage vL in the synchronized state. The signal is at time T.

FF is disconnected, and accordingly, the converted output of F+F is also at time T.

When the FF is disconnected, it is immediately detected and the switch 18 is disconnected, and the voltage at point B is maintained at ■L.

However, the voltage A1 at point A1, that is, the output voltage of the DC amplifier 17, is the voltage obtained by multiplying the center voltage of the phase comparator 15 by the gain of the DC amplifier 17, since there is no input signal from one side of the phase comparator 15. Generally, the voltage will be zero.

Then again at time T. An input signal of FtN arrives at F
When a conversion signal of 1F occurs, it is detected and the switch 18 is closed, resulting in a normal closed loop device.

As a result, the difference frequency between F
s, that is, the output voltage of the DC amplifier 17, and the voltage at point B, that is, the holding voltage vL of the low-frequency wave generator 19. There are cases where the synchronization occurs, and cases where the synchronization completely goes out as shown in the operational conceptual diagram in the same figure.

This is because the phase synchronizer's pull-in frequency range is generally much narrower than its holding frequency range.

Therefore, as is clear from the comparison of Fig. 2 a and b, in order to solve the problems with the conventional phase synchronizer and ensure retraction after the holding state, it is necessary to adjust the holding state TOFF”TON.
It is necessary that the voltage difference between the voltage at point A and the holding voltage vL at point B be set at least to an extent that satisfies the value of the pull-in frequency range of the loop at the moment the loop is closed during pull-in.

Although the frequency converter 13 is used in FIG. 1 showing an example of the configuration of a conventional phase synchronization device, for example, in a phase synchronization device in which a part of the output of the voltage controlled oscillator 12 is directly input to the phase comparator 15, the FR It is clear that the same operation will occur and the same problem will occur even when the reference signal is disconnected.

Once completely out of synchronization, synchronization becomes impossible, so with conventional equipment it is necessary to use automatic frequency control circuits, sweep circuits, etc., and it generally takes a long time to resynchronize. Become.

The purpose of the present invention is to solve the problems with the conventional phase synchronization device, and to maintain the input voltage of the voltage controlled oscillator at a constant level during the holding state in which the input signal or the reference signal is cut off, and to maintain the input voltage of the voltage controlled oscillator constant. It is an object of the present invention to provide a phase synchronization device that can reliably retract when a reference signal is restored.

According to this invention, the difference between the output of the DC amplifier that amplifies the output of the phase comparator and the output of the low-pass filter that supplies the control signal of the voltage controlled oscillator is taken by the differential amplifier, and the input signal or reference signal is When the signal, that is, the input to the phase comparator is cut off, the switching means is operated to switch the output of the differential amplifier from a predetermined potential and supply it to the DC amplifier as a reference potential for this.

In this way, when the input signal or reference signal is interrupted, the output of the DC amplifier always operates equal to the output of the low-pass P-wave generator, thus the input to the phase comparator is restored and the loop is closed. The moment it closes, it immediately becomes synchronized,
Since the synchronization is maintained, the pull-in range is expanded to the frequency range of the synchronization with equal constraints, and re-lock is reliably performed.

An example of a phase synchronization device according to the present invention is shown in FIG. 3, in which parts corresponding to those in FIG. 1 are given the same reference numerals.

According to this invention, the output of the DC amplifier 17 and the output of the low-frequency F-wave generator 19 are branched and supplied to the differential amplifier 21.

The output of the differential amplifier 21 and a predetermined potential, in this example the ground potential, are switched by a switch 22 and supplied to the DC amplifier 17 as a reference potential.

In this case, the transfer characteristics of the differential amplifier 21 must be selected taking into account the frequency characteristics, response speed, stability, etc. of this device.
Generally, a sufficiently large DC gain and appropriate low-pass filtering characteristics are required.

Preferably, the switch 22 is operated in conjunction with the switch 18.

Here, interlocking does not mean exactly the same time,
One may come first, but if one works, the other will always work as well.

The predetermined potential that becomes one input of the switch 22 is the voltage applied to the terminal that requires the reference voltage of the DC amplifier 17 when this phase synchronization device is in a normal operating state, and is generally zero voltage. .

In this configuration, when the switch 18 is on the side of the normal operating state in which the phase synchronization device is closed, the switch 22 is on the predetermined potential side, which is served as the reference terminal of the DC amplifier 17.

The interlocking operation is controlled such that when the switch 18 opens the loop of the phase synchronization device and enters the time keeping state, the switch 22 also switches to apply the output voltage of the differential amplifier 21 to the reference terminal of the DC amplifier 17. There is.

Therefore, in a normal state, the output side of the differential amplifier 21 is separated from this device and becomes only a phase synchronization device, but in a holding state, the output voltage of the DC amplifier 17 is A negative feedback circuit that returns to the reference terminal of the DC amplifier 17 through the negative feedback circuit is configured.

Therefore, the voltage at point B entering one side of the differential amplifier 21,
That is, the output of the low-frequency muddy waver 19 becomes the reference voltage of the DC amplifier 1T, and fluctuations in the input voltage of the DC amplifier 17 are corrected by the voltage on the reference terminal side, and the output of the DC amplifier 17, that is, the voltage at point A, is corrected by the voltage on the reference terminal side. It operates so that the voltage becomes equal to the voltage at point B.

That is, feedback is applied so that the voltage at point A and the voltage at point B are always equal in the holding state.

As a result, as is clear from the previous explanation of the operation, synchronization is always established in the case of retraction after the holding state.

Therefore, when the input signal of the phase comparator 15 is restored, the switch 1
By returning 8.22 to the normal state with an appropriate time constant, it becomes a normal phase synchronizer in the synchronization holding state.

As explained above, in the present invention, by adding the differential amplifier 21 and the switch 22 to the phase synchronization device having a holding function, the frequency range in which retraction can be performed after holding can be adjusted to the retraction frequency that the phase synchronization device has. By expanding the range of characteristics to the range of holding frequency characteristics, it is possible to prevent synchronization failure, which greatly expands the field of application of phase synchronizers with holding functions.
Moreover, it is only necessary to add a simple configuration, and the effect is extremely large.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional phase synchronization device with a holding function, Fig. 2 is an explanatory diagram of the operation during retraction after holding, and Fig. 3 is a phase synchronization device with a holding function according to the present invention. FIG. 2 is a block diagram showing one embodiment of the present invention. 11: Input terminal, 12: Voltage controlled oscillator, 13: Frequency converter, 14 Bidirectional coupler, 15: Phase comparator, 16
Two reference signal input terminals, 17: DC amplifier, 18: switching device, 19: low frequency muddy wave device, 20: output terminal, 21: differential amplifier, 22: switching device.

Claims (1)

[Claims] 1 A phase comparator compares the phases of the reference signal and the output signal of the voltage controlled oscillator or the frequency conversion output obtained by frequency converting this output signal and the input signal with a frequency converter, and the output is compared with the output signal of the DC amplifier and the frequency converter. A switch is provided between the DC amplifier and the low-frequency wave generator for the phase synchronization device that supplies the voltage controlled oscillator through the F-frequency wave generator, and in a holding state in which the reference signal or the input signal is cut off. In a device having a holding function of electrically interrupting the low-frequency wave transducer and the DC amplifier and holding the output signal of the low-frequency wave transducer, the output signal of the DC amplifier and the low-frequency P
a differential amplifier to which output signals of the DC amplifier are applied to two input terminals, and switching means for switching between the output signal of the differential amplifier and a predetermined potential and supplying the same to the reference voltage terminal of the DC amplifier, A phase synchronization device characterized in that it operates so that the output signal of the DC amplifier becomes equal to the output signal of the low-frequency wave transducer in the holding state.