JPH06232740A - Weak coupling oscillator utilizing multi-stage moving average processing - Google Patents

Abstract

PURPOSE:To remarkably reduce a time required for an output signal synchronously with a reference signal by executing average processing while switching dynamically a time constant from a small value to a large value sequentially in response to the lock state of the synchronization system. CONSTITUTION:A phase difference between a signal fin and an output signal fout of a reference oscillator 11 is detected by a DPC 12 and the phase difference is fed to a 1st averaging circuit 13-1 having a comparatively shorter (smaller) time constant, in which rough phase data are detected by simple average processing. A switch circuit 14 is set to select at first an output of the circuit 13-1 and the selected signal is fed to a proportion integration circuit 16. The oscillated frequency of a VCO 18 is highly stable synchronously with a signal from the reference oscillator by the action of a PLL. A threshold level used to make comparison with phase data corresponding to each averaging circuit is stored in the switch control circuit 15, and when the threshold level outputted from the selected averaging circuit at that time exceeds the threshold level or less than the threshold level, that is, the switch circuit 14 is controlled while the PLL of each averaging circuit is locked-in to select the average circuit on purpose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weakly coupled oscillator, and more specifically, it synchronizes an output signal frequency with the frequency of an input signal with high accuracy so that even if the input signal is interrupted, accurate oscillation is performed based on frequency information before that. The present invention relates to an oscillator capable of maintaining a frequency and removing a phase fluctuation mixed in an input signal and having an extremely stable phase and frequency.

[0002]

2. Description of the Related Art As a weakly coupled oscillator weakly coupled to a reference signal, one shown in FIG. 1 is known. This block includes a DPC (Digital Phase Comparator) 2 for comparing the phase of the signal f _in of the reference oscillator 1 with the phase of the output signal f _out , and the above DP.
An averaging circuit (AVERAGER) that removes short-term fluctuations in the phase data detected by C by simple averaging processing.
Circuit) 3, a proportional integration circuit 4 for proportionally integrating the averaged signal to convert it into a digital signal, and a D / A converter 5 for converting the proportionally integrated digital signal into a DC signal.
And a VCO (voltage controlled oscillator) 6 whose oscillation frequency is controlled by this DC voltage signal.
The output of CO6 becomes f _out, and part of it becomes D
It is designed to be fed back to the PC2.

The reference oscillator 1 is, for example, a thermostat type oscillator having a high stability in the long term and the short term. The averaging circuit removes a single cycle phase fluctuation of the input signal, and the reference oscillator is a true oscillator. The VCO is controlled by the DC voltage derived based on the frequency information, and an extremely stable frequency signal is generated.

In the conventional weakly coupled oscillator as described above, the time constant of the averaging circuit 3 should be set large when the phase fluctuation of the input reference signal is large, and conversely when the phase fluctuation is small. Should be set small, but in the conventional circuit, this time constant was fixed and was not configured to correspond to the phase fluctuation of the input signal. ,
It was possible to remove even large phase fluctuations.

However, if the time constant is set to a large value in this way, the period of the signal output from the averaging circuit 3 becomes long, so that it takes a long time for the VCO 6 to synchronize with the reference signal, and the weakly coupled oscillator is used. However, there was a drawback that the range of use was limited. That is, it was impossible to use when a signal was to be obtained in a relatively short time after the power was turned on.

[0006]

It is an object of the present invention to eliminate the drawbacks of the conventional weakly coupled oscillator as described above, and it is possible to deal with all the large and small phase fluctuations of the reference signal, and at the same time, make the output signal the reference signal. It is an object of the present invention to provide a weakly coupled oscillator that can significantly reduce the time required for synchronization.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a phase comparator for comparing the phases of a reference signal and an output signal, an averaging circuit having a predetermined time constant, and the averaging circuit output converted to a DC voltage. A weakly coupled oscillator having a circuit, a voltage controlled oscillator controlled by the DC voltage, and means for feeding back the voltage controlled oscillator output to the outside and feeding back a part of the voltage controlled oscillator to the phase comparator. The averaging circuit is provided with a plurality of averaging circuits having different time constants, and the averaging circuit is provided with a switching means for switching the averaging circuit according to the magnitude of the phase difference between the output and the reference oscillator signal. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The weakly coupled oscillator of the present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of the present invention. The apparatus shown here is a DPC (digital phase comparator) 2 for detecting a phase difference between a signal output from a reference oscillator 1 and an output signal. The first averaging circuit 3-1 and the second to fifth averaging circuits 3-2
Block 3 to 5 connected in parallel, and a switch circuit 14 for selecting one of the first to fifth averaging circuits
And a switch control circuit 15 which supplies the output of the first averaging circuit and the outputs of the second to fifth averaging circuits and controls the switch circuit 14 based on these signals, and proportionally integrates the output of the switch circuit. Proportional integrator circuit 16 and D that converts the digital output from the integrator circuit into an analog signal
A / A converter 17 and a voltage controlled oscillator (VCO) 18 which controls the frequency by an analog DC signal. A part of the output of the VCO 18 is fed back to the phase comparator 12. It is configured to.

The above five average circuits 13-1 to 13-13
-5 has different time constants, the first averaging circuit has the smallest time constant, the fifth averaging circuit 13-5 has the largest time constant, and the averaging circuits in the meantime differ stepwise. The time constant is set.

To explain the operation in this configuration, the phase difference between the input signal f _in of the reference oscillator 11 and the output signal f _out is detected by the DPC 12 and supplied to the next first averaging circuit 13-1. . The first averaging circuit has a relatively short (small) time constant as described above, and detects approximate phase data by performing simple averaging.

The switch circuit 14 is initially set to select the output of the first averaging circuit 13-1, and supplies it to the proportional-plus-integration circuit 16. The operations and functions of the proportional-plus-integrator circuit 16, the D / A converter 17 and the VCO are the same as those of the prior art, so that the description thereof will be omitted. However, the oscillation frequency of the VCO 18 becomes the signal of the reference oscillator due to the operation of the phase lock loop. High stability is achieved in synchronization.

However, in the above operation, since the time constant of the first averaging circuit is small, the time until the synchronization becomes short, but a large phase fluctuation cannot be followed and the frequency accuracy becomes inferior. As described below, the averaging circuit is sequentially switched.

The switch control circuit 15 stores the threshold value to be compared with the phase data corresponding to each averaging circuit, and when the phase data output from the selected averaging circuit exceeds the threshold value at that time. , Or below the threshold value, that is, in the state where the phase lock loop is locked in in each averaging circuit, the switching circuit 14 is controlled to switch the averaging circuit to be selected.

In the above averaging circuit switching method, basically, a higher-precision output signal is obtained by sequentially shifting from a smaller time constant to a larger time constant, but synchronization is once achieved with the maximum time constant. In such a state, when the observed phase fluctuation is small, it may be possible to control so as to switch to an averaging circuit suitable for this.

By sequentially switching the time constants of the averaging circuit in this way, the time from power-on to synchronization can be greatly shortened. Furthermore, even when switching to an averaging circuit with a large time constant in sequence, the averaging circuit in the previous stage has already completed the averaging processing with a small time constant, so the time required for synchronization with the next large time constant processing is shortened. There is also an effect. In addition, since moving average processing is adopted for the averaging processing in the subsequent stage, the cycle in which data is output from the averaging circuit in the subsequent step and the cycle in which data is output from the averaging circuit in the previous step are the same, so a large time constant is applied to the subsequent step. Even if the averaging circuit is selected, the VCO does not enter the uncontrolled state and a stable output signal can be obtained.

Further, when the averaging process having a large time constant is performed, the number of samples increases, and therefore the calculation process takes a long time. In the present invention, the result obtained by the averaging circuit having a small time constant is used. Since the next-stage averaging process is performed, the time required for the subsequent-stage process can be shortened, and the calculation processing load on each averaging circuit can be significantly reduced.

[0017]

As described above, according to the present invention, the averaging process is performed while dynamically switching from a small time constant to a large time constant in accordance with the pulling state of the synchronous system. Compared to the weakly coupled oscillator of
The time required for synchronization can be greatly reduced, and the device can be used in a relatively short time after the power is turned on.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional weakly coupled oscillator.

[Explanation of symbols]

1, 11 Reference oscillator, 2, 12 Digital phase comparator, 3, 13-1, 13-2, 13-3, 13-4,
13-5 Averaging circuit, 4, 16 Proportional integrating circuit,
5, 17 digital-analog converter, 6, 18 voltage controlled oscillator, 14 changeover switch, 15 switch control circuit.

Claims (1)

[Claims] 1. A phase comparator for comparing the phases of a reference signal and an output signal, an averaging circuit having a predetermined time constant, a circuit for converting the output of the averaging circuit into a DC voltage, and control by the DC voltage. In a weakly-coupled oscillator having a voltage-controlled oscillator and means for outputting the output of the voltage-controlled oscillator to the outside and feeding back a part of the voltage-controlled oscillator to the phase comparator, the averaging circuit has a plurality of time constants different from each other. A weakly coupled oscillator according to a multi-step moving average process, comprising: an averaging circuit, comprising switching means for switching the averaging circuit according to a magnitude of a phase difference between an output and the reference oscillator signal.