JPS5826860B2 - phase tracking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase tracking device for tracking the phase of a signal component in an input signal on which noise is superimposed, in an omega receiver or the like.

Conventionally, in this type of device, when pulse noise is superimposed on the signal from the input terminal, it is observed as a temporary phase fluctuation of the signal, and the phase of the phase tracking signal inside the device responds to this, resulting in unnecessary noise. It had the disadvantage of causing fluctuations.

In order to eliminate this drawback, the present invention detects fluctuations in the phase of the input signal with respect to the phase tracking signal, and temporarily stops the operation of the phase tracking system when a temporal phase fluctuation occurs, thereby detecting the pulse This makes it possible to remove unnecessary fluctuations in the phase tracking signal due to the influence of superimposed noise.
This will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a phase tracking circuit, 2 is an error detection circuit, 3 is a signal input terminal, 4 is a phase tracking control circuit, and 5 is a signal tracking identification circuit.

Next, the operation will be explained with reference to the waveform diagram of each part in FIG.

The phase tracking circuit 1 is a so-called phase-locked loop (
PLL), and its output signal, the phase tracking signal, is at the rising edge of the input signal, that is, at the 0 phase point θS (θs1
．． θs2...) is detected, and θR (θR
1, θR2...) to produce a signal that oscillates in the same phase as the input signal.

In the case of such a phase tracking circuit, the following operation is performed by utilizing the fact that the falling side of the input signal is not used for phase tracking operation.

First, the error detection circuit 2 starts from the falling edge (π phase point) of the phase tracking signal phase-tracked by the phase tracking circuit 1 to the falling edge (π phase point) of the input signal input from the signal input terminal 3.
This is a type of timer circuit that detects the time difference between the phase point and the phase point.

Note that this time difference is equivalent to the phase difference between both signals.

If the phase of the input signal changes temporarily due to pulse noise or the like, and the time difference exceeds a certain value Jt, the error detection circuit 2 immediately generates and outputs a pulse at that point.

The situation is shown in Figure 2.

FIG. 2A shows an output waveform as a result of phase tracking the input signal waveform B, and corresponds to the output of the phase tracking circuit 1.

In Figure 2, θR2→θR2 does not exceed Jt, so no pulse appears in the error detection circuit output waveform C, but θR2'→
At θ82', it exceeds At, indicating that a pulse has occurred.

The error detection circuit 2 detects θR2°θ of the phase tracking signal A in FIG.
R2...In other words, when the input signal B is observed at a point △t from the falling point, and the input signal is logic "0" at the point -At, and when the input signal is logic "0" at the point +△t, When the signal is "1", the error detection circuit output C can be generated by applying a trigger to a pulse generator such as a monostable multivibrator included in the error detection circuit 2, for example.

On the other hand, in the phase tracking circuit 1, in order to compare the rising edge of the signal waveform and the rising edge of the phase tracking output waveform, a time window is provided for a certain period of time before and after the rising point of the phase tracking output waveform, and the tracking operation is performed in this section. .

The pulse of this time window has the same waveform as the pulse used to detect the rising point of a normal digital tracking filter, and the input signal is observed with this pulse and the logic “0” is detected.
The phase of the phase tracking signal is advanced or delayed depending on whether there are many "side parts" or "logical 1" parts.

FIG. 2E shows the pulse waveform of this time window, and if this pulse is removed, phase tracking will be stopped for the removed period.

Now, the output pulse of the error detection circuit 2 is guided to the phase tracking control circuit 4 composed of a flip-flop circuit to set it in a set state.

When the phase tracking control circuit 4 is in the set state, the phase tracking circuit 1 removes the pulse of the time window (E in FIG. 2) and enters the phase tracking stopped state.

The state of the phase tracking control circuit 4 is determined by the timing when the phase tracking operation, which is performed on the rising side of the phase tracking signal, ends;
In other words, by connecting so that it is always reset according to the falling timing of the time window pulse, once the phase tracking control circuit 4 is set by the error detection circuit output generated on the falling side of the phase tracking signal, the next phase tracking is started. The phase tracking operation performed on the rising side of the signal is stopped for one cycle.

In this way, the presence or absence of pulsed noise is detected every period,
Each time it is detected, the next phase tracking operation is temporarily stopped and repeated.

On the other hand, the signal tracking identification circuit 5 monitors whether the phase tracking circuit 1 is tracking the signal within a certain error range over a sufficiently long period.

As a result, only when phase tracking is not confirmed, the output is turned ON to forcibly reset the phase tracking control circuit 4, so that initial phase tracking is not disturbed.

As a circuit for realizing the above-mentioned function, for example, a power-on time switch is used to forcibly reset the phase tracking control circuit 4 by sufficiently delaying the time required from when the power is turned on to exiting the initial state of phase tracking.

Furthermore, even if tracking is lost for some reason during operation, an input signal S/N ratio measuring circuit is added to the time switch to force the phase tracking control circuit 4 even when the signal drops until the tracking state returns to the same as the initial tracking state. Make it possible to reset.

Another method may be to measure the tracking error and forcibly reset the phase tracking control circuit 4 when a certain value is reached.

In this way, during the initial tracking process of the signal, the tracking operation is operated so as not to be disturbed, and then when pulse noise is added, the tracking operation is temporarily stopped for that period.

With the above operation, even if the phase of the input signal suddenly fluctuates temporarily, the phase tracking signal inside the device responds to this, and the adverse effect of requiring time for recovery can be reduced.

As explained above, in a device that performs a phase tracking operation such as an omega receiver, the influence of pulse noise on the input side can be removed, so there is an advantage that phase tracking can be performed stably.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the device of the present invention, and FIG.
The figure is an explanatory diagram of waveforms of each part. DESCRIPTION OF SYMBOLS 1... Phase tracking circuit, 2... Error detection circuit, 3... Signal input terminal, 4... Phase tracking control circuit, 5... ...Signal tracking identification circuit.

Claims (1)

[Claims] 1. A phase tracking circuit that controls the phase of the phase tracking signal by detecting the phase difference θS - θR between the phase point θS where the human input signal is located and the phase point θR where the phase tracking signal is located, and the phase point θ'S where the input signal is located. and an error detection circuit that detects a phase difference Iθ'S-θ/R1 between the phase tracking signal and a certain phase θ'R, and generates a pulse when the phase difference exceeds a certain phase difference;
a signal tracking identification circuit for detecting whether the phase tracking circuit is in an initial phase tracking state; and a signal tracking identification circuit that receives a pulse from an error detection circuit only when the output of the signal tracking identification circuit does not indicate the initial phase tracking state. and a phase tracking control circuit that stops the operation of the next phase tracking section, and controls the temporary phase fluctuation of the input signal at the phase point θ'si of the input signal and the phase point θ'Ri of the phase tracking signal. A phase tracking device that detects and temporarily stops a phase tracking operation at a phase point θRi+1 where a next phase tracking signal is present.