JPS628080A - Phase correcting circuit - Google Patents

Abstract

PURPOSE:To accurately detect a relative phase difference by phase-shifting the signals of one channel CH by every minute angle when a pilot signal is injected and detecting a phase angle when the difference vector between said one CH and the other CH signals becomes minimum as a phase difference between both the CH's. CONSTITUTION:When an angle generated from an angle generator 6 is increased by DELTAtheta deg., a phase shifter 2 operates as the phase shifter of a phase-shifting quantity DELTAtheta deg. and one CH signal of a latch circuit 1 is phase-shifted by the angle DELTAtheta deg.to be applied to a vector subtracter 9. The difference vector between said one and the other CH signals is calculated and compared with the minimum value stored before in a minimum value detector 10. When the difference vector is smaller than the minimum value, the present value is updatedly stored as another minimum value. In the same way, every time when an angle is generated with the increase of an increment DELTAtheta deg. by the angle generator 6, a phase shift, a vector subtraction and a reduced value decision are conducted, and, by detecting the phase difference between the CH's in the phase shifter 2, a relative phase difference can be accurately detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a phase correction circuit that corrects the phase difference between channels of video signals of a plurality of channels whose phase is detected in a digital camera or the like. It is.

[Conventional technology]

Fig. 3 is a system diagram of a conventional phase correction circuit. In the figure, 111 indicates each channel (CH, A, CIl, B).
The first sampler samples the input signal from the
(2) is a phase shifter that vectorially rotates the sampling value of one channel of this first latch circuit (1) by the phase difference between channels, (3a) and (3b) are pilot signals A phase angle detector detects the phase angle of each channel signal from the sampling value of the first latch circuit (1) during injection, and (4) is the difference in phase angle between the phase angle detectors (3a) and (3b). The subtracter (5) that calculates the subtractor (5) is a second latch circuit that latches the subtraction result of the subtracter (4) and supplies it as the phase shift amount to the phase shifter (2).

Next, the operation will be explained. The signal of each channel is sampled by the first launch circuit +11 when the pilot signal is injected, and the phase angle is detected by phase angle detectors (3a) and (3b), respectively. Phase angle detector (3a)
, (3b) are orthogonal components 1. The phase angle tan-'Q/I is calculated from the input signal expressed by Q, and an example thereof is shown in FIG. In the figure, L
The OG, anti-LOG, and jan-' arithmetic circuits are usually configured with a ROM (Read Only Memory). The calculation results of each phase angle detector (3a) and (3b) are subtracted by a subtractor (4), and the result is used as the second
is held in the launch circuit (5). After stopping injection of the pilot signal, the actual signal is transferred to the first latch circuit (1
), and after sampling by the first latch circuit +11, one channel is measured as is, and the other channel is measured by the phase shifter (2) using the pilot signal held in the second launch circuit (5). The phase is shifted by the phase difference between the channels and output. The phase shifter (2) is a vector multiplier, and its embodiment is shown in FIG.
This is done by OM.

[Problem that the invention seeks to solve]

Since the conventional phase correction circuit is configured as described above, it is necessary to detect the phase angle of each channel, and calculation of jan −' Q / [ is required. It is necessary to have a large number of circuits, resulting in a large-scale circuit, and there are also problems such as a decrease in accuracy due to constraints from the capacity of the ROM.

This invention was made in order to solve the above-mentioned problems, and aims to provide a phase correction circuit that can accurately detect the relative phase difference between the two channels without having to detect the phase difference of each individual channel. purpose.

[Means for solving problems]

The phase correction circuit according to the present invention shifts the phase of the signal of one channel by a certain minute angle when injecting the pilot signal, and calculates the phase shift angle between the channels when the difference vector with the signal of the other channel becomes minimum. This is detected as a phase difference.

This principle is shown in FIG. In the figure, vector B (
It is clear that when vector B) is rotated, the magnitude of the difference vector (A-B) becomes minimum when vectors A and B overlap. Therefore, the phase difference between vectors A and B can be detected by detecting the rotation angle of vector B when the magnitude of the difference vector becomes minimum.

[For production]

The phase shifter in this invention operates as a phase shifter in which the amount of phase shift increases sequentially by a fixed angle when a pilot signal is injected, but after performing a 360 degree phase shift and detecting the phase difference between channels, It operates as a phase shifter that shifts the phase of the signal by the phase difference between channels.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) indicates each channel (C1, A.

(2) is a phase shifter that vectorially rotates the sampling value of one channel of this first latch circuit (11); (6) is an angle generator that generates an angle that increases by a constant angle from 0 degrees to 360 degrees during the pilot signal injection period, and (7) is this angle generator (6
a second latch circuit that latches the output of ) at a predetermined time;
8) is a phase shifter (2) by switching either the output of this second latch circuit (7) or the angle generator (6).
(9) is a vector subtractor that calculates the difference vector between the signal of the other channel of the first latch circuit (1) and the output signal of the phase shifter (2), (10) is this vector This is a minimum value detector that detects the minimum value of the output of the subtracter (9) and supplies the launch timing to the second latch circuit (7).

Next, the operation will be explained. The signal of each channel is sampled by the first latch circuit (i) at the time of pilot signal injection. At this point, the output of the angle generator (6) is 0 degrees and the switch (8) has selected the output of the angle generator (6), and as a result, the phase shifter (2) It operates as a phase shifter with an amount of 0 degrees. That is, the signals of both channels sampled by the first latch circuit (11) are directly applied to the vector subtractor (9), and the difference vector between them is calculated and the minimum value is detected by the detector (10).
). Since there is no previous value, the minimum value detector (10) unconditionally stores this difference vector quantity as a minimum value, and supplies the launch timing to the second launch circuit (7). As a result, the output value of 0 degrees from the angle generator (6) is stored in the second launch circuit (7).

The angle generator (6) then generates an angle increased by Δθ. Here, Δθ is usually a value obtained by dividing 360 degrees by a power of 2 (360/2"). As a result, the phase shifter (2)
operates as a phase shifter with a phase shift amount of Δθ degrees, and the signal of one channel of the first launch circuit (1) is phase-shifted by Δθ degrees and applied to the vector subtractor (9), and the signal of the other channel is shifted by Δθ degrees. The difference vector with the signal is calculated and the minimum value detector (1
0). The minimum value detector (10) compares the previously stored minimum value, in this case with the value when the phase shift amount is 0 degrees, and if it is even smaller than the previously stored minimum value. The current value is updated and stored as the minimum value, and the launch timing is supplied to the second latch circuit (7).On the other hand, if it is greater than or equal to the previously stored minimum value, nothing is done. do not.

Similarly, the angle generator (6) sequentially generates angles incremented by Δθ degrees, and phase shift, vector subtraction, and minimum value determination are performed each time.

The above sequence ends when the angle of the angle generator (6) reaches 360 degrees, and the switch (8) selects the output of the second latch circuit (7) and supplies it to the phase shifter (2). do. After that, a real signal flows through each channel, and the first latch circuit (
1), the sampling signal of one channel is sampled at predetermined time intervals, and the sampling signal of one channel is sent to the second latch circuit (7).
The phase is shifted by the phase shifter (2) by the angle held at , and then output.

In the above embodiment, the case where the signal has two channels has been described, but even in the case of three or more channels, the same effect can be obtained by providing a plurality of circuits of the above embodiment in pairs of two channels each.

Further, in the above embodiment, the angle generator (6) is set from 0 degrees to 3 degrees.
Although it is assumed that a rotation angle of up to 60 degrees is generated, if the range of phase difference between channels is known in advance, an angle within that range may be generated.

〔Effect of the invention〕

As described above, according to the present invention, the phase shifter is also used as means for detecting the phase difference between channels using pilot signals, and is configured to directly detect the relative phase difference between the channels. This has the effect of making it cheaper.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a phase correction circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing the principle of the invention, FIG. 3 is a block diagram showing a conventional phase correction circuit, and FIG. 4 is a block diagram showing a conventional phase correction circuit. FIG. 5 is a block diagram of a phase shifter used in the present invention and a conventional phase correction circuit. (11, (7) is a latch circuit, (2) is a phase shifter, (6)
is an angle generator, (8) is a switch, (9) is a vector subtractor, and (10) is a minimum value detector. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a phase correction circuit that inputs a plurality of vector-expressed signals and corrects a phase shift between channels using a pilot signal injected at a predetermined time, the detected vector of the pilot signal in one channel is converted into a predetermined unit. means for rotating the rotated vector signal by an angle, means for detecting a difference vector amount between the rotated vector signal and the detected vector of the pilot signal in the other channel, and the rotated vector when the difference vector amount becomes a minimum. A phase correction circuit comprising means for detecting a rotation angle of a signal.