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Número de pieza

componentes Descripción

Fabricante

CXA1203N

8mm VCR PAL JOG

Sony Semiconductor 

CXA1203M/N

4. V-Invert (V Axis Inversion Circuit)

For color alignment, the DL signal which is produced by inverting the chrominance signal (TH signal) about

the B-Y axis is necessary.

The V-Invert block produces the DL signal from the TH signal. Fig. 6 shows the principle of the V-Invert

block.

Playback chrominance

signal

cos (ωt ± θ)

θ

θ

cos 2ωt

×2

TH: cos (ωt ± θ)

BPF

DL: cos (ωt ± θ)

cos (3ωt ± θ)

To

Y/C MIX BLOCK

Rejected by the BPF.

fsc (cos ωt)

Fig. 6

Define the B-Y axis of the playback chrominance signal as cos ωt and input the playback chrominance

signal and the 2fsc (cos 2ωt) to the multiplier. By means of the frequency conversion of the 2fsc, the input

chrominance signal is inverted about the B-Y axis. The three fold frequency component (cos 3ωt) is also

output, but this component is rejected by the BPF in a later stage.

Fig. 7 shows the actual V-Invert block.

Playback chrominance

signal

Dummy

CONV1

φ

V-I

LPF2

TH/DL

BF Xch

PAL

PAL-M

TH

DL

15

Main

SW

C OUT

SWD

1/2fH

2fsc

Fig. 7

BF Gate fsc

EX Burst

The V-Invert circuit constructs the TH/DL APC loop that keep the phase difference between the burst of the

TH signal and the burst of the DL signal to be 90°. This circuit detects the phase of the bursts of the TH and

DL signals and varies the delay time of the phase shifter φ with reference to the error current of APC loop.

In PAL-M mode, the APC is applied to the fsc and the DL signal. Therefore, the input burst signal has a

phase of 90° to the fsc. The CONV1 is a multiplier to obtain the DL signal.

The Dummy supplies the same gain loss and the same phase delay as produced in CONV1 to the TH

signal so that there is no gain and phase difference between the TH signal and the DL signal.

The main SW outputs the TH or DL signal according to the TH/DL select signal (output at Pin 17). When a

BF Xch pulse is supplied (in JOG mode only), the EX burst is output.

– 20 –

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