Panasonic GP 31, Technical Manual

Page: 6 / 31

6
1. Tuning Circuit
Outline
The tuner is designed for reception of the conventional frequencies to date and the
intermediate special channel frequencies. The IF stage of the tuner contains the video and
audio demodulators which are designed for most widely used TV standards.
1.1 Signal Processing
1. The purpose of the tuner is to convert the VHF/ UHF TV broadcast signal (RF) into
intermediate frequency signal, IF (38.0MHz) [Fig 1.0].
2. The aerial intercepts the TV signal and amplified by the RF amplifier.
3. The local oscillator generates basic frequency to convert RF signal into IF signal
(intermediate signal) in the mixer.
4. Here the IF signals is output to UOC IC601 for video and sound processing.
1.2 IF Control
Control of internal Tuner-IF processing is performed by the UOC IC601, the
IC601 sending control information via I²C bus input via pin 71 (SCL) and 72 (SDA).
In addition to this, AGC control of the Tuner-IF stage is controlled by the UOC
via I²C. AFC information for Tuner-IF stage is fed back to the IC601 via control line
AGC (pin 22).
Fig 1.0