Matsushita Electric KX-TC1461LAB, Service Manual

Page: 27 / 77

12.6. Transmitter/Receiver
Base Unit and Handset are mainly consists of RF (Radio Frequency) IC(IC1) and CPU(IC3).
Base Unit and Handset transmit/receive voice signal and data signal through the antenna on
carrier frequency.
Signal Pass:
*Refer to CDL TX/RX in
Signal Route ().
12.6.1. Transmitter Block
Circuit Operation:
The voice signal input from the TEL LINE interface goes to RF IC(IC1) as shown in
BLOCK DIAGRAM (Base Unit) ().
And the signal goes through the compressor and SPLATTER FILTER of RF IC, it is output to
transmitter circuit.
The signal of the data sent to the handset is applied too.
The capacitor of VARICAP (:VD502) is changing in accordance with the voice signal from
telephone line interface or TX DATA signal from CPU. Therefore, the carrier frequency which is
generated by TXVCO will be changing, and Frequency modulated RF signal is generated and
amplified by RF AMP (Doubler: Q510). It pass through the Duplexer FL501 and radiated from
Antenna.
Handset detects the voice signal or data signal in the circuit same as the following explanation
of Receiver Block.
12.6.2. Receiver Block
Circuit Operation:
The signal of 900MHz band (925.9~927.85MHz) which is input from ANT is filtered at FL501 as
shown in
BLOCK DIAGRAM (Base Unit) (), then it is input to RF IC.
The signal input to RF IC is converted through Mixer, IF filter (CF501) and Expander.
In short 1st local frequency is mixed with the received RF signal. Then it passes through IF
(CF501: 10.7 MHz Intermidiate Frequency) and filtered at F1.
The detected signal passes through the expander and Amplifier inside of RF IC to the TEL LINE
interface.
RX data (from Handset):
The data signal from handset (ex: Talk, ACK, COM) is also included in 900 MHz band same as
the voice data. After second if filter, the data signal is made square shape by data limiting AMP
27