16.6.2. Handset to Base
Circuit Operation:
The voice signal from the handset user is picked up by the microphone (MC1), voice signal passes through "Comp ressor"
process to reduce noise as shown in BLOCK DIAGRAM (HANDSET) (P.37). And the voice is FM-modula ted byVARIC AP
(DV1).
The carrier frequency is generated by TXVCO. The transmitter power transistor Q4 is turned on/off by CPU (VTX).
The carrier signal is amplified by RF AMP and sent to the handset duplexer and antenn a.
The signal of 49MHz band (49.670~49.99MHz) which is input from ANT isfiltered at DPX1 as shown in
BLOCK DIAGRAM (BASE UNIT) (P.36), then it is input to RF IC.
The signal input to RF IC is converted through Mixer inside of RF IC, RF filter (CF1, CF2) and Expande r.
The signal is transmitted from the handset and received by the base unit antenna and amplified by RF amplifier Q1, then it is
converted to10.7 MHz and 450 KHz Intermediate by RFIC. The demod ulated audio signal is output from RF IC (DET OUT) and
passed through "Expander" process to reduce noise, then voice signal is led to LINE AMP.
The signal is passed through TELEPHONE INTERFACE and Tel-line.
RX data (from Handset):
The data signal from handset (ex: Talk, ACK, COM) is also included in 49 MHz band same as the voice data. After second if
filter, the data signal is made square shape by data limiting AMP of the RF IC. RXdata is output to CPU (RX Data).
16.6.3. RF signal operation/control and PLLoperation (RFUNIT)
Base unit radio frequency signal received by antenna passes through duplexer (DPX1). RF signal is amplified by RF AMP.
RF signal received from RF IC is mixed with RX local frequency at Mixer to generate 10.7 MHz wide band IF. The reference
frequency is generated by X1 11.15 MHzcrystal.
VC1 isthe referen cefrequen cy for adjustment. The 10.7 MHz is mixed withreferen ce and 450KHz narrow band IF is generated.
The demodulation audio signal is adjusted to the maximum at T1.
RF IC iscontrol led byCPU (RF_ST B, DATA, CLK). The RXlocal frequency is generated by RXVCO.
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KX-TC1205RUB / KX-TC1205RUW / KX-TC1205R US / KX-TC1205RUF