User's Manual

14
Circuit Description
1. Frequency Configuration
The receiver utilizes double conversion. The first IF is 21.7 MHz and the second is 450
KHz. The first local oscillator signal is supplied from PLL circuit. PLL circuit in the
transmitter generates the necessary frequencies. Figure 1 shows the frequency
configuration.
Frequency range: TC1688P: 460—470MHz
(Please refer to “appendix1: TC1688P frequency chart” for more details.)
1 2 3 4
A
B
C
D
4
321
D
C
B
A
Title
Number RevisionSize
B
Date: 4-Feb-2004 Sheet of
File: D:\RPV599A V2.0\material\TC-168~2.DDBDrawn By:
ANT
ANTSW
RF AMP
MCF
21.7MHz
CF
450KHz
SYSTEM
AF AMP
SP
IF
TCXO 21.25MHz
MIC
MIC AMP
PLL
VCO
RX
TX
TX AMP
PA AMP
PLL
Fig1. Frequency Configuration
2. Receiver
The receiver utilizes double conversion super heterodyne.
1) Front-end RF Amplifier
The signal from the antenna passes through a transmit/receive switch circuit
before entering the SAW filter F1 to eliminate unwanted signals, and then is
amplified at RF amplifier Q11. The resulting amplified signal then goes to the first
mixer.
Fig.2 Receiver Section Configuration