Motorola MagOne Посібник - Сторінка 19
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Section 2
THEORY OF OPERATION
1.0
Overview
1.1
Purpose
This section defines the theory of operation (or the Circuit Description) for the radio. At the same
time, it provides a description of the circuit theory and analysis of the radio hardware design.
1.2
General Description
The radio comprises of one main PCB. This main PCB contains the RF and digital circuits. The VHF/
UHF compliant handheld transceivers consists of a receiver, a transmitter, a phase-locked loop
(PLL) frequency synthesizer, control circuits and power supply circuits.
2.0
Receiver System
LPF
ANT-SW
CR301,2
The receiver is a double conversion super heterodyne with first IF frequency at 45.1MHz and
second IF frequency at 455kHz.
2.1
Front-End
The front-end consists of a low pass filter, pre-selector filter, RF Amplifier, and a post-selector filter.
The receive signal from the antenna is applied to TX LPF (L409, L410, C426, C427, C428, C429,
C430) and then routed to an RF amplifier (Q301) after passing transmit / receive switch (CR401,
CR301, CR302) and the pre-selector. The signal from the pre-selector is amplified around 13dB at
PRESLECTOR
LNA
FILTER
Q301
F.T.V.
POST SELECTOR
1'ST MIX
Q302
FILTER
VCO
Inj FILTER
Recovered AUDIO
MCF
45.1MHz
DESCRIMI
NATOR
455C24
IF AMP
IF,MIX
U201
Q303
CF1,2
X-TAL
44.645MHz
N/S
SW
2-1