Frequency Generating Section; Block Diagrams Descriptions; Receiver Path - Motorola MTM700 Detailed Service Manual

THEORY OF OPERATION (400 MHz)

Frequency Generating Section

The frequency generating section comprises the following components:
• Reference Oscillator - TCXO
• Main Synthesizer - consists of the Main Voltage Controlled Oscillator (VCO) and Low Voltage
Fractional-N integrated circuit (LVFRACN). In receive mode, the main synthesizer provides
the local oscillator injection to the receiver first mixer. In transmit mode, this synthesizer
provides the frequency reference for the transmit frequency translation loop.
• Transmit frequency translation loop. Consists of the transmit Voltage Controlled Oscillator
(VCO) and ESCORT Near Unity Divider (NUD) Phase Locked Loop IC.

Block Diagrams Descriptions

The block diagrams descriptions cover Receiver Path, Transmitter Path, Frequency Generation
Section, and Controller Section.

Receiver Path

The received signal (see figure below) from the antenna is directed by the Antenna Switch to the
Front End Pre-selector Filter.
Antenna
Switch
Harmonic
Filter
AGC_2
Attenuator &
Buffer
16.8 MHz
Reference
from FGU
MTM700 Mobile Radio / Detailed Service Manual
Rx
AGC_0
Attenuator
Pre-selector
Tx
From Tx PA
nd
2
Mixer
LNA
Variable
Gain
Amplifier
nd
2 LO
PLL
nd
Loop
2
LO
Filter
Figure 2 Receive Path Block Diagram
st
1 LO From
FGU
AGC_1
Attenuator
Image
LNA
Mixer
Filter
Decimation
ADC
Filter
Sample
Clock
IF Digitizing
PLL
Subsystem
Sample
Loop
Clock
Filter
VCO
IF
73.35 MHz
Amplifier
First IF Filter
Formatting DSP (Part of
SSI Controller)
(BBP)
4.1 - 5
CODEC
AUDIO
PA