Motorola MTP700 - Detailed Circuit Description; Receiver Path, Detailed Circuit Description

TRANSCEIVER 800 MHz MTP700 Portable Radio / Detailed Service Manual 4.2 - 11
Detailed Circuit Description
Receiver Path, Detailed Circuit Description
See Figure 4.2-6
Figure 4.2-6 Receive Path Circuit Diagram
Antenna Switch
The signal coming from the antenna is routed to the receiver section via the harmonic fil-
ter, which is comprised of C943, L912 and C944. The signal continues to flow through
L915 and C940, to the Rx section, toward limiter diode D500. The attenuation of wanted
signal is typically 0.7dB.
Limiter
The limiter (D500) function is to limit the signal levels of signal with power higher than
5dBm, which may damage the receiver front-end. L500 resonates out the diode stray
capacitance.
Limiter
Baseband
Filter
A/D
Divide
by 2
Redcap2
(
DSP
)
GP06
GP05
WPIC
I=13mA
From
TETRA
Main VCO
Balun
XTAL
IF
Filter
109.65MHz
IL=2.5dB
SAW Filter
IL=2dB
SAW Filter
IL=2dB
Integrated
LNA
Gain=15dB
I=7.5 mA
Mixer
CG=3.0dB
I=5.0mA
LO Level=
-2 to -4 dBm
TETRA
AntSW
IL=0.7dB
From
TETRA
TX
From
VCNTO
pin of
WPIC
From
GP05
WPIC
From
GP06
WPIC
From
2
nd
LO
SSI