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

TRANSCEIVER 800 MHz

Detailed Circuit Description

Receiver Path, Detailed Circuit Description

See Figure 4.2-6
TETRA
AntSW
IL=0.7dB
From
TETRA
TX
From
VCNTO
pin of
WPIC
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.
MTP700 Portable Radio / Detailed Service Manual
Integrated
LNA
Gain=15dB
I=7.5 mA
SAW Filter
From
IL=2dB
GP05
WPIC
Limiter
Figure 4.2-6 Receive Path Circuit Diagram
Mixer
CG=3.0dB
I=5.0mA
LO Level=
SAW Filter
-2 to -4 dBm
IL=2dB
From
GP06
WPIC
Baseband
Filter
GP06
GP05
Divide
by 2
From
nd
2 LO
From
TETRA
Main VCO
XTAL
IF
Filter
Balun
109.65MHz
IL=2.5dB
WPIC
I=13mA
SSI
Redcap2
A/D
(DSP)
4.2 - 11