Block Diagrams Descriptions; Receiver Path - Motorola MTP700 Detailed Service Manual

TRANSCEIVER 400 MHz

Block Diagrams Descriptions

The block diagrams descriptions cover Receiver Path, Transmitter Path, Frequency Gen-
eration Section and Digital Section.

Receiver Path

The received signal (see Figure 4.1-2 ) from the antenna is directed by the Antenna
Switch to the Pre-selection Filter.
AntSW
IL=0.7dB
From
TETRA
TX
From
VCNTO
pin of
WPIC
The Pre-selection Filter blocks the half IF and image frequencies and reduces the RF
oscillator leakage to the antenna. The mid-frequency of this front filter is tuneable in five
steps to achieve the required selectivity for the entire receive frequency range 380-
430MHz. Additional selectivity is provided by a fixed-tuned Post-selection Filter. The fil-
tered signal is mixed (at high side) with the signal of the Main Synthesizer to create the
first IF at 109.65 MHz. The IF signal is filtered by the crystal filter and sent to the WPIC.
The WPIC performs down conversion to the baseband frequency (0 Hz). The baseband
analog signals are converted to digital In-phase (I) and Quadrature (Q) formats. This data
is sent for further processing to the Digital Signal Processor (DSP) (part of RedCap2)
over the Synchronous Serial Interface (SSI) data links.
The DSP performs: the demodulation, Forward Error Correction (FEC) and other correc-
tion algorithms for overcoming channel errors, and decoder procedure for digital speech
data decompression.
MTP700 Portable Radio / Detailed Service Manual
Integrated
LNA
Gain=18dB
Pre-selection Filter
I=7.5 mA
IL=2dB
FE_CNTL
Limiter
Figure 4.1-2 Receive Path - Block Diagram
From Main Synthesizer
LO level = 0 dBm
489.65 – 539.65 MHz
Mixer
Gain= -6dB
I=5.0m
LO Level=-4dBm
Post-selection Filter
IL=2dB
Q2200
2.775V
Baseband
Filter
GP06
GP05
Divide
XTALWARP
by 2
nd
From 2 LO
XTAL
A
IF Filter
Balun
109.65MHz
IL=2dB
Q2400
2.775V
WPIC
I=13mA
SSI
Redcap2
(DSP)
A/D
4.1 - 5