Transmitter Path - Motorola MTP700 Detailed Service Manual

4.1 - 6

Transmitter Path

When the radio is transmitting (see Figure 4.1-3), the microphone audio is sent to the
GCAP3 (CODEC). The CODEC performs 13-bit analog-to-digital conversion and the dig-
ital signal is routed to the DSP (part of RedCap2). The DSP performs coding, Error Cor-
rection and modulation. From the DSP, the digital base band signal is sent to the WPIC.
From Tx PLL
WPIC LNODCT
REDCAP2
GCAP
In the WPIC, the digital baseband I & Q signals are converted into corresponding analog
signals. These signals are also filtered. From the WPIC, I & Q signals are injected to the
LNODCT. In the LNODCT, the data is mixed with RF signal.
From the differential output of the LNODCT, the modulated RF signal is injected to the
Balun wideband transformer that transforms the differential input into single output, and
then it is routed to the antenna via TX PA, Isolator, Antenna Switch and Harmonic Filter.
The feedback signal is used for power control.
MTP700 Portable Radio / Detailed Service Manual
-1dB
-2dB
Balun
Attenuator
-8dB
Attenuator
Figure 4.1-3 Transmit Path - Block Diagram
32dB
-0.2dB
coupler
RF PA
-21dB
TRANSCEIVER 400 MHz
-0.3dB
-1dB
Antenna
Isolator
Switch
Harmonic
Filter
Power at Antenna
30dBm + 2dB