Motorola MTP700 - Transmitter Path

4.1 - 6 MTP700 Portable Radio / Detailed Service Manual TRANSCEIVER 400 MHz
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.
Figure 4.1-3 Transmit Path - Block Diagram
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.
GCAP
REDCAP2
WPIC
From Tx PLL
LNODCT
Balun
Attenuator
Attenuator
RF PA
-1dB
-2dB
32dB
-8dB
Isolator
-0.2dB
-21dB
-1dB
Antenna
Switch
Harmonic
Filter
-0.3dB
Power at Antenna
30dBm +
2dB
coupler