THEORY OF OPERATION (800 MHz) MTM700 Mobile Radio / Detailed Service Manual 4.2 - 3
Transmitter Section
The transmitter incorporates cartesian feedback circuitry to enhance transmitter linearity to reduce
power splatter into adjacent channels. The transmitter circuitry comprises the following components:
• Modulation digital to analog conversion, perfomed by:
Analog-to-Digital / Digital-to-Analog IC (ADDAG),
• Modulation up-converter, perfomed by:
Low Noise Offset Direct Conversion Transmitter integrated circuit (LNODCT),
• Balun and Attenuator,
• Linear class AB Power Amplifier (PA),
• Directional coupler,
•Isolator,
• Antenna switch, and
• Harmonic filter.
The transmitter linearization feedback signal is taken from the forward power port of the directional
coupler, attenuated, and passed to the RF feedback port of the LNODCT integrated circuit.
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