THEORY OF OPERATION (TRANSCEIVER) 4.1 - 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, performed by:
Analog-to-Digital / Digital-to-Analog IC (ADDAG),
• Modulation up-converter, performed by:
Low Noise Offset Direct Conversion Transmitter integrated circuit (JAVELIN),
• Balun and Attenuator,
• Linear class AB Power Amplifier (PA),
• Directional coupler,
• Isolator (depends on terminal model)
• 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 JAVELIN integrated circuit.
Controller Section
This section includes the Patriot Bravo, which controls the transmit, receive and synthesize
operations of the integrated circuits located in the RF section. Within the Patriot Bravo are the DSP
and the serial interfaces.
The controller section contains the following:
• Voltage regulators
• Power On/Off circuitry
• Patriot Bravo
• Host memories (FLASH and SRAM)
• Serial peripheral interface (SPI)
• RS232, USB, SB9600, SBEP serial interfaces
• RX and TX path multiplexer
• Programmable potentiometer
•CODEC
• Audio power amplifier (PA)
6866539D31.book Page 3 Tuesday, March 20, 2007 6:32 PM
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