4.1 - 2
Receiver Section
The receiver section includes the following main components:
•
Antenna Switch
•
AGC_0 Attenuator
•
Front End Pre-selector Filter
•
Low Noise Amplifier (LNA)
•
AGC_1 Attenuator
•
Second Pre-selector Filter
•
Mixer
•
IF Filter
•
IF Amplifier
•
AGC_2 Attenuator and Buffer
•
IF Digitizing Subsystem
The Receiver Path implements an Automatic Gain Control (AGC), which is required to maintain
good receiver linearity over a wide range of incoming signal levels and prevents clipping of high
level signals.
The IF Digitizing Subsystem performs the following functions:
•
Carries out amplification and down conversion of the signal into the second IF.
•
Performs IF AGC.
•
Converts the second IF analog signal into baseband digital I & Q format.
•
Transmits the I & Q baseband data to the DSP for further processing.
•
Synthesizes the second LO frequency.
•
Synthesizes the Sigma-Delta clock.
MTM700 Mobile Radio / Detailed Service Manual
THEORY OF OPERATION (400 MHz)