Agilent Technologies E8285A Manual page 32

Introduction
Product Description
CDMA Signal Analysis
The 114.3 MHz IF also goes to the CDMA LO/IF Demodulation
assembly. This assembly provides a through path to the spectrum
analyzer (Option 102) for all RF signals, and also provides down
conversion for CDMA signals, measurements and call processing.
To downconvert the CDMA signal, the 114.3 MHz IF is mixed with a
117.9864 MHz local oscillator (LO) signal to produce a 3.6864 MHz IF.
(The LO signal is from an oscillator that is phase locked to a 10 MHz
signal from the CDMA Reference module.)
The 3.6864 MHz signal is split and goes to the Receiver DSP assembly,
and also through a variable-gain IF amplifier before IQ demodulation.
The demodulated I and Q baseband signals are then routed to the
Digital Cellsite assemblies.
Under control from the Protocol Processor assembly, the Digital Cellsite
assemblies use the demodulated IQ information to set up and maintain
calls to CDMA phones. The Digital Cellsite 1 assembly also supplies
feedback to the CDMA LO/IF Demodulation assembly to control the
level of the variable-gain IF amplifier into the demodulator.
The Receive DSP assembly converts, digitizes, and provides final
analysis on the 3.6864 MHz signal to make measurements, such as rho,
timing accuracy, carrier feedthrough, and phase error.
Figure 1-5 Analyzing CDMA Signals
CDMA LO/IF Demodulation Assembly
114.3MHz IF
from Receiver
117.9864 MHz
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IQ
3.6864 MHz
Demodulator
IF Gain Control
To Spectrum Analyzer
Digital Cellsite
1 & 2 Assemblies
I data
IQ Decoding and
Q data
CDMA Generator
Data Coding
Receive DSP Assembly
CDMA IQ Modulation
Protocol
Processor
Call Setup and
Control
Measurements