Agilent Technologies E8285A Manual page 33

RF Signal Generation
The Signal Generator Synthesizer assembly creates a 500 to 1000 MHz
signal. The reference signal for the synthesizer is supplied by the High
Stability Reference assembly. The synthesizer's frequency is varied
using a divider network in the feedback circuit of the phase locked loop.
Any FM modulation signal (from the Modulation Distribution
assembly), and the frequency sweep signal for the spectrum analyzer
and tracking generator, are integrated into this feedback loop. If a
CDMA signal is not being generated, the 500-1000 MHz signal is
passed through the I/Q Modulator assembly, bypassing the I/Q
modulator.
IQ Modulation
If a CDMA signal is being generated, the signal is I/Q modulated in the
I/Q Modulator assembly, using data from the Analog Cellsite assembly.
The Analog Cellsite assembly gets its data from the two Digital Cellsite
assemblies, which are controlled by the Protocol Processor assembly. Up
to eight code channels of CDMA modulation data and noise may be
summed into the IQ modulator at one time. These channels provide
phone paging, synchronization, voice (traffic) transmission, and other
CDMA system functions.
Final Frequency Conversion and Leveling
Test Sets with firmware revision A.04.5X and above operate only at RF
NOTE
frequencies from 800 to 1000 MHz and 1700 to 2000 MHz. A text only error
message "Input value out of range" , will be displayed if invalid
frequencies are set.
The RF Output assembly performs three tasks:
• Mixes or divides the 500 to 1000 MHz signal to produce signals
• Provides AM modulation (when selected).
• Controls the signal level out of the assembly using an Automatic
The signal from the RF Output assembly is sent to one of two paths in
the Upconverter assembly. RF frequencies from 30 MHz to 1 GHz route
through the bypass path. PCS frequencies are upconverted to supply
frequencies from 1700 to 2000 MHz. The user-selected frequency
contains desired modulation (AM, FM, or CDMA), or a continuous wave
(CW) signal. The level has been adjusted to provide the required level
(after going through RF I/O assembly).
below 500 MHz (down to 30 MHz). A 1 GHz LO from the Reference
assembly is used for mixing.
Level Control (ALC) loop.
Introduction
Product Description
33