Agilent Technologies 8960 10 Series Reference Manual page 505

temperature.
The sampled input power from the directional bridge can be amplified by as many as two 18 dB range
amplifiers and then can be directed to the fast detector, or the slow detector. The input power to the fast
detector is detected by a diode detector that is part of a feedback loop. The input to the slow detector is
measured in a bridge using a pair of RMS thermal detectors in a feedback loop. Signals from the fast and slow
power detectors are calibrated with Gain DAC's. Video gain can be applied in 6 dB and 1.5 dB steps.
Signal Downconversion
The test set's downconversion receiver section has two downconversion modules; a high performance
Measurement Downconversion Module for making measurements, and a Demodulation Downconversion
Module for maintaining the radio link.
Measurement Downconverter Module The Measurement Downconverter module is a part of the receiver,
it provides high quality (wide dynamic range, spurious free) signals to the Analog To Digital Converter
module's measurement sampler input. These signals are:
• 10 KHz - 6 MHz Intermediate Frequency signal
• detected envelope of the Intermediate Frequency signal
The Measurement Downconverter module is designed for very high performance operation to ensure accurate
and repeatable measurement results. The Measurement Downconverter module contains two downconversion
stages, two local oscillators, and a logarithmic IF envelope detector . Both first and second LO synthesizers are
tunable. The first LO is used when tuning to the RF input frequency, and the second LO is used when setting
second IF frequency, which is fed to the measurement sampler on the Analog To Digital Converter module.
Demodulation Downconverter Module The Demodulation Downconverter module is used as part of the
demodulation receiver to maintain the radio link of a given TA. The IF signal from the Demodulation
Downconverter is sent to the Analog to Digital Converter, the digital data then goes to the protocol subsystem.
That data allows the Protocol Processor module to set up a call with the DUT so that testing can be performed
on the radio.
The Demodulation Downconverter module is also used as part of the BER testing path. For bit error ratio
measurements the bits tested by the Protocol Processor module are taken from this path. The demodulated
bits provided to the Protocol Processor contain the data that will be checked for errors.
Analog To Digital Converter Module
Following the Measurement Downconverter and Demodulation Downconverter modules is the Analog to
Digital Converter module. The purpose of the Analog to Digital Converter module is to convert the
downconverted analog signals into digital data streams which can be processed by the Digital Signal
Processing module.
In order to maintain the radio link of a given TA, the downconversion path through the Demodulation
Downconverter module has a dedicated A/D conversion path.
In order to optimize measurement throughput, the fast RF power detector also has a single dedicated A/D
path. This allows power measurements, in many cases, to be made concurrently with other measurements.
The two outputs from the Measurement Downconverter module, and the Audio In signal share a single
multiplexed A/D path.
The outputs of the various analog to digital converters on the Analog to Digital Converter module share a
common data bus to the Digital Signal Processing module.
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Block Diagram
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