Agilent Technologies 8960 Series Reference Manual page 490

Block Diagram
Audio 2 Path The Audio 2 path provides a secondary means for sending analog baseband signals to the FM
modulator. Audio 2 contains only one source, a DDS similar to that used for Audio 1.
Typically, the Audio 2 path DDS is used for cases where multiple signals must be summed together with the
lowest possible distortion. Another potential use of Audio 2 would be to obtain higher output levels than Audio
1 is capable of (up to twice as much), assuming the two outputs are set to the same frequency and phase, and
then summed together at the Baseband Generator module.
Audio 2 is rarely used in practice because the DDS used for Audio 2 is the same DDS that is used for the front
panel audio output.
Audio Out Path Any one of four inputs may be coupled to the front panel audio output connector. These
include a 4 channel DDS (shared with Audio 2), receiver discriminator audio from the Demodulation
Downconverter module, audio echo from the Analog To Digital Converter module, and audio vocoder.
The front panel output is capable of providing signal levels up to 9 V peak into > 600 ohm loads, and up to 0.8
V peak into an 8 ohm load (e.g. speaker). The output level is calibrated for all modes except discriminator
audio,
The discriminator audio has an uncalibrated volume control provided due to the high tolerances involved.
Typically the DDS mode is used to feed the MIC input of a radio, or it may simply be used as a general purpose
low distortion function generator.
Audio echo can be selected to route the received audio to the front panel audio output connector.
RF Sources
The test set has up to two identical RF sources. The RF sources are used to provide analog or digitally
modulated RF carriers for use in parametric testing of mobile stations encompassing a variety of cellular radio
formats. In general, the sources have a frequency range of 292 MHz to 2.7 GHz and an amplitude range of -10
dBm to -127 dBm.
The RF sources consist of a Synthesized Signal Generator module followed by a Vector Output module and an
RF Attenuator module. Baseband modulation information is supplied to the RF sources from a Baseband
Generator module preceded by an Audio Section module.
Baseband Generators
The purpose of the Baseband Generator module is to provide, for the modulation type currently in effect,
properly formatted baseband signals to the modulation circuits on the RF Source modules.
The Baseband Generator performs several functions related to the generation and processing of these
base-band modulation signals. These are:
• Transform data and clock signals from the Protocol Processor module into base-band analog I/Q modulation signals for
the I/Q modulator in the Vector Output module
• Transform data from the Protocol Processor module into baseband FSK modulation for the FM modulator in the Signal
Generator module
• Provide baseband FM path source selection, gain adjustment and summing node for analog FM signals from the Audio
module and internally generated baseband FSK signals which are output to the FM modulator in the Signal Generator
module
• Transform burst and adjacent timeslot signals from the Protocol Processor module into baseband burst modulation signals
for the burst modulator in the Vector Output module
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