Page 454 - Complete Wireless Design
P. 454
Wireless Issues
Wireless Issues 453
Figure 10.25 Transmitter speech compression in the audio section.
Figure 10.26 Companding action between a single-sideband transmitter and receiver.
Figure 10.27 A voice clipper in the audio section of a transmitter.
peak voltage over a certain preset level. This circuit consists of an operational
amplifier with back-to-back zeners, and a resistor that sets the audio gain,
with the peak value of the baseband waveform being governed by the value of
the diodes.
The form of compression called automatic level control, or RF compression,
is found in SSB, AM, and even some FM transmitters. ALC essentially uses a
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
