Accession Number:

AD0259090

Title:

VARIABLE BANDWIDTH FM TRANSMISSION SYSTEM

Descriptive Note:

Corporate Author:

RADIO CORP OF AMERICA CAMDEN N J DEFENSE ELECTRONIC PRODUCTS

Personal Author(s):

Report Date:

1961-04-30

Pagination or Media Count:

1.0

Abstract:

An important trend in modern communications is toward adaptation of some parameter of a system in order to improve or optimize system performance. While it has been common practice to design the system around the worse case expected, a system is proposed in which data rate would be varied by adjusting the transmitted bandwidth in accordance with the prevailing conditions. The major advantage of such a design technique is efficient use of the communications channel, especially in systems such as forward propagation tropospheric scatter where the received signal power varies over a wide range. By utilizing the variable bandwidth technique, a constant signalto-noise ratio is maintained at the input of a receiver detector. Detailed investigations are included of several diversity systems, feedback loop stability, effects of errors in measurement and transmission of the control signal, effects of system delay, tape machine design and over-all system configuration. Results indicate that addition of the variable bandwidth scheme to present fixed bandwidth systems can offer at least a 12 db improvement in performance. The use of variable bandwidth transmission to compensate for changes in path length, atmospheric attenuation and antenna non-isotropism in satellite communication systems is also discussed. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE