TABLE OF CONTENTS John F. Green, Ph.D.
In some ELINT applications, there is a need to collect and process signals in a manner that enables their high-fidelity demodulation. One of the most critical parameters is the minimum acceptable RF collection bandwidth. It is shown here that Carson s rule, used in communications signal engineering, can be modified appropriately to provide a relevant ELINT specification.
This modification of Carson s rule [1] is derived from an analysis of the spectrum of circular (sinusoidal) frequency-modulated signals and from an assessment of the influence of individual spectral features on demodulated signals. A quantitative evaluation is made of the degradations imposed on such signals by excessive RF spectral band limiting.
Finally, a brief derivation is presented, the results of which describe the effects of weak and moderate Gaussian noise on frequency-demodulated signals.
The intent of this section is to establish a quantitative basis for estimating the effects of an individual sinusoidal interference on phase- and frequency-demodulated signals.
If a sinusoidal interference is added to an arbitrary signal, the result can be expressed in the form:
where f o is the frequency of the sinusoidal interference and 
s( t) is the total phase of the signal, including the carrier. In (B.1), ? is taken to be a (local) constant. The analytic signal components of the signal in (B.1) are
The instantaneous phase, ( t), of the composite signal defined by (B.2) is
If...
