THRESHOLD COMPARISON OF PHASE-LOCK, FREQUENCY-LOCK, AND MAXIMUM- LIKELIHOOD TYPES OF FM DISCRIMINATORS
Abstract
IN MAKING A COMPARISON OF DEMODULATION TECHNIQUES FOR FM signals, one of the most important criteria for evaluation is the threshold input signal-to- noise ratio (SNR). It is at this value of input SNR that the output SNR begins to decrease, substantially more rapidly than a simple proportionality to the input SNR. A consistent derivation is presented of the threshold SNR for several major types of FM discriminators, namely, the phase-lock discriminator, the frequency-lock discriminator (FM discriminator with negative feedback), and the maximum-likelihood (a posteriori, most probable) computer. This last discriminator is of interest mainly because its operation provides a bound on the performance of other types. The operation of the discriminators in the presence of gaussian interfering noise is described, and the causes of threshold are investigated.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1961
- Accession Number
- AD0263454
Entities
People
- J. J. Spilker Jr.
Organizations
- Lockheed Martin Missiles and Space