Fine Synchronization of Coherent Frequency Hopping Signals
Abstract
A method for precise synchronization of receiver timing with a phase coherent frequency hopping signal has been developed. It is assumed that initial synchronization by other techniques has aligned the receiver frequency hopping sequence with the signal well enough so that the receiver operates on the same frequency as the signal for most of each hop period. Phase comparisons between the signal and a locally generated replica then can be made and summed over a large number of frequency hops to provide a sensitive measure of the remaining synchronization error. Frequency dependent errors in the phasing of quadrature channels in the experimental synchronizer produced ripple in the detector output. Additional ripple was produced by circuits used for combining the quadrature channel outputs. The observed ripple produced reversals in the slope of the error signal, and, in a complete system, would have led to limited instability of synchronization. Criteria have been developed for determining circuit characteristics necessary to reduce the ripple to an acceptable value. The effects on the synchronization method of frequency offsets and of several modulation types have been examined, and techniques have been proposed for maintaining close synchronization in the presence of these effects.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1975
- Accession Number
- ADA015939
Entities
People
- A. F. Thornhill
Organizations
- United States Naval Research Laboratory