HF Direction Finding by Wavefront Testing,
Abstract
Calculations are reported of the probability of observation of various degrees of phase-front non-linearity, for two and three signals incident from different directions upon a phase-measuring array. It is assumed that the signals fade independently, and that their amplitude probability densities are described by a Rayleigh law. It is shown that, under the worst-case conditions of equal powers in the signals, the probability of observing an rms phase deviation of 25 degrees or less from the best-fit straight line to the phase along an array, is about 0.5 when 2 rays are present, and about 0.2 when 3 rays are present. Experimental measurements over a 911-km mid-latitude path and a 2100-km trans-auroral-zone path, confirm the general behaviour predicted by the theory. It is well known that amplitude fading can be attributed to various ionospheric effects; however the measurements show that modulation imposed on the signal at the transmitter can also play an important part in decorrelating the amplitudes of signals received (after different time delays) via different ionospheric modes. In the latter case, the modulation can markedly reduce both the waiting time between phase-linear events, and their duration. The experimental program included concurrent measurements over the same path using FMCW, CW and SSB signals from a co-operative transmitter.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1980
- Accession Number
- ADA084549
Entities
People
- D. W. Rice
Organizations
- Communications Research Centre Canada