The Effect of a Specular Component on the Correlation Between the Signals Received on Spaced Antennas

Self Cite

Phase difference measurements made with an accuracy of 5° between pairs of antennas separated by up to 150 yards in three directions (N, E, and SW) show that radio waves reflected from the ionosphere are generally not sufficiently stable in direction for any particular component to be regarded as being specular in the usual sense. It is concluded that the coherence ratio should be regarded as equal to zero except in very special one‐hop cases. The equipment used for the measurements is described in general form.

Section: Assumptionsmentioning

confidence: 71%

Measurements of the Coherence Ratio of Ionospherically Propagated Radio Waves

Whale¹,

Boys²

1968

Self Cite

“…The latter is subject to df performance degradation (wave interference error) to the extent the mode contains micromultipath, unresolved in group delay. Some measure of micromultipath, however, is expected at virtually any degree of mode resolution, as suggested by various observations of single modes [Rice, 1975;Sweeney, 1970], and theories of single ionospheric mode coherence [Bramley, 1954;Whale, 1966]. In these df ionograms magnetoionic modes were unresolved, thus introducing a relatively small amoum of wave interference error, based on the estimates of magnetoionic splitting of the order of a few tenths degree made by Gething [1991].…”

Section: Mode Structurementioning

confidence: 99%

A direction finding ionosonde for ionospheric propagation research

Black¹,

Wood²,

Sonsteby³

et al. 1993

A direction finding ionosonde consisting of a seven‐element, 50‐m crossed baseline interferometer has been developed to provide group path delay, azimuth, and elevation of each resolved mode over the sounding frequency range. Direction finding (df) ionograms have been acquired automatically, using various noncooperative compatible sounder transmissions. A diurnal sequence of df ionograms obtained over a 2344‐km mid‐latitude path is reported, including plots of group delay, azimuth, and elevation versus frequency, as well as an azimuth/elevation scatterplot showing the distribution of angular occupancy for the path. The results show modes arriving closest to the great circle bearing (that is, with lowest azimuth error) arrive via the lowest elevation angles and with least group delay. Greatest bearing accuracy was observed on daytime sporadic E modes; measured at 0.85 MOF, the azimuth standard deviation was 0.3°. One‐hop F region low‐ray azimuth measured at 0.85 MOF showed standard deviations between 0.4° and 0.98°. Fractional degrees per megahertz linear azimuth gradients with frequency were also observed at various times of day. One‐hop F region high rays showed smoothly varying elevation as a function of frequency, increasing with group path delay as expected. Variable lateral deviation from the great circle plane was observed for high rays up to 5° in azimuth equatorward at various times of day; azimuth standard deviation at 0.85 MOF varied from 0.91° to 1.7°.

“…These two parameters, which we shall call respectively the "coherence ratio" and the "wavefront correlation," have been related to more directly observable statistical quantities by a number of workers. For present purposes, the work of Bramley (1951) and of Whale and Gardiner (1966) is particularly pertinent.…”

Section: Introductionmentioning

confidence: 99%

Interferometer Phase and Amplitude Measurements for Determining Coherence Ratio and Wavefront Correlation

Fremouw

Lansinger

1967

Numerical results are presented which describe the statistics of scattered signals observed with an interferometer. The ratio of nonscattered to scattered flux and the wavefront autocorrelation are related to the distributions and average characteristics of real amplitude product and phase difference. It is shown how a combination of pure amplitude and phase‐dominated information can yield unique solutions for the two wavefront parameters without a priori information concerning them. The treatment is based on assumption of a randomly phased angular spectrum.