On the Resolving Power of Ground Mapping Radar Antennas

On the Resolving Power of Ground Mapping Radar Antennas
Author: J. F. McIlvenna
Publisher:
Total Pages: 66
Release: 1965
Genre: Aerial photography
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The mapping of extended, cultural ground targets by an airborne radar is examined using communication theory concepts including those of the antenna transfer function and the target spatial frequency spectrum. Use of the set of transfer functions that correspond to Taylor aperture distributions and specification of the targets directly in terms of their spatial frequency spectra, permits one to examine the antenna images for quality and resolution. The results obtained indicate that resolution for a class of ground targets can be much better than is predicted by the two-point Rayleigh resolution criterion. It is also true that there can be situations in which the shape of the antenna images are quite independent of the radiation pattern. Several types of spatial noise were also included in the input spectrum to investigate noise effects on image quality and resolution. (Author).

A Method for Estimating Atmospheric Noise Amplitudes and Phase Errors in Quenched High-Q Receiving Circuits

A Method for Estimating Atmospheric Noise Amplitudes and Phase Errors in Quenched High-Q Receiving Circuits
Author: E. A. Lewis
Publisher:
Total Pages: 50
Release: 1965
Genre: Atmospheric electricity
ISBN:
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Very narrow-band quenched filters used for studying VLF radio signals differ from conventional narrow-band circuits in that both signal and atmospheric noise impulses cause only brief quasi-sinusoidal outputs instead of a prolonged ringing. The random overlapping of these short noise and signal bursts can cause errors in phase measurements. It is shown that the distribution of phase errors can be calculated from the amplitude distribution of the output noise envelope. The properties of the phase distribution are discussed in detail, the computation required in the general case is illustrated by means of a numerical example. A simple 'time-sequential' method for experimentally obtaining typical amplitude distributions is suggested. (Author).

Plurality-count Diversity Combining for Fading M-ary Transmissions

Plurality-count Diversity Combining for Fading M-ary Transmissions
Author: John N. Pierce
Publisher:
Total Pages: 38
Release: 1965
Genre: Alphabets
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The performance of a plurality-count diversity combiner for fading M-ary transmissions is analyzed, and calculated error probabilities are presented graphically for alphabet sizes of 2, 8, and 32. The performance is shown to be within 3 dB of that of an optimum square-law combiner for moderate alphabet sizes when there is no restriction on the allowable number of diversity branches. It is shown that a worthwhile saving in transmitted power can be effected by using nonbinary alphabets with plurality-count combining for the transmission of binary data. The availability of extra information from the combiner for use with error-correction is discussed.

Matrix Criteria for Arbitrary Reliability in Iterated Neural Nets

Matrix Criteria for Arbitrary Reliability in Iterated Neural Nets
Author: Rocco H. Urbano
Publisher:
Total Pages: 12
Release: 1965
Genre: Iterative methods (Mathematics)
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In a previous paper by this author, the problem of achieving arbitrary reliability for combinatorial nets from arbitrarily unreliable elements was reduced to the study of convergence properties of an associated polynomial system. In this paper simple criteria which specify the convergence of such a system to a nodal fixed point are obtained from known results in matrix theory. (Convergence to a nodal point implies that the corresponding net approaches reliability arbitrarily near 1 for a particular function.) Theorems are also given which show that it is possible to obtain from a single system converging to a nodal fixed point, many systems having this property.