A comparative study of linear array synthesis technique using a personal computer

Five computer programs for synthesizing low-sidelobe sum patterns from linear arrays are evaluated in terms of run time and precision. Three of the programs are based on the Dolph-Chebyshev synthesis procedure, in which all sidelobes are set at the same level. The other two programs are based on a discretized version of the Taylor synthesis procedure, in which far-out sidelobes are allowed to decay. The programs were written for use on small 8- and 16-bit personal computers. It was found that the fastest running programs are also the most precise. The only Chebyshev program that gave satisfactory precision for arrays as large as 100 elements is based on Bresler's nested product algorithm, and the only similarly acceptable Taylor program is based on Shelton's discretized synthesis.     

Optimization of a hybrid SFH/DS MFSK link in the presence of worstcase multitone jamming

The performance of a hybrid slow frequency hopped direct sequence multiple frequency shift keyed (SFH/DS MFSK) communication link in the presence of partial band multitone jamming is considered. The communication signal is characterized by a DS-spread MFSK signal bandwidth that may exceed the FH slot spacing, and the signal consists of multiple M-ary symbols per DS code period. An equation for the bit error rate (BER) is developed for the signal in the presence of multitone jamming. The equation is flexible enough to allow examination of optimization of jamming strategy. It is shown that the jamming strategy may be optimized by varying the number of tones, their placement, or both. It is shown that in the presence of optimized jamming, overlapping systems are more resistant to jamming than nonoverlapping systems with equal parameters (except for the number of FH slots). It is also demonstrated that, in some cases, the addition of DS spreading to an FH system, without increasing the total system bandwidth, can significantly improve the system's resistance to partial band multitone jamming     

Energy considerations in open and closed waveguides

Energy relations derived for a lossless closed uniform and periodic structure show that the total complex Poynting vector integrated over the cross section is identically zero for the case of an arbitrary complex wave. These results are also applicable to open structures provided certain conditions are satisfied. The application of these results in the field of leaky wave antennas is discussed. Two illustrative examples, those of the sinusoidally modulated reactance surface and the sheath helix, are worked out. It is shown that although the slope of the dispersion curve can no longer be associated with the direction of net power flow, the knowledge of the slope may still be helpful in selecting certain modes for representing a given source.     

Synthesis of planar arrays based on convolution technique

A noniterative synthesis technique for planar arrays with arbitrary triangular lattice is described. The method, using a convolution process, synthesises the pattern nulls which may be completely arbitrary. An example of a 36-element diamond array synthesis is presented.