Discussion Of SAMB Radiation Patterns 



Some general conclusions can be drawn from the analysis of the SAMB 

 antenna-radiation patterns. 



1. Beam-position shift with frequency occurs for systems not using true-time- 

 delay beam-steering techniques. Approximately 15° shift is observed for scan 

 angles on the order of 45° in the matrix-fed system over a 30-percent frequency band. 



2. The true-time-delay method exhibits good radiation-pattern behavior over 

 the 30-percent frequency band, and for all scan angles less than +45°. Side-lobe 

 levels remain under -20 dB and main beam shape is maintained 



3. If the scan angle is decreased, then the usable frequency bandwidth for 

 the time-delay method is increased. 



4. The bandwidth of the matrix method is less than that of the time-delay 

 method with respect to side-lobe level and main-beam shape. The side lobes 

 remain under -20 dB for about a 15-percent band. However, since the development 

 of the systems described, advances in the design of the hybrid matrix have ex- 

 tended the usable bandwidth of a matrix to well over an octave Hence, the matrix 

 cannot be ruled out for wideband applications. 



5. When simultaneous multiple beams are desired, the matrix offers an excel- 

 lent method for achieving them. 



34 



