This paper relates to a designing method of microstrip antenna considering the bandwidth. The bandwidth becomes a maximum for a special value of characteristic impedance of the feeder. Also, the unloaded Q and resonant frequency of the microstrip antenna are shown as a function of substrate thickness with the dielectric constant as a parameter. These relation can be shown on the drawings, which are very useful for the designing of microstrip antenna considering the bandwidth. Finally, a circular microstrip antenna, of which bandwidth for VSWR2 is 8.75%, is manufactured as a designing example by using the paper honeycomb substrate and is measured for the return loss characteristic. From the fact that the measured result agrees well with the calculated result, the usefulness in this method is verified.

An improved theory to obtain circularly polarized (CP) waves from a singly fed microstrip antenna is presented. This theory indicates that a singly fed circularly polarized (SFCP) microstrip antenna, in general, is able to produce CP waves at two different frequencies, which are just slightly separated. The two CP operating frequencies can be found through an iterative process. Furthermore, the optimum feed location loci can be determined numerically. Finally, the theoretical results for two kinds of SFCP antennas are compared with the experimental results. The agreement is quite good and the theory validity is confirmed.

A Direct Radiating Array Antenna (DRAA) concept has been introduced to international satellite communications in order to achieve multiple shaped beams which are electrically reconfigurable. The subject of this paper is to describe the new design method for a reconfigurable DRAA. The design procedure consists of three steps, 1) derivation of the initial array layout using Fourier transform method (FTM) , 2) array shape rearrangement, 3) optimization of the final array excitation with the modified constraint least mean square (MCLMS) algorithm. At the first step, it is necessary to derive the initial array layout for the desired shaped beam with respect to array shape, number of antenna elements, and excitation distribution. For this purpose, a new closed form solution of FTM using N-polygonal desired coverage is used. At the second step, the array shape is rearranged to fit the beam forming network (BFN) configuration which can reduce insertion loss and influence on frequency variation sensitivity. At the third step, the array excitation is optimized using MCLMS which is exploited to satisfy the power sum constraints caused by the restriction of the BFN configuration. The design method provides useful insight regarding the layout design of a DRAA with well-shaped coverages, the low insertion loss of the BFN and the high sidelobe isolation characteristic. The design of the reconfigurable DRAA with the specified multiple shaped (beams is demonstrated and compared with the experimental model.

Based on the MSN algorithm, an adaptive algorithm capable of controlling antenna patterns by phase weight only is derived. Then, an algorithm for phase nulling convenient in case not needing adaptive weight control is derived. This algorithm with null directions only being the parameter is convenient for pattern synthesis and pattern improvement. Finally, two examples are presented to demonstrate usefulness and validity of the technique.

This paper concerns the study on the Ku band multi-beam direct radiating array antenna technology, which provides frequency reuse and reconfigurable multi-beam capabilities in satellite communication system. The study consists of two dimensional pattern synthesis, beam forming network analysis and design, and fabrication and measurement of an experimental model. The measurement results have shown that the experimental model with 64 array elements including 14 dummy elements has a low loss of less than 2 dB in average and high sidelobe and polarization isolation of more than 27 dB and 29 dB, respectively, over 1 GHz bandwidth in the Ku band. As a result of careful evaluation, it has been confirmed that the design method established here is valid and useful for multi-beam direct radiating array antenna design.