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.

The authors propose a new circular polarization method for a slot-coupled microstrip antenna. The simple configuration antenna in which a parasitically excited slot exists in addition to a directly excited slot generates circular polarization, by the effect of higher order modes. Experimental results and numerical results using the Spatial Network Method are described to verify the performance and discuss the circular polarization generating mechanism.

Results of a DC motor driving test with a power sent by a microwave and extracted with a rectenna array are reported. No significant difference has been observed in the output DC power from the rectenna array between a motor load and a resistive load. Mechanical output could be extracted from the received microwave power with an efficiency of 26%.

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.

The authors propose a multiple shaped beam antenna which uses a single shaped reflector and simple feeds. This new type of multibeam antenna is very attractive for satellite communications and broadcasting because its beam-forming network is much simpler than conventional multibeam reflector antennas which uses cluster feeds. The design method for shaping the reflector surface is described, which is based on the concept of an equivalent array. By using this method, a design example is shown, in which the Japanese main islands are covered with four beams and twofold frequency reuse is operated. Also, the basic performance of this new antenna is clarified numerically.

A new circularly polarized microstrip antenna fed by a cross slot using an aperture coupled feed is proposed. The proposed antenna has no 90 degree hybrid coupler for circular polarization and allows easy connection to microwave devices for electronical beam scanning. In this paper, the conditions for circular polarization in this new antenna are derived, and the measured results are also described to verify the authors' proposed conditions for circular polarization. Good return loss and axial ratio characteristics have been obtained.

A new pattern synthesis method for multibeam reflector antennas is described. The Directional Constrained Minimum Power (DCMP) method, which was developed as an adaptive array algorithm, has been applied to reflector antennas with cluster feeds. The main objective of this pattern synthesis is to optimize the excitation distribution of the cluster primary feed in order to reduce the sidelobe level and to attain a high main beam gain. A desired contour beam pattern has also been attained by modifying this method. Furthermore, this paper describes other applications of this method, such as pattern optimization taking account of the frequency characteristics and the change in the radiation pattern due to an antenna pointing system, cross-polarization reduction, and monopulse pattern synthesis for an RF sensor.