Dual-band reflectarrays using microstrip ring elements and their applications with various feeding arrangements

摘要

In recent years there has been a growing demand for reduced mass, small launchvolume, and, at the same time, high-gain large-aperture antenna systems in modernspace-borne applications. This dissertation introduces new techniques for dual-bandreflectarray antennas to meet these requirements. A series of developments is presentedto show the dual-band capability of the reflectarray.A novel microstrip ring structure has been developed to achieve circularpolarization (CP). A C/Ka dual-band front-fed reflectarray antenna has been designed todemonstrate the dual-band circular polarized operation. The proposed ring structureprovides many advantages of compact size, more freedom in the selection of elementspacing, less blockage between circuit layers, and broader CP bandwidth as compared tothe patches.An X/Ka dual-band offset-fed reflectarray is made of thin membranes, with theirthickness equal to 0.0508 mm in both layers. Several degrading effects of thin substratesare discussed. To overcome these problems, a new configuration is developed byinserting empty spaces of the proper thickness below both the X and Ka bandmembranes. More than 50 % efficiencies are achieved at both frequency ranges, and the proposed scheme is expected to be a good candidate to meet the demand for futureinflatable antenna systems.An X/Ka dual-band microstrip reflectarray with circular polarization has also beenconstructed using thin membranes and a Cassegrain offset-fed configuration. It isbelieved that this is the first Cassegrain reflectarray ever developed. This antenna has a0.75-meter-diameter aperture and uses a metallic sub-reflector and angular-rotatedannular ring elements. It achieved a measured 3 dB gain bandwidth of 700 MHz at Xbandand 1.5 GHz at Ka-band, as well as a CP bandwidth (3 dB axial ratio) of more than700 MHz at X-band and more than 2 GHz at Ka-band. The measured peak efficienciesare 49.8 % at X-band and 48. 2 % at Ka-band.In summary, this dissertation presents a series of new research developments tosupport the dual-band operation of the reflectarray antenna. The results of this work arecurrently being implemented onto a 3-meter reflectarray with inflatable structures at theJet Propulsion Laboratory and are planned for other applications such as an 8-meterinflatable reflectarray in the near future.