Search

Fractal geometries are appealing in all applications where miniaturization capabilities are required, ranging from antennas to frequency selective surfaces (FSS) design. Recently, some fractal patches configurations, giving low losses, reduced size, and quite good phase ranges, have been proposed for the design of reflectarray unit cells. This paper reviews existing fractal-based reflectarrays, highlighting their benefits and limitations. Furthermore, a comprehensive analysis of an innovative reflectarray unit cell, using a fractal-shaped fixed-size patch, is presented. The miniaturization capabilities of the Minkowski fractal shape are fully exploited to obtain a compact cell offering quite good phase agility, by leaving unchanged the patch size and acting only on the fractal scaling factor. Experimental validations are fully discussed on a realized 10 GHz 0.3λ×0.3λ cell. This is subsequently adopted to synthesize various reflectarray prototypes offering single or multiple-beam capabilities over a quite large angular region (up to 50 degrees). Finally, experimental validations on a realized 15×15 elements prototype are presented to demonstrate the wide angle beam-pointing capabilities as well as a quite large bandwidth of about 6%. [ABSTRACT FROM AUTHOR]

An electronically tunable reflectarray element is proposed in this work to design beam-steering antennas useful for radar applications. A reduced size reflectarray unit cell is properly synthesized in order to extend the antenna beam scanning capabilities within a wider angular region. The radiating structure is accurately optimized to provide a full phase tuning range by adopting a single varactor load as phase shifter element. A 0.46λ-reflectarray cell is designed at the frequency of 11.5GHz, obtaining a phase agility of about 330°. The cell is successfully adopted for the design of a 21 X 21 reconfigurable reflectarray. The antenna is numerically tested for different configurations of the varactors capacitance values, and good beam-steering performances are demonstrated within a wide angular range. [ABSTRACT FROM AUTHOR]

An extensive analysis is performed on the aperture-coupled reflectarray configuration to highlight and quantify the bandwidth enhancement due to the use of reduced inter-element spacings. Bandwidth extension is directly evaluated on the phase curves relative to the reflection coefficient against frequency for different lengths of the tuning line. The operating frequency range computed with the proposed approach is numerically validated on the gain patterns of synthesized reflectarrays and a strong broadband behavior is demonstrated for reflectarrays of moderate aperture dimensions and reduced unit cell size. [ABSTRACT FROM AUTHOR]

The design of microstrip reflect arrays requires the use of a design curve to correlate the phase of the reradiated field and the size of the elements. In this Letter this parameter has been evaluated by analyzing the field scattered from an isolated reflect-array unit cell. As a test case a microstrip reflect array has been designed with the use of these data. Even if this approach neglects the mutual coupling effects, the measured reflect-array radiation pattern shows that the main beam steering agrees with the design requirements. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 411–414, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10479 [ABSTRACT FROM AUTHOR]