Analysis and Design of Reflectarray Antennas Based on Delay Lines: A Filter Perspective

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Abstract
The analysis and design of reflectarray (RA) antennas based in delay lines is introduced for the first time from a filter perspective. To this purpose, each unit-cell of the RA is considered as a network composed of two ports, one being the delay line and the other one the free-space. This approach allows to borrow the coupling matrix formalism from filter theory and apply it to design unit-cells exhibiting broadband operation together with very sharp frequency responses. The concept is demonstrated with the aid of planar printed unit-cells coupled to substrate integrated waveguides (SIWs) through slots, a configuration that offers significant advantages to shape its frequency response while providing relatively low loss. With the aim of validation, a third order filter structure integrated in SIW-based unit-cells has been experimentally tested using the waveguide simulator technique, at a center frequency of 9 GHz. Measurements demonstrate a high-quality linear phase variation and range, and large frequency selectivity together with broadband response for the element of about 18%. The experimental results show the feasibility of this approach for the design of broadband reflectarray antennas exhibiting sharp gain responses. To illustrate the concept, a medium size reflectarray has been theoretically designed using the proposed unit cell at 9 GHz, showing a directive beam with 35.8 dB gain, sharp gain selectivity over 18 dB, and confirms the wide band operation with 20.3% bandwidth for a 3 dB gain variation.
Funding Information
  • National Science Foundation (ECCS-1749177)
  • Universidad Politécnica de Madrid (ECCS-1749177)
  • Ministerio de Ciencia e Innovación (TEC2016-75103-C2-1-R, TEC2016-75934-C4-4-R)
  • China Scholarship Council (201706030132)
  • Ministerio de Ciencia y Tecnología (20147/EE/17, PRX18/0009256)

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