Reflectarray Antenna Using Novel SIW-Based Cavity Resonators With a Broadband Performance

This article introduces a novel reflectarray (RA) unit cell implemented in substrate-integrated waveguide (SIW) technology. The impinging field is coupled into a resonant cavity through a slot. The slot is designed to alter the resonant fields such that two highly isolated resonances are supported inside the cavity. The proposed cell design is suitable for the entire Ku-band (12.0–18.0 GHz) and achieves low losses with a typical value of 0.35 dB. At the center frequency of 15 GHz, the cell has a compact size of 0.4λ0 and a very thin profile of only 0.038 λ0 . Furthermore, the two resonances can be easily tuned independently of each other, providing high flexibility for multifrequency and broadband RA designs. To demonstrate these features, a multifrequency optimization technique is used to design a broadband RA antenna. The demonstrator is manufactured and measured, achieving a remarkable 1-dB fractional gain bandwidth of 33.3% between 12.5 and 17.5 GHz and a maximum gain of 29 dBi. The aperture efficiency is 38.9% and sidelobe levels (SLLs) are kept below −12.4 dB across the entire operating band.