Tunable SIW Structures: Antennas, VCOs, and Filters

Due to their high quality factor (hundreds), high power handling, and good isolation, SIW structures are excellent candidates for a variety of microwave devices, including filters, antennas, VCOs, and isolators. However, their use has been hindered due to their narrow BW and high sensitivity to the fabrication process. Tuning the SIW-based microwave structures has the advantages of covering more bands, the possibility of post-fabrication fine-tuning, and less crosstalk sensitivity. However, the conventional tuning methods applicable to regular microwave structures are not effective for SIWs. Finding a way to tune these structures over a wide tuning range while maintaining their high Q seems to be very appealing and, at the same time, very challenging. To address all these points in more detail, the main focus of this article was on frequency-tunable/ reconfigurable SIW structures. The reported tuning methods applied to SIW structures so far are studied, and their pros and cons are discussed in detail. Also, separate libraries for SIW-based tunable filters, antennas, and VCOs are provided.