Wide-stopband, Low-loss and Self-packaged SISL Bandpass Filter Based on Capacitively Loaded Patch Resonators

A new type of capacitively loaded patch resonator (CLPR) is proposed in this letter to design wide-stopband, low-loss, self-packaged bandpass filters (BPFs) in substrate integrated suspended Line (SISL) platform. It has been shown that the introduction of capacitively loaded patch can introduce a new
$TM_{00}$
mode, which can be resonant at a quiet low frequency below the traditional
$TM_{01}(TM_{10})$
mode in patch resonators. Consequently, the resonators' size will be smaller, and the performance will be wide-stop. Simultaneously, the radiation loss of the suggested BPF has been greatly decreased by the completely packed model developed by the SISL platform, resulting in a reasonably high
$Q$
factor. A BPF operating at 3.55 GHz with a fractional bandwidth of 5.00% is constructed, simulated, and tested to confirm the theory behind new type patch resonators. When compared to a conventional rectangular patch resonator with the same center frequency, a size reduction of about 67% is seen.