LAUSR

This paper presents a miniaturized RF MEMS tunable bandpass filter design developed by application of folded ridged quarter-mode substrate integrated waveguide cavity. Using packaged RF MEMS SP4T chips, a switchable reactive loading is applied to the folded ridged quarter-mode substrate integrated waveguide cavity, tuning the resonance frequency. Overall miniaturizations of 70.3% and 78.8% are achieved for inductively- and capacitively-loaded filters compared to an RF MEMS tunable filter using half-mode substrate integrated waveguide. Here, an analysis of inductive or capacitive loading along with their advantages and disadvantages are discussed. Two different two-pole folded ridged quarter-mode substrate integrated RF MEMS tunable bandpass filters are designed and measured. The first prototype employing inductive loading achieves 4.4% tuning range at a center frequency of 1.713 GHz, insertion loss of 3.10–3.92 dB, and return loss greater than 15 dB for all tuning modes. The second prototype employing capacitive loading is measured with a 35.2% tuning range at a center frequency of 865 MHz, insertion loss of 1.6–4.3 dB, and return loss greater than 10 dB for all tuning modes. The reported performance and extreme miniaturization of folded ridged quarter-mode substrate integrated waveguide cavities shows great promise for their application in tunable filter design.