Engineering spectrum and dispersion with filters for high-sensitivity radio frequency detections

Abstract

We demonstrate that engineering spectrum and dispersion with filters are an effective approach to boost sensor sensitivities for various radio-frequency (RF) sensing applications. A low-pass filter with a ∼2 GHz cutoff frequency and a band-pass filter with a ∼3 GHz center frequency are designed and incorporated into an interferometer to achieve ultra-high sensitivity RF detections. Compared with coplanar waveguides, the filters have up to 10-times longer group delays and 9-times stronger localized RF E-fields. Thus, the interactions between RF fields and material-under-test, which is a slab of polydimethylsiloxane in this work, are significantly enhanced. The interferometer sensitivities are boosted by up to 11 times for operating frequency shifts and 25 dB for magnitude change at frequencies up to 12 GHz.