Realisation of highly compact planar lowpass filter for UWB RFID applications

A novel compact microstrip lowpass filter is described that exhibits an quasi-elliptical function response with high out-of-band rejection for integration in ultra-wideband (UWB) chipless radio frequency identification (RFID) receivers. The filter's characteristics include a wide-stopband and low passband insertion loss with a passband ripple of 0.03 dB. Out-of-band attenuation of 30 dB is achieved up to about four times the cutoff frequency (4f(c)), and 20 dB up to about seven times the cutoff frequency (7f(c)). In addition, the proposed filter structure offers a high figure-of-merit of 8657 that exceeds the lowpass planar filters with an equal cutoff frequency reported in the literature to date.