A novel high selectivity bandpass filter for wireless monitoring of sleep apnoea patients

In this paper, a novel high selectivity compact dual planar microstrip bandpass filter (BPF) with compact ring resonator and two uniquely designed defected ground structures (DGSs) is proposed. By employing the inter-digital and spiral DGSs, the filter selectivity can be significantly enhanced with a wide suppression of higher order harmonics. The filter has a selectivity of 220 dB/GHz, passband insertion loss (IL) of 1.55 dB and bandwidth of 61 MHz at 2.53 GHz. Moreover, the proposed compact ring resonator saves 70.5% area compared to a conventional ring resonator. The significance of this BPF to be applied in wireless telemetry monitoring systems has been introduced in this paper.