Ultra-wideband differential mode bandpass filters embedded in self-complementary antennas

A 50 Ω. matched self-complementary antenna integrated with a four coupled-line ultra-wideband differential mode bandpass filter (BPF), a notch filter and a lowpass filter (LPF) is demonstrated. Broadside- and edge-coupled four coupled-line BPFs were found to exhibit up to 170% fractional bandwidth and to exhibit impedance trans-formation ratio of 1.2 with little bandwidth reduction. Thus, 6-stage BPFs were utilized concurrently to transform the self-complementary antenna´s constant input impedance (60 π ε_e^{- 1}2 /Ω) to 50Ω. In addition, LPFs with the BPF and notch filters with the BPF were designed and fabricated. Measured insertion losses of the total filter systems were less than 2.6dB over the ultra-wideband (UWB) band (3.1GHz to 10.6GHz). The filters were embedded in wideband self-complementary antennas to reject the radiation over the next passband and the 5GHz wireless LAN band.