Design of Multiband Notched UWB Filter Based on Parallel-Coupled Line

To eliminate the interference of narrow band signals to UWB communication systems, an UWB filter with multiband notched property is proposed. The triple band notched characteristics are achieved by cascading the compact filter unit sections composed of λ/4 parallel coupled lines. The higher harmonics are effectively suppressed by connecting the fan-shaped branch with the short-circuit branch matching line and the excellent rectangular coefficient is obtained by embedding a ring resonator into the band-stop unit. The proposed filter has a compact volume of 25. 5 mm×49. 9 mm×0. 6 mm. Simula- ted results show that the filter has bandwidth of 3-10 GHz,it realizes band-notched characteristics of triple stop-bands at 3. 5 -3. 7 GHz, 5. 7-5. 9 GHz and 7. 9-8. 1 GHz, and efficiently rejects the jamming from WiMAX (3. 3-3. 6 GHz), WLAN (5. 7-5. 8 GHz) and X-band (7. 9-8. 4 GHz) satellite communication system. The filter exhibits small pass-band insertion loss and excellent out-of-band harmonic rejection and preferable anti-jamming ability, making it suitable for all kinds of UWB communication system.