Compact UWB signal interference filter using interdigital coupled lines

An ultra-wide band (UWB) band-pass filter (BPF) based on signal interference technique is presented in this letter. The filter is connected in parallel short-ended interdigital coupled lines and a transmission line. The filter has a fractional bandwidth of 108% and two transmission zeros at both sides of pass-band, which turns into good pass-band selectivity. The filter achieves a small size of 10.55 mm × 8.9 mm (0.33 λg × 0.27 λg, where λg is the guided wavelength at 6.85GHz). For verification, a sample filter is simulated, fabricated and measured. Good agreement is found between the simulation and measurement.