MINIATURIZED SEMI-LUMPED UWB BANDPASS FILTER WITH IMPROVED OUT-OF-BAND PERFORMANCES

In this article, a miniaturized ultra-wideband (UWB) bandpass filter with improved out-of-band performance is presented, based on the combination of low-pass and high-pass filters. The UWB filter is realized in a semi-lumped technology, using microstrip transmission lines and surface-mounted capacitors. The filter design rules have been carried out and filters having a 3 dB fractional bandwidth of 142 percent, centered at 0.77 GHz, have been realized. The measured and simulated characteristics show a good agreement, with attractive return loss (better than 18 dB) and insertion loss (<0.3 dB). In addition, a technique using capacitively loaded stubs was used to extend the stopband to eight times the center frequency.