A low-loss ultra-wide band (UWB) filter is presented, which uses miniaturized parallel coupled line along with an standard printed circuit board (PCB) technology. By analyzing even- and odd-mode impedances (in comparison with conventional parallel coupled lines) of miniaturized parallel coupled line, this structure provides tight coupling, thus, relaxing the requirements on physical dimensions width and spacing when designing broadband filters. A bandpass filter for Mode 1 (the first 3 sub-bands) in the 3.1-5 GHz band for Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB is realized and compared with a conventional parallel coupled line filter. The experimental results show as much as 0.9 dB insertion loss improvement over the conventional counterpart.

This paper presents an analysis of the effects of RF filter characteristics on the system performance of an impulse radio. The impulse radio system transmits modulated pulses having very short time duration. Information can be extracted in the receiver side based on the cross-correlation between received and reference pulses. Accordingly, the pulse distortion due to in-band group delay variation can cause serious degradation in system performance. In general, RF band pass filters inevitably cause non-uniform group delays to the signal passing through the filter that are proportional to its skirt characteristic due to its resonance phenomenon. In this work, a small signal scattering parameter, S21, which is a frequency domain parameter, and its Fourier transform are utilized to characterize the output pulse waveform under the condition that the input and output ports are matched. The output pulse waveform of the filter is predicted based on the convolution integral between the input pulse and filter transfer function, and the analysis result is compared with previously reported experimental result. The resulting bit error rate performances in a bi-phase modulation and a pulse position modulation based impulse radio system are also calculated. Moreover, improvement of system performance by the pulse shaping method, a potential solution for pulse waveform distortion, is analyzed.