Effect of Group Delay in RF BPF on Impulse Radio Systems

Seong-Sik MYOUNG
Bong-Su KWON
Young-Hwan KIM
Jong-Gwan YOOK

IEICE TRANSACTIONS on Communications   Vol.E90-B    No.12    pp.3514-3522
Publication Date: 2007/12/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.12.3514
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Devices/Circuits for Communications
BPM,  filter,  group delay,  impulse radio,  PPM,  pulse waveform,  

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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.