In this paper, we have implemented and analyzed BSFs with ring resonators. The attenuation poles were obtained using the ABCD matrix. We have utilized different perturbation elements to control the attenuation poles in order to obtain good performance. The numerical calculation of the lumped elements agrees with the simulation and measurement. In addition, all the simulated and measured results of the filters have been presented and compared with the theoretical results. ABSTRACT: A frequency-domain approach for propagation measure- ments and characterization of indoor ultra-wideband (UWB) channels is presented. The approach is based on measurement of the magnitude using a scalar network analyzer and retrieving the phase from the mag- nitude data using a Hilbert transform relationship. Extensive propaga- tion data are collected in a frequency range of 1 to 12 GHz in two buildings on the Virginia Tech campus. Using the measured data, chan- nel-characterization results are obtained and compared to those based on time-domain measurements. The statistical results for small-scale fading, the path-loss exponent, and signal quality are presented. The frequency-domain results are generally in good agreement with the time-domain results, and also reaffirm the immunity of UWB propaga- tion to small-scale fading. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 118 -123, 2005; Published online in Wiley Inter- Science (www.interscience.wiley.com). DOI 10.1002/mop.20563