TOMIKI ATSUSHI

Microwave vector network analyzer (VNAs), easy to calibrate, are most commonly used as an ultra-wideband (UWB) channel sounder to measure the propagation characteristics of UWB signals. The measurement distance is, however, limited by the loss of a coaxial cable connecting a VNA output port and a transmitting antenna. A UWB over fiber transmission system was developed to replace the coaxial cable transmission which has frequency dispersion as well as the large amount of transmission loss. The developed system consists of a wideband laser diode, a single-mode optical fiber cable, and a photo diode. This system showed a transmission loss of around 27 dB, a root-mean-square loss variation of 2 dB, and a group delay of less than 0.7ps. Typically for more than 30-m transmission, this system outperforms coaxial cables in transmission loss and frequency dispersion. An experimental result of UWB propagation was shown to demonstrate the usefulness of this system.

In February 2002, thc Federal Communications Commission (FCC) conditionally waived unlicensed operation of unlic ensed of personal ultra wideband (UWB) products in thc United States. The UWB technologies have been cxploited to be able to use for super -high-speed communication, highly -accurate sensing and geolocation, low -cost RF tagging, and so forth; and to pioneer a new spectrum resource substantially. Research areas, however, remain to be fully studied such as UWB propagation characteristics and interference effects from thc UWB wireless systems to conventional narrow -band ones sharing the same frequency bands. No netheless, UWB sources have not been readily available for the experimented studies. This paper reports prototypes of impulse radio and direct sequence spread spectrum (DS -SS) UWB sources to serve for propagation, electromagnetic compatibility and other ex nerimental studies.

Ultra wideband (UWB) technologies have been developed to exploit a new spectrum resource in substance and to realize ultra-high-speed communication and high precision telelocation. However, the interference effects have not fully been studied from UWB wireless systems to conventional narrowband wireless systems sharing the same frequency bands. This report experimentally evaluated the interference from two kinds of UWB sources, namely an impulse radio UWB source and a direct-sequence spread-spectrum UWB source, to 2-GHz digital transmission. Bit error rate degradation caused by the UWB sources were measured.

Ultra wideband (UWB) technologies have-been developed to exploit a new spectrum resource in substance and to realize ultra-high-speed communication and high precision telelocation. However, the interference effects have not fully been studied from UWB wireless systems to conventional narrow-band wireless systems sharing the same frequency bands. This paper experimentally evaluated the interference from two kinds of UWB sources, namely an impulse radio UWB a sources and direct-sequence spread-spectrum UWB sources, to 2-GHz digital transmission. Bit error rate degradation caused by the UWB sources were measured. It was found that in both cases the bit error rate had floor characteristics when the relatively-strong UWB sources interfered.