What is UWB?
Ultra-wideband (UWB) communications systems can be defined as wireless
communications systems with very large bandwidth, or very large fractional bandwidth.
Fractional bandwidth is defined as the ratio of the -10 dB bandwidth
occupied by the signal to the center frequency of the signal:
Traditional communications systems typically use
signals having a fractional bandwidth less than 0.01. Wideband CDMA
has a fractional bandwidth of approximately 0.02. Many in the
radar and communications fields consider signals with 0.25 or greater
fractional bandwidth measured at the -3 dB points to be ultra-wideband
(see Figure 1 for a comparative illustration of fractional
bandwidths). A DARPA report which coined the term “ultra-wideband”
used a 0.25 fractional bandwidth definition. In its First Report and Order allowing the
commercial use of UWB systems, the FCC defined UWB signals as those which have a
fractional bandwidth greater than 0.20 or a bandwidth greater than 500
MHz measured at the -10 dB points.
1: Fractional bandwidth comparison