Multicode ultra-wideband scheme using chirp waveforms

We propose an ultra-wideband (UWB) scheme that employs chirp waveforms. Signals satisfying the Federal Communications Commission (FCC) requirements for UWB applications are formed by using multiple linear frequency-modulated (chirped) waveforms. This scheme has the merits of both the multiband orthogonal frequency-division multiplexing (OFDM) UWB scheme such as continuous-wave transmission, and the pulsed UWB scheme, such as accurate timing, imaging capabilities, and rich frequency diversity. Another advantage unique to the proposed scheme is that completely passive, low-cost implementation of matched filters/correlators using surface acoustic wave devices is possible, whereas OFDM-UWB must rely on high-speed sampling combined with powerful digital signal processing. We present the details of chirp waveforms for UWB signaling, explore the correlation properties of the multicodes, and study the receiver structures. We also derive the error performance of the proposed scheme in indoor lognormal fading environments and discuss issues with the proposed scheme.