Code-Multiplexed UWB Transmitted-Reference Radio

In traditional transmitted reference (TR) ultra-wideband systems the reference component is time-shifted and orthogonal relative to the data-bearing signal. This paves the way to a correlation receiver in which the local template is derived from the incoming waveform using a delay line. As analog delay lines are difficult to implement with current technology, an alternative TR system has recently been proposed in which reference and data components are made orthogonal by a frequency shift rather than a time shift. The resulting receiver has no delay lines and has better performance compared to the traditional scheme. In the present paper we discuss a third way to achieve orthogonality, i.e., by modulating reference and data components with two distinct code sequences. Even in this case the receiver has no delay lines. However, it is simpler to implement and has better performance than the frequency-shift based receiver.