A Spatial RAKE receiver for Real-Time UWB-IR Applications

Abstract

The concept of ultra wideband impulse radio has interesting properties. The wide transmission band makes penetration through different ma­ terials better than narrow band transmission. The lack of carrier may be traded for low power solutions provided a power efficient receiver may be implemented. Unlike narrow band radio, demanding statistical computation must be carried out. This is often done in a parallel archi­ tecture. Although several portable applications are striving for higher bandwidth, there is an increasing demand for short­range low bandwidth mobile communication units. In several of these applications ultra low power is important. In addition other properties of impulse radio trans­ missions may be appreciated such as interference immunity and penet­ ration. The purpose of this thesis is to explore a low­power solution for correlator­ based impulse radio receivers. A mixed­mode parallel RAKE structure is realized in a standard 0.12 m CMOS technology. The receiver is imple­ mented as a RAKE structure combining digital shift registers with analog computation in a series of parallel taps of a synchronizing delay line. In each parallel bit stream the incoming signal is cross­correlated with a stored template. By combining a delay line and a mixed­mode correl­ ator we can explore multipath reflections in a time domain statistical computation for symbol recovery. Simulations are presented showing promising results with regard to power consumption and overall func­ tionality. Measurements are performed conforming the basic functional­ ity of the circuit.