In a receiver architecture, for example for use in receiving pulses in an Ultra Wideband system, a received signal is applied to a mixer, together with pulses which correspond to expected received pulses. The mixer output is applied to a block, which can be configured either as an integrator or as a filter. When no pulses are being received, this block is configured as a filter, allowing it to lock quickly to any new sequence of pulses, while, when the system has locked to a sequence of pulses, the block is configured as an integrator, so that an improved signal-noise ratio can be achieved.