Hybrid direct sequence and frequency hopping spread spectrum receiver with oversampling above the chip rate for only part of signal

摘要

The invention concerns a radio receiver arranged to sample a hybrid spread spectrum input signal generated by modulating a carrier signal with a predetermined spreading sequence of pseudo-noise code symbols or chips, and then frequency hopping the centre frequency of the carrier signal. The receiver stores hop information and spreading sequences. The receiver synchronises itself with the frequency hopping cycle and with the spreading sequence by repeating a correlation and accumulation operation between the received signal and the stored spreading sequence at different phases of the hopping sequence and of the spreading sequence so as to maximise the output data. The invention lies in performing the correlation and accumulation operation at a higher sampling rate over a high-resolution portion of one spreading sequence cycle than over the remainder of that spreading sequence cycle. Preferably, the sampling is an integer multiple of the chip rate for the high resolution portion but at the chip rate for the remainder of the spreading sequence cycle. The invention reduces the amount of RAM and number of processing operations required, thus reducing power consumption in portable receivers. The invention finds application in the fields of communication and positioning.