Method and apparatus for reducing cross spectral terms of a spreading waveform for a navigation signal

摘要

A method of reducing cross spectral terms of a spreading waveform for a navigation signal and signal generator are disclosed. The signal generator (600) comprises means to generate first and second temporally successive portions of the signal. The first portion represents an additive combination of first respective portions of first and second Binary Offset Carrier (BOC) signals having a first phase state and the second portion represents an additive combination of second respective portions of the first and second BOC signals. The second respective portions have a second phase state that is opposite to the first phase state. The additive combination of the first respective portions of the first and second BOC signals can be time multiplexed portions of the first and second BOC signals and in which additive combination of the second respective portions of the first and second BOC signals can be time multiplexed portions of the first and second BOC signal. Also disclosed is a receiver for receiving and processing a navigation signal. The navigation signal comprises a ranging code modulated by a spreading waveform and the spreading waveform comprises first and second portions that are temporally successive. The first portion represents an additive combination of first respective portions of first and second binary offset carrier signals having a first phase state and the second portion represents an additive combination of second respective portions of the first and second Binary Offset Carrier signals. The second respective portions having a second phase state that is opposite to the first phase state. The receiver comprises an antenna for receiving the navigation signal; an RF processor for amplifying, filtering and frequency changing the received navigation signal, and producing digitised received signal samples therefrom; a signal replica generator adapted to output a multi-level replica signal produced from combing the outputs of a carrier replica generator, a ranging code generator and a spreading waveform replica generator; and a correlation processor for correlating the multi-level replica signal and the digitised received signal samples.