Apparatus for rapid interference cancellation and despreading of a CDMA waveform

A method for despreading an input multiple code division multiple access (CDMA) signal generated from a spreading code, the method having the capability of adaptively cancel interference due to one or more narrow band signals, the method comprising the steps of:

• generating a Fourier transform of the CDMA signal, thereby generating a frequency domain version of the CDMA signal;
• normalizing the magnitude of the frequency domain version of the CDMA signal while preserving its phase information, thereby performing a whitening function on the frequency domain version of the CDMA signal and adapting to changes in interference;
• generating a frequency domain version of at least one of a plurality of spreading sequences of the spreading code;
• multiplying the normalized frequency domain version of the CDMA signal by the at least one of the plurality of spreading sequences of the frequency domain version of the spreading code, thereby generating at least one despread signal;
• and
• generating an inverse Fourier transform of the at least one despread signal, thereby providing a time domain version of the at least one despread signal.

An adaptive interference canceler despreader for despreading an input multiple code division multiple access (CDMA) signal generated from a spreading code and supplied at an input whereby the input CDMA signal may include interference due to one or more narrow band signals, the adaptive interference canceler despreader comprising:

• a first fast Fourier transform (FFT) for generating the Fourier transform of the input CDMA signal supplied at the input, thereby generating a frequency domain version of the CDMA signal;
• normalization means for normalizing the magnitude of the frequency domain version of the CDMA signal while preserving its phase information, thereby performing a whitening function on the frequency domain version of the CDMA signal and adapting to changes in interference;
• a second FFT for generating a frequency domain version of at least one of a plurality of spreading sequences of the spreading code;
• at least one multiplier for multiplying the normalized frequency domain version of the CDMA signal by the at least of the plurality of spreading sequences of the frequency domain version of the spreading code, thereby generating at least one despread signal;
• and
• an inverse fast Fourier transform for determining the inverse Fourier transform of the at least one despread signal, thereby providing a time domain version of the at least one despread signal.