Abstract: A predistortion system and method uses an inner predistortion function to adjust a signal being input into a distortion generating circuit and at least one outer predistortion function to adjust the signal being input into the inner predistortion function. Thus, the inner predistortion function can reduce the distortion from the distortion generating circuitry, and any remaining distortion can be reduced by the outer predistortion function.

Abstract: Quasi-Walsh function systems are developed which allow multiple access as well as spectral spreading for interception and jamming prevention. Mutual interference is minimal due to orthogonal spreading. High signal hiding capability occurs by utilizing a large number of distinct orthogonal codes. An encoding algorithm is presented which allows a simple way of “keeping track” of the different systems of Quasi-Walsh systems as well as determining appropriate values for given users at specified chip values.

Abstract: A predistortion system uses a predistortion function which is a combination of functions which are dependent on one of a plurality of time spaced samples of the input signal and independent of the other samples. Using such a structure for the predistortion function enables an easier and low cost implementation. For example, a plurality of time spaced samples are used by predistortion circuitry to produce the predistorted signal. The predistortion circuitry includes first function ciruitry which produces a current sample output value depending on a current input sample and independent of a delayed input sample. A second function produces a delayed sample output value depending on the delayed input sample and independent of the current input sample. Each of any additional functions produces an additional delayed sample output value depending on an additional delayed input sample and independent of any other input samples. The sample output values are combined to produce the predistorted sample.

Abstract: A multiple stage and/or nested predistortion system and method uses an inner predistortion function to adjust a signal being input into a distortion generating circuit and at least one outer predistortion function to adjust the signal being input into the inner predistortion function. Thus, the inner predistortion function can reduce the distortion from the distortion generating circuitry, and any remaining distortion can be reduced by the outer predistortion function. For example, in an adaptive predistortion system where the distortion generating circuit is an amplifier, an inner predistortion loop comprises an inner predistortion function which distorts the signal on the main signal path prior to the amplifier. The inner predistortion function can be produced using an output of the inner predistortion function and an output of the amplifier. An outer predistortion loop comprises an outer predistortion function which distorts the input signal prior to the inner predistortion function.