An Adaptable Digital Predistorter for COFDM Signal Implemented by Dual Ram

The DAB system adopts COFDM transmission technology which possesses the advantages of high use ratio of frequency spectrum and suitability for mobile receiving. While the envelope of the modulation signal has high PAPR. When the HPA in the transmitter works in nonlinear area, the frequency spectrum diffuses and out-off-band interference will be produced. To make linear for the HPA, the paper designs an adaptable digital predistorter using the characteristic of the dual RAM, and gives a variable iteration factor algorithm for error correction which shows good iteration ability. The circuit test result show that the predistorter can effectively improve the nonlinear area of the amplifier, and performs good limitation to the harmonic distortion and second order intermodulation distortion.