| 摘要 |
PURPOSE: To obtain an adaptive predistortion circuit capable of reducing the diffusion of respective points on an original star char into infinite points by using predistortion having two predistortion circuits and an adapting circuit. CONSTITUTION: An encoder 51 generates data bK, cK based on input data aK and data b'K, c'K distorted by predistortion circuits 521 , 522 are mutually added by an adder 53. A signal obtained from the adder 53 is sent through a D/A converter 54, and LPF 55, a modulator 56, and a power amplifier 57. On the other hand, an output signal from the amplifier 57 is demodulated by a demodulator 58 and filtered by an LPF 59. AN output signal from the LPF 59 is sampled by a sampler 601 at a moment KT and by a sampler 602 at a moment KT+T/2. Respective samplers 601 , 602 supply (sample X KT) and sample ×(KT+T/2)} to respective adapting circuits 61, 61 and compared with the data bK, cK to obtain control signal 701 , 702 for optimizing a distortion circuit. |
