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Abstract: The traditional design method for digital audio graphic equalizer using infinite impulse response filters usually has some deficiencies, including center frequency shift, narrower bandwidth at high frequency and inaccurate gain. In this paper, an improved method based on the modified bilinear transformation is proposed to design a digital audio graphic equalizer. The new bilinear mapping can compensate the center frequency shift, and pre-distorting the quality factors and optimizing the gains can correct the bandwidth and gain of each sub-band respectively. Experimental results reveal that both center frequency and bandwidth of the proposed digital graphic equalizer are strictly equal to the desired ones, and the average gain error decreases at least 2 dB. [Copyright &y& Elsevier]

Since the satellite communication goes in the trend of high-frequency and fast speed, the coefficients updating and the precision of the traditional pre-distortion feedback methods need to be further improved. On this basis, this paper proposes dual loop feedback pre-distortion, which uses two first-order Volterra filter models to reduce the computing complexity and a dynamic error adjustment model to construct a revised feedback to ensure a better pre-distortion performance. The computation complexity, iterative convergence speed and precision of the proposed method are theoretically analyzed. Simulation results show that this dual loop feedback pre-distortion can speed the updating of coefficients and ensure the linearity of the amplifier output. [ABSTRACT FROM AUTHOR]