New current attenuator circuit in the current mode FFT LSI for OFDM

To achieve the high performance of current-mode fast-Fourier-transform (FFT) large-scaled integration (LSI) for orthogonal frequency division multiplexing (OFDM) system, a new current-attenuator circuit without a DC offset-current error is proposed. The attainable maximum scale accuracy to the input current is theoretically -80 dB in the proposed attenuator circuit. The circuit consists of N-current mirrors simply connected in parallel with one another. The output current of the circuit is reduced to 1/N of the input current. The proposed circuit exerts high accuracy on the current attenuation and enables us to design the current-mode 64-point FFT LSI for OFDM system.