Abstract
We propose a design method of fast Fourier transform (FFT) large-scaled integration (LSI) for an orthogonal frequency division multiplexing (OFDM) system. The proposed FFT LSI is designed with simple current mode circuits, wired-OR connection and gate-width-ratioed current mirror. For a low power consumption, two design methods are proposed, current-cut (CC) and rounding process. The CC operation is performed with on-off operation of a current source. The rounding process is adopted for the component of the FFT matrix. Bit error rate (BER) in the OFDM system is simulated from "0.1" rounding step to "1.0". The BER performance of the FFT matrix with the "0.2" rounding step has little degradation from that of the original FFT matrix. The 8-point FFT LSI with the "0.2" rounding step is designed and implemented using a 0.8 µm complementary metal-oxide semiconductor (CMOS) technology. On the basis of measurement of the 8-point FFT LSI, the power consumption of the 64-point FFT LSI using CC can be estimated as being less than 10 mW.