An OFDM-specified lossless FFT architecture

In this paper, a VLSI architecture based on radix-2² integer fast Fourier transform (IntFFT) is proposed to demonstrate its efficiency. The IntFFT algorithm guarantees the perfect reconstruction property of transformed samples. For a 64-points radix-2² FFT architecture, the proposed architecture uses 2 sets of complex multipliers (six real multipliers) and has 6 pipeline stages. By exploiting the symmetric property of lossless transform, the memory usage is reduced by 27.4%. The whole design is synthesized and simulated with a 0.18-mum TSMC 1P6M standard cell library and its reported equivalent gate count usage is 17,963 gates. The whole chip size is 975 mumtimes977 mum with a core size of 500 mumtimes500 mum. The core power consumption is 83.56 mW. A Simulink-based orthogonal frequency demodulation multiplexing platform is utilized to compare the conventional fixed-point FFT and proposed IntFFT from the viewpoint of system-level behavior in items of signal-to-quantization-noise ratio (SQNR) and bit error rate (BER). The quantization loss analysis of these two types of FFT is also derived and compared. Based on the simulation results, the proposed lossless IntFFT architecture can achieve comparative SQNR and BER performance with reduced memory usage