Area-Efficient FFT Kernel with Improved Use of GI for Multistandard MIMO-OFDM Applications

This study presents a fast Fourier transform (FFT) kernel for multistandard applications, which employ multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM). The proposed design uses a mixed-radix, mixed-multipath delay-feedback ((MRMDF)-D-2) structure, which enables 4/5/6-stream 64/128-point FFT. This approach allows the effective usage of guard intervals (GI) in conjunction with a novel resource-sharing scheme to improve area efficiency. An area-reduced constant multiplication unit and sorting buffer with minimal memory size further reduced an area overhead. A test chip was designed using UMC 90-nm technology, and was evaluated through post-layout simulation. The proposed design outperformed previous works in terms of the throughput per area.