*Article* **Area-E**ffi**cient FFT Kernel with Improved Use of GI for Multistandard MIMO-OFDM Applications**

#### **Song-Nien Tang 1,\* and Yuan-Ho Chen 2,\***


Received: 17 May 2019; Accepted: 16 July 2019; Published: 18 July 2019

**Abstract:** 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 (MRM2DF) 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.

**Keywords:** fast Fourier transform; FFT; kernel; MIMO; OFDM; multistandard
