Demonstration of a 47.8 GHz High-Speed FFT Processor Using Single-Flux-Quantum Technology

A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence at high speed. FFT can convert a signal from time domain to frequency domain, and is wildly used in digital signal processing field. In this paper, a high-speed, low-power FFT processor is demonstrated up to 47.8GHz with the measured power consumption of 5.3mW, using single-flux quantum (SFQ) logic. This is the first complete FFT processor implementation using superconducting technology, performing 8-point 7-bit FFT in a bit-serial computing manner. The test chip fabricated using a 1.0 μm 9-layer process consists of 17 455 Nb/AlO
_x
/Nb Josephson junctions (JJs), rendering itself the largest superconducting digital circuit capable of iterative data computing. The correct operation of the chip has been experimentally confirmed at a maximum operating frequency of 47.8GHz (word speed 8GHz) by conducting on-chip high-speed testing.