Analog DFT processors for OFDM Receivers: Circuit mismatch and system performance analysis

processor based on analog CMOS current mirrors that operate in the strong inversion region is presented. It is shown that tran-sistor mismatch can be modeled as an input-referred noise source that can be used in system-level studies. Simulations of a radix-2, 256-symbol fast Fourier transform (FFT) show that the model pro-duces equivalent results to those of a model that incorporates a mis-match term into each current mirror. It is shown that in general, high-radix FFT structures and specifically the full-radix DFT have reduced sensitivity to mismatch and a reduced number of current mirrors compared to radix-2 structures and have some key advan-tages in terms of transistor count with respect to comparable dig-ital implementations. Simulations of an orthogonal frequency-di-vision multiplexing system with forward error control coding, that take into account current mirror nonidealities such as mismatch, show that an analog DFT front end loses only 0.5 dB with respec