Real-time emulation of block-based analog circuits on an FPGA

Abstract

In order to provide a real-time emulation platform for analog signal processing circuits, we propose a block based approach with a constant worst case runtime. We evaluate an FPGA-based implementation of this approach by comparing its output for different test cases to a non-real-time SPICE simulation. The implementation runs at a sampling rate of 88.2 kHz and features roundtrip times as low as 0.096 ms (12 bit ADC) and 0.190 ms (16 bit ADC). A completely automated process is introduced for fitting model parameters of filters and various nonlinear blocks. The fitting process is evaluated based on 35 block examples with R2 values ranging from 0.967 to 0.999. For complex filter structures we were able to replicate the frequency responses predicted by a SPICE AC analysis accurately. Furthermore we compare measured transient responses of the FPGA-based emulation with SPICE and discuss advantages and disadvantages of the approach.