This paper presents the hardware implementation of a 3rd-order low-pass finite impulse response (FIR) filter based on time-mode signal processing circuits. The filter topology consists of a set of novel building blocks that perform the necessary functions in time-mode including z⁻¹ operation, time addition and time multiplication. The proposed time-mode low-pass FIR filter was designed in a 28 nm Samsung fully-depleted silicon-on-insulator FD-SOI process under 1 V supply voltage with 5 MHz sampling frequency. Simulation results validate the theoretical analysis. The FIR filter achieves a signal-to-noise-plus-distortion ratio (SNDR) of 38.6 dB at the input frequency of 50 KHz consuming around 200 μW.

This paper presents a novel circuit of a z⁻¹ operation which is suitable, as a basic building block, for time-domain topologies and signal processing. The proposed circuit employs a time register circuit which is based on the capacitor discharging method. The large variation of the capacitor discharging slope over technology process and chip temperature variations which affect the z⁻¹ accuracy is improved using a novel digital calibration loop. The circuit is designed using a 28 nm Samsung FD-SOI process under 1 V supply voltage with 5 MHz sampling frequency. Simulation results validate the theoretical analysis presenting a variation of capacitor voltage discharging slope less than 5% over worst-case process corners for temperature between 0 °C and 100 °C while consuming only 30 μA. Also, the worst-case accuracy of z⁻¹ operation is better than 33 ps for input pulse widths between 5 ns and 45 ns presenting huge improvement compared with the uncalibrated operator.