The output of the anti-alias filter is monitored by channel 1 of the TDFS instrument. The TDFS oscillator stimulus voltage is applied to the anti-alias filter’s input. It is not possible to perform a standard AC analysis of the entire filter, because of the discrete states used to describe the digital behavior. The TDFS instrument measures the transfer function of each stage of the filter, both separately and combined. This includes both the analog anti-aliasing low-pass filter, as well as an 8-bit, second-order digital BPF. The above example shows the use of TDFS to measure the frequency response of a mixed-signal band-pass filter (BPF) circuit.
