Fast digital filter for frequency discriminator

The frequency discriminator is a circuit to detect signal frequency, it is widely used in various high-precision transducer. Frequency discriminators in optically pumped magnetometers (OPM) require fast tracking of the magnetic resonance center frequency, in which a fast-digital filter is necessary. This paper designs a high-speed digital filter, and is verified in field programmable gate array (FPGA). The designed filter is composed of a cascaded integrator-comb (CIC) digital filter and infinite impulse response (IIR), the CIC filter is developed to filter out harmonics and reduce the sampling rate, IIR filter is designed to further filter out high-frequency signals and pick up direct-current(DC)information. Compared with traditional Butterworth filters, the designed IIR filter saves about 40% stabilization time with less resources.