Analysis of the Bulk Acoustic Wave (BAW) resonator modeled as a two-port device is presented for applications in Sigma Delta Modulator (ΣΔM) based Analog-to-Digital Converter (ADC). The design of BAW-based Continuous Time (CT) ΣΔM starting from a Discrete Time (DT) model, which is designed from scratch, is presented and explained in details. In order to convert a DT ΣΔM into CT BAW-based ΣΔM, Finite Impulse Response (FIR) filters are used in the feedback path increasing the degrees of freedom. We discuss and validate the calculation of the FIR filter coefficients by using a design example of BAW-based ΣΔMs.