STMicroelectronics AN2874 BQD Filter Design Equations Application Note

About this manual

The document formulates generalized sets of equations for designing first-order and second-order low-pass and high-pass filters. It also includes specialized equations for parametric biquad equalization (EQ) filters.

Key parameters discussed include filter cut-off frequency, sampling rate, Q factor, and boost/cut gain values. The text details how to calculate transfer function coefficients for digital z-domain filters.

What's inside

• Introduction
• Low-pass and high-pass filter design
• First-order filter design
• Second-order filter design
• Parametric EQ filter design
• Filter stability conditions
• STA309X coefficient formatting

Specifications

Frequently asked questions

What filter types does this note cover?

It covers first-order and second-order low-pass, high-pass, and parametric biquad EQ filters.

What devices can use this document to design filters?

This document is used with ST digital audio devices that have EAQ filters onboard, such as the STA309A and STA321.

What format must filter coefficients be in for the STA309X GUI?

The coefficients must be a 24-bit signed fixed-point integer within the range [0x800000, 0x7FFFFF].