Fixed-Point DSP

Introduction In fixed-point DSP systems, IIR filters may exhibit persistent oscillations even when the input signal is zero. This phenomenon, known as a limit cycle, is caused by finite word-length effects and nonlinear quantization behavior. Unlike floating-point simulations, fixed-point arithmetic introduces rounding and saturation effects that can sustain artificial oscillations indefinitely. Why Limit Cycles Occur In IIR structures: feedback paths amplify quantization error rounding behaves nonlinearly zero-input does not guarantee zero-output Small residual quantization noise becomes trapped in feedback loops. ...

Introduction Most DSP filter designs fail not in theory — but in embedded deployment. Fixed-point systems introduce: quantization overflow feedback amplification limit cycles Without explicit engineering safeguards, instability is inevitable. Why Floating-Point Designs Break in Fixed-Point Hardware Key failure modes: coefficient truncation reduced dynamic range nonlinear saturation feedback noise growth IIR structures are especially vulnerable. Scaling as a First-Class Design Variable Proper deployment requires: per-section scaling headroom budgeting bounded internal states Blind normalization is insufficient. ...