Also known as: CMA equalizer, constant-modulus algorithm

A CMA equalizer uses the constant-modulus algorithm — a blind adaptive filter — to counteract multipath distortion without needing a known training sequence.¹

A CMA equaliser blindly undoes channel distortion (multipath), pulling smeared symbols back to tight clusters.

How it works

It adjusts its taps to drive the output toward a constant modulus (the property of constant-envelope modulations), undoing intersymbol interference and tightening the constellation.

Relevance to SDR

A CMA equalizer can rescue decoding in reflective urban environments where multipath otherwise smears the symbols.

Sources

1. Constant modulus algorithm — Wikipedia, on the blind adaptive equalization technique. ↩

See also

• Multipath propagation
• Demodulation
• Clock recovery
• Constellation diagram

Learn it step by step

• Tuning for a clean lock

From the blog

• SDR Internals, Part 8: Equalization, diversity & the FFT