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Sum of Two Equal-Frequency Sinusoids

Sum of Two Equal-Frequency Sinusoids

Rick Lyons
TimelessAdvanced

The sum of two equal-frequency real sinusoids is itself a single real sinusoid. However, the exact equations for all the various forms of that single equivalent sinusoid are difficult to find in the signal processing literature. Here we provide those equations.


Summary

This paper provides complete, closed-form equations for expressing the sum of two equal-frequency real sinusoids as a single equivalent real sinusoid. Readers will find explicit derivations and special-case formulas that are often missing or scattered in signal processing literature, enabling accurate amplitude–phase conversion and practical handling of edge cases.

Key Takeaways

  • Derive closed-form amplitude and phase expressions for the single equivalent sinusoid resulting from two equal-frequency real sinusoids.
  • Convert sums of sine and cosine components into standard amplitude–phase (C cos(ωt+φ)) or alternative single-sinusoid forms.
  • Apply the formulas to simplify spectral interpretation, phasor addition, and signal reconstruction in communications and audio contexts.
  • Handle special cases and numerical pitfalls (phase wrapping, zero-amplitude conditions) using the provided conditional expressions.

Who Should Read This

Advanced DSP engineers, researchers, and graduate students working on signal representation, spectral analysis, communications, or audio/speech processing who need exact formulas for combining equal-frequency sinusoids.

TimelessAdvanced

Topics

FFT/Spectral AnalysisCommunicationsAudio ProcessingStatistical Signal Processing

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