Mixer Spur Calculator

Mixer spurs are unwanted frequency components generated when signals mix in a non-linear device. They occur at frequencies of the form M×fLO ± N×fRF, where M and N are integers, creating interference that can degrade system performance. See also our Directional Coupler Calculator.

The M×N chart shows all possible spurious products based on harmonic mixing. M represents LO harmonics, N represents RF harmonics, and the order (|M|+|N|) indicates the spur strength - lower order spurs are typically stronger and more problematic.

High-side injection means the LO frequency is higher than the RF frequency (fLO > fRF), while low-side injection means fLO < fRF. The choice affects which spurs fall within your IF passband and system image rejection requirements.

Spurs can cause interference, desensitization, and false signals in your receiver. By analyzing spurs early in design, you can choose appropriate LO frequencies, add filtering, or adjust system architecture to minimize problematic interference. You might also find our RF Power Density Calculator useful.

Spur levels depend on mixer type, drive levels, and circuit implementation. This calculator provides theoretical estimates based on typical mixer models. Actual spur performance should be verified through measurement or detailed circuit simulation.

Start with orders 2-5 for initial analysis. Higher-order spurs (6+) are typically weaker but may still be significant in sensitive applications. The calculator allows up to 10th order for comprehensive analysis.

Use appropriate filtering before and after the mixer, choose LO frequencies that place spurs outside your signal band, use balanced mixers for better spur suppression, and optimize drive levels to balance conversion gain with spurious performance.