This calculator estimates the interference-free dynamic range (SFDR) of an RF receiver from the third-order intercept point (IIP3) and the minimum detectable signal (MDS). It helps evaluate the receiver’s ability to distinguish a useful signal from a spurious or intermodulation signal.
Useful for RF engineers, receiver designers and measurement technicians looking to improve the linearity and sensitivity of their systems.
Formula
SFDR = (2/3) × (IIP3 − MDS)
If IIP3 is expressed in watts:
IIP3 (dBm) = 10 × log10(IIP3 × 1000)
Explanation of the formula
- SFDR indicates the useful power range between minimum detectable noise (MDS) and the point where nonlinear distortions become dominant.
- IIP3 is a measure of system linearity, expressed in dBm or watts.
- A higher SFDR value reflects better performance and greater ability to handle weak signals in a noisy environment.
SFDR calculation with IIP3 = 10 dBm and MDS = -120 dBm
Input : IIP3 = 10 dBm, MDS = -120 dBm
Output : SFDR = (2/3) × (10 − (−120)) = 86.67 dB
Benefits and uses
- Measures the spectral purity and dynamics of the receiver.
- Useful for designing low distortion, high fidelity systems.
- Allows you to compare performance between different RF equipment.
- Essential for laboratory linearity and sensitivity testing.