IMD, IP3 & OIP3 — Three RF Parameters That Are Often Confused

2026-07-24


When an amplifier becomes less linear, it generates more IMD. Engineers use IP3 to estimate this linearity, while OIP3 expresses the same linearity at the amplifier output.

Have you ever wondered why IMDIP3, and OIP3 are often mentioned together in RF amplifier specifications?

Although closely related, they describe different aspects of amplifier linearity.

  • IMD (Intermodulation Distortion) refers to the unwanted signals generated by amplifier nonlinearity when multiple tones are amplified.
  • IP3 (Third-Order Intercept Point) is a theoretical indicator used to estimate how linear an amplifier is.
  • OIP3 (Output Third-Order Intercept Point) is the output-referenced form of IP3 and is the value most commonly listed in RF power amplifier datasheets.

Think of it this way: 

When an amplifier becomes less linear, it generates more IMD. Engineers use IP3 to estimate this linearity, while OIP3 expresses the same linearity at the amplifier output.

In general, lower IMD3 means higher OIP3, indicating better linearity and cleaner signal transmission under the same operating conditions.

Understanding these three parameters makes it much easier to interpret amplifier specifications and compare RF amplifier performance.

SWR vs. Return Loss — How Do You Interpret Them?

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SWR vs. Return Loss — How Do You Interpret Them?

VSWR and Return Loss often appear together in RF specifications. What do these two parameters actually tell us, and how should we interpret their values?

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