Third-Order Intercept Point

OIP3 = Pout + (IIP3 − Pin)

Quick answer

This calculator solves OIP3 = Pout + (IIP3 − Pin) for Output IP3 (dBm). With Output Power (dBm) -4.4 dBm, Input IP3 (dBm) -9.4 dBm, Input Power (dBm) -0.94 dBm, the result is -12.86 dBm.

Calculator

Result
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Formula

OIP3 = Pout + (IIP3 − Pin)

Description

The third-order intercept point (IP3) is a figure of merit for the linearity of an amplifier or mixer. It is the theoretical power level where the fundamental output and third-order intermodulation products would be equal (this point is never actually reached because the device compresses first). Higher IP3 means better linearity and less intermodulation distortion. OIP3 = IIP3 + Gain. The spurious-free dynamic range (SFDR) of a receiver is bounded by IP3 at the top and noise floor at the bottom.

Variables

  • OIP3 — Output third-order intercept point (dBm)
  • Pout — Fundamental output power per tone (dBm)
  • IIP3 — Input third-order intercept point (dBm)
  • Pin — Input power per tone (dBm)

Practical Notes

Third-order IMD products (at 2f1-f2 and 2f2-f1) are problematic because they fall close to the desired signals and cannot be filtered. IMD3 level = 3×Pin - 2×IIP3 for small signals. For cascaded stages, the system IIP3 degrades with each stage (noise and linearity trade off against each other). High-linearity LNAs and mixers are essential for receivers in crowded RF environments.

Symbols and units

Symbol Meaning Default unit Accepted units
OIP3 Output IP3 (dBm) dBm dBm
Pout Output Power (dBm) dBm dBm
IIP3 Input IP3 (dBm) dBm dBm
Pin Input Power (dBm) dBm dBm

Step by step

  1. 1. What you know: Output Power (dBm) -4.4 dBm, Input IP3 (dBm) -9.4 dBm, Input Power (dBm) -0.94 dBm
  2. 2. The relation: OIP3 = Pout + (IIP3 − Pin)
  3. 3. Substitute: Pout = -4.4 dBm, IIP3 = -9.4 dBm, Pin = -0.94 dBm
  4. 4. Result: Output IP3 (dBm) = -12.86 dBm

Worked examples

Minimum range

Given: Output Power (dBm) -4.4 dBm, Input IP3 (dBm) -9.4 dBm, Input Power (dBm) -0.94 dBm

Result: Output IP3 (dBm) = -12.86 dBm

Low range

Given: Output Power (dBm) -44 dBm, Input IP3 (dBm) -94 dBm, Input Power (dBm) -9.4 dBm

Result: Output IP3 (dBm) = -128.6 dBm

High range

Given: Output Power (dBm) 66 dBm, Input IP3 (dBm) 141 dBm, Input Power (dBm) 14.1 dBm

Result: Output IP3 (dBm) = 192.9 dBm

Maximum range

Given: Output Power (dBm) 660 dBm, Input IP3 (dBm) 1410 dBm, Input Power (dBm) 141 dBm

Result: Output IP3 (dBm) = 1929 dBm

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Frequently asked questions

How do you calculate Third-Order Intercept Point?

Use OIP3 = Pout + (IIP3 − Pin). With Output Power (dBm) -4.4 dBm, Input IP3 (dBm) -9.4 dBm, Input Power (dBm) -0.94 dBm, Output IP3 (dBm) works out to -12.86 dBm.

What is the formula for Third-Order Intercept Point?

The formula is OIP3 = Pout + (IIP3 − Pin). The third-order intercept point (IP3) is a figure of merit for the linearity of an amplifier or mixer.

Related Concepts

All Signal & RF formulas →
Wavelength Free Space Path Loss Signal-to-Noise Ratio Nyquist Sampling Rate Link Budget Antenna Gain Skin Depth Third-Order Intercept Point

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