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IIP3 calculator from OIP3 calculation | IIP3 formula

The IIP3 calculator does IIP3 calculation using IIP3 formula based on gain and OIP3 values. OIP3 calculation is performed using fundamental (f1, f2) and third order intermodulation product powers.

When two or more signals are fed at the input of nonlinear RF components such as amplifier or mixer, it produces undesired signals in addition to the desired ones. The undesired signals include harmonics, spurious and intermodulation products of the fundamental input signals. The IMD (Intermodulation distortion) products include second order, third order, fourth order and so on. The major interference is caused by third order intermodulation products which are located at 2F1-F2 and 2F2-F1.

IP3 measurement setup for IIP3 and OIP3

The figure depicts block diagram of IM3 measurement setup. It shows Wa and Wb as fundamental frequencies. It shows 2*Wa - Wb and 2*Wb - Wa as IMD products. In the figure, power of fundamentals is designated as Pout and power of third order products as Pout_3. The ΔP is calculated as difference of Pout and Pout_3. The same is being used by OIP3 calculator and IIP3 calculator. Refer IIP3 and OIP3 basics.

OIP3 calculation using OIP3 calculator

Following OIP3 calculator is used for OIP3 calculation using power of fundamental signals (i.e. Pout) and power level difference (i.e. ΔP ) between fundamental and IMD products (i.e. Pout_3).

Pout (Input)   :

ΔP (Input)  , dBc :

OIP3 (output) :

EXAMPLE of OIP3 calculation :
INPUT: Pout in dBm = -10 , ΔP = +30dBc
OUTPUT: OIP3 in dBm = +5 dBm
Note: If IM3 products (i.e. 2f1-f2 and 2f2-f1) are measured at power level of -40dBm and fundamental signal frequencies (i.e. f1, f2) at -10 dBm, then ΔP can be calculated as -10 dBm - (-40dBm) = + 30 dBc

IIP3 formula for IIP3 calculation based on OIP3

First OIP3 is calculated using OIP3 formula based on fundamental signal powers and IMD signal powers. It is assumed that power levels of signal at f1 and f2 is equal. It is also assumed that power levels of signals at IMD products viz. 2F1-F2 and 2F2-F1 are also equal. Following IIP3 formula is used for IIP3 calculation.

IIP3 formula

IIP3 calculation using IIP3 calculator

Following IIP3 calculator is used for IIP3 calculation based on OIP3 and gain of the device.

OIP3 in dBm (Input)   :

Gain in dB (Input)   :

IIP3 in dBm (output) :

EXAMPLE of IIP3 calculation :
INPUT: OIP3 = 5 dBm , Gain = 7 dB
OUTPUT: IIP3 = -2 dBm

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