IIP2 Calculator: Calculate 2nd Order Intercept Point (IP2)

The IIP2 calculator uses the IP2 formula for IIP2 and OIP2 calculations. This article describes the IP2 (2nd order intercept point) measurement test setup used for the IP2 calculator purpose.

Introduction

When a nonlinear device, such as an amplifier or mixer, is fed with two or more frequency tones, it produces intermodulation products (IMD) in addition to the desired outputs. These IMD products include second order (IP2), third order (IP3), fourth order (IP4) products, and so on.

The second-order and third-order IMD products are the ones that cause interference to the desired output signals. IP2 (Second Order Intercept Point) and IP3 (Third Order Intercept Point) are used to measure the performance of non-linear devices.

The figure above depicts a block diagram of an IM2 (Second Order Intermodulation Product) measurement setup. It shows W_a and W_b as fundamental frequencies. It also shows W_b + W_a and W_b - W_a as Intermodulation second-order products.

In the figure, the power of fundamentals is designated as “Po”, the power of third-order products as “Po_3”, and the power of second-order products as “Po_2”.

The ΔP is calculated as the difference between Po and Po_2. The same is being used by the OIP2 calculator and the IIP2 calculator.

The figure above depicts the IP2 (Second Order) curve, showing IIP2 (Second-order intercept point @input) and OIP2 (Second-order intercept point @output).

OIP2 Calculator

The OIP2 calculator is used for OIP2 calculation using the power of fundamental signals (i.e., P_o) and the power level difference (i.e., ΔP) between the fundamental and 2nd order IMD product (i.e., P_{o_2}).

EXAMPLE of OIP2 calculation:

• INPUT: Pout in dBm = -10, ΔP = +50dBc
• OUTPUT: OIP2 in dBm = 40 dBm

Note: If IM2 products (i.e., f2+f1 and f2-f1) are measured at a power level of -60dBm and fundamental signal frequencies (i.e., f1, f2) at -10 dBm, then ΔP can be calculated as -10 dBm - (-60dBm) = + 50 dBc

IIP2 Formula and OIP2 Formula for IP2 Calculations

First, OIP2 is calculated using the OIP2 formula based on fundamental signal powers and IMD signal powers. It is assumed that the power levels of the signal at f1 and f2 are equal. It is also assumed that the power levels of signals at 2nd order IMD products viz. F2+F1 and F2-F1 are also equal.

The following IIP2 formula is used for IIP2 calculation.

IIP2 Calculator Using OIP2 Calculator

The IIP2 calculator is used for IIP2 calculation based on OIP2 and the gain of the device.

EXAMPLE of IP2 calculator:

• INPUT: OIP2 = 30 dBm, Gain = 22 dB
• OUTPUT: IIP2 = 8 dBm