Graph of P1dB, IP2, IP3, and Saturation
See cascade calculations for NF, IP2, IP3, and
P1dB.

When two or more tones are present in a nonlinear device, intermodulation products are created as a result. A
power series describes all of the possible combinations of generated frequencies. 2ndorder products lie far in
frequency to the two input tones and are therefore not very likely to fall inband at the output in a narrow band
system. As a device is driven farther into its nonlinear region, the amplitudes of the 2ndorder products increase
while the powers of the input tones decrease. If the device was not limited in output power, then the powers of
the intermodulation products would increase in power until they were eventually equal in power with the input tones
at the output.
Assuming a gain of 1 (0 dB) the slope of the fundamental gain line would be 1:1; the slope of the 2ndorder gain
line would be 2:1. Accordingly, the 2ndorder products increase in power at the same rate as the input tones and
are always two times farther away from the IP2 than the input tones when not near saturation.
The power of the 2ndorder products can be predicted when the IP2 is known, or the IP2 can be predicted when
the relative amplitudes of the 2ndorder tones and the input tones are known.
P_{2ndorder products} = 2 · P_{input tones@output}  IP2 {dBm}
IP2 =2 · P_{input tones@output}  P_{2ndorder products} {dBm}
Cascading IP2 Values in a Chain of Components
Click here to view an example of a cascaded system. 
Calculating the cascaded values for 2ndorder intercept point (IP2) for the system budget requires use
of ratios for gain and power levels for IP2 (do not use dB and dBm values, respectively). The
standard format for indicating decibel values is to use upper case letters; i.e., IP2 for units of dBm.
The standard format for indicating power values is to use lower case letters; i.e., ip2
for units of mW.
Conversions: ip2 = 10^{IP2/10} ↔ IP2 = 10 * log_{10} (ip2)
where ip2 has units of mW and IP2 has units of dBm
A Typical Chain of Cascaded Components

Combining 2 Stages at a Time for Calculations

This equation gives the method for calculating cascaded output ip2 (oip2) values based
on the oip2 and gain of each stage. When using the formula in a software program
or in a spreadsheet, it is more convenient and efficient to calculate each successive cascaded stage with the one
preceding it using the following format, per the drawing (aboveright).
These formulas are used to convert back and forth between input and outputreferenced IP2 values:
IP2_{Output} = (IP2_{Input} + Gain) {dBm}
IP2_{Input} = (IP2_{Output}  Gain) {dBm}
