IP3 is an important quantity in systems analysis of wireless/RF systems. It is a measure of the performance of an amplifier and is related to the 1 dB compression point of an amplifier. To put it simply IP3 can be interpreted as an unwanted signal that comes out of the noise level in an amplifier system ( or a mixer ) and climbs at a rate of 3X the amplifier input – output characteristic. It is, as mentioned above, an unwanted signal and therefore care is taken to calculate it as it sets a boundary on achieveable performance of the circuit. A good paper on this and other related quantities ( such as 1 dB compression point, IP2 ) is presented in the “Engineer’s Corner” in our website located at www.signalpro.biz>Engineering_Pages for interested readers. As young RF engineers it took us a while to completely understand the ramifications of IP3 and associated quantities. To be able to understand intermodulation intuitively is neccessary for good RF/wireless design.