Meaning
The generation of unwanted signals from the non-linear mixing of two closely spaced frequencies can corrupt adjacent channels in a wireless receiver. Engineers measure third order intermodulation to characterize the non-linear behavior of amplifiers, mixers, and switches under multi-carrier conditions. This distortion product falls close to the original signals and cannot be filtered out.
Spectral Impact
The resulting spurious signals appear at frequencies equal to twice one input frequency minus the other. Because these products lie within the active passband of the system, they directly degrade the signal-to-noise ratio of the receiver. This interference reduces the data throughput of the wireless connection and can cause dropped packets.
System Metric
The third-order intercept point is a hypothetical power level where the power of the intermodulation products would equal the power of the fundamental signals. Designers use this mathematical value to compare the linearity of different RF components. A higher intercept point indicates that the component can handle larger signal levels before third order intermodulation begins to degrade the transmission.
Testing Protocol
Verification requires a test bench with two high-quality signal generators, a power combiner, and a spectrum analyzer. The generators apply two clean tones of equal amplitude to the device under test while the analyzer measures the amplitude of the resulting spurs. Automated test routines run this sweep across different power levels and frequencies to build a complete linearity profile of the module.
This detailed testing confirms that the component complies with international wireless standards before it is approved for mass assembly.
