Meaning
Nonlinear distortion effect where multiple high frequency signals interact to produce new frequencies within the spectrum above one hundred gigahertz. This sub terahertz intermodulation occurs when two or more tones pass through a component with a non-linear transfer function, such as a mixer or an amplifier. It creates interference that can overlap with the desired signal or pollute adjacent channels in ultra high speed communication systems.
Mechanism Creation
Physical imperfections in the transmission lines or the semiconductor junctions generate these unwanted products. At these extremely short wavelengths, even the surface roughness of the metal can contribute to sub terahertz intermodulation. The mathematical sum and difference of the input frequencies define the location of the new spectral components.
Third order products are the most problematic because they usually fall closest to the original carrier.
Bandwidth Limitation
Modern wireless backhaul systems require wide channels for high data rates. Sub terahertz intermodulation increases the noise floor and limits the achievable modulation order. This reduction in the signal to noise ratio directly lowers the total throughput of the link.
Designers use high linearity components and balanced circuit topologies to minimize the formation of these intermodulation products.
Testing Environment
Measuring these effects requires specialized waveguides and extremely stable signal sources. Because the frequencies are so high, the sub terahertz intermodulation is sensitive to thermal expansion in the test fixtures.
