The measurement of mismatched noise sources without isolators

A simple correction for mismatch only applies when the noise contribution from a receiver is the same for all noise sources. But amplifier noise is affected by the match it ´sees´ at its input; hence the requirement for isolators to be inserted between source and receiver to ensure constant receiver noise. Unfortunately, isolators are unavailable at low MHz frequencies. An alternative solution is considered which is based on characterising the receiver so that its noise contribution is known for any noise source impedance.<>