Nonlinear junction detector

A bumblebee with a transponder acting as a non-linear junction for tracking the animal by way of harmonic radar.

The non-linear junction detector, or an NLJD, is a device that illuminates a small region of space with high-frequency RF energy. Any "non linear junction" in the vicinity—for example, and particularly, the p-n junction -- will receive this energy, and because of the non-linear nature of the junction, it will rectify it, re-emitting some of it on multiples of the illumination frequency (see harmonic). The detector has a sensitive receiver tuned to these harmonics, as well as appropriate processing and displays to make their presence known to the user of the device. Because the basis of almost all semiconductor electronics is the p-n junction, an NLJD is correspondingly capable of detecting almost any un-shielded electronic device containing semiconductors, whether the electronics are on or off. It can also detect things that are not themselves electronic in nature, so the use of the device requires a modicum of skill and experience.

See also

• Covert listening device

External links

• Non-Linear Junction Detector Review and Tutorial
• http://www.google.com/patents?id=3QgEAAAAEBAJ&dq=patent:6057765
• GBPPR Non-Linear Junction Detector Homebrew non-linear junction detector project.