The art and science of radio hardware design has been to some degree about minimizing, avoiding and, if possible, altogether eliminating unwanted spurious signals that find their way into the receive path of a radio. Typical sources of such signals are usually the multitude of two or more terminal devices that contain active semiconductor junctions such as diodes, transistors and ICs made up of them. These junctions with their nonlinear current voltage characteristics can be a rich source of harmonics and various intermodulation products, especially if more than one signal is present across them. Though magnetic materials commonly encountered in electronic circuits of most kinds are also a potential source of such nonlinearities, these components are usually used in blocking low level, low frequency ripples and occasional spikes in voltage or current and rarely interfere with communication signals unless poorly designed and selected.
展开▼
