Active devices:
diodes, transistors, and electron tubes used for signal detection, mixing, amplification, frequency
multiplication, and switching, and as sources of RF and microwave signals.
Semiconductor Microwave Devices
Most microwave devices are fabricated on a GaAs substrate because of its high
mobility.
A silicon substrate, on the other hand, has the advantages of low cost and high yield. The following table summarizes the various microwave solid-state devices and their applications.
Microwave Diodes
A microwave diode is much more than just a two-element device which has limited capabilities.
It is a complex device which an integral part of many sophisticated microwave systems. Many devices have been developed using the non-linear I-V and C-V characteristics of the p-n or Schottky-barrier junction.
Schottky Diodes
The classical p-n junction diode commonly used at low frequencies has a relatively large junction capacitance that makes it unsuitable for high frequency application. The Schottky barrier diode, however, relies on a semiconductor–metal junction that results in a much lower junction capacitance allowing
operation at higher frequencies. The primary application of Schottky diodes is in frequency conversion
of an input signal (conversion to DC), detection (demodulation of an amplitude-modulated signal), and mixing (frequency shifting).
