Amplification in Linear Mode
1.1. Principles of microwave amplification
An amplifier is a device used to convert some of the power supplied by a direct current (DC) signal from a continuous power source into alternating current (AC) power at the frequency of the microwave signal applied on the input. It consists of the following elements:
– active components used for the amplification of the signal, such as bipolar (HBTs, etc.) and field-effect (MESFETs, HEMTs, etc.) transistors;
– passive components used for the polarization and impedance matching networks, such as transmission line segments, resistors, inductors an d capacitors.
Figure 1.1. Principle of amplification
It is possible to essentially classify microwave amplifiers according to various criteria, although this list is not exhaustive:
– Output power:
- low power: output power of a few tens of mW, operating in linear mode;
- medium power: output power ranging from a few hundred mW to a few W, essentially operating in nonlinear mode;
- high power: output power greater than a few W, operating in nonlinear mode, taking the phenomena of power dissipation into account.
– Frequency band of operation:
- narrowband: relative bandwidth
a percentage of several ...