OVERVIEW

Microwave frequencies refer to the frequency range starting from 300 MHz up to 300 GHz, or equivalently to the wavelength range from 1 meter down to 1 millimeter. Since the dimensions of circuit and circuit components designed to operate in microwave frequencies can easily be comparable to the wavelength, they cannot be considered as point-like objects as in the case of lumped model approximations. In lumped circuit analysis, as taught in circuit analysis and electronics courses in electrical and electronics engineering curriculum, the main assumption is that the current through a series arm and the voltage across parallel branches don't change by distance because the dimensions of the circuits are extremely small as compared to the wavelength of the signal. As a result, node voltages and loop currents become sufficient to analyze such circuits. However, if the dimensions of the circuit components become comparable to signal wavelength, the assumption no longer holds; that is, the current through a component and voltage across parallel branches vary as one moves along the circuit. This is mainly due to the finite propagation time required for an electrical disturbance, like current and voltage, to move in a circuit. Thus, the distributed nature of the circuit must be taken into account at microwave frequencies to accurately model the phase change and attenuation of signals while traveling along the circuit. To account for changes of the current and voltage along a conducting line or through a circuit component, these elements can be modeled, from a...