RF and Microwave Engineering: Fundamentals of Wireless Communications

6.1 Equivalent Circuits of Concentrated Passive Components

At low frequencies the electrical behaviour of real concentrated electrical components like resistors, capacitors and inductors is approximated by idealized nominal values. With increasing frequency parasitic effects become more pronounced and have to be considered for realistic circuit design. Parasitic effects result from losses in conductors and dielectric or magnetic material, inductances of wire leads and capacitances of contact terminals.

We will derive simple and physically reasonable equivalent circuits of the most important concentrated elements: resistor, capacitor and inductor. Each of these equivalent circuits consists of three ideal elements and is quite useful and sufficiently accurate for many practical applications.

We can further improve the accuracy, extend the frequency range and expand the scope of applications by considering more complex equivalent circuits [1] including more than three elements. However, it is more difficult to determine the elements of the complex equivalent circuits, for example from measurements. Furthermore, with increasing frequency the physical mounting condition effects the component behaviour. Coupling effects between the electrical component and the circuit environment have to be considered.

6.1.1 Resistor

Resistors come in different shapes and package types. High-frequency circuits commonly use surface mounted device (SMD) components. These components are rectangular in shape ...