### Abstract

The two-port equivalent circuits are widely used in radio frequency (RF) and microwave circuit design to describe the electrical behavior of both active devices and passive networks [1–4]. The two-port network impedance Z-parameters, admittance Y-parameters, or hybrid H-parameters are very important to characterize the nonlinear properties of the active devices, bipolar or field-effect transistors. The transmission ABCD-parameters of a two-port network are very convenient for designing the distributed circuits like transmission lines or cascaded elements. The scattering S-parameters are useful to characterize linear circuits, and are required to simplify the measurement procedure. Transmission lines are widely used in matching circuits in power amplifiers, in resonant circuits in the oscillators, filters, directional couplers, power combiners, and dividers. The design formulas and curves are presented for several types of transmission lines including stripline, microstrip line, slotline, and coplanar waveguide. Monolithic implementation of lumped inductors and capacitors is usually required at microwave frequencies and for portable devices. Knowledge of noise phenomena, such as the noise figure, additive white noise, low-frequency fluctuations, or flicker noise in active or passive elements, is very important for the oscillator modeling in particular and entire transmitter design in general.