It is common knowledge that both analog and digital design engineers are continually developing and refining circuits for higher and higher operational frequencies. Analog circuits for wireless communication in the GHz range and the ever increasing clock speeds of computer circuits in high performance mainframes, workstations, and of course personal computers exemplify this trend. Global positioning systems require carrier frequencies in the range of 1227.60 and 1575.42 MHz. The low noise amplifier in a personal communication system may operate at 1.9 GHz and fit on a circuit board smaller in size than a dime. Satellite broadcasting in the C-band involve 4 GHz uplink and 6 GHz downlink systems. In general, due to the rapid expansion of wireless communication, more compact amplifier, filter, oscillator, and mixer circuits are being designed and placed in service at frequencies generally above 1 GHz. There is little doubt that this trend will continue unabated, resulting in engineering systems with unique capabilities, but also special design challenges not encountered in conventional low frequency systems. This chapter reviews the evolution from low to high frequency circuit operations. It motivates and provides the physical rationales that have prompted the need for new engineering approaches to design and optimize these circuits. The example of a cellular phone circuit, components of which will be analyzed in more detail in later chapters, serves as a vehicle to outline goals and objectives of this textbook and its organization.

The chapter begins with a brief historical discussion explaining the transition from direct current (DC) to high frequency modes of operation. As the frequency increases and the associated wavelengths of the electromagnetic waves becomes comparable to the dimensions of the discrete circuit components such as resistors, capacitors, and inductors, these components start to deviate in their electric responses from their ideal frequency behavior. It is the purpose of this chapter to provide the reader with an appreciation and understanding of high frequency passive component characteristics. In particular, due to the availability of sophisticated measurement equipment, the design engineer must know exactly why and how high frequency behavior of his/her circuit differs from the low frequency realization. Without this knowledge it will be impossible to develop high performance systems.