Introduction to Microwave and RF Engineering :
Modern microwave and radio frequency (RF) engineering is an exciting and dynamic field, due in large part to the symbiosis between recent advances in modern electronic device technology and the explosion in demand for voice, data, and video communication capacity that started in the 1990s and
continues through the present.
Prior to this revolution in communications, microwave technology was the nearly exclusive domain of the defense industry; the recent and dramatic increase in demand for communication systems for such applications as wireless paging, mobile telephony, broadcast video, and tethered as well as untethered computer networks has revolutionized the industry.
These communication systems are employed across a broad range of environments, including corporate offices, industrial and manufacturing facilities, infrastructure for municipalities, as well as private homes. The
diversity of applications and operational environments has led, through the accompanying high production volumes, to tremendous advances in cost-efficient manufacturing capabilities of microwave and RF products.
This in turn has lowered the implementation cost of a host of new and cost-effective wireless as well as wired RF and microwave services. Inexpensive handheld GPS navigational aids, automotive collision-avoidance radar, and widely available broadband digital service access are among these.
Microwave technology is naturally suited for these emerging applications in communications and sensing, since the high operational frequencies permit both large numbers of independent channels for the wide variety of uses envisioned as well as significant available bandwidth per channel for high-speed communication.
The most fundamental characteristic that distinguishes RF engineering from microwave engineering is directly related to the frequency (and thus the wavelength, λ) of the electronic signals being processed. This distinction arises fundamentally from the finite speed of propagation of electromagnetic waves (and thus, by extension, currents and voltages).
In free space, λ = c/f , where f is the frequency of the signal and c is the speed of light. For low-frequency and RF circuits (with a few special exceptions such as antennae), the signal wavelength is much larger than the size of the electronic system and circuit components. In contrast, for a microwave system the sizes of typical electronic components are often
comparable to (i.e., within approximately 1 order of magnitude of) the signal wavelength.