Radio communications: components, systems and networks [Series Editorial]

The history of radio communications has been characterized by a constant march toward ever higher frequencies. Early spark and continuous wave (CW) communications at kilometer wavelengths soon gave way to medium wave transmissions in the 500 kHz range (i.e., wavelengths of hundreds of meters). Increasing spectrum congestion and the discovery of ionospheric reflection shifted focus during the middle of the last century to the shortwave band where wavelengths are measured in meters. Satellite and terrestrial digital communications required much higher bandwidths and better spectrum sharing, pushing the use of UHF (ultra high frequency) wavelengths approaching 1 GHz. In the last two decades the explosion of cellular and high-speed digital links have caused us to reach for the centimeter band in earnest; modern cellular and wireless LAN systems use frequencies in the 2???5 GHz range (15???6 cm).