An Introduction to RF Theory, Practices, and Components The Ins and Outs of RF
By JJ DeLisle for Mouser Electronics
Published October 31, 2025
A wide range of technologies used for wireless communication, power transfer, navigation, and sensing have become vital to virtually all human activities, from daily life to space exploration. Many of these devices and systems operate within the radio frequency (RF) spectrum, which ranges from approximately 3kHz up to the infrared light spectrum, near 30THz. RF technology is responsible for the vast number of communication services we use daily (and, in some cases, nearly constantly). It is responsible for the sensing and navigation technologies that keep planes in the air and ships on course; it is even behind the microwave energy generators that cook, sanitize, and seal much of the world’s food and personal products. Due to the diversity of applications and markets, RF technology knowledge is also very diverse. While this diversity has led to various naming conventions across the different applications, which can sometimes be confusing to those new to the field, this article will help decipher some of these colloquialisms.
This article explains high-level concepts associated with RF and provides a basic overview of the key principles of RF phenomena and technology. In that light, the article is meant to provide a primer on RF technology concepts to help initiate readers into the field or offer a shallow review for those familiar with the topic.
What Is RF?
Within the RF frequency range, there exists an extremely diverse range of natural and artificial electromagnetic radiation sources and systems. RF generators include celestial objects like the sun, which generates broad-spectrum radiation (RF and beyond), terrestrial sources such as lightning and atmospheric interactions with space weather, and the myriad human-made RF sources and systems.
Because RF technology originated in wireless communications, some schools of thought limit RF to relatively low-frequency wireless communications. In some cases, the term RF is used to describe all radiation that could be encompassed within the RF spectrum, whether made by humans or of natural origin. RF is generally considered to encompass a frequency range from roughly 3kHz to 300GHz, with some now considering it to extend into the terahertz (THz) range. The submillimeter-wave spectrum (above 300GHz to 30THz) is being actively studied for sensing and short-range, extremely high-data-rate communications.[1]
Nomenclature for RF technologies and phenomena is often specific to the application, industry, or field of science that uses the concepts. For instance, one engineer may refer to the microwave spectrum as a subset of the RF spectrum, while another may use it to describe the shorter-wavelength and higher-frequency electromagnetic radiation beyond legacy RF communications frequencies.
The millimeter-wave (mmWave) spectrum—typically assigned the range of 30GHz to 300GHz but may be extended to 3THz in some contexts—has a higher frequency range than the microwave spectrum. In this case, "millimeter" is used to describe the range of wavelengths that are on the order of a millimeter to hundreds of millimeters. Terahertz, like mmWave, is a physically accurate descriptor that describes the submillimeter-wave frequencies beyond mmWave frequencies and below optical frequencies (which are in the tens of terahertz).
Many applications and industries have specific terms for regions of the RF spectrum and frequency bands, such as the radar frequency bands designated using letters, the International Telecommunication Union (ITU) spectrum designations, NATO radar bands, and cellular communications frequency ranges.
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