What is Radio Frequency?
RF is the lowest portion of the electromagnetic spectrum, familiar as a medium of analog and modern digital wireless communication systems. It spreads in the range between 3 kHz and 300 GHz. All known transmission systems work in the RF spectrum range, including analog radio, aircraft navigation, marine radio, amateur radio, TV broadcasting, mobile networks, and satellite systems. Let’s take a look at each of the Radio Frequency bands and their uses.
The International Telecommunication Union (ITU) has provided designations for each band that are still used today. The IEEE has played a major role in assigning radio frequency bands for use in radar, terrestrial, and satellite applications. To better organize the microwave range of the electromagnetic spectrum, they designated each sub-band with a letter and standardized the classification. The table below gives the IEEE classification of frequency bands.
| Band Name | Abbreviation | ITU band | Frequency | Wavelength |
|---|---|---|---|---|
| Extremely low frequency | ELF | 1 | 3–30 Hz | 100,000–10,000 km |
| Super low frequency | SLF | 2 | 30–300 Hz | 10,000–1,000 km |
| Ultra low frequency | ULF | 3 | 300–3,000 Hz | 1,000–100 km |
| Very low frequency | VLF | 4 | 3–30 kHz | 100–10 km |
| Low frequency | LF | 5 | 30–300 kHz | 10–1 km |
| Medium frequency | MF | 6 | 300–3,000 kHz | 1,000–100 m |
| High frequency | HF | 7 | 3–30 MHz | 100–10 m |
| Very high frequency | VHF | 8 | 30–300 MHz | 10–1 m |
| Ultra high frequency | UHF | 9 | 300–3,000 MHz | 100–10 cm |
| Super high frequency | SHF | 10 | 3–30 GHz | 10–1 cm |
| Extremely high frequency | EHF | 11 | 30–300 GHz | 10–1 mm |
| Terahertz or tremendously high frequency | THF | 12 | 300–3,000 GHz | 1–0.1 mm |
Extremely Low Frequency (ELF)
Frequency starting from 3Hz to 3 kHz is known as Extremely Low Frequency or ELF range in the electromagnetic spectrum. According to IEEE band designation, these ranges are divided into three sub-bands:
ELF – Extremely Low Frequency, ranging from 3Hz to 30Hz.
SLF– Super Low Frequency, ranges from 30 to 300Hz.
ULF – Ultra Low Frequency, ranging from 300 to 3000Hz (3 KHz).
This range is highly vulnerable to disturbance and easily distorted by atmospheric changes. Designing a system in this range is challenging because the larger wavelengths require long antennas, which are practically impossible to achieve.
Scientists use this frequency band in seismic studies to understand natural activities in the Earth’s atmosphere and communication with submarines.
Very Low Frequency (VLF)
Very Low Frequency is the starting range of RF and practical radio transmission systems which span from 3 kHz to 30 kHz. However, the design and implementation of the antenna system are extremely complicated due to the wavelength.
It has been used in submarines and still using in time radio stations which synchronizes clock signals between two remote locations.
Low Frequency (LF)
Low frequency is in the range of 30 kHz to 300 kHz. One of the important properties of LF signals is that they will get reflected by the earth’s ionosphere and thus, it is suitable for long-distance communication. Since it’s a long wavelength and less attenuation from big terrains like mountains, it is generally called a ground wave.
Amateur radio operators use low-frequency signals; it is one of the most important sources of information transfer when another kind of communication source fails during some situations like natural disasters. Other areas are military applications like submarines, RFID tags in near-field communication, and some low-frequency radio broadcasting.
Medium Frequency (MF)
Medium frequency was one of the most popular frequency bands since the beginning of wireless radio transmission in the early nineteenth century. MF operates in the range of 300 kHz to 3 MHz. The transmitters, receivers, and antenna design is relatively less complex than other high-frequency transmission bands.
Medium Frequency has been widely used in AM radio transmission, navigation systems for ships and aircraft, emergency distress signals, coast guards, and other experimental applications.
High Frequency (HF)
High-frequency signals range between 3 MHz and 30 MHz. This frequency band is also known as a short wave. It also gets reflected by the earth’s ionosphere, and it is one of the suitable bands for long-distance communication.
The high-frequency band is mainly used by the aviation industry, near-field communication (NFC), government systems, amateur radio operators, and weather broadcasting stations.
Very High Frequency (VHF)
Very high frequency is one of the most commonly used RF bands, with an operating range from 30 MHz to 300 MHz. VHF frequency has been widely used in analog TV broadcasting since it started a few decades ago. FM radio broadcasting from 88 to 108 MHz operates in the VHF frequency band.
Air traffic controllers and airline pilots communicate between 118 MHz to 137 MHz. Other uses include private and business radio stations, medical equipment (magnetic resonance imaging), amateur radio, and military applications. It is usually affected by big terrains but is suitable for short-distance communication.
Ultra High Frequency (UHF)
Ultra High Frequency is modern wireless communication systems’ most critical radio frequency band. It begins from 300 MHz to 3 GHz and is highly complicated to design and implement the system. UHF has many sub-frequency bands; some are restricted and assigned only to particular applications.
It is used in GPS navigation systems, satellites, pagers, Wi-Fi, Bluetooth, television broadcasting, and most importantly, GSM, CDMA, and LTE mobile transmission.
Super High Frequency (SHF)
Super High Frequency is in the range of 3 GHz to 30 GHz. It can only operate in a line of sight path since any obstruction between the transmitter and receiving station will break the communication.
It is commonly used in point-to-point communication, satellite systems, digital TV broadcasting in the Ku band (DTH service – direct to home), Wi-Fi (5GHz channel), microwave ovens, and mobile networks. Waveguides are suitable between the transmitter and antenna due to the higher losses of standard RF cables. System design is extremely hard in the SHF band due to its smaller wavelength and complexity.
Extremely High Frequency (EHF)
The extremely high-frequency band is the highest in the RF frequency spectrum, which ranges between 30 GHz and 300 GHz. EHF is only used in advanced communication systems due to its complex nature and line of sight requirement.
EHF is used in radio astronomy and remote sensing (weather analysis). Due to large bandwidth availability, it is suggested to use high-speed internet systems like 5G technology for future transmission networks.
Find more about the Applications of Millimeter Waves
Tremendously High Frequency (THF) – Above 300GHz
This band is above the RF band range of 300GHz; in terahertz imaging technology, this is an alternate frequency spectrum for X-rays. Other applications included terahertz spectroscopy applications and supercomputers.
Conclusion
RF is a broad spectrum, and many of its characteristics have not been experimented with yet. It has a lot of possibilities in medical applications like MRI technology (even up to 12 Tesla for medical research), seismography, and oceanic studies. RF transceivers are significant components in interplanetary missions such as the Mars exploration. Our future digital communication systems may rely on high-frequency bands of the RF spectrum since they can support higher bandwidth.
