Views: 2398 Author: James Wu Publish Time: 2021-05-10 Origin: Site
What is Radio Frequency (RF)?
RF is the lowest portion in the electromagnetic spectrum familiar as a medium of analogue and modern digital wireless communication system. It spreads in the range between 3 KHz and 300 GHz. All known transmission systems works in the RF spectrum range including analogue radio, aircraft navigation, marine radio, amateur radio, TV broadcasting, mobile networks and satellite systems.
Radio Frequency (RF) is a broad spectrum and many of its characteristic has not been experimented yet. It has 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 Mars exploration mission.
Let's take a look on each of the RF sub bands and the areas of RF spectrum uses.
Extremely Low Frequency (ELF)
Frequency starting from 3Hz to 3 KHz is known as extremely low frequency or ELF range in electromagnetic spectrum. This range is highly vulnerable to disturbance and easily gets distorted by atmospheric changes. It is hard to design a system in this rage is challenging because of the larger wavelengths required long antennas which are practically impossible to achieve. Scientists use this frequency band in seismic studies to understand natural activities in earth’s atmosphere.
Very Low Frequency (VLF)
Very low frequency is the starting range of RF and practical radio transmission system which span from 3 KHz to 30 KHz. However, design and implementation of the antenna system is extremely complicated due to the wavelength. It has been using in submarines and still used in time radio station 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 it will get reflected by earth’s ionosphere and thus it is suitable for long distance communication. Since it’s long wavelength and less attenuation from big terrains like mountains, it is generally called ground waves.
Low frequency signals are used by amateur radio operators; it is one of the most important sources of information transfer when other kind of communication sources fails during some situation 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. Design of transmitters, receivers and antenna are relatively less complex than other high frequency transmission bands. MF has been widely using in AM radio transmission, navigation systems for ships and aircraft, emergency distress signals, cost guards and other experimental applications.
High Frequency (HF)
High frequency signals ranges between 3 MHz and 30 Mhz. This frequency band is also known as short wave. It also gets reflected by earth’s ionosphere and it is one of the suitable band for long distance communication. High frequency band is mostly used by 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 bands which has an operating range from 30 MHz to 300 MHz. VHF frequency is widely used in analog TV broadcasting since it has started few decades back. FM radio broadcasting at 88 MHz to 108 MHz operates in VHF frequency band.
Air traffic controllers and airline pilots using frequency between 118 MHz to 137 MHz to communicate. Another uses includes private and business radio station, medical equipment (magnetic resonance imaging), amateur radio and military applications. It usually affected by big terrains but suitable for short distance communication.
Ultra High Frequency (UHF)
Ultra high frequency is the most important frequency bands for modern wireless communication systems. It begins from 300 MHz to 3 GHz and extremely complicated to design and implement the system. It has many sub frequency bands, some are restricted and assigned only for 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 line of sight path since any obstruction in 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 Ku band (DTH service – direct to home), Wi-Fi (5GHz channel), microwave ovens and mobile networks. Waveguides are suitable between transmitter and antenna due to higher losses of usual RF cables. System design is extremely hard in SHF band due to its smaller wavelength and complexity.
Extremely High Frequency (EHF)
Extremely high frequency band is the highest in RF frequency spectrum which range 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). It is suggested to use for high speed internet systems like 5G technology for future transmission networks due to large bandwidth availability.
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