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Radio Waves vs Microwaves

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- Comparison between Microwaves and mmWaves

Microwaves and millimeter waves (mmWaves) are both forms of radio frequency signals - the only difference is the frequency range they cover.

While the terms tend to be used rather loosely in some contexts, there are definitions for both microwave and millimeter wave, with millimeter wave explaining where these frequency bands fit within the overall radio spectrum.

Microwaves are a subclass of radio waves. The frequency of radio waves can take values between 300 GHz and 3 kHz, but the frequency of microwaves is defined as between 300 GHz and 300 MHz. General radio waves have long-distance communication capabilities, but microwaves do not have these capabilities.

Radio waves are electromagnetic radiation with the longest wavelengths on the electromagnetic spectrum, typically at frequencies of 300 gigahertz (GHz) and below. At 300GHz, the corresponding wavelength is 1 millimeter, which is shorter than a grain of rice. At 30Hz, the corresponding wavelength is about 10,000 kilometers (6,200 miles) longer than the Earth's radius. 

Like all electromagnetic waves, radio waves travel at the speed of light in a vacuum and at a similar but slightly slower speed in Earth's atmosphere. Radio waves are generated by charged particles undergoing acceleration, such as a time-varying current. Naturally occurring radio waves are emitted by lightning and celestial bodies as part of the black body radiation emitted by all warm objects.

- Radio Waves

Radio waves are artificially generated by an electronic device called a transmitter, which is connected to an antenna that radiates the waves. They are received by another antenna connected to a radio receiver, which processes the received signal.

Radio waves are generated by a transmitter and detected by a receiver. Antennas allow radio transmitters to send energy into space and receivers to receive energy from space. Transmitters and receivers are usually designed to operate within a limited frequency range.

Radio waves are electromagnetic waves with the lowest energy, the lowest frequency, and the longest wavelength. They are created when alternating current flows through the antenna, spreads out and travels through the atmosphere. 

Radio waves are not strongly absorbed by the atmosphere. Another antenna acts as a detector, where the waves create an alternating current whose frequency matches that of the radio waves. Anyone with a receiver can tune it to that frequency to receive radio waves, so they're suitable for broadcasting (for example, radio and TV programs) to large groups of people. 

One advantage is that this method of communication does not require wires to transmit information. The disadvantage is that radio stations using similar transmission frequencies can sometimes cause interference.

Radio waves are used very extensively in modern technology for fixed and mobile radio communications, broadcasting, radar and radio navigation systems, communication satellites, wireless computer networks and many other applications.


- Radio Wave Transmissions

Radio waves of different frequencies have different propagation characteristics in the Earth's atmosphere; longer waves can bypass obstacles such as mountains and diffract along the contours of the Earth (ground waves), and shorter waves can reflect from the ionosphere and return to Earth beyond the horizon (sky waves), while shorter wavelengths bend or diffract very little and continue down a line of sight, so their propagation distance is limited to the event horizon.

To prevent interference between different users, the artificial generation and use of radio waves is strictly regulated by law and coordinated by an international body called the International Telecommunication Union (ITU), which defines radio waves as "any frequency below 3,000 GHz electromagnetic waves" that travel through space without human guidance. The radio spectrum is divided into radio bands according to frequency, which are allocated to different uses.


- The Microwave Spectrum

Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. 

The microwave spectrum is usually defined as a range of frequencies ranging from 1 GHz to over 100 GHz. This range has been divided into a number of frequency bands, each represented by a letter. There are a number of organizations that assign these letter bands.

Different sources define different frequency ranges as microwaves; the above broad definition includes UHF, SHF and EHF (millimeter wave) bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 0.3 m and 3 mm). 
In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.


Please refer to Wikipedia: Microwave for more details.


- Microwave Radio Transmission

Point-to-point microwave transmission is a critical component of the national communications infrastructure. Microwave paths enable broadband data transmission that supports telephone, cellular, and personal communication service (PCS) networks, wireless internet providers, audio and video transmission from television studios to transmitter sites, as well as many other industry/utility applications.

Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do. This frequency reuse conserves scarce radio spectrum bandwidth. Another advantage is that the high frequency of microwaves gives the microwave band a very large information-carrying capacity; the microwave band has a bandwidth 30 times that of all the rest of the radio spectrum below it. A disadvantage is that microwaves are limited to line of sight propagation; they cannot pass around hills or mountains as lower frequency radio waves can.


- Infrared Waves

Infrared waves are electromagnetic waves with a frequency range between 300 GHz and 400 GHz. These cannot travel long distances. These waves are used for short-range communications, and they also use line-of-sight for propagation. These waves cannot pass through solid objects such as walls. These also cannot penetrate walls. 

The most common applications for infrared waves are remote controls for televisions, DVD players, and stereo systems.



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