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For the cooking appliance, see Microwave oven. A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range. The atmospheric attenuation of microwaves and far infrared radiation in dry air with a precipitable water vapor level of 0.
The downward spikes in the graph correspond to frequencies at which microwaves are absorbed more strongly. In a microwave beam directed at an angle into the sky, a small amount of the power will be randomly scattered as the beam passes through the troposphere. A sensitive receiver beyond the horizon with a high gain antenna focused on that area of the troposphere can pick up the signal. This technique has been used at frequencies between 0. Waveguide is used to carry microwaves. Their short wavelength also allows narrow beams of microwaves to be produced by conveniently small high gain antennas from a half meter to 5 meters in diameter. The term microwave also has a more technical meaning in electromagnetics and circuit theory.
As a consequence, practical microwave circuits tend to move away from the discrete resistors, capacitors, and inductors used with lower-frequency radio waves. The grey assembly attached to the end of the copper-colored horn antenna is the Gunn diode which generates the microwaves. High-power microwave sources use specialized vacuum tubes to generate microwaves. All warm objects emit low level microwave black-body radiation, depending on their temperature, so in meteorology and remote sensing, microwave radiometers are used to measure the temperature of objects or terrain.
Wireless LAN protocols, such as Bluetooth and the IEEE 802. 11 specifications used for Wi-Fi, also use microwaves in the 2. 16, designed to operate between 2 and 11 GHz. Commercial implementations are in the 2. 9 GHz in the Americas and elsewhere, respectively.
Most satellite communications systems operate in the C, X, Ka, or Ku bands of the microwave spectrum. These frequencies allow large bandwidth while avoiding the crowded UHF frequencies and staying below the atmospheric absorption of EHF frequencies. ASR-9 airport surveillance radar which radiates a narrow vertical fan-shaped beam of 2. Radar is a radiolocation technique in which a beam of radio waves emitted by a transmitter bounces off an object and returns to a receiver, allowing the location, range, speed, and other characteristics of the object to be determined. The short wavelength of microwaves causes large reflections from objects the size of motor vehicles, ships and aircraft. Chile, observes the universe in the millimetre and submillimetre wavelength ranges.