Information: - In electronics and telecommunications a transmitter or radio transmitter is an electronic device which generates a radio frequency alternating current. When a connected antenna is excited by this alternating current, the antenna emits radio waves. - In parabolic antennas such as satellite dishes , a feedhorn ( or feed horn ) is a small horn antenna used to convey radio waves between the transmitter and / or receiver and the parabolic reflector . In transmitting antennas , it is connected to the transmitter and converts the radio frequency alternating current from the transmitter to radio waves and feeds them to the rest of the antenna , which focuses them into a beam . In receiving antennas , incoming radio waves are gathered and focused by the antenna 's reflector on the feed horn , which converts them to a tiny radio frequency voltage which is amplified by the receiver . Feed horns are used mainly at microwave ( SHF ) and higher frequencies . The feedhorn also selects the polarization of the waves to be received , which helps to attenuate unwanted signals from adjacent channels and transponders , and from other communications satellites at nearby orbital positions . This can be either horizontal or vertical if the polarization is linear , or clockwise or counterclockwise ( also called left - and right - handed ) if it is circular . Certain devices can also allow a feedhorn to accept both linear and circular , though these cause a slight insertion loss to all incoming signals . When used with a parabolic reflector or lens antenna , the phase center of the horn is usually placed at the focal point of the reflector , with the 3 dB points of the horn 's radiation pattern set to be at the edge of the reflector . On a satellite dish , the feedhorn is what is mounted at the end of a mast from the center of the dish , or on tripod legs mounted to the edge of the dish . In satellite dishes , part of the receiver electronics , the RF front end , is usually mounted in a box just behind the feed horn . This converts the high satellite microwave downlink frequencies to a lower frequency so it can be more easily sent through the coaxial cable feedline to the receiver inside the building . This is called the low - noise blockconverter ( LNB ) , and the unit... - A waveguide is a structure that guides waves, such as electromagnetic waves or sound waves. They enable a signal to propagate with minimal loss of energy by restricting expansion to one dimension or two. This is a similar effect to waves of water constrained within a canal, or why guns have barrels that restrict hot gas expansion to maximize energy transfer to their bullets. Without the physical constraint of a waveguide, signals will typically be radiated and decreased according to the inverse square law as they expand into three dimensional space. - Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the object(s). Radio waves (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed. Radar was developed secretly for military use by several nations in the period before and during World War II. The term "RADAR" was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging or RAdio Direction And Ranging. The term "radar" has since entered English and other languages as a common noun, losing all capitalization. - In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a transmission medium such as air or water. In physiology and psychology, sound is the "reception" of such waves and their "perception" by the brain. Humans can hear sound waves with frequencies between about 20Hz and 20kHz. Sound above 20kHz is ultrasound and below 20Hz is infrasound. Other animals have different hearing ranges. - In physics, a standing wave also known as a stationary wave is a wave in a medium in which each point on the axis of the wave has an associated constant amplitude. The locations at which the amplitude is minimum are called nodes, and the locations where the amplitude is maximum are called antinodes. - In the physics of wave propagation, a plane wave (also spelled planewave) is a wave whose wavefronts (surfaces of constant phase) are infinite parallel planes. Mathematically a plane wave takes the form in which the arbitrary (scalar or vector) function formula_2 gives the variation of the wave's amplitude, and the fixed unit vector formula_3 is the wave's direction of propagation. The solutions in formula_4 of comprise the plane with normal vector formula_6. Thus, the points of equal field value of formula_7 always form a plane in space. This plane then shifts with time formula_8, along the direction of propagation formula_6 with velocity "c". - A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300MHz. They are used as feed antennas (called feed horns) for larger antenna structures such as parabolic antennas, as standard calibration antennas to measure the gain of other antennas, and as directive antennas for such devices as radar guns, automatic door openers, and microwave radiometers. Their advantages are moderate directivity, low standing wave ratio (SWR), broad bandwidth, and simple construction and adjustment. - In radio engineering and telecommunications, standing wave ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave's amplitude at an antinode (maximum) to the amplitude at a node (minimum) along the line. - Radio frequency (RF) is any of the electromagnetic wave frequencies that lie in the range extending from around to , which include those frequencies used for communications or radar signals. RF usually refers to electrical rather than mechanical oscillations. However, mechanical RF systems do exist (see mechanical filter and RF MEMS). - A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis. The parabolic reflector transforms an incoming plane wave traveling along the axis into a spherical wave converging toward the focus. Conversely, a spherical wave generated by a point source placed in the focus is reflected into a plane wave propagating as a collimated beam along the axis. - Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter; with frequencies between and . This broad definition includes both UHF and EHF (millimeter wave) bands, and various sources use different boundaries. In all cases, microwaves include the entire SHF band (3 to 30GHz, or 10 to 1cm) at minimum, with RF engineering often restricting the range between 1 and 100GHz (300 and 3mm). Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, K, K, or K band, or by similar NATO or EU designations. - In physics, a wave is an oscillation accompanied by a transfer of energy that travels through a medium (space or mass). Frequency refers to the addition of time. "Wave motion" transfers energy from one point to another, which displace particles of the transmission mediumthat is, with little or no associated mass transport. Waves consist, instead, of oscillations or vibrations (of a physical quantity), around almost fixed locations. - In physics, the wavelength of a sinusoidal wave is the spatial period of the wavethe distance over which the wave's shape repeats, and thus the inverse of the spatial frequency. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter "lambda" (). The concept can also be applied to periodic waves of non-sinusoidal shape. The term "wavelength" is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Given the paragraphs above, decide what entity has the relation 'physically interacts with' with 'waveguide'.
feed horn