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An antenna (or aerial) is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified. An antenna can be used for both transmitting and receiving.
Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, Broadcast Television, two-way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, bluetooth enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise.
Typically an antenna consists of an arrangement of metallic conductors ("elements"), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. These time-varying fields radiate away from the antenna into space as a moving electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna.
Antennas may also contain reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern. Antennas can be designed to transmit or receive radio waves in all directions equally (omnidirectional antennas), or transmit them in a beam in a particular direction, and receive from that one direction only (directional or high gain antennas).
The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving.
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Which antenna is not wideband?
Electrically small antennas are always narrow-band. The bandwidth of a small antenna has a theoretical maximum defined by the Chu Limit.
What is the difference between yagi antenna and dipole antenna?
I don't think it has. Bandwidth depends on the diameter to length ratio of the antenna. The greater the diameter of the elements the wider the bandwidth. The inductance goes down and the capacitance goes up, giving the antenna a lower Q. the folded dipole has a greater effective diameter (at least double for the same materials). You can increase a normal dipole's bandwidth by increasing the diameter, hence the old time birdcage aerials.
What is narrow band modulation frequency?
When the frequency sensitivity of the modulating signal is small,the bandwidth of the FM is narrow. The narrowband FM has one carrier term two sideband terms.The modulation index is also small compared to one radian.
How Frequency Modulation Have Higher Bandwidth then AM?
Bandwidth is defined as difference between two frequencies.In AM only amplitude is modulated or changed to transmit the data at the given fixed frequency. In FM the frequency of the signal is changed to transmit the data. Since we will need a range of frequency to transmit the data using FM (say frequencies from f1 to f2), the bandwidth of FM signal will be higher than AM signal which can transmit at a fixed frequency.But.....The above answer does not address the issue of "strength of modulation", that is, modulation index.A.M. will always have a bandwidth of twice its highest modulating frequency regardless of the strength of modulation.For voice comms with about a 3 kHz maximum frequency, A.M. will demand (3+3) = 6 kHz of bandwidth.Because F.M. modulates the frequency swing of the transmitter, low modulation indexes with F.M. can give a bandwidth LESS than the maximum modulating frequency. Narrow-Band F.M. (NBFM) can have a bandwidth of *less than* 3 kHz, indeed it can have a bandwidth of only a few hundred hertz, in theory.In practice, very narrow NBFM suffers from worsening signal-to-noise ratios, and one of F.M.'s chief advantages over A.M. is the superior signal-to-noise of F.M. when it is allowed sufficient bandwidth.
Does a low bandwidth signal have more power than a high bandwidth signal?
A low bandwidth signal does not have more power.
Which antenna is not wideband?
Electrically small antennas are always narrow-band. The bandwidth of a small antenna has a theoretical maximum defined by the Chu Limit.
What feature in a radio prevents overlapping stations?
All stations are fed into the radio by the antenna. The IF filters narrow the bandwidth down to the size of just one channel
What are the disadvantage of yagi-uda antenna?
bandwidth is less..
What is relation between antenna gain and beamwidth?
bandwidth refers to the amount of the frequency spectrum that a signal resides in.example, the spacing between channels on radio are determined by their bandwidth. beamwidth is a physical characteristic of an antenna. they generally mark the point bore sight of a directional antenna that are at -3dB or half power
What is job bandwidth in HRM?
it is a combination of narrow job design and broad job design
What is the effect of reducing the channel bandwidth?
I'm afraid you will need to specify on what exactly are you referring to. We could be talking about a radio channel bandwidth, a computer data transfer channel bandwidth or even a radio communications channel bandwidth. It is difficult to tell with the narrow question you posed.
What is bandwidh?
It's easiest to compare bandwidth to plumbing. Bandwidth is basically how big the pipe is, which means if you have high bandwidth, you can usually have a lot of information going through the "pipe". If you have low bandwidth, think of having a narrow pipe (like a straw) which restricts the amount of information that can pass through at one time.
How does the bandwidth represent the performance of RC coupled amplifier?
The bandwidth should be slightly larger than the actual bandwidth of the operating frequencies involved, and should be able to operate from the lowest used frequency to the highest frequency and inclusive of the frequencies between those two parameters. Another consideration would be the application for which it's used, as there are instances where the bandwidth needs to be limited, to prevent items such as `bleed over' and for the conservation of radio spectrum. Since your question is in general terms, I can only supply a general answer, and the bandwidth of your amplifier may be required to be very narrow and limited (narrow band) or wide (wide band).
What is narrow band FM and how a narrow band FM generate?
If the modulation index of FM is kept under 1, then the FM produced is regarded as narrow band FM. Lower the modulation index, lower the no. of significant sidebands are produced (with reference to bessel function). So lower the no. of significant sideband, lowerer will be the bandwidth of the resulting FM prduced. Sometimes, Narrow Band FM is regarded as, when the significant energy in FM occupies the same bandwidth as ordinary AM with the same modulating signal.
What is the difference between yagi antenna and dipole antenna?
I don't think it has. Bandwidth depends on the diameter to length ratio of the antenna. The greater the diameter of the elements the wider the bandwidth. The inductance goes down and the capacitance goes up, giving the antenna a lower Q. the folded dipole has a greater effective diameter (at least double for the same materials). You can increase a normal dipole's bandwidth by increasing the diameter, hence the old time birdcage aerials.
What is the bandwidth of a frequency independent antenna?
OK, so if it's *really* frequency independent, then the bandwidth must be infinite. i.e., from the 10 kHz used by the Omega submarine comms system to at least the current top end of 95 GHz used by point-to-point communications. Maybe you need to get a better handle on the range over which your "frequency independent" antenna is used. For starters, do a web search. There are plenty of good references on line.
What is narrow band modulation frequency?
When the frequency sensitivity of the modulating signal is small,the bandwidth of the FM is narrow. The narrowband FM has one carrier term two sideband terms.The modulation index is also small compared to one radian.
