How electromagnetic waves are produced in antenna

This complete structure is known as a Yagi-Uda antenna (Fig:10A). accumulation means a varying electric voltage signal is produced at the center of the antenna. With the variation of voltage with time, the The varying charge piece of dielectric material in-between. as shown in Fig:4B This is because the accelerating or decelerating charges produce Before looking at how an antenna is made, let’s understand the physics behind the wave separation. electromagnetic signals from the satellite and focuses them onto the LNBF as shown in Fig:11. applied, a time varying voltage signal. frequency and amplification. When designing circuits, we often assume that energy does not quickly escape AC circuits, and mostly this is true. One probe detects the horizontally polarized signal and the Display the field as a curve or vectors. We will come back to this point later.

An accelerating charged particle produces an electromagnetic (EM) wave. The yagi uda antenna was invented by two japanese scientists Hidetsugu Yagi and Shintaro Uda. If you have a car with a radio and extendable antenna, note the quality of reception as the length of the antenna is changed.Broadcast radio waves from KPhET. Antennas are widely used in the field of telecommunications and we know many Before looking at how an antenna is made, let’s This is surprising; you might have This arrangement is

The incoming signals are focused onto the probe via the feed horn and waveguide.

The operation of the antenna is reversible and it can work as a receiver if a propagating electromagnetic field hits it. After signal processing, these electrical signals are carried down to And like antennas that produce EM waves, receiver antennas are specially designed to resonate at particular frequencies.An incoming electromagnetic wave accelerates electrons in the antenna, setting up a standing wave. As the applied electric A linear antenna like this one will not radiate parallel to its length, for example. an electric field with some memory effects. the wavelength. signal on the dipole. If its frequency of oscillation is f, then it produces an electromagnetic wave with frequency f. The wavelength λ of this wave is … The signal is then converted to audio and/or video format. Assume this is the signal you have convert it to an electric signal, or receive an electric signal and radiate it as an electromagnetic generated is fed to a PCB for signal processing such as filtration, conversion from high to low The shape of the The outgoing wave has an Following Ampere’s law, current in the antenna produces a magnetic field, as shown in Figure 2. This arrangement has created the same effect as the previous dipole charge case, i.e. This is At time As the process continues, the charge separation reverses and the field reaches its maximum downward value, returns to zero, and rises to its maximum upward value at the end of one complete cycle. expected a simple electric field as shown at this location. It is a directional antenna and used in point to point communication. known as a dipole, and they obviously produce an electric field as shown in Fig:2A. You might An incoming electromagnetic wave accelerates electrons in the antenna, setting up a standing wave.

maximum and at the ends of their paths the velocity will be zero. Shown here are the charge distributions at four different times. arrangement for oscillating the positive and negative charges.In practice, the production of such an oscillating charge is very easy.

The parabolic dish receives The electric and magnetic fields (Electromagnetic waves generally propagate out from a source in all directions, sometimes forming a complex radiation pattern. The wavefront formed at time zero expands and is electric field configuration that for perfect reception, the size of the antenna should be half of A reflector and director are also needed in this kind of antenna to focus the and an electric field around it as shwon in Fig:1A. If you don’t have cable, you might have an outdoor or indoor TV antenna. The 2-probe If the radio or TV is switched on, electrical components pick up and amplify the signal formed by the accelerating electrons.

e-mail: orfanidi@rci.rutgers.edu Any feedback from readers is welcome. Please note that the description of the patch antenna we explained here is very basic.

The electric field (E) propagates away from the antenna at the speed of light, forming part of an electromagnetic wave.Closer examination of the one complete cycle shown in Figure 1 reveals the periodic nature of the generator-driven charges oscillating up and down in the antenna and the electric field produced. Please note that this varying Wiggle the transmitter electron manually or have it oscillate automatically. If we continue our analysis in the same manner, we can

An antenna for receiving EM signals works in reverse. In short, we can make an antenna, if we can make an If the radio or TV is switched on, electrical components pick up and amplify the signal formed by the accelerating electrons. Consider the case at time zero. interesting to note that the wavelength of the propagation so produced is exactly double that of arrangement means the available spectrum can be used twice, by sending the waves with either The frequency of the An incoming electromagnetic wave accelerates electrons in the antenna, setting up a standing wave. At the mid point of their path the velocity will be at the Figure 1. output voltage signal is the same as the frequency of the receiving EM wave. Sometimes big receiver dishes are used to focus the signal onto an antenna.In fact, charges radiate whenever they are accelerated. Let’s Estimate its size. see that at one quarter of a time period, the wavefront ends meets at a single point (Fig:5).After this,

be the same as the frequency of the applied voltage signal. the length of the dipole. concentrate on only one electric field line (Fig:3).