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  The antenna arrays as seen above, are used for the improvement of gain and directivity. A  parasitic element  is an element, which depends on other’s feed. It does not have its own feed. Hence, in this type of arrays we employ such elements, which help in increasing the radiation indirectly. These parasitic elements are not directly connected to the feed. The above image shows an example of a parasitic array. The mesh structure seen in the picture, is nothing but a set of reflectors. These reflectors are not electrically connected. They increase the signal strength by increasing the directivity of the beam. Construction & Working of Parasitic Array Let us look at the important parts of a Parasitic array and how they work. The main parts are − Driven element Parasitic elements Reflector Director Boom Driven element The antennas radiate individually and while in array, the radiation of all the elements sum up to form the radiation beam. All the elements of the array need not be con

  The physical arrangement of   end-fire array   is same as that of the broad side array. The magnitude of currents in each element is same, but there is a phase difference between these currents. This induction of energy differs in each element, which can be understood by the following diagram. The above figure shows the end-fire array in top and side views respectively. There is no radiation in the right angles to the plane of the array because of cancellation. The first and third elements are fed out of phase and therefore cancel each other’s radiation. Similarly, second and fourth are fed out of phase, to get cancelled. The usual dipole spacing will be λ/4 or 3λ/4. This arrangement not only helps to avoid the radiation perpendicular to the antenna plane, but also helps the radiated energy get diverted to the direction of radiation of the whole array. Hence, the minor lobes are avoided and the directivity is increased. The beam becomes narrower with the increased elements. Radiation

  The antenna array in its simplest form, having a number of elements of equal size, equally spaced along a straight line or axis, forming collinear points, with all dipoles in the same phase, from the same source together form the   broad side array . Frequency range The frequency range, in which the collinear array antennas operate is around  30 MHz to 3GHz  which belong to the  VHF  and  UHF  bands. Construction & Working of Broad-side Array According to the standard definition, “An arrangement in which the principal direction of radiation is perpendicular to the array axis and also to the plane containing the array element” is termed as the  broad side array . Hence, the radiation pattern of the antenna is perpendicular to the axis on which the array exists. The following diagram shows the broad side array, in front view and side view, respectively. The broad side array is strongly directional at right angles to the plane of the array. However, the radiation in the plane will b

  A   Collinear array   consists of two or more half-wave dipoles, which are placed end to end. These antennas are placed on a common line or axis, being parallel or collinear. The maximum radiation in these arrays is broad side and perpendicular to the line of array. These arrays are also called as  broad cast  or  Omni-directional arrays . Frequency range The frequency range in which the collinear array antennas operate is around  30 MHz to 3GHz  which belong to the  VHF  and  UHF  bands. Construction of Array These collinear arrays are  uni-directional antennas  having high gain. The main purpose of this array is to increase the power radiated and to provide high directional beam, by avoiding power loss in other directions. The above images show the pictures of collinear arrays. In figure 1, it is seen that collinear array is formed using folded dipoles, while in figure 2, the collinear array is formed by normal dipoles. Both types are half-wave dipoles used commonly. Radiation Patt

  An antenna, when individually can radiate an amount of energy, in a particular direction, resulting in better transmission, how it would be if few more elements are added it, to produce more efficient output. It is exactly this idea, which led to the invention of   Antenna arrays . An antenna array can be better understood by observing the following images. Observe how the antenna arrays are connected. An  antenna array  is a radiating system, which consists of individual radiators and elements. Each of this radiator, while functioning has its own induction field. The elements are placed so closely that each one lies in the neighbouring one’s induction field. Therefore, the radiation pattern produced by them, would be the vector sum of the individual ones. The following image shows another example of an antenna array. The spacing between the elements and the length of the elements according to the wavelength are also to be kept in mind while designing these antennas. The antennas rad

  Parabolic Reflectors   are Microwave antennas. For better understanding of these antennas, the concept of parabolic reflector has to be discussed. Frequency Range The frequency range used for the application of Parabolic reflector antennas is  above 1MHz . These antennas are widely used for radio and wireless applications. Principle of Operation The standard definition of a parabola is - Locus of a point, which moves in such a way that its distance from the fixed point (called  focus ) plus its distance from a straight line (called  directrix ) is constant. The following figure shows the geometry of parabolic reflector. The point  F  is the focus (feed is given) and  V  is the vertex. The line joining F and V is the axis of symmetry. PQ are the reflected rays where  L  represents the line directrix on which the reflected points lie (to say that they are being collinear). Hence, as per the above definition, the distance between F and L lie constant with respect to the waves being focu

  The parabolic reflector antenna which is often called the dish antenna provides an antenna solution applicable for VHF and above where high gain and directivity are needed. https://www.electronics-notes.com/articles/antennas-propagation/ Log periodic antenna includes: Parabolic / dish antenna basics       Parabolic antenna theory & equations       Parabolic antenna gain & directivity       Parabolic antenna feed systems      The parabolic reflector or dish antenna is the form of antenna which finds many uses in domestic satellite television reception, terrestrial microwave data links, general satellite communications and many more. Its size means that it is generally limited to use above 1GHz, although larger antennas may be used for frequencies down to about 100MHz. The parabolic reflector antenna or dish antenna is known for its distinctive shape, its high gain, and narrow beamwidths. It is the performance which can be achieved by using one is the reason it is so widely use