Project Report1

Antennas (Satellite Dish)An Idea....

In this paper, the kinematics model of the satellite antenna dish three-axis platform is developed, and the detailed formulation of these equations for the stable member is presented. The x, z, y Euler sequence is used to represent the kinematics models. By using the principle of Level maintenance, it has been investigated the intrinsic properties including the Euler angle variation of the platform, the angular speed and the angular acceleration of each part of the system. These results provide practical guidelines for promoting the utilization and popularization of the ship carried stabilized platform. The basic concept of all these kinematic study is to give general idea for the communication dish’s and help us in advance research going and helping in today’s growing world.

2011

Mubeen Khan & Fahad MuradN.W.F.P UET ATD.

6/16/2011

Antennas (Satellite Dish)

CONTENTS

Introduction

Types of Antenna

Satellite Dish Antenna

Geometry

Mathematical Modelling

Mechanism

Applications

References

Type Of Antenna

Antennas (Satellite Dish)

INTRODUCTION

Antennas

An antenna is defined by Webster’s Dictionary as “a usually metallic device (as a rod or wire) for

Radiating or receiving radio waves.”

The IEEE Standard Definitions of Terms for Antennas (IEEE Std 145–1983)

The antenna or aerial as “a means for radiating or receiving radio waves.” In other words the

Antenna is the transitional structure between free-space and a guiding device.

In other words the antenna is the transitional structure between free-space and a guiding device.

Transmission line may take the form of a coaxial line or a hollow pipe

(Waveguide), and it is used to transport electromagnetic energy from the transmitting

Source to the antenna, or from the antenna to the receiver. In the former case, we have

A transmitting antenna and in the latter a receiving antenna.

Type Of Antenna

Antennas (Satellite Dish)

Types OF Antennas Horn antenna (redirect from Types of horn antenna)

A horn antenna or microwave horn is an antenna that consists of a flaring metal.

Micro strip antenna

In telecommunication, there are several types of microstrip antennas (also known as printed

antennas) the most common of which is the microstrip patch antenna or patch antenna

HRS antenna HRS type antennas are more or less the standard antenna used for long distance high power

shortwave Broadcasting (> 1000 km).

Radio telescope

Type Of Antenna

Antennas (Satellite Dish)

A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of

antennas are also used in tracking and collecting data from satellites and space probes. In their astronomical role they

differ from optical telescopes in that they operate in the radio frequency portion of the electromagnetic spectrum where

they can detect and collect data on radio sources. Radio telescopes are typically large parabolic ("dish") antennas

used singly or in an array.

Sector antenna

A sector antenna is a type of directional microwave antenna with a sector-shaped radiation pattern. The largest

use of these antennas is as antennas for cell phone base-station sites. They are also used for other types of mobile

communications, for example in Wi-Fi networks. They are used for limited-range distances of around 4 to 5 km.

Plasma antenna

A plasma antenna is a type of radio antenna currently in development in which plasma is used

instead of the metal elements of a traditional antenna. A plasma antenna can be used for both transmission

and reception. Although plasma antennas have only become practical in recent years, the idea is not new; a

patent for an antenna using the concept was granted to J Hettinger in 1919.

Indoor antenna

An Indoor antenna is a type of radio or TV antenna placed indoors, as opposed to being mounted on the roof.

Ground dipole (redirect from Ground antenna )

A Ground dipole, or Ground antenna, is a special type of antenna which consists of two electrodes positioned

in the ground.

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Antennas (Satellite Dish)

Ground dipole antennas are usually used for transmitting and receiving on the ELF and VLF bands. The antenna consists of two

electrodes, planted in the ground at some distance from each other. Radio signal currents are sent along wires to the

electrodes. The current flows in a loop, around the above-ground wires and through the Earth (where conductive), forming a

large conducting loop, which radiates electromagnetic waves.

Antenna array (electromagnetic)

An antenna array is a group of isotropic radiators such that the currents running through them are

of different amplitudes and phases. These are radiators of electromagnetic frequency and energy. Antenna

arrays are the solution to the problem defined as the limitations of operating a single antenna.

Parabolic antenna ( dish Antenna)

A parabolic antenna is an antenna that uses a parabolic reflector, a surface with the cross-sectional

shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly

called a dish antenna or parabolic dish. The main advantage of a parabolic antenna is that it is highly

directive; it functions analogously to a searchlight or flashlight reflector to direct the radio waves in a narrow

beam, or receive radio waves from one particular direction only. Parabolic antennas have some of the highest

gains that are they can produce the narrowest beam width angles, of any antenna type.

Parabolic Antenna / dish Antenna

A parabolic antenna is an antenna that uses a parabolic reflector, a surface with the cross-sectional shape of a

parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or

parabolic dish. The main advantage of a parabolic antenna is that it is highly directive; it functions analogously to a searchlight

or flashlight reflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only.

Parabolic antennas have some of the highest gains that are they can produce the narrowest beam width angles, of any antenna

type. In order to achieve narrow beam widths, the parabolic reflector must be much larger than the wavelength of the radio

waves used, so parabolic antennas are used in the high frequency part of the radio spectrum, at UHF and microwave (SHF)

frequencies, at which wavelengths are small enough that conveniently sized dishes can be used.

Parabolic antennas are used as high-gain antennas for point-to-point communication, in applications such as

microwave relay links that carry telephone and television signals, wireless WAN/LAN links for data communications, satellite and

spacecraft communication antennas, and radio telescopes. Their other large use is for ground based and airborne radar

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Antennas (Satellite Dish)

antennas. With the advent of TVRO and DBS satellite television dishes, parabolic antennas have become a ubiquitous feature of

the modern landscape.

DESIGN:

The operating principle of a parabolic antenna is that a point source of radio waves at the focal point in front of a

parabolic reflector of conductive material will be reflected into a collimated plane wave beam along the axis of the reflector.

Conversely, an incoming plane wave parallel to the axis will be focused to a point at the focal point.

A typical parabolic antenna consists of a parabolic reflector with a small feed antenna at its focus, pointed back toward the

reflector. The reflector is a metallic surface formed into a paraboloid of revolution and usually truncated in a circular rim that

forms the diameter of the antenna. In a transmitting antenna, radio frequency current from a transmitter is supplied through a

transmission line cable to the feed antenna, which converts it into radio waves. The radio waves are emitted back toward the

dish by the feed antenna and reflect off the dish into a parallel beam. In a receiving antenna the incoming radio waves bounce

off the dish and are focused to a point at the feed antenna, which converts them to electric currents which travel through a

transmission line to the receiver.

The reflector can be of sheet metal, metal screen, or wire grill construction, and it can be either a circular "dish" or various other

shapes to create different beam shapes. A mesh screen reflects radio waves as well as a solid metal surface as long as the holes

are smaller than 1/10 of a wavelength, so screen reflectors are often used to reduce weight and wind loads on the dish. To

achieve the maximum gain, it is necessary that the shape of the dish be accurate within a small fraction of a wavelength, to

ensure the waves from different parts of the antenna arrive at the focus in phase. Large dishes often require a truss structure

behind them to provide the required stiffness.

(Wire grid-type parabolic antenna used for WLAN data link at 2.4 GHz. It transmits horizontally polarized radio waves).

A reflector made of a grill of parallel wires or bars oriented in one direction acts as a polarizing filter as well as a reflector. It only

reflects linearly polarized radio waves, with the electric field parallel to the grill elements. This type is often used in radar

antennas. Combined with a linearly polarized feed horn, it helps filter out noise in the receiver and reduces false returns.

Type Of Antenna

Antennas (Satellite Dish)

The feed antenna at the reflector's focus is typically a low-gain type such as a half-wave dipole or more often a small horn

antenna called a feed horn. In more complex designs, such as the Cassegrain and Gregorian, a secondary reflector is used to

direct the energy into the parabolic reflector from a feed antenna located away from the primary focal point. The feed antenna

is connected to the associated radio-frequency (RF) transmitting or receiving equipment by means of a coaxial cable

transmission line or waveguide.

Feed pattern

Radiation from the feed that falls outside the edge of the dish is called "spillover" and is wasted, reducing the gain and

increasing the back lobes, possibly causing interference or (in receiving antennas) increasing susceptibility to ground noise.

However, maximum gain is only achieved when the dish is uniformly "illuminated" with a constant field strength to its edges. So

the ideal radiation pattern of a feed antenna would be a constant field strength throughout the solid angle of the dish, dropping

abruptly to zero at the edges. However, practical feed antennas have radiation patterns that drop off gradually at the edges, so

the feed antenna is a compromise between acceptably low spillover and adequate illumination. For most front feed horns,

optimum illumination is achieved when the power radiated by the feed horn is 10 dB less at the dish edge than its maximum

value at the center of the dish.

History

The idea of using parabolic reflectors for radio antennas was taken from optics, where the power of a parabolic mirror

to focus light into a beam has been known since classical antiquity. The designs of some specific types of parabolic antenna, such

as the Cassegrain and Gregorian, come from similarly named analogous types of reflecting telescope, which were invented by

astronomers during the 15th century.

German physicist Heinrich Hertz constructed the world's first parabolic reflector antenna in 1888. The antenna was a cylindrical

parabolic reflector made of zinc sheet metal supported by a wooden frame, and had a spark-gap excited dipole along the focal

line. Its aperture was 1.2 meters wide, with a focal length of 0.12 meters, and was used at an operating frequency of about 450

MHz. With two such antennas, one used for transmitting and the other for receiving, Hertz demonstrated the existence radio

waves which had been predicted by James Clerk Maxwell some 22 years earlier.

The first parabolic antenna used for satellite communications was constructed in 1962 at Goon hilly in Cornwall, England, UK to

communicate with the Telstar satellite.

GAIN:

The directive qualities of an antenna are measured by a dimensionless parameter called its gain, which is the

ratio of the power received by the antenna from a source along its beam axis to the power received by a hypothetical

isotropic antenna. The gain of a parabolic antenna is:[5]

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Antennas (Satellite Dish)

where:

A is the area of the antenna aperture, that is, the mouth of the parabolic reflector

d is the diameter of the parabolic reflector

λ is the wavelength of the radio waves.

eA is a dimensionless parameter called the aperture efficiency. The aperture efficiency of typical parabolic antennas is

0.55 to 0.70.

Geometry

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Antennas (Satellite Dish)

An antenna radiation pattern or antenna pattern is defined as “a mathematical function Or a graphical

representation of the radiation properties of the antenna as a function Of space coordinates. In most cases, the

radiationpatternis determined in the far field Region and is represented as a function of the directional coordinates.

Radiation Properties include power flux density, radiation intensity, field strength, directivity, Phase or polarization.”

The radiation property of most concern is the two- or three-dimensional spatial distribution of radiated energy as a

function of the observer’s Position along a path or surface of constant radius.

For an antenna, the

A. field pattern (in linear scale) typically represents a plot of the magnitude of theElectric or magnetic field as a function of the angular space.B. power pattern (in linear scale) typically represents a plot of the square of theMagnitude of the electric or magnetic field as a function of the angular space.C. power pattern (in dB) represents the magnitude of the electric or magnetic field, indecibels, as a function of the angular space.

Type Of Antenna

Antennas (Satellite Dish)

To demonstrate this, the two-dimensional normalized field pattern (plotted in linear scale), power pattern (plotted in linear

scale), and power pattern (plotted on a logarithmic dB scale) of a 10-element linear antenna array of isotropic sources, with a

Spacing of d = 0.25λ between the elements, are shown in Figure 2.2. In this and subsequent patterns, the plus (+) and minus (−)

signs in the lobes indicate the relative polarization of the amplitude between the various lobes, which changes (alternates).

As the nulls are crossed. To find the points where the pattern achieves its half-power (−3 dB points), relative to the maximum

value of the pattern, you set the value of the

A. Field pattern at 0.707 value of its maximum.

B. Power pattern (in a linear scale) at its 0.5 value of its maximum,

C. power pattern (in dB) at −3 dBvalue of its maximum

Mathematical ModellingBy the Th´evenin and Norton equivalent circuits of, that an antenna can be represented by equivalent

impedanceZA [ZA = (Rr + RL) + jXA].

Type Of Antenna

Antennas (Satellite Dish)

The equivalent impedance is attached across two terminals. The impedance of an antenna depends on many factors

including its frequency of operation, its geometry, its method of excitation, and its proximity to the surrounding objects.

Because of their complex geometries, only a limited number of practical antennas have been investigated analytically. For many

others, the input impedance has been determined experimentally.

Electrostatic Charge Distribution

In electrostatics, the problem of finding the potential that is due to a given charge distributionis often

considered. In physical situations, however, it is seldom possible to specify a charge distribution. Whereas we may connect a

conducting body to a voltage source, and thus specify the potential throughout the body, the distribution of charge is obvious

only for a few rotationally symmetric geometries. In this section we will consider an integral equation approach to solve for

the electric charge distribution once the electric potential is specified.

We know that a linear electric charge distribution ρ(r) creates an electric potential, V (r),

RECIPROCITY AND REACTION THEOREMS

We are all well familiar with the reciprocity theorem, as applied to circuits, which states that “in any network

composed of linear, bilateral, lumped elements, if one places a constant current (voltage) generator between two

nodes (in any branch).

Type Of Antenna

Antennas (Satellite Dish)

Mechanism

The parabolic shape of a dish reflects the signal to the dish’s focal point. Mounted on brackets at the dish's

focal point is a device called a feed horn? This feed horn is essentially the front-end of a waveguide that gathers the

signals at or near the focal point and 'conducts' those to a low-noise block down converter or LNB. The LNB converts

the signals from electromagnetic or radio waves to electrical signals and shifts the signals from the down linked C-

band and/or Ku-band to the L-band range. Direct broadcast satellite dishes use an LNBF, which integrates the feed

horn with the LNB. (A new form of omnidirectional satellite antenna, which does not use a directed parabolic dish and

can be used on a mobile platform such as a vehicle.

The theoretical gain (directive gain) of a dish increases as the frequency increases. The actual gain depends on many

factors including surface finish, accuracy of shape, feed horn matching. A typical value for a consumer type 60 cm satellite dish

at 11.75 GHz is 37.50 dB.

With lower frequencies, C-band for example, dish designers have a wider choice of materials. The large size of dish required for

lower frequencies led to the dishes being constructed from metal mesh on a metal framework. At higher frequencies, mesh type

designs are rarer though some designs have used a solid dish with perforations.

A common misconception is that the LNBF (low-noise block/feed horn), the device at the front of the dish, receives the signal

directly from the atmosphere. For instance, one BBC News downlink shows a "red signal" being received by the LNBF directly

instead of being beamed to the dish, which because of its parabolic shape will collect the signal into a smaller area and deliver it

to the LNBF.

Modern dishes intended for home television use are generally 43 cm (18 in) to 80 cm (31 in) in diameter, and are fixed

in one position, for Ku-band reception from one orbital position. Prior to the existence of direct broadcast satellite

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Antennas (Satellite Dish)

services, home users would generally have a motorized C-band dish of up to 3 meters in diameter for reception of

channels from different satellites. Overly small dishes can still cause problems, however, including rain fade and

interference from adjacent satellites.

Systems design

In a single receiver residential installation there is a single cable from receiver to LNB and the receiver

uses different power supply voltages (14/18V) to select polarization and pilot tones (22 kHz) to instruct the LNB to select one of

the two frequency bands. In larger installations each band and polarization is given its own cable, so there are 4 cables from the

LNB to a switching matrix, which allows the connection of multiple receivers in a star topology using the same signaling method

as in a single receiver installation.

Types

Motor-driven dish

Multi-satellite

VSAT

Automatic Tracking Satellite Dish

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Antennas (Satellite Dish)

Applications

Communications satellite

A communications satellite (sometimes abbreviated to COMSAT) is an artificial satellite stationed in space for

the purpose of telecommunications. Modern communications satellites use a variety of orbits including geostationary

orbits, Molniya orbits, other elliptical orbits and low (polar and non-polar) Earth orbits.

Linear canonical transformation

In Hamiltonian mechanics, the linear canonical transformation (LCT) is a family of integral transforms that generalizes

many classical transforms. It has 4 parameters and 1 constraint, so it is a 3-dimensional family, and can be visualized as

the action of the special linear group SL2(R) on the time–frequency plane (domain).

The LCT generalizes the Fourier, fractional Fourier, Laplace, Gauss–Weierstrass, Bargmann and the Fresnel transforms

as particular cases. The name "linear canonical transformation" is from canonical transformation, a map that preserves

the symplectic structure, as SL2(R) can also be interpreted as the symplectic group Sp2, and thus LCTs are the linear

maps of the time–frequency domain which preserve the symplectic form.

Satellite t elevision

Digital video recorder (section Applications )

Antenna (radio)

o Wireless LAN, mobile telephony, radar, and satellite communications.

Satellite Internet access (section Geostationary unsuitable for low-latency applications )

o Satellite Internet access is Internet access provided through satellite parabolic reflector (redirect

from Parabolic dish)

DVB-S

o DVB-S is an abbreviation for Digital Video Broadcasting — Satellite

XM Satellite Radio (section iPhone, iPod Touch, BlackBerry and Android applications)

XSatellite radio (section Business applications)

Polar mount

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Sirius Satellite Radio

Cantenna

Parabolic microphone

ASTRA2Connect (Industrial Applications).

References En.Wikipedia.org

Google.com

en.allexperts.com/q/Geometry-2060/specific-angle.htm

The ARRL Antenna Book

Constantine A. Balanis, Antenna theory (Analysis and Design),3rd edition, Wiley-Interscience pub.

PARABOLIC DISH ANTENNAS, Paul Wade n1Bwt,(c) 1994,1998

EDS-soft. mft

Type Of Antenna