Line of sight propagation ppt

Documentation Help Center. RF propagation describes the behavior of electromagnetic radiation from a point of transmission as it travels through the surrounding environment. The analysis of RF propagation is essential in understanding how electromagnetic waves incur losses from a transmitter to a receiver in different scenarios.

You can use propagation models to calculate the coverage, SINR, signal strength, path loss, and link loss between a transmitter and a receiver in basic, urban, terrain, and multipath environments. Troubleshooting Site Viewer. When you start Site Viewer up on showing a txsite or rxsite object, a check is made to make sure that you have an internet connection to retrieve the default basemap and terrain data.

Propagation Models. When to use the different propagation models based on frequency, type, and limitations.

Antenna Theory - Types of Propagation

Access Basemaps and Terrain in Site Viewer. Plan a radar network using propagation modelling over terrain. DTED level-1 terrain data is imported for a region that contains five candidate monostatic radar sites. The best three sites are selected for detection of a target that is flying at meters above ground level. The scenario is updated to model a target that is flying at meters above ground level. Radar coverage maps are shown for both scenarios.

Compute and visualize outdoor wireless coverage between a transmitter and receiver. This includes:. Plan a fixed wireless access FWA link over terrain using 5G technologies. FWA is a use case for 5G to enable broadband service to homes or enterprises where wireline services are either unavailable or underperforming. At the high frequencies required for 5G, terrain and path loss impairments like foliage and weather play an important role in determining link success.

Calculate an antenna's field strength on flat earth and display it on a map. Calculate and visualize signal strength between a transmitter and multiple receivers. The visualizations include an area coverage map and colored communication links.

Propagation Losses

The example also shows selection of a directional antenna in order to achieve a communication link to a specific location. Visualize the changing pattern and coverage map of an antenna array as it scans a sweep of angles.

The array is designed to be directional and radiate in the xy-plane to generate a maximum coverage region in the geographic azimuth. Transmitter and receiver sites are created and shown on a map, and the pattern and coverage map are displayed as the antenna array is steered. Construct a 5G urban macro-cell test environment and visualize the signal-to-interference-plus-noise ratio SINR on a map.

EVAL] [1] for evaluating 5G radio technologies. This report defines several test environments and usage scenarios in Section 8. The test environment in this example is based on the urban environment with high user density and traffic loads focusing on pedestrian and vehicular users Dense Urban-eMBB. Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select:.

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Submit Search. Home Explore. Successfully reported this slideshow. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime. Chapter 5. Upcoming SlideShare. Like this presentation? Why not share! Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Published in: Engineering. Full Name Comment goes here. Are you sure you want to Yes No.Antenna and Wave propagation plays a vital role in wireless communication networks.

An idealized isotropic antenna radiates equally in all directions. Ground wave propagation follows the contour of the earth, while sky wave propagation uses reflection by both earth and ionosphere.

Line of sight propagation requires the transmitting and receiving antennas to be within the line of sight of each other. Depending upon the frequency of the underlying signal, the particular mode of propagation is followed. Examples of ground wave and sky wave communication are AM radio and international broadcasts such as BBC.

Above 30 MHz, neither ground wave nor sky wave propagation operates and the communication is through line of sight. In this section, we will discuss the various limitations that affect electromagnetic wave transmissions.

line of sight propagation ppt

Let us start with attenuation. The strength of signal falls with distance over transmission medium. The extent of attenuation is a function of distance, transmission medium, as well as the frequency of the underlying transmission.

Since signals at different frequencies attenuate to different extents, a signal comprising of components over a range of frequencies gets distorted, i.

A standard method of resolving this problem and recovering the original shape is to amplify higher frequencies and thus equalize attenuation over a band of frequencies. Dispersion is the phenomenon of spreading of a burst of electromagnetic energy during propagation. Bursts of data sent in rapid succession tend to merge due to dispersion. The most pervasive form of noise is thermal noise, which is often modeled using an additive Gaussian model.

Thermal noise is due to thermal agitation of electrons and is uniformly distributed across the frequency spectrum. Inter modulation noise caused by signals produced at frequencies that are sums or differences of carrier frequencies. Impulse noise irregular pulses of high energy caused by external electromagnetic disturbances. While an impulse noise may not have a significant impact on analog data, it has a noticeable effect on digital data, causing burst errors.

The above figure clearly illustrates how the noise signal overlaps the original signal and tries to change its characteristics. The most common causes of fading in the wireless environment are multipath propagation and mobility of objects as well as the communicating devices. In wireless media, signals propagate using three principles, which are reflection, scattering, and diffraction. Reflection occurs when the signal encounters a large solid surface, whose size is much larger than the wavelength of the signal, e.

Diffraction occurs when the signal encounters an edge or a corner, whose size is larger than the wavelength of the signal, e. Scattering occurs when the signal encounters small objects of size smaller than the wavelength of the signal.

line of sight propagation ppt

One consequence of multipath propagation is that multiple copies of a signal propagation along multiple different paths, arrive at any point at different times. So the signal received at a point is not only affected by the inherent noise, distortion, attenuationand dispersion in the channel but also the interaction of signals propagated along multiple paths. Suppose we transmit a probing pulse from a location and measure the received signal at the recipient location as a function of time.

The signal power of the received signal spreads over time due to multipath propagation. The delay spread is determined by the density function of the resulting spread of the delay over time. Average delay spread and root mean square delay spread are the two parameters that can be calculated. This is a measure of spectral broadening caused by the rate of change of the mobile radio channel. It is caused by either relative motion between the mobile and base station or by the movement of objects in the channel.

When the velocity of the mobile is high, the Doppler spread is high, and the resulting channel variations are faster than that of the baseband signal, this is referred to as fast fading.

When channel variations are slower than the baseband signal variations, then the resulting fading is referred to as slow fading. Propagation Losses Advertisements.

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To view this presentation, you'll need to allow Flash. Click to allow Flash After you enable Flash, refresh this page and the presentation should play. View by Category Toggle navigation. Products Sold on our sister site CrystalGraphics. Title: Lecture 2: Antennas and Propagation. Tags: antennas ionospheric lecture propagation. Latest Highest Rated. Waves with wavelengths much shorter than the size of the object will be reflected Waves with wavelengths much larger than the size of the obstacle will pass virtually unaffected.

Waves with intermediate wavelengths curve around the edges of the obstacles in their propagation diffraction. Diffraction allows radio signals to propagate around the curved surface and propagate behind obstacles.

Slimane 12 Propagation in the Atmosphere The atmosphere around the earth contains a lot of gazes molecules It is most dense at the earth surface 90 of molecules below a height of 20 km. It gets thinner as we reach higher and higher attitudes. The refractive index of the air in the atmosphere changes with the Height This affects the propagation of radio waves.

The straight line propagation assumption may not be valid especially for long distances.

line of sight propagation ppt

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Get the plugin now. Toggle navigation. Help Preferences Sign up Log in. To view this presentation, you'll need to allow Flash. Click to allow Flash After you enable Flash, refresh this page and the presentation should play. View by Category Toggle navigation. Products Sold on our sister site CrystalGraphics. Question: What are reasons why wireless signals are hard to send and receive?

Tags: loss mobile path propagation radio scale. Latest Highest Rated. Question What are reasons why wireless signals are hard to send and receive? Reflection Diffraction Scattering In urban areas, there is no direct line-of-sight path between the transmitter and the receiver, and where the presence of high- rise buildings causes severe diffraction loss. Multiple reflections cause multi-path fading 7 Reflection, Diffraction, Scattering Reflections arise when the plane waves are incident upon a surface with dimensions that are very large compared to the wavelength Diffraction occurs according to Huygens's principle when there is an obstruction between the transmitter and receiver antennas, and secondary waves are generated behind the obstructing body Scattering occurs when the plane waves are incident upon an object whose dimensions are on the order of a wavelength or less, and causes the energy to be redirected in many directions.

As a result of the above three mechanisms, macro cellular radio propagation can be roughly characterized by three nearly independent phenomenon Path loss variation with distance Large Scale Propagation Slow log-normal shadowing Medium Scale Propagation Fast multipath fading. Small Scale Propagation Each of these phenomenon is caused by a different underlying physical principle and each must be accounted for when designing and evaluating the performance of a cellular system.

They have an impact on the wave propagation in a mobile communication system The most important parameter, Received power is predicted by Large Scale Propagation models based on the physics of reflection, diffraction and scattering 11 Radio Propagation Mechanisms Illustration.

This is probably the most common of the radio propagation modes at VHF and higher frequencies. Radio signals can travel through many non-metallic objects, radio can be picked up through walls.

This is still line-of-sight propagation. Examples would include propagation between a satellite and a ground antenna or reception of television signals from a local TV transmitter. The free space propagation model assumes a transmit antenna and a receive antenna to be located in an otherwise empty environment.

Neither absorbing obstacles nor reflecting surfaces are considered. In particular, the influence of the earth surface is assumed to be entirely absent.

Satellite communication systems and microwave line-of-sight radio links typically undergo free space propagation. Rx power Pr vs. L system losses antennas, transmission lines between equipment and antennas, atmosphere, etc. L 1 for zero loss d T-R separation distance m Signal fades in proportion to d2 19 Friis Free Space Equation The ideal conditions assumed for this model are almost never achieved in ordinary terrestrial communications, due to obstructions, reflections from buildings, and most importantly reflections from the ground.

The Friis free space model is only a valid predictor for Pr for values of d which are in the far-field of the Transmitting antenna 20 Free Space Propagation Model Thus in practice, power can be measured at d0 and predicted at d using the relation 21 Example 1 Find the far-field distance for an antenna with maximum dimension of 1 m and operating frequency of MHz. If 50 watts is applied to a unity gain antenna with a MHz carrier frequency, find the received power in dBm at a free space distance of m from the antenna, What is Pr 10 km?Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising.

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Shahriyar Bhutto. Wasim Ghafar. Show More.In this chapter, let us go through different interesting topics such as the properties of radio waves, the propagation of radio waves and their types. Radio waves are easy to generate and are widely used for both indoor and outdoor communications because of their ability to pass through buildings and travel long distances. Since radio transmission is Omni directional in nature, the need to physically align the transmitter and receiver does not arise.

At low frequencies, the waves can pass through obstacles easily.

line of sight propagation ppt

However, their power falls with an inverse-squared relation with respect to the distance. The higher frequency waves are more prone to absorption by rain drops and they get reflected by obstacles.

Due to the long transmission range of the radio waves, interference between transmissions is a problem that needs to be addressed. The maximum transmission ranges of these waves are of the order of a few hundred kilometers.

They are used for low bandwidth transmissions such as Amplitude Modulation AM radio broadcasting. However, a portion of the radiation, called the sky waveis radiated outward and upward to the ionosphere in the upper atmosphere.

The ionosphere contains ionized particles formed due to the Sun's radiation. These ionized particles reflect the sky waves back to the Earth. A powerful sky wave may be reflected several times between the Earth and the ionosphere.

Sky waves are used by amateur ham radio operators and for military communication. In Radio communication systemswe use wireless electromagnetic waves as the channel. The antennas of different specifications can be used for these purposes.

The sizes of these antennas depend upon the bandwidth and frequency of the signal to be transmitted. In these frequency ranges, communication signals practically propagate around the world. The channel band widths are small. Therefore, the information is transmitted through these channels has slow speed and confined to digital transmission.

Among the modes of propagation, this line-of-sight propagation is the one, which we commonly notice. In the line-of-sight communicationas the name implies, the wave travels a minimum distance of sight. Which means it travels to the distance up to which a naked eye can see. Now what happens after that? We need to employ an amplifier cum transmitter here to amplify the signal and transmit again.

The figure depicts this mode of propagation very clearly. The line-of-sight propagation will not be smooth if there occurs any obstacle in its transmission path.

Antenna Fundamentals 1 Propagation

As the signal can travel only to lesser distances in this mode, this transmission is used for infrared or microwave transmissions. Ground wave propagation of the wave follows the contour of earth. Such a wave is called as direct wave. Such a wave can be termed as reflected wave. The above figure depicts ground wave propagation. The direct wave and reflected wave together contribute the signal at the receiver station.

When the wave finally reaches the receiver, the lags are cancelled out. In addition, the signal is filtered to avoid distortion and amplified for clear output. Sky wave propagation is preferred when the wave has to travel a longer distance.


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