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Answered Same Day Aug 21, 2020


Vignesh answered on Aug 24 2020
141 Votes
1. Antennas and their types
An antenna is defined as an electromagnetic radiator, which is capable of creating an electromagnetic field, which propagates from transmitting to the receiver antenna. There are various kinds of the antenna, which are
oadly classified as directional, omni-directional and semi-directional.
· Semi-directional antenna propagates in constricted fashions, at specific angles.
· The omni-directional antenna can propagate in all the directions.
· A directional antenna has a na
ow “beam” which propagates highly directional signals; most common types of directional antenna are yagi, horn and parabolic antennas.
Most common directional antennas
Yagi-Uda Antenna
Yagi-Uda antenna makes use of various elements to form directional a
ays. The element called dipole acts as a driven element helps in propagating RF energies. The re-radiation of RF energy is done by the elements called reflectors and directors, which keeps RF energies in and out of phase. The bandwidths of the yagi antenna range from 30 degrees to 80 degrees. The frequency range of this antenna is 30 MHz to 3 GHz. It is the most common kind of antenna for TV reception over many years.
· It is lightweight and compact.
· It uses a folded dipole and thus provides a wider bandwidth.
· It is cost-effective and simpler in design.
· It provides a reasonably good unidirectional radiational pattern.
· It provides a reasonable gain and directivity, better than dipole antennas.
· Using standard fixings, this antenna can easily be mounted on the vertical poles.
· It is frequency-sensitive.
· It has an obstructive design.
· The gain offered by this antenna is not too high; it provides only a moderate gain of 7dB. Antenna length should be increased to get better gain.
Horn Antenna
Horn antenna is another directional antenna, which is an example for an aperture antenna. In horn antenna, the electromagnetic fields would pass through the antenna aperture. If the frequency is above 1GHZ then, horn antennas are popular as they give very good gain, wide bandwidth and low VSWR. Various horn configurations include conical, pyramidal and sectoral horns. They are mostly used for microwave and astronomical applications.
· Formation of minor lobes
· Best impedance matching
· Na
ower bandwidth
· Best directivity
· Avoidance of standing waves
· Flare angle design decides directivity
· The length and flare angle should never be too small
Most common type of Omni-directional antenna
Half-wave dipole antenna
The dipole antennas are omnidirectional in nature and are available in quarter or half wave sizes. The half wave dipole antenna is generally termed as ‘doublet’. The operating range of these antennas is 3KHz to 300 Gigahertz. This type of antenna is commonly used in radio receivers.
· Non-sensitive input impedance.
· Perfect matching with the transmission impedance
· Length of antenna matches perfectly with directivity and size.
· Reasonable length
· Efficiency is less due to presence of single element.
· Works better only with combinational antennas.
· Most-common type of semi-directional antenna
Most common type of Semi-directional antenna
Micro-strip Antenna
These are semi-directional antennas, which are for low-profile applications for frequencies above 100 MHz. This is also called as patch antenna as a metal patch is mounted at ground levels using dielectric materials. The most common applications of this kind of antenna are in space crafts, aircraft and low-profile antennas.
· Easier installation
· Light-weighted
· Cost is low
· Bandwidth has na
ow frequencies
· Inefficient radiation pattern
An antenna which would be dominant in medium and long-range wireless communications in future:
Broadband printed dipole antenna or PDA has improved features for radiation, which is most suitable for medium and long wireless, 5G applications. For feeding the dipole,
oadband-based balun is used; balun consists of one elliptical slot and a microstrip line. The triangular dipole has better radiation characteristics, which improve antenna gain. The bandwidth covered is about 26.3 GHz to 40 GHz, which includes dual 5G bands. The most common promises of this antenna are flat gain, end-fire pattern and better radiation efficiency by the available frequency bands.
2. Most recent advanced research technologies- three most important wireless networking protocols and their security concerns
RPL is Routing Protocol (IPV6) used for LLN (Low-Power &Lossy Networks) according to RFC6550. RPL is enabled only on the main interface.
RPL does not work while multiple links use the similar link-local address.
Probing parameters cannot be configured in root templates in this type of implementation. These probing parameters are needed even in root templates.
The RPL features in RFC6550, which are never supported:
· Secured RPL Control Message
· Unicast DIS
· Recepting of DAO-ACK
· Unicast DIO
· Virtual DODAG roots
· Non-storing modes
· Multicast DAO
· Metric and constraint
· DIO Destination prefixes
· Non-storing modes for DAO route
· Local confidence
· Interface level links for latency calculation
· Values of instances like OCP, DODAG ID and ID options cannot be changed
· Cannot use to enable commands
Low power and Lossy Network or (LLNs) is a network class, which both routers and interconnection set constrained: The LLN routers normally operate using...

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