Wireless Network Assignment | Antennas

Added on - 23 Feb 2020

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Question 1Antennas are one of the most vital necessity in systems meant for communications. An antenna is agadget that is used to transmute a radio frequency signal, transmitting via conductor throughelectromagnetic wave is space which is free. Reciprocity is a property demonstrated by antennaindicating that an antenna always maintains its similar features regardless whether it is receiving nortransmitting. The following are some of the major types of antenna that exists[CITATION Eri15 \l7177 ].Yagi antennaThese are antennas which were used by TV inreceiving signals and since they were designedto transmit one frequency at a time, hence notsuitable for transmitting wide rangefrequencies. This type of antenna is made up ofa single element that is driven, a singlereflector and a single or many directors. Thistubes are made of aluminium.The three components are always organized inthat the director precedes the radiator andwhich in turn precedes the reflector. How thethree components relate determine the powerthat will go in to the Yagi’s direction, henceidentifying gain of Yagi antenna.Horn antennasThistype of antenna derives its name from its feature flared in appearing. The portion that is flared itcan be of different shapes may it be square, rectangle, cylindrical or even in cone shape[CITATIONAni17 \l 7177 ].It is uniqueness is in that the direction of thoroughgoing radiations matches with thehorn axis.
They are commonly used as the basic elements of a dish antenna. In dependence of their flaring naturethey can be three different horn types whose gains can be summarized as follows. The calculation forgetting the gain for a pyramid horn is shown here below.Gain = [4 pi k A] λ2Where k is 0.5 - 0.6 depending on the amplitude of electromagnetic fields displacement across theaperture.λ= wavelength in metersA= aperture in m2The bandwidth of the horn of the pyramidal horn is calculated as shown below:B= 80/ [w/λ]B= beam width in0W= horn antenna widthΛ = wavelengthCellular antennaThey are many types of antenna but their specific configurations can make them more efficient andthis will only be clear only after the gain has been improved. These are antennas that we are allfamiliar with as they are everywhere globally. They have brought connectivity in areas where it wasnever anticipated it will be depending on the antenna stations set. In these stations there exists twobasic antenna types namely:(a)Omnidirectional antennasAn antenna that exhibit a radiation pattern thatis circular operating in all directions virtually.The figure above shows antennas which arevertical and polarized. Rural sites applied is900horizontal bandwidth models.(b)Directional/Sector antennas
Antenna that operates in directions that arespecific and most covering an arc of 1200oreven less depending on the capability of therequirementCellular antenna is very different from other antenna types of communication in that it can be reused.By “Reuse” we mean the cell can be reused in that it can be increased network capacity.In my opinion cellular antenna features such as radiation pattern, antenna gain, front-to-back ratiomake it more suitable to deal with modern way of communications[CITATION Jav14 \l 7177 ].Thecellular base stations play a major role in making it easy to make this antenna signals reach to differentranges with a constant frequency. The principal of reuse in it make it a dominant player in future whenit comes medium and long-distance wireless links.Question 2FDMAis the Frequency Division Multiple Access where there exists band of frequencies that isdivided in to multi radio frequencies channels, where each carrier is allocated to particular differentusers. In an example to elaborate more on FDMA:In GSM the band frequency of 25MHZ entirely is divided in to 124 radio frequencies channels with abandwidth of 200KHz in each. When it comes to application in satellites the transponder band offrequency 500MHz is divided in to 24 carriers with a bandwidth of 40MHz each where 36MHz is foruseful and 4MHz for guard band[CITATION Lil16 \l 7177 ]. The two main types of Frequency DivisionMultiple Access applied in satellite networks are the Single Channel per Carrier (SCPC) and MultipleChannel per Carrier (MSPC). The MCPC usesboth TDM and FDM as the multiplexing schemes.The two most known types of FDMA in general are the Fixed Assignment Multiple Access(FAMA)where there is pre-allocation of frequencies to users and the Demand Assignment MultipleAccess (DAMA) where the allocation of frequencies is done based on the request.Code Division Multiple Access(CDMA) is type of multiplexing scheme where th bandwidth is sharedby assigning codes which are unique among users who are different unlike in FDMA. The followingexplanation shows how the bandwidth is shared among different various channels and each with aunique code in CDMA,
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