Antennas and Propagation Review/Recap - Lecture 17

Antennas and PropagationReview/RecapLecture 17Overview2Antenna FunctionsIsotropic AntennaRadiation PatternParabolic Reflective AntennaAntenna GainSignal Loss in Satellite CommunicationNoise TypesRefractionFadingDiffraction and ScatteringFast and Slow FadingFlat and Selective FadingDiversity Techniques Review Question: Antenna FunctionalityQ:- What two functions are performed by an antenna?3Antenna Definition An antenna is defined as usually a metallic device (as a rod or wire) for radiating or receiving radio waves. The IEEE Standard Definitions of Antenna defines 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, as shown in Figure4Why Antennas of Different ShapesIn addition to receiving or transmitting energy, an antenna in an advanced wireless system is usually required to optimize or accentuate the radiation energy in some directions and suppress it in others.Thus the antenna must also serve as a directional device in addition to a probing device.It must then take various forms to meet the particular need at hand, and it may be a piece of conducting wire, an aperture, a patch, an assembly of elements (array), a reflector, a lens, and so forth. For wireless communication systems, the antenna is one of the most critical components. A good design of the antenna can relax system requirements and improve overall system performance.The antenna serves to a communication system the same purpose that eyes and eyeglasses serve to a human5Basic Antenna FunctionsAs Antenna resides between cable/waveguide and the medium air, the main function of antenna is to match impedance of the medium with the cable/waveguide impedance. Hence antenna is impedance transforming device. The second and most important function of antenna is to radiate the energy in the desired direction and suppress in the unwanted direction. This basically is the radiation pattern of the antenna. This radiation pattern is different for different types of antennas. 67The Role of AntennasAntennas serve four primary functionsSpatial filterdirectionally-dependent sensitivityPolarization filterpolarization-dependent sensitivityImpedance transformertransition between free space and transmission linePropagation mode adapterfrom free-space fields to guided waves(e.g., transmission line, waveguide)8Spatial filterAntennas have the property of being more sensitive in one direction than in another which provides the ability to spatially filter signals from its environment.Directive antenna.Radiation pattern of directive antenna. 9Polarization filterAntennas have the property of being more sensitive to one polarization than another which provides the ability to filter signals based on its polarization.In this example, h is the antenna’s effective height whose units are expressed in meters.10Impedance transformerIntrinsic impedance of free-space, E/HCharacteristic impedance of transmission line, V/IA typical value for Z0 is 50 .Clearly there is an impedance mismatch that must be addressed by the antenna.11Propagation Mode AdapterIn free space the waves spherically expand following Huygens principle: each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves.Within the sensor, the waves are guided within a transmission line or waveguide that restricts propagation to one axis.12Propagation Mode AdapterDuring both transmission and receive operations the antenna must provide the transition between these two propagation modes.1314Antenna purposeTransformation of a guided EM wave in transmission line (waveguide) into a freely propagating EM wave in space (or vice versa) with specified directional characteristicsTransformation from time-function in one-dimensional space into time-function in three dimensional space The specific form of the radiated wave is defined by the antenna structure and the environment Space waveGuided wave15Antenna functionsTransmission linePower transport medium - must avoid power reflections, otherwise use matching devices RadiatorMust radiate efficiently – must be of a size comparable with the half-wavelength ResonatorUnavoidable - for broadband applications resonances must be attenuated Ans:- Two functions of an antenna are: For transmission of a signal, radio frequency electrical energy from the transmitter is converted into electromagnetic energy by the antenna and radiated into the surrounding environment (atmosphere, space, water); For reception of a signal, electromagnetic energy impinging on the antenna is converted into radio-frequency electrical energy and fed into the receiver.16Q:- What two functions are performed by an antenna?Review Question: Antenna Functionality17Isotropic AntennaQ:- What is an isotropic antenna?18Isotropic AntennaIsotropic antenna or isotropic radiator is a hypothetical (not physically realizable) concept, used as a useful reference to describe real antennas. Isotropic antenna radiates equally in all directions. Its radiation pattern is represented by a sphere whose center coincides with the location of the isotropic radiator.19Reference Antenna for Gain Gain is Measured Specific to a Reference Antenna isotropic antenna often used - gain over isotropicIsotropic antenna – radiates power ideally in all directionsGain measured in dBiTest antenna’s field strength relative to reference isotropic antenna at same power, distance, and angle-Isotropic antenna cannot be practically realizede.g. A lamp is similar to an isotropic antenna 20Isotropic2122An Isotropic Source: GainEvery real antenna radiates more energy in some directions than in others (i.e. has directional properties)Idealized example of directional antenna: the radiated energy is concentrated in the yellow region (cone). Directive antenna gain: the power flux density is increased by (roughly) the inverse ratio of the yellow area and the total surface of the isotropic sphereGain in the field intensity may also be considered - it is equal to the square root of the power gain. Isotropic sphere23Antenna Gain Measurement Antenna Gain = (P/Po) S=S0Actual antennaP = Power delivered to the actual antennaS = Power received(the same in both steps)Measuring equipmentStep 2: substitutionReference antennaPo = Power delivered to the reference antennaS0 = Power received (the same in both steps)Measuring equipmentStep 1: referenceIsotropic AntennaQ:- What is an isotropic antenna?Ans:- An isotropic antenna is a point in space that radiates power in all directions equally.24Isotropic sphere25Review: Radiation PatternQ:- What information is available from a radiation pattern?26Radiation PatternIn the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the directional (angular) dependence of the strength of the radio waves from the antenna or other source.Particularly in the fields of fiber optics, lasers, and integrated optics, the term radiation pattern may also be used as a synonym for the near-field pattern or Fresnel pattern. This refers to the positional dependence of the electromagnetic field in the near-field, or Fresnel region of the source. The near-field pattern is most commonly defined over a plane placed in front of the source, or over a cylindrical or spherical surface enclosing it.The far-field pattern of an antenna may be determined experimentally at an antenna range, or alternatively, the near-field pattern may be found using a near-field scanner, and the radiation pattern deduced from it by computation. The far-field radiation pattern can also be calculated from the antenna shape by computer programs such as NEC. Other software, like HFSS can also compute the near field.27Antenna Radiation PatternRadiation patternGraphical representation of radiation properties of an antennaDepicted as two-dimensional cross sectionThe radiation pattern of an antenna is a plot of the far-field radiation from the antenna. More specifically, it is a plot of the power radiated from an antenna per unit solid angle, or its radiation intensity U [watts per unit solid angle]. This is arrived at by simply multiplying the power density at a given distance by the square of the distance r, where the power density S [watts per square metre] is given by the magnitude of the time-averaged Poynting vector:U=r²S2829Radiation pattern The radiation pattern of antenna is a representation (pictorial or mathematical) of the distribution of the power out-flowing (radiated) from the antenna (in the case of transmitting antenna), or inflowing (received) to the antenna (in the case of receiving antenna) as a function of direction angles from the antennaAntenna radiation pattern (antenna pattern): is defined for large distances from the antenna, where the spatial (angular) distribution of the radiated power does not depend on the distance from the radiation sourceis independent on the power flow direction: it is the same when the antenna is used to transmit and when it is used to receive radio waves is usually different for different frequencies and different polarizations of radio wave radiated/ received 30Power Pattern Vs. Field pattern The power pattern is the measured (calculated) and plotted received power: |P(θ, ϕ)| at a constant (large) distance from the antenna The amplitude field pattern is the measured (calculated) and plotted electric (magnetic) field intensity, |E(θ, ϕ)| or |H(θ, ϕ)| at a constant (large) distance from the antenna Power or field-strength meterAntenna under testTurntableGeneratorAuxiliaryantenna Large distanceThe power pattern and the field patterns are inter-related:P(θ, ϕ) = (1/)*|E(θ, ϕ)|2 = *|H(θ, ϕ)|2P = powerE = electrical field component vectorH = magnetic field component vector = 377 ohm (free-space, plane wave impedance)31Normalized patternUsually, the pattern describes the normalized field (power) values with respect to the maximum value.Note: The power pattern and the amplitude field pattern are the same when computed and when plotted in dB.323-D patternAntenna radiation pattern is 3-dimensionalThe 3-D plot of antenna pattern assumes both angles θ and ϕ varying, which is difficult to produce and to interpret3-D pattern332-D patternTwo 2-D patternsUsually the antenna pattern is presented as a 2-D plot, with only one of the direction angles, θ or ϕ variesIt is an intersection of the 3-D one with a given plane usually it is a θ = const plane or a ϕ= const plane that contains the pattern’s maximum34Example: a short dipole on z-axis35Principal PatternsPrincipal patterns are the 2-D patterns of linearly polarized antennas, measured in 2 planesthe E-plane: a plane parallel to the E vector and containing the direction of maximum radiation, and the H-plane: a plane parallel to the H vector, orthogonal to the E-plane, and containing the direction of maximum radiation36Example37Antenna Mask (Example 1)Typical relative directivity- mask of receiving antenna (Yagi ant., TV dcm waves)38Antenna Mask (Example 2)Reference pattern for co-polar and cross-polar components for satellite transmitting antennas in Regions 1 and 3 (Broadcasting ~12 GHz) 0dB-3dBPhiReview: Radiation PatternQ:- What information is available from a radiation pattern?Radiation Patterns in Polar and Cartesian Coordinates Showing Various Types of LobesAns:- A radiation pattern is a graphical representation of the radiation properties of an antenna as a function of space coordinates.3940Parabolic Reflective AntennaQ:- What is the advantage of a parabolic reflective antenna?41Two Main Purposes of AntennaImpedance matching: matches impedance of transmission line to the intrinsic impedance of free space to prevent wanted reflection back to source.Antenna must be designed to direct the radiation in the desired direction.So a parabolic antennais a high gain reflector antenna. It is used for television, radio and data communications. It may also be used for radar on the UHF and SHF sections of the electromagnetic spectrum. 42Reflector AntennaReflector antenna such as parabolic antenna are composed of primary radiator and a reflective mirror.43Parabolic Reflector Antenna Any electromagnetic wave incident upon the paraboloid surface will be directed to the focal point.Primary antenna is used at the focal point of the parabolic reflector antenna instead of isotropic antenna. The isotropic antenna would radiate and receive radiation from all directions resulting in spillover.Primary antenna should be designed to “illuminate” just the reflector uniformly.44Loss45CharacteristicsAperture:r= radius of the diameterLarger dish has more gain than smallerClear line of sight is important46CalculationsPhysical area:D= DiameterEffective area: = illumination efficiency Wavelength:Gain:3db beamwidth:47Half Power BeamwidthThe half power graph showing the angle between the half power point on either side of maximum48Radiation Pattern for Parabolic Antenna49Advantage of a Parabolic AntennaThe advantage of a parabolic antenna is that it can be used as primary mirror for all the frequencies in the project, provided the surface is within the tolerance limit; only the feed antenna and the receiver need to be changed when the observing frequency is changed.An advantage of such a design is the small irradiation loss, which allows for an optimum antenna gain.It is an advantage of such an arrangement that the exciter system and/or the exciter 3 are/is protectively located within the parabola or the parabolic reflector.Parabolic antenna is the most efficient type of a directional antenna - large front/back ratio, sharp radiation angle and small side lobes. It fits well for noisy locations where other antennas factually do not work.The antenna's Gain is adequate to the area of the reflector. The reflector can be central-focused(the focus is in the center of the dish) or offset (the focus is off the axis of the dish). In general, they serve for connection of end users (so-called last mile) to a wireless network. However, in areas with lower intensity of Wi-Fi networks, they can be successfully used also for back-bone links. In fact, this frequency is used for connections up to maximum 10 km50Parabolic Reflective AntennaQ:- What is the advantage of a parabolic reflective antenna?A parabolic antenna creates, in theory, a parallel beam without dispersion. In practice, there will be some beam spread. Nevertheless, it produces a highly focused, directional beam.5152Antenna GainQ:- What factors determine antenna gain?53Antenna Gain Antenna Gain (Directivity)Power output, in a particular direction, compared to that produced in any direction by a perfect omnidirectional antenna [usual reference is an isotropic antenna (dBi) but sometimes a simple ½  antenna is a more practical reference; good sales trick to use an isotropic reference when a dipole is inferred resulting in a 1.64 power gain]Antenna gain doesn’t increase power; only concentrates effective radiation patternEffective area (related to antenna aperture) Expressed in terms of effective areaRelated to physical size and shape of antenna related to the operational wavelength of the antennaChange in coverage by focusing the area of RF propagation54Passive GainFocusing isotropic energy in a specific patternCreated by the design of the antennaUses the magnify glass concept55Passive GainAntennas use passive gainTotal amount of energy emitted by antenna doesn’t increase – only the distribution of energy around the antennaAntenna is designed to focus more energy in a specific directionPassive gain is always a function of the antenna (i.e. independent of the components leading up to the antenna56Passive GainAdvantageDoes not require external powerDisadvantageAs the gain increases, its coverage becomes more focusedHighest-gain antennas can’t be used for mobile users because of their tight beam57Active GainProviding an external power sourceAmplifierHigh gain transmittersActive gain involves an amplifier58Antenna GainRelationship between antenna gain and effective areaG = antenna gainAe = effective areaf = carrier frequencyc = speed of light (≈ 3 x 108 m/s) = carrier wavelength59Antenna gainAntenna gain is increased by focusing the antennaThe antenna does not create energy, so a higher gain in one direction must mean a lower gain in another.Note: antenna gain is based on the maximum gain, not the average over a region. This maximum may only be achieved only if the antenna is carefully aimed. This antenna is narrower and results in 3dB higher gain than the dipole, hence, 3dBD or 5.14dBiThis antenna is narrower and results in 9dB higher gain than the dipole, hence, 9dBD or 11.14dBi60Antenna gainInstead of the energy going in all horizontal directions, a reflector can be placed so it only goes in one direction => another 3dB of gain, 3dBD or 5.14dBiFurther focusing on a sector results in more gain.A uniform 3 sector antenna system would give 4.77 dB more.A 10 degree “range” 15dB more.The actual gain is a bit higher since the peak is higher than the average over the “range.”Mobile phone base stations claim a gain of 18dBi with three sector antenna system. 4.77dB from 3 sectors – 13.33 dBi An 11dBi antenna has a very narrow range. 61Antenna GainThe power gain G, or simply the gain, of an antenna is the ratio of its radiation intensity to that of an isotropic antenna radiating the same total power as accepted by the real antenna. When antenna manufacturers specify simply the gain of an antenna they are usually referring to the maximum value of G.62Antenna gain and effective areasType of antennaEffective areaPower gainIsotropicג2/41Infinitesimal dipole or loop1.52/41.5Half-wave dipole1.642/41.64Horn, mouth area A0.81A10A/ 2Parabolic, face area A0.56A7A/ 2turnstile1.152/41.1563Antenna GainQ:- What factors determine antenna gain?Ans:- Effective area and wavelength6465Satellite CommunicationQ:- What is the primary cause of signal loss in satellite communications?66Basics: How do Satellites WorkTwo Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means.The two stations can use a satellite as a relay station for their communicationOne Earth Station sends a transmission to the satellite. This is called a Uplink.The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink.67Basics: Advantages of SatellitesThe advantages of satellite communication over terrestrial communication are:The coverage area of a satellite greatly exceeds that of a terrestrial system.Transmission cost of a satellite is independent of the distance from the center of the coverage area.Satellite to Satellite communication is very precise.Higher Bandwidths are available for use.68Basics: Disadvantages of SatellitesThe disadvantages of satellite communication:Launching satellites into orbit is costly.Satellite bandwidth is gradually becoming used up.There is a larger propagation delay in satellite communication than in terrestrial communication. 69Basics: Factors in Satellite CommunicationElevation Angle: The angle of the horizontal of the earth surface to the center line of the satellite transmission beam.This effects the satellites coverage area. Ideally, you want a elevation angle of 0 degrees, so the transmission beam reaches the horizon visible to the satellite in all directions.However, because of environmental factors like objects blocking the transmission, atmospheric attenuation, and the earth electrical background noise, there is a minimum elevation angle of earth stations.70Basics: Factors in satellite communication .Coverage Angle: A measure of the portion of the earth surface visible to a satellite taking the minimum elevation angle into account.R/(R+h) = sin(π/2 - β - θ)/sin(θ + π/2) = cos(β + θ)/cos(θ) R = 6370 km (earth’s radius) h = satellite orbit height β = coverage angle θ = minimum elevation angle71Basics: Factors in satellite communication.Other impairments to satellite communication:The distance between an earth station and a satellite (free space loss).Satellite Footprint: The satellite transmission’s strength is strongest in the center of the transmission, and decreases farther from the center as free space loss increases.Atmospheric Attenuation caused by air and water can impair the transmission. It is particularly bad during rain and fog. 72Atmospheric LossesDifferent types of atmospheric losses can disturb radio wave transmission in satellite systems:Atmospheric absorptionAtmospheric attenuationTraveling ionospheric disturbances73Atmospheric AbsorptionEnergy absorption by atmospheric gases, which varies with the frequency of the radio waves.Two absorption peaks are observed (for 90º elevation angle):22.3 GHz from resonance absorption in water vapour (H2O)60 GHz from resonance absorption in oxygen (O2)For other elevation angles:[AA] = [AA]90 cosec Source: Satellite Communications, Dennis Roddy, McGraw-Hill74Atmospheric AttenuationRain is the main cause of atmospheric attenuation (hail, ice and snow have little effect on attenuation because of their low water content).Total attenuation from rain can be determined by:A = L [dB]where  [dB/km] is called the specific attenuation, and can be calculated from specific attenuation coefficients in tabular form that can be found in a number of publicationswhere L [km] is the effective path length of the signal through the rain; note that this differs from the geometric path length due to fluctuations in the rain density. 75Traveling Ionospheric DisturbancesTraveling ionospheric disturbances are clouds of electrons in the ionosphere that provoke radio signal fluctuations which can only be determined on a statistical basis.The disturbances of major concern are:Scintillation;Polarisation rotation.Scintillations are variations in the amplitude, phase, polarisation, or angle of arrival of radio waves, caused by irregularities in the ionosphere which change over time. The main effect of scintillations is fading of the signal.76Satellite CommunicationQ:- What is the primary cause of signal loss in satellite communications?Ans:- Free space loss.7778ImpairmentsQ:- Name and briefly define four types of noise.79Transmission ImpairmentsSignal received may differ from signal transmitted causing:Analog - degradation of signal qualityDigital - bit errorsMost significant impairments areAttenuation and attenuation distortionDelay distortionNoise80NoiseSignal strength falls off with distance over any transmission mediumVaries with frequency81Unwanted signals inserted between transmitter and receiveris the major limiting factor in communications system performanceCategories of Noise82Thermal noisedue to thermal agitation of electronsuniformly distributed across bandwidthsreferred to as white noiseIntermodulation noiseproduced by nonlinearities in the transmitter, receiver, and/or intervening transmission mediumeffect is to produce signals at a frequency that is the sum or difference of the two original frequenciesCategories of NoiseCrosstalk:a signal from one line is picked up by anothercan occur by electrical coupling between nearby twisted pairs or when microwave antennas pick up unwanted signalsImpulse Noise:caused by external electromagnetic interferencesnoncontinuous, consisting of irregular pulses or spikesshort duration and high amplitudeminor annoyance for analog signals but a major source of error in digital data83NoiseThermal noise due to thermal agitation of electrons.Present in all electronic devices and transmission media.As a function of temperature.Uniformly distributed across the frequency spectrum, hence often referred as white noise.Cannot be eliminated – places an upper bound on the communication system performance.Can cause erroneous to the transmitted digital data bits.84Noise: Noise on Digital DataError in bits85Thermal NoiseThe noise power density (amount of thermal noise to be found in a bandwidth of 1Hz in any device or conductor) is:N0 = noise power density in watts per 1 Hz of bandwidthk = Boltzmann's constant = 1.3803  10-23 J/KT = temperature, in kelvins (absolute temperature) 0oC = 273 Kelvin86Thermal NoiseNoise is assumed to be independent of frequencyThermal noise present in a bandwidth of B Hertz (in watts):or, in decibel-watts (dBW),87Noise TerminologyIntermodulation noise – occurs if signals with different frequencies share the same mediumInterference caused by a signal produced at a frequency that is the sum or difference of original frequenciesCrosstalk – unwanted coupling between signal pathsImpulse noise – irregular pulses or noise spikesShort duration and of relatively high amplitudeCaused by external electromagnetic disturbances, or faults and flaws in the communications system8889ImpairmentsQ:- Name and briefly define four types of noise.Ans:- Thermal noise is due to thermal agitation of electrons. Intermodulation noise produces signals at a frequency that is the sum or difference of the two original frequencies or multiples of those frequencies. Crosstalk is the unwanted coupling between signal paths. Impulse noise is noncontinuous, consisting of irregular pulses or noise spikes of short duration and of relatively high amplitude.9091Refraction?Q:- What is refraction?92Law of refraction A refracted ray lies in the plane of incidence and has an angle θ2 of refraction that is related to the angle of incidence θ1 by: the symbols n1   and n2    are dimensionless constant, called the index of refraction 93Refraction94Refraction occurs when an RF signal changes speed and is bent while moving between media of different densities.Refraction95Refraction?Q:- What is refraction?Ans:- Refraction is the bending of a radio beam caused by changes in the speed of propagation at a point of change in the medium96FadingQ:- What is fading?97Fading in a Mobile EnvironmentThe term fading refers to the time variation of received signal power caused by changes in the transmission medium or paths.Atmospheric condition, such as rainfallThe relative location of various obstacles changes over time98Types of FadingFast fadingSlow fadingFlat fadingSelective fadingRayleigh fadingRician fading99Fading in the Mobile EnvironmentFading: time variation of received signal power due to changes in the transmission medium or path(s)Kinds of fading:Fast fadingSlow fadingFlat fading  independent from frequencySelective fading  frequency-dependentRayleigh fading  no dominant path Rician fading  Line Of Sight (LOS) is dominating + presence of indirect multipath signals100FadingQ:- What is fading?Ans:- The term fading refers to the time variation of received signal power caused by changes in the transmission medium or path(s).101102Q:- What is the difference between diffraction and scattering?103Diffraction104Diffraction is a change in the direction and/or intensity of a wave as it passes by the edge of an obstacle.Diffraction occurs because the RF signal slows down as it encounters the obstacle and causes the wave front to change directionsDiffraction is often caused by buildings, small hills, and other larger objects in the path of the propagating RF signal.DiffractionDiffraction - occurs at the edge of an impenetrable body that is large compared to wavelength of radio wave105Scattering106Scattering happens when an RF signal strikes an uneven surface causing the signal to be scattered. The resulting signals are less significant than the original signal.Scattering = Multiple ReflectionsScatteringScattering – occurs when incoming signal hits an object whose size in the order of the wavelength of the signal or less.Irregular objects such as walls with rough surfaces,furniture and vehicles and foliage and the like scatter rays in all the direction in the form of spherical waves.107Multipath Propagation108Diffraction and ScatteringQ:- What is the difference between diffraction and scattering?Ans:- Diffraction occurs at the edge of an impenetrable body that is large compared to the wavelength of the radio wave. The edge in effect become a source and waves radiate in different directions from the edge, allowing a beam to bend around an obstacle. If the size of an obstacle is on the order of the wavelength of the signal or less, scattering occurs. An incoming signal is scattered into several weaker outgoing signals in unpredictable directions109Summary110Antenna FunctionsIsotropic AntennaRadiation PatternParabolic Reflective AntennaAntenna GainSignal Loss in Satellite CommunicationNoise TypesRefractionFadingDiffraction and Scattering111Complimentary Session for Antennas and Propagation (Lecture 17)112Antenna Gain (Q)113WhereSol114QQ:- For each of the antenna types listed in Table above , what is the effective area and gain at a wavelength of 30 mm? Repeat for a wavelength of 3 mm. Assume that the actual area for the horn and parabolic antennas is m2 .115Antenna Gain116WhereAns117Q:- For each of the antenna types listed in Table above , what is the effective area and gain at a wavelength of 30 mm? Repeat for a wavelength of 3 mm. Assume that the actual area for the horn and parabolic antennas is m2 .118Q119Question:-Solution120Q121Question122Thermal Noise123WhereQuestion:-124The Expression Eb /N0in decibel notation,125Question:-126Q:- It is often more convenient to express distance in km rather than m and frequency in MHz rather than Hz. Rewrite Equation using these dimensions.Solution:- The equations from Text Book areSolution:-127128QQ:- Suppose a transmitter produces 50 W of power.Express the transmit power in units of dBm and dBW.If the transmitter's power is applied to a unity gain antenna with a 900-MHz carrier frequency, what is the received power in dBm at a free space distance of 100 m?Repeat (b) for a distance of 10 km.Repeat (c) but assume a receiver antenna gain of 2.129Q/A.b)Therefore, received power in dBm = 47 – 71.52 = –24.52 dBm130Q:- Suppose a transmitter produces 50 W of power.Express the transmit power in units of dBm and dBW.If the transmitter's power is applied to a unity gain antenna with a 900-MHz carrier frequency, what is the received power in dBm at a free space distance of 100 m?Repeat (b) for a distance of 10 km.Repeat (c) but assume a receiver antenna gain of 2.Q/Ac)d) 131Q:- Suppose a transmitter produces 50 W of power.Express the transmit power in units of dBm and dBW.If the transmitter's power is applied to a unity gain antenna with a 900-MHz carrier frequency, what is the received power in dBm at a free space distance of 100 m?Repeat (b) for a distance of 10 km.Repeat (c) but assume a receiver antenna gain of 2.132Free Space Loss133Free Space Loss134135136