Small Satellite Link Budget Calculation
Small Satellite Link BudgetCalculationMarcos Arias (Universidade de Vigo)Fernando Aguado (Universidade de Vigo and CINAE)marcos@com.uvigo.esSantiago de Chile. November 20161/46
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsTable of Contents1Critical points in a Satellite Link2Received powerFriis formulaAntennasPolarizationPropagation3NoiseRadio NoiseAntenna Noise4Signal to noise ratioRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterference5Conclusions2/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsCritical points in a Satellite LinkCritical points in a Satellite LinkAvailable power at the Ground StationAvailable power at the satelliteSensitivity of the ReceiverSNR at the ReceiverReception level at the Earth to avoid interferences3/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio link chain4/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis ON ITU-R P.525-2RECOMMENDATION ITU-R P.525-2Friis formula was first published in 1946: H. T. Friis, ’A noteon a simple transmission formula,’ Proc. IRE 34, 254–256(1946) 2 1λpr pt · (1 Γt 2 ) · gt · 4π·d· am · gr · (1 Γr 2 ), where Γtand Γr are the reflection coefficients of the antennas and gtand gr the gain of the antennaspr pt · (1 Γt 2 ) · gt ·Aeff λ24π gr14π·d 2·1am· Aeff · (1 Γr 2 ), whereis the effective area of recepction5/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationFree-space basic transmission lossFree-space basic transmission lossIf the distance d between the antennas is much greater thanthe wavelength λ, the free-space attenuation (free-space basic transmission loss) in decibels will be: Lbf 20 · log10 4π·dλWith a low-orbit satellite with elliptical orbit, the distancemust be calculated using the worst case, that means when thesatellite is with the lowest elevation angle and in the directionof the major axis of the ellipse6/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationMaximum distanceMaximum distanceThe maximum distance with a satellite with maximum heightH and minimum elevationangle α is:qdmax RE sin α (RE sin α)2 H 2 2 · RE · HSatellite distancedαRE HRE7/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationHUMSAT: Distance and timeOrbitaltitude um linkdistance (Km)59851245788276168311591006907Linktime (s)60433090654511987618/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis ON ITU-R P.341-5RECOMMENDATION ITU-R P.341-5The basic transmission loss of a radio link (Lb ) is the additionbetween the free-space basic transmission loss (Lbf ) and theloss relative to free space (Am ): Lb Lbf AmMain types of losses for satellite communications:absorption loss (ionospheric, atmospheric gases orprecipitation)effective reflection or scattering loss as in the ionospheric caseincluding the results of any focusing or defocusing due tocurvature of a reflecting layerpolarization coupling loss from any polarization mismatchbetween the antennas for the particular ray path consideredeffect of wave interference between the direct and reflectedrays from the ground, other obstacles or atmospheric layers9/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationAntenna Gain and BeamwidthAntenna Gain and BeamwidthThe Beamwidth of a pattern is defined as the angularseparation between two identical points on opposite side ofthe pattern maximumOne of the most widely used beamwidths is the Half-PowerBeamwidth (HPBW) that can vary with the azimuth angleAn approximate relation between the antenna gain and itsHPBW is gmax HPBWE4π·HPBWH10/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis PolarizationThe polarization in the link can be Lineal, Horizontal orVertical, or Circular, Left Hand (LHCP) or Right Hand(RHCP)Both antennas (satellite and earth station) should have thesame polarization.Theoretically, using two orthogonal polarizations, radio-linkcapacity can be the double, but a crosspolarizationinterference can appear in the reception11/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis on ITU-R P.618-12Propagation data and prediction methods required for the designof Earth-space telecommunication systemsIn the design of Earth-space links for communication systems,several effects must be considered:absorption in atmospheric gases; absorption, scattering anddepolarization by hydrometeors and emission noise fromabsorbing media and they are especially important atfrequencies above about 10 GHzloss of signal due to beam-divergence of the earth-stationantenna, due to the normal refraction in the atmospherea decrease in effective antenna gain, due to phase decorrelationacross the antenna aperture, caused by irregularities in therefractive-index structure12/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis on ITU-R P.618-12 (II)Propagation data and prediction methods required for the designof Earth-space telecommunication systemsContinue:relatively slow fading due to beam-bending caused bylarge-scale changes in refractive index; more rapid fading(scintillation) and variations in angle of arrival, due tosmall-scale variations in refractive indexpossible limitations in bandwidth due to multiple scattering ormultipath effects, especially in high-capacity digital systemsattenuation by the local environment of the ground terminalshort-term variations of the ratio of attenuations at the upand down-link frequencies, which may affect the accuracy ofadaptive fade countermeasuresfor non-geostationary satellite (non-GSO) systems, the effectof varying elevation angle to the satelliteSmall Satellite Link Budget Calculation13/46
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis on ITU-R P.618-12 (III)Ionospheric effects (see Recommendation ITU-R P.531)Effects of the non-ionized atmosphere become critical aboveabout 1 GHz and for low elevation anglesThese effects are:Faraday rotation: a linearly polarized wave propagatingthrough the ionosphere undergoes a progressive rotation of theplane of polarization;dispersion, which results in a differential time delay across thebandwidth of the transmitted signal;excess time delay;ionospheric scintillation: inhomogeneities of electron density inthe ionosphere cause refractive focusing or defocusing of radiowaves and lead to amplitude and phase fluctuations termedscintillations14/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationAttenuation by atmospheric gases. RecommendationITU-R P.676-1015/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationAttenuation by rainAttenuation by rainThe attenuation by rain is calculated using the Specificattenuation (dB/Km) and the Effective rain path (Km)Specific attenuation γR is computed with the rainfall rate Rp(mm/h) exceeded for % of an average year, typically p 0.01that provides a QoS of 99.99%.The effective path length Le is computed including the effectof the height of the terrain, elevation angle, longitude andlatitude.16/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationRainfall Rate17/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationAttenuation by rain p 6 0.01Attenuation by rain p 6 0.01The rain attenuation for different availability of 99.99%(p 0.01%) can be computed using the following graph:18/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationRain, fog and cloudsCross polarization due to the rainThe rain drop shape is elongatedThis implies that the rain can be considered as an isotropicmedia for the electromagnetic wave propagation.Crossing the wave through a rain area, a cross polarizationeffect appears due to this effect.Attenuation due to clouds and fog. Recommendation ITU-RP.840-5It is quite equivalent to the rain attenuation methodThe attenuation values are smaller19/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationEstimated ionospheric effects for elevation angles of about30oEstimated ionospheric effects for elevation angles of about 30oThe effects at 500 MHz are:Faraday rotation 1.2 rotationsPropagation delay 1µsRefraction 2.40Variation in the direction of arrival (r.m.s.) 48”Absorption (auroral and/or polar cap) 0.2dBAbsorption (mid-latitude) 0.04dBDispersion 0.0032 ps/HzScintillation up to 27.5 dB20/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationFaraday rotationFaraday rotationWhen propagating through the ionosphere, a linearly polarizedwave will suffer a gradual rotation of its plane of polarizationdue to the presence of the geomagnetic field and theanisotropy of the plasma medium21/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis nScintillationScintillations are created by fluctuations of the refractiveindex, which are caused by inhomogeneities in the mediumIt is important for signals below 3 GHz but the effects may beobserved occasionally up to 10 GHzGeographically, there are two intense zones of scintillation,one at high latitudes and the other centered within 20o of themagnetic equator. In the middle latitudes scintillation occursexceptionally, such as during geomagnetic storms. In theequatorial sector, there is a pronounced night-time maximumof activity22/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsFriis formulaAntennasPolarizationPropagationHUMSAT-D: Atmospheric losses at 437 MHzElevation51015MinimumLatm (dB)0.020.020.02MaximumLatm (dB)0.220.110.08MinimumLsci (dB)0.020.020.02MaximumLsci (dB)0.370.160.123/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseRecommendation ITU-R P.372-12Radio NoiseThe noise can be produced by:Radiation from lightning dischargesAggregated unintended radiation from electrical machinery,electrical and electronic equipments, power transmission lines,or from internal combustion engine ignition (man-made noise)Emissions from atmospheric gases and hydrometeorsThe ground or other obstructions within the antenna beamRadiation from celestial radio sources24/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseNoise modelNoise modelAdditive Gaussian White NoiseNoise power spectral density of n0 constantNoise Power n n0 · b where b is the bandwidthEffective noise temperature (Kelvin) at a reference point ofthe circuit t nk0 where k 1.379 · 10 23 W · Hz 1 · K 1So, n k · b · t25/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseInternal effective noise temperatureInternal effective noise temperatureEffective noise temperature tef of a two port circuit (forexample, an amplifier) referred at the entrance:nout (nin nef ) · g k · b · (tin tef ) · g k · b · tout tout (tin tef ) · gInternal noise factor: fn 1 temperature T0 290KtefT0where the referencetinT0tin tefT0External noise factor: fa System noise factor: f Noise Figure F 10 · log10 f26/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseEffective Noise Temperature of a transmission LineEffective Noise Temperature of a transmission LineThe effective noise temperature for a resistive attenuator(with attenuation a) at physical temperature tphy temperatureis tef tphy · (a 1)This model is applied for any attenuator includingtransmission lines for both transmission and reception chains27/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseHUMSAT-D: Ground Station Receiver ChainGain (dB)GainNoise Figure (dB)Noise Temp. (K)Total noisetemp. at inputTransm.Line 1-0.90.8130.966.866.8Transm.Line 2-0.110.9750.117.47.466.8 0.813 75.9Preamplifier201000.966.866.875.9 0.793 160.14Transm.Line 3-1.530.7031.53122.5160.14 122.579.3 161.6828/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseAntenna NoiseAntenna NoiseThe antenna noise is modelled by an equivalent temperaturetAThe antenna noise picks up an average of the brightnesstemperature of the radiation bodies around the antenna,weightedR byR the antenna pattern radiation:1tA 4πtB · gr (θ, φ) sin θdθdφ29/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseNoise temperature of a satellite antennaNoise temperature of a satellite antennaFor the uplink, satellites with attitude control and a directiveantenna that points to the Earth, the antenna temperaturecan be considered as T0 290K , but this value is consideredas default if we don’t have further informationFor the downlink, the antenna noise sources are thetemperature of clear sky tCS , the temperature due to radiationsources tFR (Sun, Moon), the temperature of the groundtGROUND (by side lobes), the additional temperature when itis raining tRAIN with a hydrometeor temperature tm andm ·(aRAIN 1)attenuation aRAIN : tA tCS tFR t tGROUNDaRAIN30/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseRECOMMENDATION ITU-R P.372-1231/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRadio NoiseAntenna NoiseHUMSAT-D: Total NoiseAntennaNoiseGainGain (dB)Noise Temp. (K)Total noisetemp. at input400400SystemNoise55.7517.5161.8400 161.8 561.8ReceiverNoise24002400561.8 55.75 604.832/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterferenceRate carrier / noiseRate carrier / noiseC /N: Relation between the power of the modulated carrier Cand the noise powerC /N0 : Relation between the power of the modulated carrier Cand the noise power spectral density N0 k · t. It cancharacterize the channel without the final information aboutthe bandwidthEIRPgrLbgr 1C /N0 k·t EIRPLbt k33/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterferenceDoppler effectDoppler effectThe Doppler effect is the change in frequency of a wave for anobserver moving relative to its sourceAll non-geostationary satellite moves relative to theEarth-Station, so a Doppler effect appears.The change in frequency can be calculated as f vc f0This shift increases with the frequency of the carrier f0 and inLEO. At 800 Km and 435 MHz, the doppler shift can be 9.76KHz at low elevation anglesThe receiver must compensate this shift estimating theposition of the satellite or it must increase the bandwith andthe noise34/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterferenceEb /N0Eb /N0For the purposes of link budget analysis, the most importantaspect of a given modulation technique is the Signal-to-NoiseRatio (SNR) necessary for a receiver to achieve a specifiedlevel of reliability in terms of BEREb /N0 SNR · Rbb where Rb is the system data rate and Eb isthe energy per bit of informationIn general, the modulation technique dictates the requiredsystem bandwidth35/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterferenceReceiver sensitivityReceiver sensitivityThe first step in performing the link budget is determining therequired signal strength at the receiver input. This is referredto as receiver sensitivityAs described previously, this is a function of the ModulationTechnique and the desired BERAs an example, PSK modulation requires Eb /N0 9.5dB toachive a BER 10 5 . Then its sensitivity will be the internalnoise plus 9.5 dB.36/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterferenceHUMSAT-D: Receiver noiseSensitivity (dBm)Sensitivity (dBW)SNR (dB)Bandwidth (kHz)Noise Temperature (K)-118-148132.410 14.8101.3 ·2400·1.379·10 23 240037/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsRate carrier / noiseDoppler effectEb /N0Receiver sensitivityInterferenceInterference38/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived powerNoiseSignal to noise ratioConclusionsSummary for computation of the Link BudgetSummary for computation of the Link BudgetCompute the received power at the entrance of the receiver.It must be higher than the sensitivityCompute the noise received by the antennaDefine the reference point to compute the performance of theLink Budget. Typically at the entrance of the receiver or atthe entrance of the LNAUse the SNR and/or Eb /N0 methods to determine if we haveachieved the required margins39/46Small Satellite Link Budget Calculation
Critical points in a Satellite LinkReceived
Critical points in a Satellite Link Received power Noise Signal to noise ratio Conclusions Friis formula Antennas Polarization Propagation RECOMMENDATION ITU-R P.525-2 RECOMMENDATION ITU-R P.525-2 Friis formula was rst published in 1946: H. T. Friis, ’A note on a simple transmission formula,’ Proc. IRE 34, 254{256 (1946) p r p t (1 j tj2 .
the satellite output power to the maximum level, additional noise is introduced into the link from satellite to hub. Therefore, an accurate calculation of the SNR for the entire RTN link must consider: 1. the SNR of the terminal-to-satellite link 2. the SNR of the satellite-to-hub link When the output power of the satellite is at a maximum, SNR .
presents the rudiments of a satellite link design in a tutorial form with numerical examples. Index Term—Satellite communications, Link analysis, Link design, EIRP, SNR, CNR. I. INTRODUCTION The satellite link is essentially a radio relay link, much like the terrestrial microwave radio relay link with the singular
Satellite Communication Lecture # 9 Link Budget Link Budget Introduction Overall design of a complete satellite communications system involves many complex trade-offs to obtain a cost-effective solutions Factors which dominate are Downlink EIRP, G/T and SFD of Satellite Earth St
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c. Satellite: Internet access provided through satellites orbiting the Earth. Satellite service requires a satellite Internet subscription from an Internet satellite service provider and a satellite dish. Carriers that provide satellite Internet service are DIRECTV, Dish Network, HughesNet, and Wildblue. d.
Apr 23, 2019 · The budget narrative, sometimes called the budget justification, is a companion to the budget (table, spreadsheet, or forms). While the budget table gives the total cost for each category of the budget, the budget narrative giv
Examples of items that can be included in the cost share portion of the budget form: . those in the Excel budget form! . teams must select the “AEIF Budget Form” link to download the Excel budget spreadsheet. Please only use this form. Enter all the budget details on the form, save it on your computer, and upload it to your proposal .
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