 Hello everyone, welcome to the session. I am Mr Pravin Yalapakumbar. Today we want to see uplink design. The learning outcome of this topic is at the end of the session student will be able to explain the concept of uplink design in satellite communication. The contents of this topics are introduction, design for specified C by N that is combining C by N and C by I values in satellite links and overall C by N with uplink and downlink attenuation. Introduction. Mostly in the satellite communication there are uplink as well as downlink design. For uplink design is easier than the downlink. Since we accurately specified carrier power must be presented at the satellite transponder and feasible to use much higher power transmitter at our stations. Reset systems uses our station with small antennas and transmitter power below the 5 volt that gives low uplink EIRP. Satellite telephone handset are restricted to transmitting powers below 1 watt that use for low risk of EM radiation hazards. The cost of transmitter tends to be high compared with the cost of receiving equipment in satellite communication system. Therefore, the major growth in satellite communication is point-to-multipoint transmission that is we use in direct broadcast satellite television. Earth station transmitter power is set by the power level required at the input to the transponder. There are two ways we want to specify that is first one with the help of specific flux density is required at the satellite and second one is specific power level is required at the input to the transponder. For example, at the C-band for uplink earth station we require 100 watt power and the antenna of height we require 9 meters. Therefore, the flux density for this combination that is uplink earth station and for this height specified we require flux density is 100 watt per meter square. Analysis of the uplink requires calculation of the power level at the input to the transponder and from that one we calculate the uplink of C by N ratio. The noise power referred to the transponder input is nxp is equal to k plus txp plus bn the unit of that one is db watt where txp is system noise temperature for the transponder in dbk and bn is is the noise bandwidth in db hertz where k is a Boltzmann constant. The power received at the input to the transponder is prxp is equal to pt plus gt plus gr minus lp minus lup the unit of this received power is db watt where ptgt is the uplink earth station arp in db watt gr is satellite antenna gain in db in the direction of the uplink earth lp is the path losses in db lup is the for all uplink losses other than path losses the value of c by n for the up at the lna input of the satellite receiver is given by c by n is equal to 10 log to the base 10 pr divided by kts into bn is equal to after the simplification of this equation we get prxp minus nxp that is a c by n ratio the unit of that one is db the received power at the transponder input is also given by prxp is equal to n plus c by n the unit of that prxp is db watt in general the received power prxp is equal to p sat minus bo0 minus gxp the unit of that received power is db watt where p sat is saturated power output of the transponder in db watt bo0 is the output back off in db gxp is gain of the transponder in db designed for specified c by n that is combining c by n and c by i values in satellite links s by n ratio is defined as the ratio of carrier power to the noise power in the if amplifier at the input to the demodulator noise present in the if amplifier first receiver thermal noise second noise related by the atmosphere gases and third one is rain in the slant path the overall c by n is measured in the earth station at the output of the if amplifier is c by n is equal to 1 upon 1 by c by n 1 plus 1 by c by n 2 plus 1 by c by n 3 up to and equation this equation is 6 is referred as the reciprocal cn formula and after the simplification of this equation number 6 we get c by n 0 is equal to 1 upon n 1 by c plus n 2 by c plus n 3 by c after the simplification of this equation we get c by n 1 plus n 2 plus n 3 that is equation number 7 in decibel units c by n is equal to c db watt minus 10 log to the base 10 in bracket n 1 plus n 2 plus n 3 that is what in db to calculate the performance of a satellite link we have to determine first the uplink c by n up in transponder and the downlink that is c by n dn in the earth station receiver some useful rules of a thumb for estimating c by n from two different c by n values is if two c by n values are the same then overall c by n is 3 db lower than the either of these two values if the second c by n values is lower than the first c n by values is by 10 db then overall c by n value is less than the lower values of 0.4 db and if c n 1 value is more than the c n 2 values by 20 db then overall c by n value is equal to the lower one that is c by n 2 overall c by n 0 with uplink and downlink attenuation the effect of a change in the uplink c by n ratio has a different impact on the overall c by n 0 depending on first operating mode of the transponder and second gain of the transponder there are three different transponder types or operating modes the first one is linear transponder second one is non-linear transponder and third word is regenerative transponder the first the linear transponder is p out is equal to p in plus gsp the unit of that p out is db wet second non-linear transponder p out is equal to p in plus gsp minus delta g the unit of that p out is db wet now third one is regenerative transponder that is p out is equal to constant the unit of that p out is db wet where p in is the power delivered by the satellite receiving antenna to the input of the transponder p out is the power delivered by the transponder to the input of the satellite transmitting antenna gsp is the gain of the transponder and delta g is the loss of gain a question is a thermal noise in an r station receiver results in a c by n dn ratio of 20 db a signal is received from a band pipe transponder with a cn up is equal to 20 db then what is the value of overall c by n at the r station now recall the formula of overall c by n ratio okay now the formula is c by n zero is equal to one upon one by c by n up plus one upon c by n down then put the values of this c by n up and c by n down and we get one upon zero point zero one plus zero point zero one now here c by n in db is equal to 20 now we convert into the normalized function we get that is a hundred then put this value into here one by hundred is equal to zero point zero one and cn down is again 20 db again convert into normalized function that we get the hundred then one by hundred is equal to zero point zero one and solve this one and we get the 50 the overall c by n is 50 the references for this topic is thank you