4 However, the model is only valid for any voltage waveform without minor loops. Because of limitations in power required for transmitting and gain of the antenna.The modified Bertotti model with variable coefficients is extended by the form factor of Grätzer. The designing of down link is more critical than the designing of uplink. $P_R$ stands for the received power, which is measured in dBW.Now the decibel equation for received power can be written as PL stands for polarization mismatch loss. RFL stands for received feeder loss and units are db. Now, we can write the loss equation for free sky as These are taken care by atmospheric absorption loss given by “AA” and measured in db. Similarly, when signal comes from the satellite towards earth it collides with earth surface and some of them get absorbed. so we take AML (Antenna misalignment losses) into account. If antenna is not aligned properly then losses can occur. If we are taking ground satellite in to consideration, then the free space spreading loss (FSP) should also be taken into consideration. $$\left(\frac \right ]_D - \left _D -K-B$$ Link Budget Its mathematical equation can be written as It is the process in which earth is transmitting the signal to the satellite and satellite is receiving it. There are two types of link budget calculations since there are two links namely, uplink and downlink. Then in 2 nd step, we can calculate the losses due to foul weather condition. Therefore, our procedure includes the calculation of losses due to clear weather or clear sky condition as 1 st because these losses are constant. Means if the sky is not clear signal will not reach effectively to the satellite or vice versa. The sky and weather condition is an example of this type of loss. No matter what precautions we might have taken, still these losses are bound to occur.Īnother type of loses are variable loss. The losses which are constant such as feeder losses are known as constant losses. The losses can be categorized into 2 types. The difference between the power sent at one end and received at the receiving station is known as Transmission losses. Where, G is the Gain of Transmitting antenna and $P_s$ is the power of transmitter. Equivalent Isotropic Radiated PowerĮquivalent isotropic radiated power (EIRP) is the main parameter that is used in measurement of link budget. And, $\Psi_i$ is the power flux density of isotropic radiator (antenna). Where, $\Psi_m$ is the maximum power flux density of practical antenna. Therefore, the Gain of Antenna or Antenna gain, G is The gain of practical antenna is defined as the ratio of maximum power flux density of practical antenna and power flux density of isotropic antenna. But, it’s maximum value will be in one particular direction only. In general, the power flux density of a practical antenna varies with direction. Power flux density, $\Psi_i$ of an isotropic radiator is We know that power flux density is the ratio of power flow and unit area. Power flux densityĪssume an isotropic radiator is situated at the center of the sphere having radius, r. We can compare the performance of all real (practical) antennas with respect to this antenna. Basic TerminologyĪn isotropic radiator (antenna) radiates equally in all directions. The unit of power is decibel.įirst, let us discuss the basic terminology used in Link Budget and then we will move onto explain Link Budget calculations. In general, these calculations are called as Link budget calculations. Those are transmitting power and receiving power calculations. In satellite communication systems, there are two types of power calculations.
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