Why uplink frequency is greater than downlink frequency can you provide me these details with technical data?

Answer 1

see the reason is that....

1) On the Earth Station we have to penetrate the atmosphere to reach the satellite station..so we need a lot of power to be generated...This is only possible with the help of High power transmitter circuits....which cannot be installed on the satellite....so uplink is at higher freq with higher power.

2)Now as the frequency is increased the amount of interference caused by the atmosphore reduces...as higher frequency signal has more signal energy in it....so it can penetrate the atmosphere more easily...(the same reason why we use modulation with higher frequency)

3) Unwanted distortion like rain (main cause of attenuation), fog, other frequency in neighbourhood, etc cause distortion....so we have to count to these factors and increase the frequency band to 100-1000Ghz range...

Now the Satellite is a small piece of equipment and needs to be light weight...so it cannot have high power amplifiers on board so by default the freq is lower than uplink...

i hope this is informative....if it is press thanks...Cheers...

Answer 2

A satellite is a repeater in space. It must receive on one frequency, and transmit on another. When it comes to transmitting, it is more efficient to generate high power at a LOWER frequency.

On the other hand, the higher the frequency, the narrower the beamwidth from the same diameter antenna. This becomes important in a crowded geostationary orbit with satellites orbiting only a few degrees apart. If you increase frequency and the diameter of the dish antenna on earth remains the same, the effective radiated power of the signal increases because the beamwidth decreases (becomes more focused).

As a final reason to support a higher input frequency for satellite transmission, when the space program first began, the transmit klystron tubes and power transistors available were so inefficient that they required massive amounts of input power to generate a small amount of power output. This power could easily be supplied on earth, but hard to come by and store in space when the bird is in the shadow of the earth, and the solar panels are not charging the spacecraft's batteries.

Conclusion: Using a higher receive frequency and a lower transmit frequency will reduce the power requirements for a communications satellite, and allow closer satellite spacing and lower earth station transmit power with a smaller antenna.

Answer 3

It is because a mobile is operated on a battery with low power and therefore it sends signals on low(uplink) frequencies whereas a base station is driven by high power and can easily send signals on high(downlink) frequencies. This can be verified by Friis equation which says Transmitted power and Transmitted frequency are directly proportional.