2. Link Budgets Flashcards
(9 cards)
What is an acceptable BER for
1. speech communication
2. Data communication
- 10^-4 bits per error
- 10^-6 - 10^-8 bits per error
In the basic link budget equation what assumptions are made about the antenna alignment and the path?
- Both antennas are perfectly aligned, therefore there are no additional losses from XPD.
- The path is free space. In reality object such as building, rainfall to cause additional losses that need to be factored in
What is the difference between C/N and C/N_o?
C/N is the carrier to noise measured in dBWHz, C/N_o is dBW per Hz and N_o is the noise density
How is the BER determined from the carrier to noise ratio?
The total loss profile for a communication link is made up from which three contributions?
- Path loss
- Shadowing (from large structures such as buildings going into the line of sight)
- Fast fading (Pickup from other channels in the RF environment for example other mobile phone links etc)
What are some of the environmental sources of noise?
- Sun
- Trees
- Ground
- Buildings
- Sky
In terms of the carrier signal, how can the attenuation of a raincloud be written
C_in - C_out
When finding the receiver gain, where is the reference plane placed?
After the feed loss at the input of the LNA. Therefore it is calculated from G_ant_Rx - L_feed
What is the difference between a co-polar and a cross-polar signal?
refers to the alignment between the transmit and receive antennas. For linearly polarised antennas, they are cross polar when one is vertical and the other is horizontal.
