Chapter 5: Communications Link

Here is the work-script for chapter 5

8 November  2017

We learned about all the parameters that we need to develop the link equation.
We derived the equation for the received power and explained the meaning of free space loss.
Then we derived the link equation.

10 November  2017
We derived the link equation. We talked about system noise, introduced C/N, derived the simple equation for the noise power
spectral density in the limit for radio waves, listed types of thermal noise and plotted the curve for sky noise as a
function of radio frequency.


13 November  2017
We derived the equation for the system temperature. We talked about the 3K cosmic background radiation and 
Penzias and Wilson who discovered  it. Click here for the latest results from the Planck mission.
We introduced the noise factor and looked at absorptive network noise.

15 November  2017
We learned how the equivalent noise temperature of a device can be referred to the input and then also to the output of the device. We looked at the differences between amplifiers and passive attenuators.  We looked at a block diagram of a receiver and the equivalent input temperatures at different sections of the receiver. Then we used an example and went through the computation of the system temperature of the antenna and the receiver. We also found and expression for the noise power spectral density at the receiver output.
We realized what Penzias and Wilson needed to consider to conclude that there is a 3K cosmic microwave background (CMB)
radiation in the universe.

17 November  2017
We talked about LNA's. And then we turned to the C/N ratio.

20 November  2017
We introduced the saturation flux density, the effective aperture of an isotropic antenna and the back-off from the saturation point of a transponder amplifier which is related to the non-linearity of the amplification curve.
We looked at the combined uplink and downlink C/N. Then we distinguished
between different kinds of noise, thermal noise, intermodulation noise and intrasystem interference noise and learned that the overall C/N is computed by adding the N/C's for the different kinds of noise. Then we looked at an example of a multicarrier satellite circuit at C-band and computed the overall C/N ratio.