1. ECE 5233 Satellite Communications
Prepared by:
Dr. Ivica Kostanic
Lecture 11: Satellite link design
(Section 4.4)
Spring 2011

2. Outline Output power of the transponder Rain effect on the uplink
Case study of a Ku satellite link design
Important note: Slides present summary of the results. Detailed derivations are given in notes.

3. Output power of a transponder
Two kinds of the transponders
Bent pipes
Regenerative repeaters
For bent pipes the gain is linear (as long as the input is in linear region)
For regenerative repeaters, the power output is constant (as long as the input signal to noise ratio is above required threshold)
Gain of a bent pipe transponder
Note 1: Regenerative transponder operates at the constant power – less restricted on linearity requirements of the HPA
Note 2: Backoff of the bent pipe transmitter depends on the type of waveform
Note 3: In regenerative repeaters the noise does not accumulate. The overall S/N is the same as the S/N of the last stage
Gain of a regenerative transponder

4. Rain effects on UL
Uplink and downlink are effected differently by rain
On downlink
Signal decreases
Noise increases
On uplink
Negligible impact on noise
On uplink noise temperature may vary K

5. Satellite Communication Link Design
Determine operating frequency
Determine communication parameters of the satellite
Determine TX and RX parameters of the ground stations
Start at the TX side – establish the UL parameters and (C/N)up
Find output power of the transponder
Establish the downlink power budget and calculate (C/N)down and total (C/N)
Calculate S/N (or BER) at the baseband channel
Calculate system margins and system reliability (outage times)
Iterate through steps 1-8 until the requirements are met

6. System design example – 4.8.1
Example presented in notes.