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ECE 5233 Satellite Communications

ECE 5233 Satellite Communications. Prepared by: Dr . Ivica Kostanic Lecture 11: Satellite link design (Section 4.4). Spring 2011. Outline . Output power of the transponder Rain effect on the uplink Case study of a Ku satellite link design.

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ECE 5233 Satellite Communications

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  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 • Signal decreases • Negligible impact on noise • On uplink noise temperature may vary 270-300K

  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.

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