What satellite orbits are used?

GEO (35,786 km): stationary relative to earth, one satellite covers one-third of globe, 240 ms round-trip latency. Used for broadcast TV, weather, and traditional VSAT. Requires only 3 satellites for near-global coverage. MEO (2,000 to 35,786 km): O3b/SES at 8,000 km with 150 ms latency, 20 satellites per plane. Used for maritime, aviation, and cellular backhaul. LEO (160 to 2,000 km): Starlink at 550 km with 20 to 40 ms latency, requires 600 to 6000+ satellites for continuous coverage. Higher throughput per user, lower latency, but complex constellation management with satellite handovers every few minutes. Orbital period: GEO 24 hours, MEO 6 to 12 hours, LEO 90 to 120 minutes.

How is a satellite link budget calculated?

The satellite link budget calculates the carrier-to-noise ratio (C/N) at the receiver. C/N(dB) = EIRP plus G/T minus path_loss minus k minus atmospheric_loss minus rain_fade. EIRP = transmitter power plus antenna gain (dBW). G/T = receive antenna gain minus system noise temperature (dB/K). Free-space path loss at GEO: FSPL = 32.4 plus 20 log(f_MHz) plus 20 log(d_km). At 12 GHz and 36,000 km: FSPL = 32.4 plus 81.6 plus 91.1 = 205.1 dB. Boltzmann constant k = minus 228.6 dBW/K/Hz. For a typical Ku-band DTH link: EIRP = 52 dBW, G/T = 12 dB/K, FSPL = 205 dB: C/N = 52 plus 12 minus 205 plus 228.6 minus 10 log(BW) minus margins.

What frequency bands are used?

C-band (uplink 5.925 to 6.425 GHz, downlink 3.7 to 4.2 GHz): lowest rain fade, largest antennas (2 to 5 m). Being reallocated to 5G in many markets. Ku-band (uplink 14 to 14.5 GHz, downlink 10.7 to 12.75 GHz): most common for DTH satellite TV and VSAT, moderate rain fade, 60 to 120 cm dishes. Ka-band (uplink 27.5 to 31 GHz, downlink 17.7 to 21.2 GHz): highest throughput (HTS satellites use spot beams), significant rain fade (up to 10 to 20 dB), 30 to 75 cm dishes. V-band (uplink 47.2 to 50.2 GHz, downlink 37.5 to 42.5 GHz): next-generation ultra-high throughput, severe rain fade, used for inter-satellite links and very high capacity feeder links.

Wireless Systems

Satellite Communications

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Radio links via orbiting spacecraft. GEO (35,786 km): fixed coverage, 240 ms latency, 3 satellites for global. LEO (550 km): 20-40 ms, 600-6000+ satellites (Starlink). Bands: C (4/6 GHz, low rain fade), Ku (12/14 GHz, DTH/VSAT), Ka (20/30 GHz, HTS spot beams). Link: C/N = EIRP + G/T − FSPL − k − rain fade. GEO FSPL @ 12 GHz: 205 dB.

GEO: 35,786 km

LEO: 550 km

FSPL: ~205 dB

Understanding Satellite Communications

Satellite communications provide connectivity where terrestrial infrastructure cannot reach: oceans, remote areas, aircraft, and ships. A satellite acts as a relay station in space, receiving uplink signals from earth stations, amplifying and frequency-translating them, and retransmitting as downlinks covering vast geographic areas. A single GEO satellite can cover one-third of Earth's surface.

The satellite industry is undergoing a revolution. Traditional GEO satellites provided reliable but high-latency service. New LEO mega-constellations (Starlink: 6,000+ satellites, OneWeb: 600+) provide fiber-like latency (20-40 ms) with multi-Gbps throughput, enabled by advanced phased array antennas, inter-satellite laser links, and Ka/V-band spot beams. The RF engineering challenges of tracking fast-moving LEO satellites with flat-panel electronically steered antennas are driving innovation in phased array and beamforming technology.

Satellite Orbit Comparison

Orbit	Altitude	Latency	Constellation	Application
GEO	35,786 km	240 ms	3 for global	DTH TV, weather
MEO	8,000 km	120 ms	20/plane	O3b backhaul
LEO	550 km	20-40 ms	600-6000+	Starlink broadband
HEO	Variable	200+ ms	3-6	Arctic coverage
ISL (inter-sat)	N/A	<1 ms	Mesh	Laser crosslinks

Common Questions

Frequently Asked Questions

What orbits?

GEO: 35,786 km, stationary, 240 ms, 3 satellites = global. DTH TV, weather. MEO: 8,000 km, 120 ms, O3b. LEO: 550 km, 20-40 ms, 600-6000+ sats (Starlink), handovers every few minutes. Orbital period: GEO 24h, LEO 90 min. LEO = lower latency, higher throughput per user, complex management.

Link budget?

C/N = EIRP + G/T − FSPL − k − rain. GEO @ 12 GHz: FSPL = 205 dB. EIRP=52 dBW, G/T=12 dB/K: C/N = 52+12−205+228.6−10log(BW)−margins. k=−228.6 dBW/K/Hz. Ka-band rain fade: 10-20 dB in heavy rain. HTS uses spot beams for frequency reuse.

Frequency bands?

C (3.7-4.2/5.9-6.4 GHz): lowest rain fade, 2-5 m dishes, being reallocated to 5G. Ku (10.7-12.75/14-14.5 GHz): DTH/VSAT, 60-120 cm, moderate rain. Ka (17.7-21.2/27.5-31 GHz): HTS, highest throughput, 10-20 dB rain fade, 30-75 cm. V (37-50 GHz): next-gen, severe rain, feeder/ISL.

Related Terms

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Satellite Systems

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