The first Global Positioning System (GPS) satellite launched in 1978, pioneering the concept of global navigation satellite systems (GNSS). Twenty years later, Iridium launched a satellite-based telephony service, the first to use handsets the size of cell phones rather than briefcases. And in 2022, 3GPP Release 17 ushered in the era of Non-Terrestrial Networks (NTN), where 5G cellular leverages satellite to extend service to the 600 million people at sea, in rural areas, and in other places without mobile coverage.
Those are just a few examples of how satellite technology has evolved and become a key part of everyday life. Many fundamental concepts apply to all satellite constellations. Understanding those concepts is an important first step toward choosing the right antenna, radio module, and other components for devices that provide satellite-based services, such as autonomous vehicles, fitness wearables, asset trackers, and more.
Orbits
Orbits are the paths satellites follow around the Earth. There are three main types, which determine the satellite’s coverage area and the applications it can support:
- Geostationary Orbit (GEO) satellites are 35,786 kilometers above the equator. At this height, they can cover a large portion of the Earth’s surface. They also take 24 hours to orbit the Earth; hence their name. The combination of height and a fixed position makes them ideal for continuous services like TV broadcasting and weather monitoring, which require a stable signal. DirecTV and SiriusXM are two examples of services that use GEO constellations.
- Medium Earth Orbit (MEO) satellites orbit between 2,000 and 35,786 kilometers. They cover wider areas than LEO satellites and thus require fewer satellites to provide global coverage. GNSS services such as GPS use MEO constellations.
- Low Earth Orbit (LEO) satellites orbit between 160 and 2,000 kilometers. Being closer to Earth reduces latency on the uplink and downlink, making them a good fit for home broadband services and 5G cellular NTN. SpaceX/Starlink is one example of a LEO constellation operator.
The orbit type affects the antenna choice and its integration. For example, GNSS signals are relatively weak by the time they reach Earth, and they can be further attenuated by foliage and tall buildings. Depending on the application, a directional antenna can be critical for providing the receiver with a usable signal. (For more tips, see “GNSS Antennas: How to Choose Between Directional and Omnidirectional Designs.”)
Spectrum
Each type of satellite system uses a specific set of frequencies. For example, GNSS constellations operate between 1164 MHz and 1610 MHz.
One type of GNSS system is referred to as “L-Band,” which can be confusing because it operates in a band that is not the same as GNSS signals that share the same letter. L-Band services are used to augment GNSS signals to achieve positioning accuracy down to the centimeter level. (For a deeper dive, see “How to Leverage the L-Band to Balance Accuracy and Affordability for GNSS Applications.”)
GNSS systems are continually evolving with new satellites and new frequencies. These provide device OEMs, systems integrators, and end users with additional options for increasing the accuracy of positioning and timing. (For more information, see “How the GNSS Evolution Enables Future Proofing.”)
Using signals from multiple constellations — such as GPS, GLONASS, and BeiDou — is another way to increase accuracy. This option requires an antenna capable of covering each system’s frequencies. (For more information, see “Navigating the L1, L2 and L5 Band Options for GNSS.”)
Cellular Integration
LEO constellation operators such as SpaceX/Starlink, Amazon/Kuiper, and OneWeb have significantly lowered the costs of satellite connectivity. This has enabled Internet of Things (IoT) use cases that were previously considered impractical or too costly to use satellite. One example is IoT modules that monitor and control equipment in remote areas that lack cellular coverage, such as agriculture and oil wellheads.
Another key development is the integration of NTN in 3GPP standards. This allows seamless, hybrid connectivity across cellular and satellite networks. An example is continuously tracking high-value assets that travel through locations where cellular coverage is unavailable, such as shipping containers at sea.
In addition to IoT services, NTN is enabling mobile operators and smartphone OEMs to offer new types of consumer applications. For example, T-Mobile’s partnership with Starlink, and Apple’s partnership with Globalstar, give customers the ability to stay connected in areas where 4G and 5G coverage is unavailable. (To learn more, see “Combining Satellite and Cellular to Unlock New Business Opportunities.”)
Many LEO and 5G bands are close enough that a single antenna can cover both. In fact, that’s why modules that support both cellular and satellite have a single RF connector for the antenna. This synergy is another reason why NTN is rapidly becoming an attractive option for consumer and business applications. To learn more about how to select the right antenna, speak to Taoglas’ Engineering team by clicking on the button below.
