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Now, 16 years later, this project has resulted in major advances in satellite communications and new trends in mobile phone development.
“Tenttsu” means “connected to heaven” and reflects the Biblical story of the Tower of Babel.
Currently, ordinary mobile phone users in China can dial any number via the Tiantong satellite, even in areas with poor reception, such as deserts and remote islands, by paying an additional monthly fee of 10 yuan (US$1.38).
Direct satellite connectivity for mobile phones has become a new development trend, and satellite communication will gradually become popular with the general public.
Until now, it was thought that it would be impossible for telecommunications satellites to exchange information with large numbers of mobile phones on the ground. In the Biblical story, the Tower of Babel failed because the workers began speaking different languages and confused each other. Similar interference can occur with satellite communications.
These randomly occurring signals can degrade the quality of satellite calls and in severe cases can cause the entire system to collapse.
Since the 1970s, nearly all commercial communications satellite networks operated by the United States, Europe, and international organizations have experienced significant failures due to the presence of these signals within their reception frequency bands.
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This problem is known among telecommunications engineers as passive intermodulation (PIM) and has become a bottleneck for further development of satellite communication technology. Many people are keen to solve this problem, but at present there is no universally effective technique to suppress the occurrence of PIM.
China’s Tiantong project brings together communications technology elites from across the country to tackle this “technical challenge of common interest in the international aerospace community,” according to Cui’s team.
The various metal parts inside the giant satellite antenna come into contact with each other and are the main cause of PIM. Chinese physicists have delved deep into microscopic physical mechanisms such as quantum tunneling and thermal radiation at contact interfaces and discovered a new set of physical laws that accurately describe silver-plated and gold-plated microwave components.
We also established a physical model that can predict the occurrence of PIM effects under various contact conditions, connection pressures, temperatures, vibrations, and other external factors with unprecedented accuracy.
This powerful software has helped Chinese engineers develop effective PIM suppression techniques such as dielectrically isolated capacitors and optimized mesh antenna wire preparation and weaving.
Cui’s team has further developed the world’s most sensitive PIM detection technology. This allows us to instantly pinpoint where PIM occurs if it occurs at very low levels.
This allows the satellite to achieve unprecedented reception sensitivity, allowing signals from smartphones to be captured and identified by antennas tens of thousands of kilometers away, without an external antenna.
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Each Tiantong satellite is designed for a 12-year lifespan, and its antenna simultaneously transmits and receives electromagnetic waves in 800 different frequency bands while being exposed to daily temperature changes of 160 degrees Celsius (320 degrees Fahrenheit) .
Solving PIM problems under such harsh working conditions is extremely difficult. “The development of the Tiantong-1 satellite system is inseparable from several important technological advances. Its success is a testament to the project team’s dedicated efforts and China’s leading position in this technology field worldwide. ,” Choi’s team said in the paper.
China has filed numerous patents for the Tiantong satellite, meaning Chinese tech companies won’t have to worry about patent barriers or sanctions from Western countries when using this innovative technology. .
These satellites operate in low Earth orbit at an altitude of several hundred kilometers and have a small antenna area, which reduces PIM interference. However, since satellites can only stay in the sky for a short period of time, it is necessary to deploy a large number of satellites to cover a wide area at all times.
Currently, most of the more than 5,000 Starlink satellites launched by SpaceX do not have the ability to connect to mobile phones.
As Starship technology matures, the launch speed of Starlink satellites could increase significantly, but China has not yet developed a mature, recoverable rocket technology that can compete.
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