ENTRE News – China has just introduced its newest satellite called Tiantong. With this satellite, Chinese citizens can make calls even without a signal. Satellite internet technology has several challenges, one of which is the problem of signal interference. How does Tiantong satellite overcome these problems?
The satellite name Tiantong means “contacting heaven”. The name of this project refers to the story of the Tower of Babel in the Bible. Direct communication between satellites in space and large numbers of mobile phones on the ground was previously believed to be impossible. In the Biblical story, the Tower of Babel failed to be built because the workers began speaking different languages and became confused with each other. Similar interference can occur with satellite communications.
To reach many smartphones on Earth, satellites need to produce very strong signals. When a large number of high-power signals flood a satellite transmitting antenna simultaneously, the signals can interfere with each other and produce new signals. These randomly appearing signals can degrade the quality of satellite communications and, in severe cases, can cause the entire system to fail.
Since the 1970s, almost all commercial communications satellite networks run by the United States (US), Europe and international organizations have experienced major failures because the signals appeared in the receiving frequency band.
This problem, known as passive intermodulation (PIM) among telecommunications engineers, has become an obstacle to the further development of satellite communications technology. Although many people want to solve this problem, there is currently no universally effective technology to suppress the occurrence of PIM FOR4D.
According to Cui Wanzhao, head of the research team from the Chinese Academy of Space Technology, the Tiantong project has brought together communications technology elites from across the country to address “technical challenges of common concern in the international aerospace community.”
He explained that different metal components on large satellite antennas come into contact with each other, leading to the main source of PIM. Chinese physicists have studied microscopic physical mechanisms such as quantum tunneling and thermal emission at contact interfaces. The study yielded a new set of physical laws that accurately describe silver-plated and gold-plated microwave components.
Quoted from SCMP, the researchers have also established a physics model that can predict the occurrence of PIM effects with unprecedented accuracy in various contact states, joint pressures, temperatures, vibrations and other external factors.
Based on this research, Chinese scientists developed the world’s first universal PIM simulation software. This software is said to be able to numerically analyze and evaluate the possible presence of PIM in microwave components with complex structures under the influence of external factors such as electricity, heat and pressure with a very low error rate.
The advanced software is said to have helped Chinese engineers develop effective PIM suppression techniques, including dielectric isolation capacitors and optimized methods for preparing and weaving mesh antenna wire. Furthermore, Cui and his team have also developed the world’s most sensitive PIM detection technology, which can immediately locate the location of PIM when it occurs at very weak levels. This allows satellites to achieve high reception sensitivity, allowing signals from smartphones without external antennas to be captured and identified by satellite antennas tens of thousands of kilometers away.
Each Tiantong satellite is designed to have a lifetime of 12 years, and its antennas experience daily temperature changes of up to 160 degrees Celsius while simultaneously transmitting and receiving electromagnetic waves in 800 different frequency bands. Currently there are three ‘heaven satellites’ circulating in orbit, which were launched in 2016, 2020 and 2021. Another satellite is planned to launch in 2024. The three existing satellites form a network in geosynchronous orbit at an altitude of 36 thousand kilometers. This network can serve communications throughout Asia-Pacific, from the Middle East to the Pacific Ocean FOR4D.
Huawei Technologies has launched the first smartphone that supports satellite telephony in September 2023. The phone can connect to the Tiantong satellite. Several other Chinese companies, Xiaomi, Honor and Oppo, followed in Huawei’s footsteps.