May 1, 2023
mmWave LEO Satellites Coming Over the HorizonFrom the front lines of the Russia-Ukraine war to Earth observation missions to high-speed communications at home, commercial LEO satellites are proving to be transformative. To continue their impact, they must adopt millimeter-wave (mmWave) frequencies. mmTron is developing disruptive MMICs offering higher output power, efficiency, and linearity at mmWave frequencies — a performance that will enable new system capabilities. This blog article by James Sowers of Maxar Space Infrastructure and an Advisor to mmTron explains the opportunity for the coming generation of satellite systems and the need to tap mmWave frequencies to truly realize the vision propelling satellite communications (Satcom). Low Earth orbit (LEO) satellites — first used to track weather and climate, now offering broadband internet access from space — have extended their capabilities to global geopolitical conflicts, with the Russia-Ukraine conflict dubbed the world’s first “commercial space war.” Since Russia’s invasion of Ukraine a year ago, LEOs have captured real-time convoy and radar imagery, helping track Russian troop movements and military tactics, enabling Ukraine to quickly respond to evacuate civilians, and even verify war crimes. As well as providing a communications link to coordinate military operations, SpaceX’s Starlink satellite constellation has been a communications lifeline for the citizens of the besieged Eastern European country. Arguably, satellites, many in LEO, have given Ukraine a tactical advantage over a vastly larger enemy, considering Russia’s military has nearly 5x more active troops than its smaller neighbor. Given the unforeseen demand for satellite bandwidth from this conflict, as well as commercial markets seeking connectivity, can LEO constellations support the demand without tapping higher frequencies offering more bandwidth? Not likely. Like all infrastructure, LEO constellations are subject to society’s demand for greater data rates. It’s Getting Crowded Up There As the data demand through each satellite increases, the performance of the LEO constellation — data rate and latency — will degrade. This is reflected in Ookla’s speed test data for the Starlink constellation: the Q2 2022 report shows latency for U.S. customers increased from 43 to 48 ms, as reported by Ars Technica. Although one solution may be to launch more satellites and grow the size of the constellation, using the same frequency bands, this seems costly and, at some point, impractical. A more feasible alternative is to increase the data capacity of each satellite by using higher frequencies with their attendant bandwidth to increase data rates. While satellites may exist in a vacuum, their ecosystems don’t. The spectrum that has long been the domain of satellites is under contention for mobile use, such as the current argument over allocating the Ku-Band spectrum for 5G. 6G applications, as they are defined, will likely add to calls for sharing or taking more satellite spectrum. Moving satellite usage from Ku-Band to bands above 30 GHz would eliminate interference while adding data capacity. Technical Challenges The move to higher throughput via higher frequencies isn’t straightforward, however. It requires new technology and component designs, a manufacturing and supply chain infrastructure, and costs that support the business model. Consider the ongoing challenge faced by 5G, which developed high data rate mmWave links for mobile phones. Adoption has been slow for multiple technical and economic reasons, including component power consumption and the associated heat generated in the handsets: they get too hot to handle according to several device makers. At Mobile World Congress, Jonathan Goldberg, founder of the technology and financial consulting firm D2D, said the “heat budget” for new 5G phones in 2019 was 67 percent higher than current phones. (The heat budget is the total thermal energy generated by the IC when a device is operating.) This same issue affects satellites, which operate in a vacuum. Heat must be transferred by conduction, and because the payload is enclosed in a small volume, the capacity to remove heat is limited. Moving from Ku-Band to mmWave downlinks adds the challenge of higher signal attenuation through the atmosphere, with rain fading in tropical areas. To compensate, the satellite requires higher gain antennas and higher power transmitters, challenging power amplifier suppliers to develop highly efficient devices that are also highly linear to handle the complex modulation used for high data rates. Wanted: A Trusted Semiconductor Partner To realize this vision of LEO satellites with mmWave links, service providers and satellite developers will need a mmWave semiconductor partner with the expertise to work with system designers to partition the link budget, then optimize MMIC performance to balance power, efficiency, and linearity in the transmit chain and noise, gain, and linearity in the receive chain. Because of the space environment, the designs — from semiconductor to module — must meet a new class of commercial space requirements to assure the payload meets the design lifetime of the LEO satellite. To enable this market, the semiconductor industry needs a new standard for linearity and efficiency. Fortunately, mmTron is targeting this trade space to solve these technical challenges, whether for LEO or terrestrial 5G. The mmTron team has developed MMICs for high-throughput satellites requiring 15-year orbital lifetimes and is extending that expertise to develop a family of power amplifiers that will enable LEOs to rocket to their full potential. Watch for our product releases this year. James Sowers is a distinguished engineer at Maxar Space Infrastructure and an mmTron advisor. mmTron was formed in 2020 to address the need for wide bandwidth, highly efficient and highly linear mmWave power amplifiers. The same performance capabilities required by LEO constellations apply to 5G, instrumentation, and defense systems, markets which mmTron also serves. mmTron’s product roadmap includes the complementary small-signal components used in these same systems.