MEMS nanocapacitors unlock upper 5G bands for 6G
Nanusens in the UK has created an RF front end for 6G using its CMOS-based MEMS technology to create nanocapacitors on a chip.
Nanusens has used its patented MEMS technology to create numerous, digitally tunable, nanoscale capacitors within the CMOS layers of a chip along with the control circuitry.
The RF Digitally Tunable Capacitors (DTCs) address the issue of current antenna systems becoming increasingly power hungry in the higher frequency bands for 6G. The key to reducing the power is the very high Q factor of above 100 at 1GHz and, importantly, the Q factor continues to be high up through to the higher bands to keep power losses very low.
The practical result is an increase in range by around 14% or more which improves user experience as there are fewer dropped calls or poor reception areas. The performance comes from the improved linearity of 90 dBc for IMD3 which is the 5G requirement. As the nano-capacitors are more power efficient, talk times are up to 30% better and thus solving the current issue of decreased efficiency.
Using a standard CMOS means that the DTC can be made at the same time and on the same chip as other RF front end components, such as the power amplifier, low noise amplifier and transceivers, to reduce interconnect parasitics while making them reconfigurable. The nanocapacitor design will fit in ultra-small, low profile, low cost WLCSP packages and this integration also reduces the BOM and saves board area compared to competitors’ multi-component solutions.
The nanocapacitors are built as the Inter Metal Dielectric (IMD) is etched away through the pad openings in the passivation layer using vapour HF (vHF) to create the nano-structures. The holes are then sealed and the chip packaged as necessary. As only standard CMOS processes with minimal post-processing are used and the devices can be directly integrated with active circuitry as required with high yields similar to CMOS devices. This also means that the production is fab-independent.
“This builds on and extends the company’s work of using its unique technology to enable the upper 5G bands to be used cost effectively. We have test chips for this with customers and they are impressed with their performance and actually advised us to use this technology to also create solutions for 6G as the industry really has a challenge,” said Josep Montanyà, CEO of Nanusens.
“The issue is that 6G needs to be able to handle many more and possibly higher frequencies than 5G. To do this requires additional antennas to be integrated into the phone to handle more bands but, due to them having to be smaller to fit more of them inside the phone, their efficiency decreases. In order to get the best possible performance from each antenna, each needs to be tuned to reconfigure to different bands and to avoid mismatch with the power amplifier. This is currently done by means of tunable capacitors.”
“Not only for phones but also for other applications in industry and automotive due to its much lower latencies and data rates that are 50 times better than 5G at 1000 gigabits per second. That is a huge potential 6G market that is measured in the hundreds of millions of new devices a year. driven by the rapidly growing needs of data intensive applications such as AI, virtual reality, augmented reality and IoT. Our technology of just using standard CMOS techniques in any CMOS fab means that we can produce in virtually unlimited volumes to meet this demand,” said Dr Marc Llamas, CTO at Nanusens.
The array of RF capacitive switches opens up the implementation of antenna tuning for the higher 6G bands. This solves the low Q factor problem as there is no ON state resistance in this design resulting in a very high Q factor of above 100 at 1GHz and, importantly, the Q factor continues to be high up through to the higher bands to keep losses very low, where the Q factor of rivals drops down significantly.
The Nanusens DTC nanocapacitors have successfully passed over four billion switching cycles in the lab without degradation. They are also very robust having been successfully tested for shock, vibration, thermal cycling, MSL 1 and HTSL.
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