Nanusens has unveiled a novel solution to improve RF front ends for 6G, leveraging its groundbreaking MEMS-within-CMOS technology.
“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,” explained 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.”
Nanusens has used its patented technology to construct numerous digitally tunable, nanoscale capacitors within CMOS layers, alongside control circuitry. This integrated, single-chip solution is smaller than competing products and offers superior performance due to its exceptional linearity, virtually eliminating distortion. Furthermore, these nano-capacitors are more power-efficient, enhancing talk times by up to 30% and addressing the current efficiency issues.
These RF Digitally Tunable Capacitors (DTCs) also address the increasing power demands of higher frequency bands. With a very high Q factor of over 100 at 1GHz, which remains high even in higher bands, power losses are kept minimal. This results in approximately a 14% increase in range, enhancing user experience by reducing dropped calls and poor reception areas.
Dr Marc Llamas, CTO, Nanusens, said: “Our unique solution for the 5G and 6G RF Front End is exciting the major RF corporations that we have shown it to who need a better solution. We believe that this is RF Front End solution that they have been looking for to enable the 6G market to really take off. 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 unique technology of just using standard CMOS techniques in any CMOS fab means that we can produce in virtually unlimited volumes to meet this demand.”
Issues with competing solutions
Solid-state switches suffer from low Q factors due to their ON state resistance, which worsens at higher frequencies. RF MEMS tunable capacitors face reliability issues due to dielectric charging, leading to failure and limited peak-to-peak voltage tolerance.
Nanusens’ solution avoids these issues by using an array of RF capacitive switches, eliminating ON state resistance and maintaining a high Q factor across all frequency bands. Unlike RF MEMS, Nanusens’ design does not use dielectric, thus avoiding charging and breakdown issues, resulting in superior reliability with over four billion switching cycles tested successfully. They have also passed rigorous tests for shock, vibration, thermal cycling, MSL 1, and HTSL.
Key performance parameters
The critical factors for DTCs are the Q factor and linearity. Nanusens’ DTCs achieve a Q factor above 100 at 1GHz, matching state-of-the-art RF MEMS solutions and surpassing solid-state switches. They also exhibit excellent linearity, exceeding the 90 dBc IMD3 requirement for 5G.
Minimum capacitance can be very low, with Coff at 30 fF for a single capacitor off state, and even less for future iterations. The capacitance ratio is currently 2.2, with expectations to improve to 4 in the next product iteration.
As performance nears ideal (low off-state capacitance and high Q), parasitic interconnects increasingly impact performance. Nanusens’ solution, built using standard CMOS, allows DTCs to be integrated on the same chip as other RF front end components, reducing parasitic losses. These single-chip, reconfigurable solutions fit in ultra-small, low-profile, low-cost WLCSP packages, reducing the bill of materials and saving board space compared to multi-component solutions.
Nanusens creates nano-structures by etching away the Inter Metal Dielectric (IMD) through pad openings in the passivation layer using vapour HF (vHF). The holes are then sealed, and the chip is packaged as needed. Using standard CMOS processes with minimal post-processing allows for high yields and direct integration with active circuitry, making the production fab-independent.
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