Imec introduces best-in-class ADCs for base stations and smartphones, propelling beyond-5G communications

LEUVEN (Belgium), JUNE 19, 2024 — At this week’s IEEE Symposium on VLSI Technology & Circuits, imec – a world-leading research and innovation hub in nanoelectronics and digital technologies – introduces two state-of-the-art ADCs for base stations and handsets. The base station ADC supports RF sampling, operates across multiple frequency bands (up to 5GHz), and combines high resolution and high linearity with low power consumption. Complementing this is a single-channel handset ADC that achieves record-breaking power efficiency through multi-bit pipelined stages and background calibration. Both ADCs, available for licensing, represent a key step toward scalable, high-performance beyond-5G solutions – such as cloud-based AI and extended reality apps.

Beyond-5G technology will be a key enabler of increasingly bandwidth-intensive mobile services, such as cloud-based AI and extended reality apps. But it also comes with the use of higher frequencies (with mobile operators currently exploring frequencies up to 5GHz), and the deployment of ever more advanced infrastructure equipment – including large antenna arrays.

“This will require a transformation of operators’ mobile networks, particularly in the design of transceivers – and the underlying ADCs – at both the base station and handset ends. Key transceiver requirements will include a small footprint and low power consumption, along with support for features that enhance network capacity, such as multiband operation and Massive MIMO. We are addressing these needs with the introduction of two new ADCs at this year’s VLSI Symposium,” said Joris Van Driessche, program manager at imec.

A low-power RF-sampling ADC excelling in resolution and linearity at the widest bandwidth

Base station radios typically achieve multiband operation by assigning a transceiver to each frequency band, increasing the radios’ size and power consumption. In contrast, imec’s new RF-sampling ADC – which covers all bands below 5GHz and features GHz-level sampling speeds – operates seamlessly across multiple frequency bands. Additionally, while the large antenna arrays required for massive MIMO are usually equipped with numerous power-hungry, discrete transceivers, imec’s approach allows for a much more efficient system-on-chip implementation.   

Joris Van Driessche: “To help base station radios cope with interference from other wireless signals, our ADC leverages built-in wideband-linear signal buffering to provide higher Effective Number of Bits (ENOB) than comparable systems – without the need for digital nonlinear distortion correction engines. In addition, its design incorporates a novel hierarchical interleaver architecture that further enhances the ADC’s linearity and speed.”

Imec’s CMOS-based 10GS/s hierarchical time-interleaved ADC for RF-sampling applications delivers 9/8.2 ENOB at low/Nyquist frequencies with SFDR > 60dB up to a 5GHz bandwidth, all within a power budget of only 350mW. As such, this ADC combines the highest effective resolution with superior linearity at the widest bandwidth and exceptionally low power consumption.

A single-channel smartphone ADC exploiting multi-bit pipelined stages and background calibration for high linearity, bandwidth, and record power efficiency

To accommodate beyond-5G connectivity at the user end, imec introduces a single-channel mobile handset ADC that leverages multi-bit pipelined stages based on ring amplification.

Joris Van Driessche: “While the multi-bit approach is known to offer several advantages, such as high linearity, bandwidth, and power efficiency, it also presents challenges. Our implementation addresses these through the use of background calibration to calibrate DAC mismatch and inter-stage gain.”

Imec’s handset ADC achieves a 10.91 ENOB and 81dB SFDR at 1GS/s, while consuming only 17.8mW – resulting in a Walden FoM of 9.2 fJ/conv.-step. With these specifications, it sets a new standard for power efficiency.

Open to licensing agreements

“With these ADCs, both of which are available for licensing, we are introducing two key building blocks for enabling beyond-5G communications. Our next goal is to develop base station ADCs that support FR3 frequencies (6 to 20GHz) while maintaining high linearity and low power consumption, using advanced sub-5nm CMOS nodes,” concluded Joris Van Driessche.

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About imec

Imec is a world-leading research and innovation center in nanoelectronics and digital technologies. Imec leverages its state-of-the-art R&D infrastructure and its team of more than 5,500 employees and top researchers, for R&D in advanced semiconductor and system scaling, silicon photonics, artificial intelligence, beyond 5G communications and sensing technologies, and in application domains such as health and life sciences, mobility, industry 4.0, agrofood, smart cities, sustainable energy, education, … Imec unites world-industry leaders across the semiconductor value chain, Flanders-based and international tech, pharma, medical and ICT companies, start-ups, and academia and knowledge centers. Imec is headquartered in Leuven (Belgium), and has research sites across Belgium, in the Netherlands and the USA, and representation in 3 continents. In 2023, imec's revenue (P&L) totaled 941 million euro.

Further information on imec can be found at www.imec-int.com.

Imec is a registered trademark for the activities of imec International (IMEC International, a legal entity set up under Belgian law as a “stichting van openbaar nut”), imec Belgium (IMEC vzw supported by the Flemish Government), imec the Netherlands (Stichting IMEC Nederland supported by the Dutch Government),  imec Taiwan (IMEC Taiwan Co.), imec India (IMEC India Private Limited), imec San Francisco (IMEC Inc.) and imec Florida (IMEC USA Nanoelectronics Design Center Inc.).