At the 'IEEE Symposium on VLSI Technology & Circuits', which took place in Hawaii from June 16 to 20, 2024, imec presented two new ADCs for base stations and cell phones. The base station ADC supports RF sampling, operates in multiple frequency bands and combines high resolution and linearity with low power consumption.
The single-channel ADC for cell phones achieves outstanding energy efficiency through multi-bit pipeline stages and background calibration. According to imec, the ADCs represent an important step towards Beyond 5G solutions, including cloud-based AI and augmented reality apps. Beyond 5G technology requires a transformation of operators' mobile networks, particularly in the development of transceivers - and the underlying ADCs - both at the base station and at the terminal. Key requirements for transceivers include small footprint and low power consumption, as well as support for features that increase network capacity, such as multi-band operation and massive MIMO (Multiple Input Multiple Output Antennas). With the introduction of two new ADCs, imec is taking further steps towards meeting future requirement profiles, says Program Manager Joris Van Driessche. In contrast to conventional base station devices, which implement multi-band operation with a separate transceiver for each frequency band, imec's new RF sampling ADC, which covers all bands below 5 GHz, works across several frequency bands, thus saving space and power consumption. To help base station radios cope with interference from other radio signals, Van Driessche says the ADC uses built-in broadband linear signal buffering to achieve a higher Effective Number of Bits (ENOB) than comparable systems - without the need for digital engines to correct for non-linear distortion. To support Beyond 5G connectivity on the user side, imec introduces a single-channel ADC for cell phones that utilizes multi-bit pipeline stages based on ring amplification. While the multi-bit approach is known to offer several advantages, such as high linearity, bandwidth and power efficiency, it also brings challenges. These challenges are addressed by imec's new design through the use of background calibration to calibrate the DAC mismatch and gain between stages. Both ADCs are available for licensing.
