When integrated into an electrical-balance duplexer (EBD), it enables FDD duplexing with antennas in real-world environments, paving the way to high-performance, low-power, low-cost solutions for mobile communication.
An electrical balance duplexer is a tunable RF front-end concept that seeks to address several key challenges of 4G and 5G mobile systems. It balances an on-chip tunable impedance, the so-called balance network, with the antenna impedance, to provide transmit-to-receive (TX-to-RX) isolation and avoid unwanted frequency components in the received signal. It is a promising alternative to the fixed frequency surface-acoustic wave (SAW) filters implemented in today’s mobile phones as more and more SAW duplexers would be needed to support the ever growing amount of bands adopted by operators, increasing size and cost of these devices. Unlike filter-based front-ends, electrical-balance duplexers provide signal cancellation, which could help enable in-band full-duplex for double capacity and increased network density, among other benefits, for next-generation standards.
Imec and VUB’s dual-frequency balance network is the first FDD balance network that allows balancing the on-chip tunable impedance profile with the impedance profile of an antenna at two frequencies, simultaneously. This is crucial, because in real-world situations, the frequency-dependent impedance of an antenna varies over environmental conditions and limits the achievable isolation bandwidth. The balance network can generate, for any LTE band within 0.7-1GHz, a simultaneous transmit-frequency impedance and receive-frequency impedance to provide high TX-to-RX isolation at both frequencies. It is fabricated in a 0.18µm partially depleted RF SOI CMOS technology, which allows it to better withstand the large voltages present in the EBD during full-power TX operation. The active area of the balance network, which consists of 19 switched capacitors and 10 inductors, is 8.28mm2. The balance network is tuned by an in-house developed custom algorithm, which can optimize the tuning codes of all 19 capacitor banks using only the isolation at the TX and RX frequencies as input.
These results were presented at this month’s IEEE International Solid-State Circuits Conference (ISSCC2016). Imec is present at Mobile World Congress 2016 (February 22-26, 2016, Flanders Investment & Trade booth, Hall 7, G71) to showcase its 5G radio technology, mm-wave communication and sensing, ultra-low power radio, sensors and IoT networks, wearable technologies for health, and IC design services.
Imec (imec.be) performs world-leading research in nanoelectronics. Imec leverages its scientific knowledge with the innovative power of its global partnerships in ICT, healthcare and energy. Imec delivers industry-relevant technology solutions. In a unique high-tech environment, its international top talent is committed to providing the building blocks for a better life in a sustainable society. Imec is headquartered in Leuven, Belgium, and has offices in Belgium, the Netherlands, Taiwan, US, China, India and Japan. Its staff of more than 2,300 people includes almost 700 industrial residents and guest researchers. In 2014, imec's revenue (P&L) totaled 363 million euro.
Imec is a registered trademark for the activities of 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, part of Holst Centre which is supported by the Dutch Government), imec Taiwan (IMEC Taiwan Co.) and imec China (IMEC Microelectronics (Shanghai) Co. Ltd.) and imec India (Imec India Private Limited).
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