First-Of-Its-Kind Tunable Balance Network For Electrical Balance Duplexers Supporting LTE Bands From 0.7-1GHz

Leuven (Belgium) –– Nanoelectronics research center imec and Vrije Universiteit Brussel (VUB) present a frequency division duplex (FDD) balance network, capable of dual-frequency impedance tuning for all LTE bands in the 0.7-to-1GHz range. 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.

About imec

Imec 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. Further information on imec can be found at www.imec.be. Stay up to date about what’s happening at imec with the monthly imec magazine, available for tablets and smartphones (as an app for iOS and Android), or via the website www.imec.be/imecmagazine

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).

About VUB—Vrije Universiteit Brussel, in the heart of Europe

Over 14,200 students, representing more than 120 nationalities study at VUB to take the next step in their career. 3000 of our students – more than 21% of our student population - are international students, making our institute a vibrant and truly global one.

VUB supports more than 100 English-taught programs with both outstanding research and a modern campus. Everything you need is at your fingertips and available on-site, near Brussels' bustling city center: an extensive library, modern computer labs, state-of-the-art sports facilities, and exciting restaurants as well as interesting cultural activities, language courses and an invaluable job service.

In VUB's eight faculties, students can choose to study and explore beyond their own discipline where they can exchange experiences, cultures, ideas and values. The University's open-door policy means students build rapport with both faculty members and assistants, and staff are happy to answer student questions. Small group workshops are also in place to provide close interaction and hands-on experience.

Thanks to its expertise and location in Brussels, VUB is an ideal partner for prestigious research and education with an outlook on Europe and the world. With a research budget of EUR 86 Million, VUB covers some 2,200 publications and 24 reported inventions annually, supporting 150 research groups.

VUB is a haven for education and research, combining the best of both on American-style green campuses. It is listed in the top 200 QS World University Ranking and 251 – 275 in the Times Higher Education Ranking. The university has more than 75 cooperation contracts in 38 countries. It offers postgraduate degrees in English and awards Bachelor’s and Master’s degrees in a range of academic fields covering human sciences, life sciences and medicine, sciences and engineering. Doctorates are offered in all subjects for which the university issues academic degrees. VUB counts more than 1,800 PhD students.