Introduction
Our capability to handle and process low-power RF signals over the smallest possible scales is a prominent need in radiofrequency front-end circuits, especially with the emergence of 6G. We specialise in the use of switched CMOS RFIC for various applications. We are working in particular on true-time-delay circuits and circulators with applications in full-duplex front-end for next generation communications.
How it works
Very small RF circuits typically cannot offer the long time delays required in many advanced signal processing applications. Similarly, linear time-invariant CMOS circuits are constrained by wave reciprocity that force wave transmission to be symmetrical between two RF ports, allowing for back reflections and self-interferences that ultimately limit any communication system.
We are working on lifting these problematic limitations by designing temporally switched integrated RF circuits, namely circuits whose branches are sequentially switched on and off at a speed close to, or sometimes even higher than the RF signal. Such periodic switching breaks fundamental constraints dictated by size (such as the delay bandwidth product) or time-reversal (such as reciprocity), opening ways to manipulate waves over ultra small chips, such as conferring long reconfigurable delays to a signal or transmitting it in a non-reciprocal fashion, with high-isolation.
The challenge is to perform the desired task without degrading the RF performances, such as insertion loss, matching, linearity of the device and power handling and consumption. We optimise our device to operate on broadband OFDM signals for communication applications.
What we’ve done so far
We worked on an integrated circulator (CMOS 65nm technology) operating near 7GHz and have demonstrated its proper operation with up to 35dB isolation and 8dB insertion losses. We are preparing a journal publication on this chip.
We also work on a CMOS 28nm true time delay circuit with 5 bit reconfigurability between 0 and 2ns, with around 8dB insertion losses and a remarquable P1dB of 4dBm, compatible with OFDM signals of up to 1GHz bandwidth with EVM below a percent and state-of-the-art ACLR.
Involved LWE researchers
Mohammad Tavakkoli (Ph.D. student)
Zhechen Zhang (Postdoc)