Research Projects

Due to the massive spectrum congestion at cellular frequencies below 6 GHz, 5G millimeter-wave (mm-wave) new radio (NR), covering 26-52 GHz, is emerging as a key enabling technology due to the promise of higher bandwidths and directional communication manifested through compact phased-array beamforming transceivers. However, high path loss at mm-wave frequencies and absorption by terrestrial objects like buildings, trees etc. has led to slow and limited adoption – furthermore, mm-wave 5G has been shown to work best in dense cell networks with a link length of less than a few hundred metres. 5G Fixed Wireless Access (FWA) has emerged as one of the most viable uses of 5G mm-wave technology. With channel bandwidths of up to 800 MHz, 5G FWA enables high-capacity, low-cost fiber-like internet speeds to homes/users in rural areas with last-mile connectivity challenges. In fact, leading Indian Telecom providers have already purchased spectrum in the 26 GHz mm-wave bands (n257/n258 covering 24-29.5 GHz) citing FWA as the most likely immediate use-case for 5G mm-wave. To address the urgent need for indigenous radio technology at mm-wave frequencies, accelerated research and development is therefore crucial. Mm-wave communication links are established through line-of-sight directional beams created through large-aperture phased-array beamforming/beamsteering systems where an array of wireless transmitters (Tx) or receivers (Rx) with adjustable delays are used to create complex electromagnetic interference patterns in space. Silicon-based phased arrays (operating below 50 GHz) exploiting innovative RF circuit techniques have emerged as the key enabling technology to realize low-cost and power-efficient implementations. This proposal will develop new architectures using a class of filters known as transformer-based coupled-resonators to realize Tx/Rx building blocks like LNAs, PAs, quadrature-hybrids (QH) and phase-shifters. In addition, these coupled-resonator filters will be explored for creating RF notch filters and implementing LO distribution circuits – applications for which no prior art currently exists. A key differentiator for these phased-array architectures would be compactness – beamforming transceivers with NxN elements can become prohibitively large requiring expensive and modular multi-chip solutions. To validate these ideas, a 4-element bidirectional 26-GHz beamforming transceiver front-end (covering 24-29 GHz) will be designed and taped-out in a commercial CMOS technology. Extensive continuous-wave (CW) as well as modulated-signal characterization of the chip will be performed. If successively demonstrated, this technology will have the potential to be licensed through US/India patents and can attract further funding to develop higher-order beamforming systems capable of being validated through complex over-the-air measurements.