Integrated RF Transmitter Front-End for Frequency Reconfigurable Antenna Clusters

During recent years, the next generation integrated RF transceivers have continuously come up with stringent user demands and related arduous design challenges. The major requirements of wideband spectrum coverage and higher data rates have been achieved with frequency agile multiantenna systems. However, the system complexity that has resulted from such systems has created challenges for the interfacing hardware community: RF integrated circuit (IC) design in search of compact and efficient on-chip solutions needed to drive multiantenna systems. This dissertation presents advances related to an RF transmitter front-end for the sub-6 GHz and Ka-band, with special focus on the driving and tuning of frequency reconfigurable antenna clusters. Specifically, this work addresses the antenna cluster tuning concept from the implementation perspective, and provides an integrated transmitter front-end design which can tune the antenna cluster frequency response with only weighted signal generation. This unique concept developed at Aalto University, eliminates the required on-chip/off-chip matching components residing at the transmitter and antenna interface. The research work is demonstrated with one transmitter IC implementation and five peer-reviewed scientific publications. In the context of integrated transmitter front-end design, this thesis focuses on the replacement of typical tuning solutions based on discrete electronics for frequency-agile antenna. The antenna prototypes used in this work have been provided by the Radio group at Aalto University, Finland. The transmitter IC fabricated in a 28-nm CMOS technology, provides a robust on-chip weighted signal generation for two antenna prototypes: Firstly, the prototype demonstration in an anechoic chamber has validated the antenna tuning concept with a four-monopole cluster driven with the transmitter IC. This prototype provides antenna cluster tuning of across a wideband from 1. 5 GHz to 5 GHz without using any tuning components. Afterwards, the experimental verification was extended to investigate a modulated signal transmission feature. Also, the design optimization case study is presented from a scaling perspective which also addresses the challenges at the TX and antenna interface. Finally, the same transmitter IC verified the operation of another antenna cluster prototype consisting of 8 elements operating as an MIMO for the first time from the 0.5 GHz to 4.5 GHz spectrum along with an envelope correlation coefficient residing below 0.4. The second transmitter front-end study has been conducted for Ka-band (26.5 GHz- 40 GHz applications where the switched-mode power amplifier topology named switched-capacitor power amplifier topology operation is analyzed and studied for the first time. In particular, the operation at 30 GHz reveals that the simulation with foundry device models can provide an output power of 18.6 dBm with a drain efficiency of 20%, and the OFDM-modulated signals of bandwidth 100 MHz and 400 MHz result into adjacent channel leakage ratio of -34.4 dB and -32.8 dB respectively.