Analysis of Millimeter-Wave Array Frontend Architectures for High EIRP: Comparing Various Beamforming and Power Combining Techniques

This paper analyzes various beamforming array antenna frontend architectures for future 6G communication systems, focusing on enabling high-data-rate global connectivity over long distances. The analysis is centered on the use of upper millimeter-wave frequency bands, specifically between 75 and 110 GHz, to achieve the targeted performance. Key challenges include efficient millimeter-wave RF power generation in the array transmitter and accurate beam steering and tracking through antenna design. We build on state-of-the-art research to compare different beamforming array designs, including: (i) conventional active phased arrays with full beamforming control and on-element power combining, (ii) switched beam modular arrays with spatial power combining, and (iii) architectures that integrate joint power combining and beamforming through quasi-optical networks. To support our analysis, we use simplified models of array transmitters, incorporating literature data and based on our design experience with commercial (PIN-)pHEMT (Al)GaAs processes. To illustrate these concepts, we present a case study of a 50 dBi reflector antenna fed by a phased-array feed designed for W-band backhaul links. The design curves obtained from our analysis show the effective isotropic radiated power (EIRP) of the frontend as a function of the number of combined PAs in different array architectures, providing insights into the trade-offs involved in achieving optimal performance with minimal energy consumption.