Enhanced EIRP and Reconfigurable Polarization Antenna for Millimeter-Wave Digital Beamforming using Circular Arrays

Abstract

The move towards millimeter wave (mm-wave) frequency bands in wireless communication has been driven by the need for higher data rates. However, some of the major challenges faced with the shift to mm-wave are high free space propagation path loss and limited output power of power amplifier (PA). As a result, phased arrays have emerged as a crucial technology in delivering higher effective isotropic radiated power (EIRP) whereby numerous antenna elements, each driven by PAs, are combined over the air. To increase the overall EIRP, the number of PAs can be increased and consequently, the number of antenna elements are also increased. However, this approach results in larger array panel sizes and narrower beamwidth, which may not be suitable in certain 5th generation (5G) scenarios, such as mobile applications. The narrow beamwidth can potentially make the alignment between the transmitter and receiver difficult and result in signal degradation. Alternatively, the output power of the transmitter can be increased by utilizing multiple PA channels in conjunction with on-chip power combining. On-chip power combining techniques such as Wilkinson power combining, direct power combining, or transformer-based power combining have been widely used in the literature. However, as the number of PA channels to be combined increases, on-chip power combining becomes less feasible due to the limited Q-factor of on-chip passive components. On-antenna power combining has been proposed to use the antenna as both a radiating element and power-combining passive. Through the use of multi-feed antennas, multiple PA channels can be used to drive a single radiating element. This thesis presents a multi-feed active antenna module that offers enhanced EIRP and polarization reconfigurability operating from 37 GHz to 40 GHz. Additionally, the active antenna module is suitable for use in antenna arrays. First, the return loss of the multi-feed active antenna module is analyzed and the overall active antenna module design is optimized. Next, a short parametric study on planar circular array configuration is conducted to find an optimal antenna array design using the active antenna module. Lastly, a seven element fully-digital beamforming array using the active antenna module is proposed, capable of polarization reconfigurability operating from 37 GHz to 40 GHz.