Beamforming Performance in Arrays with Subarray Architectures : Modeling and Evaluation of Subarray Architectures and Beamforming Methods

Sammanfattning

This thesis studies beamforming performance in antenna arrays using subarray architectures. The work is motivated by the hardware complexity of fully digital beamforming, where each antenna element requires its own digital signal chain. Subarray architectures can reduce the amount of data and processing required, but also introduce limitations in beam-steering capability and array-pattern quality. A 64-element uniform rectangular array is modeled and evaluated using analog subarrays, digital subarrays, and a fully digital reference array. Different beamforming methods are implemented and compared, with focus on field-of-view performance and null placing capability. The results show that analog subarrays perform well close to broadside, but their performance decreases when steering further away. Digital subarrays give more flexibility since element-level weights can be changed, which makes it possible to improve the field of view and form better beams in more directions. However, the result depends strongly on how the element-level weights are chosen. For null placing, both evaluated methods can suppress interference, but the digital subarray architecture gives more robust performance over the full angular region. Overall, the work shows that digital subarrays can improve beamforming performance compared to analog subarrays, while still reducing the amount of data sent to later processing stages. They do not reach the full flexibility of a fully digital array, but provide a useful compromise between performance and implementation complexity.