About the session
With the substantial growth of various 5G applications, massive multiple-input and multiple-output (MIMO) antenna arrays have been paid progressively increasing attention to. Due to a huge amount of antenna elements (over hundreds) in base station, the integrated system implementations become a preferred cost-effective option.
In current practice, in order to make sure the mismatching of antenna array (can be partly due to mutual coupling) has no effect on power amplifiers (PAs), ferromagnetic isolators exhibiting high isolation and power-handling capability are often implemented between antenna array and power amplifiers. However, they are unfavorable due to integration-incompatible and bulky.
In the literature, there are three different methods in progress to realize the PA-antenna integrated system. 1) The first one is using active isolators but they are severely limited in their linearity, noise performance and isolation bandwidth. 2) The second method achieves non-reciprocity and builds isolators without ferromagnetic materials by exploiting time varying circuits, but it has a limited power handling. 3) The third method is removing the isolator components, which overcomes the aforementioned challenges in designing integrated isolators. We will focus on this method in this presentation. When removing the isolators, in order to protect the power amplifier from unexpected situations (such as open-circuit output ports and high power injected from the output ports), a feedback loop protection circuit is often used on power amplifier bias, which can be easily implemented on a monolithic power amplifier die without any extra area. In the absence of the isolators, the mutual coupling between antenna elements will lead to significant load-pull issues facing power amplifiers. However, few works talk about the system performance without isolators.
In this presentation, we analyze the end-to-end system performance without isolators, which involves wireless channel model, pre-coding, power amplifier load-pull effect and its reliable working zone, as well as antenna array. By optimizing the pre-coding matrix, high efficient system with maximum capacity/Joule can be achieved.
