Highly robust microwave low-noise amplifiers

天线之后的无线电接收机的第一个组件通常是低噪声放大器（LNA）。需要将通常非常微弱的信号放大到足够高的功率水平，以忽略后续电子级的任何附加噪声。因此，LNA是一种非常敏感的低功耗元件。然而，无线电接收器通常也会接收到比预期更多的信号。如果附近有一个强大的发射器，功率水平很容易超过接收器的平均功率水平1000倍。这很容易破坏LNA。许多通信应用集成了发射机和接收机，例如雷达或卫星通信。在这些情况下，需要一个保护电路，以信号衰减为代价阻止大功率信号，从而降低整个系统的信噪比。此外，保护电路通常不能与LNA集成，系统体积大，制造成本高，可靠性可能降低。最近的文献表明，GaH-HEMT技术允许将最大输入功率从GaAs-HEMT技术的典型100 mW增加到约10 W。但必须指出的是，这一成功是基于一个相当简单的电路拓扑结构，并且到目前为止还没有发表关于鲁棒性限制因素的详细理论分析。因此，GaN LNAs坚固性的提高主要反映了器件技术的改进。这标志着这次调查的起点。基于堆叠gan - hemt的新电路拓扑有望提高最大安全输入功率，因为LNA输入处的有效击穿电压更高。但它还没有被证明，也低噪音性能是可能的，在这个概念。这种新方法，以及传统的LNA电路拓扑将从理论上进行研究，以探索和解释最大鲁棒性的限制因素。基于测量，将研究GaN hemt中的降解机制，以了解器件立即破坏水平以下的临界应力极限。本研究的目标是提出一个分析模型，在充分理解晶体管的临界应力条件的基础上优化GaN LNAs的坚固性，并通过优化电路拓扑将最大安全输入功率显著推向更高的功率水平。

The first component of a radio receiver that follows the antenna is commonly the low-noise amplifier (LNA). It is required to amplify the usually very weak signal to a power level high enough to ignore any additive noise of subsequent electronic stages. Therefore, an LNA is a very sensitive low-power component. However, a radio receiver usually also reveceives more signals than just the intended one. If a powerful transmitter is nearby, the power level easily exceeds the average receiver power level by a factor of 1000. This can easily destroy the LNA. Many communication applications integrate transmitter and receiver, for example RADAR or satellite communication. In these cases, a protection circuit is required, that blocks high-power signals at the expense of attenuating the signal, and thereby lowering the signal-to-noise ratio of the whole system. Furthermore, the protection circuit usually can't be integrated with the LNA, and the system gets bulky, more expensive in fabrication, and reliability might be reduced. It was shown in the literature recently, that GaH-HEMT technology allows to boost the maximum input powers to be increased from the typical 100 mW for GaAs-HEMT technologies to about 10 W. But it has to be stated, that this success is based on a rather simple circuit topology, and that no detailled theoretical analysis of the limiting factors regarding robustness was published so far. The improvements in ruggedness of GaN LNAs therefore mainly reflect the improvements in device technology. This marks the starting point of this investigation. A new circuit topology based on stacked GaN-HEMTs promises to improve maximum safe input powers, due to the higher effective breakdown voltage at the LNA input. But it has yet to be shown that also low noise performance is possible in this concept. This new approach, but also the traditional LNA circuit topology will be theoretically investigated in order to explore and explain the limiting factors for maximum robustness. Based on measurement, the degradation mechanisms in GaN HEMTs will be investigated in order to understand the limits of critical stress below the level of immediate destruction of the device. It is the goal of this investigation to present an analytical model to optimize the ruggedness of GaN LNAs on the basis of well understood critical stress condidtions for the transistors, and also to push the maximum safe input power significantly towards higher power levels though optimized circuit topologies.