Low-Power Wideband InP-Based Low Noise Amplifiers for the Square Kilometre Array Radio Telescope

The largest perceived radio astronomy project known as the Square Kilometre Array (SKA) is now being planned. This radio telescope will require a large number of antenna elements to massively increase its effective collecting area and hence achieve extremely high sensitivity. The presence of a high performance low noise amplifier (LNA) with each antenna element is essential. The main objective of this work was to develop feasible Microwave Integrated Circuit (MIC) and Monolithic Microwave Integrated Circuit (MMIC) LNA designs that meet the challenging specifications of the SKA while having the ability to be easily integrated in the receiver chain of the radio telescope. In this work accurate linear and nonlinear models have been developed for 1 gm gate length strained channel InGaAs/InAlAs/InP pHEMTs based on extensive experimental on-wafer measurements. An effective method has been devised to optimise an initial set of extracted parameters using a multiple bias point optimisation technique. Accurate predictions for device DC and RF characteristics have been achieved for both active and passive devices displaying excellent agreement between measured and modelled data. These models have been used in the design and simulation of an MMIC coplanar waveguide (CPW) LNA using an in-house InP process flow. The measured data of a high gain, very low power (< 75 mW) single-ended MMIC LNA design showing excellent match with the predicted response of the model is presented. The strategy pursued in this work has addressed not only noise figure and gain specifications of the LNA but also differential to single-ended interfaces and low-power consumption issues. While this work is focused more on exploring the potentials of MMIC LNAs based on novel in-house fabricated InGaAs/InAlAs pHEMTs in response to the challenging requirements of the SKA, parallel designs of hybrid MIC LNAs using commercially available GaAs pHEMTs have also been conducted. It is thus demonstrated that low-power, high-performance differential to single-ended LNAs can only be achieved using the custom tailored InP material system and while the commercial GaAs hybrid MIC LNA designs fulfil the low noise and high gain requirements of the SKA, it is only at the expense of a much higher power dissipation.