Research Projects

This project presents the combination of research as well as technology development activities. The overall objective is to explore various schemes to design ultra wideband 5-18 GHz PA in Monolithic Microwave Integrated Circuit (MMIC) technology. The targeted output power is 8-10 W. The proposal will investigate design feasibility for broadband switch-mode power amplifiers (SMPA) operating in continuum of classes such as Class B/J and E/F. Such designs require precise control of harmonics to shape the output current and voltage waveforms for minimum power dissipation across the device. In particular, an inappropriate voltage waveform may results into high voltage swing as well as impractical loads (non-foster loads with anti-clockwise impedance trajectory in Smith chart) at extrinsic plane resulting into unfeasible output matching. The proposal explores a specific engineering approach for circumventing these problems resulting into extraction of feasible design space with wide bandwidth and high efficiency operation. Due to unavailability of explicit information of device parasitic by MMIC foundries, the research will also involve device characterization and parasitic extraction for applying appropriate waveform engineering at current generator plane of Gallium nitride (GaN) High-electron-mobility transistor (HEMT) device. Apart from harmonic control, these parasitic reactance can also be useful in exploring the usability of travelling wave power amplifier (TWPA) which are also known as distributed amplifiers for ultra-wideband applications. This topology can overcome the limitations of finite gain-bandwidth by adding the individual transconductances of HEMTs while absorbing their parasitic capacitances into the transmission lines combining these devices. Moreover, the high power applications require device combining with efficient and broadband power combiners. The proposal will also investigate combiner with biasing and matching embedded into its topology. The project will lead to well-thought-out design methodologies for broadband and high efficiency MMIC PA design along with identification of an appropriate technology for device combining and parasitic absorption in TWPA. The key deliverables are in terms of know-how generation for broadband GaN MMIC based PA design covering 5-18 GHz frequency band. This will lead to development of prototypes in GaN MMIC technology ready for product development. This anticipated end-product is under restricted technology requiring import licenses. Therefore, the product development in this area provides sustainability in the area of strategic development. Astra microwave products limited which is industry partner in this project can take up the further product development activities.

1

Three MMIC Designs have been attempted for realizing 5-18 GHz GaN MMIC power amplifier using commercial GaN MMIC fabrication process. These MMIC designs are primarily focused on the two topologies: (a) Reactively Matched PA with corporate combining, (b) Traveling Wave Power Amplifier (TWPA). DESIGN 1 utilizes a non-uniform TWPA design is carried out for implementing the C-Ku band MMIC PA. A 3-stage TWPA is designed and simulated using a commercial 0.25-?m GaN HEMT process PDK.

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3

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