HEMT-based Wideband Low-noise Amplifiers for Laser Rangefinding and Radio Astronomy Applications

This thesis describes the design, realization and characterization of low-noise amplifiers for different application, all based on the use of a High Electron Mobility Transistor (HEMT) device as key element for obtaining the desired level of noise. The work is divided in two parts, each describing a research project in the field of HEMT-based, low-noise amplifier design. The first project described, in collaboration with Vectronix AG (Heerbrugg, Switzerland), a leading company in the optoelectronic field providing state-of-the-art laser rangefieders (LRF), concerns the design, realization and characterization of a wideband low-noise transimpedance front-end for laser rangefinding portable devices. A DC – 20MHz, APD-based receiver with equivalent input current noise (EICN) density lower than 400fA/√Hz in the whole bandwidth has been designed, realized and tested, both in laboratory and on-the-field within Vectronix LRF binoculars, showing very good results and will be implemented in next-production LRFs by Vectronix. The work reports also the preliminary results obtained in the design (still on-going) of a pin-based receiver with EICN lower than 25fA/√Hz. The second project, carried out during a six-month stay at Universidad de Cantabria (Santander, Spain) within the Radio Astronomy Receiver Group, concerns the design realization and characterization of cryogenic broadband intermediate frequency low-noise amplifiers (LNAs) which find application in millimeter and sub-millimeter radio astronomy receivers aimed at the study of the Cosmic Microwave Background Radiation (CMBR). Three LNAs have been realized and tested, both at room and cryogenic temperature. All are hybrid amplifiers based on a commercial InGaAs HEMT, which represent a low-cost alternative to the InP HEMTs exploited in state-of-the-art LNAs for such applications. Two LNAs cover the frequency range 4 – 8 GHz (C-band, LNA1 and LNA2) while the third covers the range 4 – 12 GHz (C- to X-band, LNA3). LNA1 proved able to reach noise temperatures comparable with state-of-the-art InP LNAs, while finalization of LNA3 is still on-going.