In this work significant improvements for measurements of the radio-frequency (RF) radiation properties of small antennas have been proposed and investigated. The main focus is on electrically small antennas as used in mobile communications systems. The methods proposed and evaluated in this thesis allow the minimisation of the dimensions of measurement chambers, and the methods also allow patt...

Faculdade de Ciências e Tecnologia Departamento de Engenharia Eletrotécnica e de Computadores Mestrado Integrado em Engenharia Eletrotécnica e de Computadores por David Jorge Tiago Amoêdo In this thesis we present a balun low noise amplifier (LNA) in which the gain is boosted using a double feedback structure. The circuit is based in a Balun LNA with noise and distortion cancellation. The LNA i...

Microwave circuits embedded in a multi-layer resin PCB are demonstrated using low loss resin materials. Resin materials for microwave frequencies were compared with conventional FR-4 with respect to dielectric and conductor loss factors, which proved that losses could be reduced drastically with the low loss material and design optimizations. Baluns, switches and BPFs were designed and fabricat...

In this paper, a number of reconfigurable antennas are designed to support multiband and wideband wireless applications in different frequency bands in the range between 1 GHz and 6 GHz. The proposed designs consist of microstrip-fed two dipoles through simplified balun. By controlling the lengths of the dipoles by connecting or disconnecting slots, we are able to change the antenna operating f...

A miniaturized V-band active transmit balun suitable for direct attachment to an integrated on-chip dipole antenna is proposed in this work. The circuit is constructed using a 0.35 μm SiGe HBT bipolar process (Infineon fT / fmax=170/250 GHz) operating at 55-65 GHz is fabricated and measured. The circuit exhibits a more than 11 dB conversion gain with magnitude imbalance less than 1 dB and phase...