ANALYSIS OF SOLAR ENERGY POTENTIAL BY REMOTE SENSING TECHNIQUES IN VARAŽDINSKA COUNTY, CROATIA

Renewable energy becomes more and more considered as energy production due to great benefits and less environmental impact then traditional energy sources. As a part of the European Union, Croatia agreed upon certain energy efficiency goal that need to be achieved during certain period. In this paper we analyse solar energy potential in northern part of Croatia, Varaždinska county. Remotely sensed data, CORINE land cover, digital elevation model, is used to perform multicriteria analysis. There are different solar panels considered: mono-crystalline silicon panels, poly-crystalline silicon panels, amorphous silicon panels, gallium arsenide panels and cadmium tellurium panels. Based on remote sensing data estimated yearly production of electric energy from solar potential could be from 8.40*107 to 2.43*1010 kWh depending on different slope of solar panels. Gallium arsenide panels shows best usability depending on slope estimated energy production is from 2.52*1010 to 7.30*1010 kW.

Gallium arsenide buffer amplifier

The circuitry of a buffer amplifier (BA) implemented on gallium arsenide n-channel field-effect transistors with a control p-n junction and gallium arsenide bipolar p-n-p transistors is considered. The results of computer simulation of the amplitude characteristics of the BA in the LTspice environment are presented. The proposed circuit solutions are recommended for use in RC filters of the Sallen Key family

Gallium arsenide buffer amplifier

The circuitry of a buffer amplifier (BA) implemented on gallium arsenide n-channel field-effect transistors with a control p-n junction and gallium arsenide bipolar p-n-p transistors is considered. The results of computer simulation of the amplitude characteristics of the BA in the LTspice environment are presented. The proposed circuit solutions are recommended for use in RC filters of the Sallen Key family

Optical Pump–Terahertz Probe Study of HR GaAs:Cr and SI GaAs:EL2 Structures with Long Charge Carrier Lifetimes

The time dynamics of nonequilibrium charge carrier relaxation processes in SI GaAs:EL2 (semi-insulating gallium arsenide compensated with EL2 centers) and HR GaAs:Cr (high-resistive gallium arsenide compensated with chromium) were studied by the optical pump–terahertz probe technique. Charge carrier lifetimes and contributions from various recombination mechanisms were determined at different injection levels using the model, which takes into account the influence of surface and volume Shockley–Read–Hall (SRH) recombination, interband radiative transitions and interband and trap-assisted Auger recombination. It was found that, in most cases for HR GaAs:Cr and SI GaAs:EL2, Auger recombination mechanisms make the largest contribution to the recombination rate of nonequilibrium charge carriers at injection levels above ~(0.5–3)·1018 cm−3, typical of pump–probe experiments. At a lower photogenerated charge carrier concentration, the SRH recombination prevails. The derived charge carrier lifetimes, due to the SRH recombination, are approximately 1.5 and 25 ns in HR GaAs:Cr and SI GaAs:EL2, respectively. These values are closer to but still lower than the values determined by photoluminescence decay or charge collection efficiency measurements at low injection levels. The obtained results indicate the importance of a proper experimental data analysis when applying terahertz time-resolved spectroscopy to the determination of charge carrier lifetimes in semiconductor crystals intended for the fabrication of devices working at lower injection levels than those at measurements by the optical pump–terahertz probe technique. It was found that the charge carrier lifetime in HR GaAs:Cr is lower than that in SI GaAs:EL2 at injection levels > 1016 cm−3.

60-GHz Half-Mode Substrate-Integrated Waveguide Bandpass Filter in 0.15-μm GaAs Technology

A compact 60-GHz on-chip bandpass filter (BPF) is presented using gallium arsenide (GaAs) technology. The miniaturization is achieved by the half-mode substrate-integrated waveguide (HMSIW) structure. Finally, a prototype of the BPF is fabricated and tested to validate the proposed idea, whose simulated and measured results are in good agreement. The measurements show that it has a center frequency at 58.6 GHz with a bandwidth of 17.9%, and the minimum insertion loss within the passband is 1.2 dB. The chip, excluding the feedings, is only about 0.38λg × 0.58λg, where λg is the guided wavelength at the center frequency.