Nano-light-emitting-diodes based on InGaN mesoscopic structures for energy saving optoelectronics

in Applied Physics Letters (2016), 109

Vertically integrated III-nitride based nano-LEDs (light emitting diodes) were designed and fabricated for operation in the telecommunication wavelength range in the (p-GaN/InGaN/n-GaN/sapphire) material ... [more ▼]

Vertically integrated III-nitride based nano-LEDs (light emitting diodes) were designed and fabricated for operation in the telecommunication wavelength range in the (p-GaN/InGaN/n-GaN/sapphire) material system. The band edge luminescence energy of the nano-LEDs could be engineered by tuning the composition and size of the InGaN mesoscopic structures. Narrow band edge photoluminescence and electroluminescence were observed. Our mesoscopic InGaN structures (depending on diameter) feature a very low power consumption in the range between 2 nWand 30 nW. The suitability of the technological process for the long-term operation of LEDs is demonstrated by reliability measurements. The optical and electrical characterization presented show strong potential for future low energy consumption optoelectronics. [less ▲]

An adaptive biasing method for SRD comb generators

in 2016 German Microwave Conference (GeMiC) (2016)

This paper presents an adaptive biasing method for step recovery diode based comb generators which are controlled by a software routine. The aim is to provide the maximum possible harmonic output power ... [more ▼]

This paper presents an adaptive biasing method for step recovery diode based comb generators which are controlled by a software routine. The aim is to provide the maximum possible harmonic output power for a given configuration and different input frequencies during input power variation. This increases the usefulness of comb generators as harmonic phase reference sources for non-linear VNA measurements in the millimeter wave range. The effects are studied on a SRD comb generator which is able to generate -30...-20 dBm harmonics in the 50 to 60 GHz range when wideband terminated. It is shown that depending on the combination of input power and frequency, different bias level behaviors for maximum harmonic output power over frequency exist. Data for maximum power level bias is provided for output frequencies up to 60 GHz. Additionally the effect of subharmonic comb frequency generation is demonstrated. [less ▲]

A new Single-phase PLL based on the input voltage magnitude estimation

Scientific Conference (2015, December 17)

Many automatic control applications such as wide scale power grid management and local power conditioning rely on the fast and accurate detection of the voltage signal phase and amplitude. These ... [more ▼]

Many automatic control applications such as wide scale power grid management and local power conditioning rely on the fast and accurate detection of the voltage signal phase and amplitude. These information are almost all the time given by the Phase –locked Loop (PLL) systems and can be single-phase or three-phase and have many different structures. Many single-phase PLLs core structure are based on the regulation to zero of the voltage direct component in the rotating d-q frame obtained through the Park-transform. Their accuracy and dynamic rely on how quick and accurate the second voltage’s component in the static α-β frame is estimated. This paper presents a new single-phase PLL structure, also based on the same core structure as described before, but implementing a novel voltage β-component generation. A brief review of some single-phase PLLs is made, then the proposed novel PLL structure is detailed and its performance is compared with that of the other PLL’s taking into consideration the following signal disturbances: amplitude variations, phase step variation and frequency fluctuations as well as harmonic distortion. [less ▲]

Ultra-Broadband Bow-tie Antenna

in NNGT International Journal on Networking and Communication (2015), 4

An ultra-broadband bow-tie with a VSWR < 2 from 5 to 60 GHz is revealed. The bow-tie antenna shows frequency independence properties and resonates periodically at multiples of its resonance frequency of 7 ... [more ▼]

An ultra-broadband bow-tie with a VSWR < 2 from 5 to 60 GHz is revealed. The bow-tie antenna shows frequency independence properties and resonates periodically at multiples of its resonance frequency of 7.7 GHz with the return loss always less than -10 dB. The antenna is linearly polarized and has a maximum directivity of 6 dBi in both the elevation and azimuth planes in the farfield. The antenna is a symmetrical design with straight ends and a flare angle of 90°. It is a simple metal layer on top of a substrate layer which is fed on the metal layer right at the center with closely spaced coplanar striplines. The flare angle and the straight-end of the bow-tie antenna are varied and the 90° straight-end bow-tie antenna is compared with three other bow-tie antennas with flare angle of 60° and round-ends. All four bow-tie antennas have a low VSWR. The E-fields, H-fields and impedance plots of the ultra-broadband bow-tie antenna are shown. The impedance plot is in fact the impedance of frequency independent antennas of 189Ω or 60π across all frequencies. [less ▲]

A Novel Stacked Slotted Bow-Tie Antenna Element at 11.7 GHz

in NNGT International Journal on Networking and Communication (2015), 4

This paper reveals a novel stacked slotted bow-tie antenna element with a large bandwidth resonating at 11.7 GHz for satellite TV broadcasts. The simple, cost effective antenna is built on common ... [more ▼]

This paper reveals a novel stacked slotted bow-tie antenna element with a large bandwidth resonating at 11.7 GHz for satellite TV broadcasts. The simple, cost effective antenna is built on common dielectrics and is a layered version of the popular patch antenna. It is shaped in a bow-tie and converted into the slotted version in order to increase the antenna radiating surface. The dual polarized antenna element offers a large directivity of 7.2 dBi in the farfield direction. It is terminated with a coplanar waveguide feedline which is ideal to preserve its large bandwidth in an antenna array configuration. In order to appreciate its results and its design simplicity, a comparison of its S-parameters, radiation patterns, E-fields and H-fields are made with five other popular elements at the center frequency of 11.7 GHz. [less ▲]

Numerical study of high impedance T-match antennas for terahertz photomixers

in Optical and Quantum Electronics (2015), 47

This paper outlines an efficient numerical method to design terahertz photomixers. The simulations are benchmarked using measured power levels from results published in the literature. Next, the method is ... [more ▼]

This paper outlines an efficient numerical method to design terahertz photomixers. The simulations are benchmarked using measured power levels from results published in the literature. Next, the method is applied to two new photomixer designs based on the high impedance T-match antenna with bias supply DC-blocking structures for either a uniplanar layout or amultilayer structure for improved device reliability. Manufacturability is favoured by avoiding the use of airbridges, substrate thinning or under-etching. The estimated output power of the improved design is 9.0μW, which is an improvement of three times over the reference photomixer. [less ▲]

Distributed Harmonic Compensation for Power Quality in Smart Grids

in Cahier Scientifique - Revue Technique Luxembourgeoise (2014)

It is now well known that the quality of electric power is a key factor for the electricity service. It defines how good the characteristics (amplitude and frequency) of the supplied power meet the rated ... [more ▼]

It is now well known that the quality of electric power is a key factor for the electricity service. It defines how good the characteristics (amplitude and frequency) of the supplied power meet the rated ones. Voltage dip (or sag) and swell, short and long interruptions, voltage spike, under and over voltage, harmonic distortion, voltage unbalance are the common power quality problems. Among these last, the harmonics issue is getting more and more important over the last decades and this trend will surely continue its race. This is essentially due to the widespread use of electronic components in electric equipment: it changes the nature of the electric loads from linear to non-linear and makes them, on the one hand, responsible for the harmonics generation in the power grid but very sensitive to the power quality problems on the other hand. [less ▲]

Novel Double-Level-T-Gate Technology

in Conference Proceedings The 10th International Conference on Advanced Semiconductor devices and Microsystems (2014, October)

We developed a novel double-level-T-gate technology based on wet etching of a metal gate interlayer. With the help of this technological process we prepared T-gate feet with widths as small as 200 nm. The ... [more ▼]

We developed a novel double-level-T-gate technology based on wet etching of a metal gate interlayer. With the help of this technological process we prepared T-gate feet with widths as small as 200 nm. The major advantage of our process is its use of only standard optical lithography. It allows the fabrication of 100 nanometer size T-gates for transistors. High electron mobility transistors (HEMTs) were fabricated on an AlGaN/GaN/sapphire material structure with an original gate length Lg of 2 μm. Their cutoff frequency of 6 GHz was improved to 60 GHz by etching the gate to a 200 nm length double T-gate contact. [less ▲]

Polarization shift keying over satellite - Implementation and demonstration in Ku-band

in Advanced Satellite Multimedia Systems Conference and the 13th Signal Processing for Space Communications Workshop (ASMS/SPSC), 2014 7th (2014)

Polarization Shift Keying is a digital modulation method using the state of polarization of an electromagnetic wave as the signalling quantity. The technique comes from fibre communications, where the ... [more ▼]

Polarization Shift Keying is a digital modulation method using the state of polarization of an electromagnetic wave as the signalling quantity. The technique comes from fibre communications, where the channel offers two orthogonal states of polarization. This paper develops on the idea to adapt this technology to satellite communications, where comparable channel conditions exist. For this purpose, a digital Polarization Shift Keying transceiver was implemented on programmable logic. Detection performance of the modem was measured in different set-ups with thermal noise and non-linear distortion and the results compared to simulations. Finally, the implemented system was used to demonstrate a 16-state Polarization Shift Keying link over commercial satellite in Ku-band. [less ▲]

Highly Transparent Conducting Polymer Top Contacts for Future III–Nitride Based Single Photon Emitters

in Japanese Journal of Applied Physics (2013), 52