RF electro-thermal modeling of LDMOSFETs for power-amplifier design

  • Akhtar S.
  • Ding X.
  • Kasick J.
  • Lee S.
  • Roblin P.
  • Strahler J.
  • Yu S.

A new approach for the electro-thermal modeling of LDMOSFETs for power-amplifier design that bypasses pulsed-lVs and pulsed-RF measurements is presented in this paper. The existence of low-frequency dispersion in LDMOSFETs is demonstrated by comparing pulsed IVs with iso-thermal IVs. The modeling technique uses iso-thermal IV and microwave measurements to obtain ...

Computing the performance of unitary space-time group codes from their character table

  • Shokrollahi A.

Multiple antennas can greatly increase the data rate and reliability of a wireless communication link in a fading environment. Their success, however, depends on the design of codes that achieve these promises. It is well known that unitary matrices can be used to design differentially modulated space-time codes. These codes ...

Writing sequences on the plane

  • Soijanin E.

The problem of arranging two-dimensional arrays of data into one-dimensional sequences comes up in image processing, color quantization, and optical and magnetic data recording. A good arrangement should enable the one-dimensional sequences to be modeled as Markov chains or shifts of finite type. Since this is not possible in general, ...

Low-power flyback converter with synchronous rectification for a system with AC power distribution

  • Barcia L.
  • Fernandez A.
  • Hernando M.
  • Sebastian J.
  • Villegas P.

IEC 1000-3-2 regulations impose a reduced harmonic content on any converter with an input power higher than 75 W. However, if the power architecture of the system is based on small on-board converters, and the total power is higher than 75 W, IEC regulations must be fulfilled although each individual ...

Thermal modeling and management in ultrathin chip stack technology

  • Bailbe J.
  • Beyne E.
  • Huan M.
  • Marco S.
  • Marty A.
  • Morante J.
  • Pinel S.
  • Tasselli J.
  • Van Hoof R.
  • Vendier O.

This paper presents a thermal modeling for power management of a new three-dimensional (3-D) thinned dies stacking process. Besides the high concentration of power dissipating sources, which is the direct consequence of the very interesting integration efficiency increase, this new ultra-compact packaging technology can suffer of the poor thermal conductivity ...

Time-sharing of compensators as a PMD mitigation approach for multichannel transmission systems

  • Moller L.
  • Sinsky J.

We study several new techniques for reducing polarization-mode disperison (PMD) induced system outage probabilities for wavelength-division-multiplexed systems. In all cases, we provide equalization of the channel(s) with the worst performance. Realizations based on shared single channel compensators are discussed.

Dependence of optically preamplified receiver sensitivity on optical and electrical filter bandwidths - Measurement and simulation

  • Pauer M.
  • Pfennigbauer M.
  • Strasser M.
  • Winzer P.

In this letter, we investigate both experimentally and by means of simulations, the dependence of receiver sensitivity on the optical filter bandwidth as well as on the bandwidth of the detection electronics for the optical noise limited direct detection case. The experiment is in good agreement with simulations employing advanced ...

The multimodulus blind equalization and its generalized algorithms

  • Dumont G.
  • Werner J.
  • Yang J.

This paper presents a new blind equalization algorithm called multimodulus algorithm (MMA). This algorithm combines the benefits of the well-known reduced constellation algorithm (RCA) and constant modulus algorithm (CMA). In addition, MMA provides more flexibility than RCA and CMA, and is better suited to take advantage of the symbol statistics ...

Estimation of the transfer function of a subscriber loop by means of a one-port scattering parameter measurement at the central office

  • Boets P.
  • Bostoen T.
  • Pollet T.
  • Rabijns D.
  • Van Biesen L.
  • Zekri M.

In order to qualify a subscriber loop for xDSL transmission, the channel capacity has to be estimated, which depends on the transfer function of the network. In this paper, a method is provided to estimate the transfer function of the subscriber loop only measuring the one-port scattering parameter at the ...

Hot phonons and Auger related carrier heating in semiconductor optical amplifiers

  • Dagens B.
  • Deveaud B.
  • Dupertuis M.
  • Emery J.
  • Fehr J.
  • Hessler T.
  • Kappei L.
  • Marti D.
  • Nomura M.
  • Salleras F.

We have directly measured the carrier temperature in semiconductor optical amplifiers (SOAs) via spontaneous emission and we demonstrate an unexpectedly high carrier temperature. The direct correlation of the temperature increase with the carrier density suggests Auger recombination as the main heating mechanism. We have developed a model based on rate ...

Quantum cascade lasers: Ultrahigh-Speed operation, optical wireless communication, narrow linewidth, and far-infrared emission

  • Bethea C.
  • Capasso F.
  • Cho A.
  • Colombelli R.
  • Gmachl C.
  • Hwang H.
  • Liu H.
  • Martini R.
  • Myers T.
  • Paiella R.
  • Sergent A.
  • Sivco D.
  • Taubman M.
  • Unterrainer K.
  • Whittaker E.
  • Williams R.

Following an introduction to the history of the invention of the quantum cascade (QC) laser and of the band-structure engineering advances that have led to laser action over most of the mid-infrared (IR) and part of the far-IR spectrum, the paper provides a comprehensive review of recent developments that will ...

QoS routing for anycast communications: Motivation and an architecture for DiffServ networks

  • Ammar M.
  • Hao F.
  • Zegura E.

Much research in QoS routing has focused on the unicast communication paradigm. However, another communication paradigm - anycasting - has grown in importance in recent years. In the anycast paradigm, one endpoint is specified and the other is selected from a set of ``equivalent{''} endpoints. An anycast service in a ...

Unified wireless access in hot-spot environment

  • Nikolaou N.
  • Zahariadis T.

Convergence, interoperability, and mobility are the major advances and factors of differentiation in 3G networks, while the inherent IP support will boost new personalized multimedia services. However, the deployment of a global all-IP wireless/mobile network is not a straightforward decision. A phased approach, focusing on ``hot-spot{''} locations with complementary wireless ...

Sensitive detection of methane and nitrous oxide isotopomers using a continuous wave quantum cascade laser

  • Baillargeon J.
  • Capasso F.
  • Cho A.
  • De Natale P.
  • Gagliardi G.
  • Gmachl C.
  • Hutchinson A.
  • Sivco D.
  • Tamassia F.

A continuous wave quantum cascade laser (QCL), operating near 8.1 mum, was used for wavelength modulation spectroscopy of methane (CH4) and nitrous oxide (N2O) stable isotopes. Several rotational transitions of (N2O)-N-14-O-16, (NNO)-N-15-N-14-O-16, (N2O)-N-14-O-18, (N2O)-N-14-O-17, (CH4)-C-13 and (CH4)-C-12 fundamental bands were detected. The noise-equivalent absorbance was measured to be less than ...

Using a wavelength-modulated quantum cascade laser to measure NO concentrations in the parts-per-billion range for vehicle emissions certification

  • Baillargeon J.
  • Capasso F.
  • Chase R.
  • Cho A.
  • Gmachl C.
  • Hutchinson A.
  • Remillard J.
  • Richert J.
  • Sivco D.
  • Weber W.

Measurements of NO concentrations at sub-ppm levels in vehicle exhaust are needed for emissions certification of future ultra-low emission vehicles. We demonstrate a wavelength-modulation, laser-based, NO detection system suitable for this purpose. A quantum cascade distributed feedback laser (QC-DFB) operating continuous wave (cw) at similar to100 K is frequency modulated ...

Nonlinear macroscopic polarization in GaN/AlxGa1-xN quantum wells

  • Cho A.
  • Menoni C.
  • Ng H.
  • Patel D.
  • Vaschenko G.

We present experimental evidence of the nonlinear behavior of the macroscopic polarization in GaN/AlxGa1-xN quantum wells. This behavior is revealed by determining the barrier-well polarization difference as a function of applied hydrostatic pressure. The polarization difference and corresponding built-in electric field in the wells increase with applied pressure at a ...

Dielectric and piezoelectric enhancement due to 90 degrees domain rotation in the tetragonal phase of Pb(Mg1/3Nb2/3)O-3-PbTiO3

  • Cheong S.
  • Koo T.

The anomalous enhancement in dielectric (epsilon>6000) and piezoelectric constant (d(33)>600 pC/N) in the tetragonal side (x=35%) of morphotropic phase boundary (MPB) has been observed in polycrystalline (1-x)Pg(Mg1/3Nb2/3)O-3-xPbTiO(3) (PMN-PT). On the other hand, x-ray peak position shifts under electric field (E) demonstrate that the intrinsic piezoelectric response becomes maximum at MPB ...

Mid-infrared (lambda approximate to 7.4 mu m) quantum cascade laser amplifier for high power single-mode emission and improved beam quality

  • Capasso F.
  • Cho A.
  • Gmachl C.
  • Sivco D.
  • Troccoli M.

A quantum cascade laser amplifier has been developed. It was used to obtain high power single-mode emission at lambdaapproximate to7.4 mum from a quantum cascade distributed feedback laser, together with enhanced beam quality. Laser and amplifier are directly coupled in a master oscillator power amplifier configuration. Peak optical powers of ...

SOP and PMD monitoring with WDM polarimeter

  • Chandrasekhar S.
  • Dutta R.
  • Moller L.
  • Westbrook P.
  • Wielandy S.

A broadband WDM polarimeter is used in online determination of the state of polarisation (SOPs) of WDM channels. Wavelength resolved SOP measurements and the degree of polarisation of a single channel indicate signal distortions which are caused by PMD, and may be applied to multi channel PMD compensation.

Simultaneously at two wavelengths (5.0 and 7.5 mu m) singlemode and tunable quantum cascade distributed feedback lasers

  • Capasso F.
  • Cho A.
  • Gmachl C.
  • Sergent A.
  • Sivco D.
  • Straub A.

Quantum cascade distributed feedback (QC-DFB) lasers based on a heterogeneous-cascade two-wavelength active waveguide core and a multisectioned cavity featuring two different Bragg gratings are demonstrated. Optimised lasers display singlemode emission at lambda similar to 5.0 and 7.5 mum simultaneously and a tunability on both modes equal to single-wavelength QC-DFB lasers.