Characterization of Transmission Losses

In this paper, characterizing transmission losses according to their origin is carried out. Transmission loss is decomposed into three components. The first is due to the current flow from generators to loads. The second is due to the circulating current between generators. The third represents the contribution of network structure and controls to increasing or decreasing transmission losses. Analytical proofs of the proposed loss decomposition are presented along with methods of allocating each component to the parties contributing to it. Illustration on simple dc and ac systems is presented. Results of application of the proposed method compared with other methods are also presented.

Optical transmission of periodic annular apertures in metal film on high-refractive index substrate: The role of the nanopillar shape

The influence of annular aperture parameters on the optical transmission through arrays of coaxial apertures in a metal film on high refractive index substrates has been investigated experimentally and numerically. It is shown that the transmission resonances are related to plasmonic crystal effects rather than frequency cutoff behavior associated with annular apertures. The role of deviations from ideal aperture shape occurring during the fabrication process has also been studied. Annular aperture arrays are often considered in many applications for achieving high optical transmission through metal films and understanding of nanofabrication tolerances are important. (C) 2010 American Institute of Physics.

2.4 GHz high-efficiency power-combining Class-E amplifier with transmission-line harmonic traps

Experimental assessments of the modified power-combining Class-E amplifier are described. The technique used to combine the output of individual power amplifiers (PAs) into an unbalanced load without the need for bulky transformers permits the use of small RF chokes useful for the deployment in the EER transmitter. The modified output load network of the PA results in excellent 50 dBc and 46 dBc second and third-harmonic suppressions, dispensing the need for additional lossy filtering block. Operating from a 3.2 V dc supply voltage, the PA exhibits 64% drain efficiency at 24 dBm output power. Over a wide bandwidth of 350 MHz, drain efficiency of better than 60% at output power higher than 22 dBm were achieved. © 2010 IEICE Institute of Electronics Informati.

Distributed passive intermodulation generation in coplanar waveguide transmission lines

A phenomenology of distributed passive intermodulation generation in coplanar waveguide transmission line is presented. The theoretical analysis is based upon the generalised nonlinear transmission line model, which accounts for the coupling of two propagating modes. The case of weak substrate nonlinearity is considered and the model is given qualitative verification through the mapping of passive intermodulation products generated in coplanar waveguide fabricated on a commercial laminate. Implications for future research are discussed. © 2012 IEEE.

MALTS: A Tool to Simulate Lorentz Transmission Electron Microscopy From Micromagnetic Simulations

Here we describe the development of the MALTS software which is a generalized tool that simulates Lorentz Transmission Electron Microscopy (LTEM) contrast of magnetic nanostructures. Complex magnetic nanostructures typically have multiple stable domain structures. MALTS works in conjunction with the open access micromagnetic software Object Oriented Micromagnetic Framework or MuMax. Magnetically stable trial magnetization states of the object of interest are input into MALTS and simulated LTEM images are output. MALTS computes the magnetic and electric phases accrued by the transmitted electrons via the Aharonov-Bohm expressions. Transfer and envelope functions are used to simulate the progression of the electron wave through the microscope lenses. The final contrast image due to these effects is determined by Fourier Optics. Similar approaches have been used previously for simulations of specific cases of LTEM contrast. The novelty here is the integration with micromagnetic codes via a simple user interface enabling the computation of the contrast from any structure. The output from MALTS is in good agreement with both experimental data and published LTEM simulations. A widely-available generalized code for the analysis of Lorentz contrast is a much needed step towards the use of LTEM as a standardized laboratory technique.

Amplitude modulated signal transmission through a phase conjugating lens

Free space transmission of an on-off modulated sinusoidal signal through a phase conjugating lens (PCL) is theoretically examined using a combined time/frequency domain approach. The on-off keyed (OOK) signal is generated by a dipole antenna located in the far-field zone of the lens. The PCL consists of a dual layer of antenna elements interconnected via phase conjugating circuitry. We demonstrate that electromagnetic interference between antenna elements creates spatially localised areas of good-quality reception and zones where the signal is significantly denigrated by interference. Next, it is shown that destructive interference and packet desynchronisation effects critically depend on bit rate. It is also shown that a circular concave lens can be used to produce high-quality signal reception in a given direction while suppressing signal reception in all other directions. The effect that the bandwidth of the phase conjugating unit has on the transmitted signal properties for the cases of high and low bit rate OOK modulation are studied and a signal quality characterisation scheme is proposed which uses cross-correlation. The results of the study yields understanding of the performance of phase conjugating arrays under OOK modulation. The work suggests a novel approach for realising a secure communication wireless system.

Reflection and Transmission at a Phase Discontinuous Interface

In this paper we extend the derivation of the modified form Snells's law that occurs when an additional phase profile is introduced at the material interface. We show that this permits electromagnetic (EM) beam steering, negative refraction and retrodirective action opportunities for such engineered surfaces even if they are immersed in a uniform dielectric. Simple expressions for the retrodirected and negatively refracted beams are derived along with the propagation conditions that occur at the boundary interface inside the critical angle range. It is also demonstrated how the transmission and reflected power levels are affected by the additional phase taper introduced at the surface.