Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 6 Articles
Microwave processing of materials has been found to deliver enormous advantages over\nconventional processing methods in terms of mechanical and physical properties of the materials.\nHowever, the non-uniform temperature distribution is the key problem of microwave processing,\nwhich is related to the structure of the cavity, and the placement and physical parameters of the\nmaterial. In this paper, a new microwave cavity structure with a sliding short based on phase-shifting\nheating is creatively proposed to improve the temperature uniformity. An electronic mathematical\nmodel based on the Finite Element Method (FEM) is built to predict the temperature distribution.\nMeanwhile, a new computational approach based on the theory of transformation optics is first\nprovided to solve the problem of the moving boundary in the model simulation. At first, the\nexperiment is carried out to validate the model, and heating results from the experiment show\ngood agreement with the modelââ?¬â?¢s prediction. Based on the verified model, materials selected\namong a wide range of dielectric constants are treated by stationary heating and phase-shifting\nheating. The coefficient of variation (COV) of the temperature and temperature difference has\nbeen compared in detail between stationary heating and phase-shifting heating. A significant\nimprovement in heating uniformity can be seen from the temperature distribution for most of\nthe materials. Furthermore, three other materials are also treated at high temperature and the\nheating uniformity is also improved. Briefly, the strategy of phase-shifting heating plays a significant\nrole in solve the problem of non-uniform heating in microwave-based material processing. A\n25%ââ?¬â??58% increase in uniformity from adapting the phase-shifting method can be observed for the\nmicrowave-processed materials....
A simple equation for heat spreading angle is derived which is useful for cases with a single layer\nthermal spreader. The derivation starts with Fourier�s heat transfer law. Heat spreading in two\ndimensions is then introduced which results in a quadratic equation relative to spreading angle.\nThe result is a closed form equation for heat spreading angle. Calculations using the equation are\ncompared to 3D finite element simulations which show agreement acceptable for most practical\napplications and over a wide range of physical dimensions and thermal conductivities. A normalized\ndimensional parameter is defined which is used to generate a curve fit equation of the\nspreading angle. A three step procedure is then presented which allows the calculation of the\nspreading angle and temperature rise in the thermal spreader. The result has application for initial\ncalculations of temperature rise in microwave hybrid modules and electronic packages such\nas heat sinks for high power amplifiers. This is because it is common for these types of modules\nand packages to use a single layer heat spreader in copper-tungsten (CuW) or copper-molybdenum\n(CuMo) connected to a cold plate. An important benefit of this method is that it allows microwave\nhybrid designers and high power amplifier packaging engineers a method to quickly\nperform trade studies to determine the maximum mounting temperature for integrated circuits....
For satisfactory traffic management of an intelligent transport system, it is vital that traffic\nmicrowave radar detectors (TMRDs) can provide real-time traffic information with high accuracy. In\nthis study, we develop several information-aided smart schemes for traffic detection improvements\nof TMRDs in multiple-lane environments. Specifically, we select appropriate thresholds not only for\nremoving noise from fast Fourier transforms (FFTs) of regional lane contexts but also for reducing\nFFT side lobes within each lane. The resulting FFTs of reflected vehicle signals and those of clutter\nare distinguishable. We exploit FFT and lane-/or time stamp-related information for developing\nsmart schemes, which mitigate adverse effects of lane-crossing FFT side lobes of a vehicle signal.\nAs such, the proposed schemes can enhance the detection accuracy of both lane vehicle flow and\ndirectional traffic volume. On-site experimental results demonstrate the advantages and feasibility of\nthe proposed methods, and suggest the best smart scheme....
An inherent element of research and applications in photonics is a beam of light. In magnonics, which\nis the magnetic counterpart of photonics, where spin waves are used instead of electromagnetic\nwaves to transmit and process information, the lack of a beam source limits exploration. Here, we\npresent an approach enabling generation of narrow spin wave beams in thin homogeneous nanosized\nferromagnetic films by microwave current. We show that the desired beam-type behavior can be\nachieved with the aid of a properly designed coplanar waveguide transducer generating a nonuniform\nmicrowave magnetic field. We test this idea using micromagnetic simulations, confirming numerically\nthat the resulting spin wave beams propagate over distances of several micrometers. The proposed\napproach requires neither inhomogeneity of the ferromagnetic film nor nonuniformity of the biasing\nmagnetic field. It can be generalized to different magnetization configurations and yield multiple spin\nwave beams of different width at the same frequency....
Asingle-port uniplanar antenna with a built-in tunable filter is presented for operation inmultiple LTE bands for cognitive femtocell\napplications. The antenna is based on a monopole microstrip patch fed by coplanar waveguide.The frequency reconfigurability is\nachieved by using two PIN diodes to couple or decouple a ring slot resonator filter fromthe antenna feed line. By switching the PIN\ndiodes, the proposed design can operate in either wideband or narrowband modes.When the antenna operates in the narrowband\nstate, two varactor diodes are used to continuously tune the narrowband frequency from 2.55 to 3.2GHz, while the wideband\nstate is obtained over the 1.35ââ?¬â??6.2GHz band. The diodes and their biasing networks have nearly no severe effect on the antenna\ncharacteristics. Prototypes of the proposed structure using ideal and real switches, with and without varactors, are fabricated and\ntested. Measured and simulated results are in good agreement, thus verifying the good performance of the proposed design. The\nobtained results show that the proposed antenna is very suitable for cognitive radio applications, in which the wideband mode is\nused for spectrum sensing and the narrowband mode for transmission at different frequency bands....
Single-photon detection is a requisite technique in quantum-optics experiments in both the\noptical and the microwave domains. However, the energy of microwave quanta are four to five\norders of magnitude less than their optical counterpart, making the efficient detection of\nsingle microwave photons extremely challenging. Here we demonstrate the detection of a\nsingle microwave photon propagating through a waveguide. The detector is implemented\nwith an impedance-matched artificial L system comprising the dressed states of a driven\nsuperconducting qubit coupled to a microwave resonator. Each signal photon deterministically\ninduces a Raman transition in the L system and excites the qubit. The subsequent\ndispersive readout of the qubit produces a discrete ââ?¬Ë?clickââ?¬â?¢. We attain a high single-photondetection\nefficiency of 0.66Ã?±0.06 with a low dark-count probability of 0.014Ã?±0.001 and a\nreset time of B400 ns. This detector can be exploited for various applications in quantum\nsensing, quantum communication and quantum information processing....
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