1,705 research outputs found
Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers
Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method
Design And Optimization Of Nanostructured Optical Filters
Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or complicated conversions between optical and electrical signals. This dissertation explores three classes of nano-scale optical filters in an effort to obtain different types of dispersive response functions. First, dispersive waveguides are designed using a sub-wavelength periodic structure to transmit a single TE propagating mode with very high second order dispersion. Next, an innovative approach for decoupling waveguide trajectories from Bragg gratings is outlined and used to obtain a uniform second-order dispersion response while minimizing fabrication limitations. Finally, high Q-factor microcavities are coupled into axisymmetric pillar structures that offer extremely high group delay over very narrow transmission bandwidths. While these three novel filters are quite diverse in their operation and target applications, they offer extremely compact structures given the magnitude of the dispersion or group delay they introduce to an incident signal. They are also designed and structured as to be formed on an optical wafer scale using standard integrated circuit fabrication techniques. A number of frequency-domain numerical simulation methods are developed to fully characterize and model each of the different filters. The complete filter response, which includes the dispersion and delay characteristics and optical coupling, is used to evaluate each filter design concept. However, due to the complex nature of the structure geometries and electromagnetic interactions, an iterative optimization approach is required to improve the structure designs and obtain a suitable response. To this end, a Particle Swarm Optimization algorithm is developed and applied to the simulated filter responses to generate optimal filter designs
Active dielectric antenna on chip for spatial light modulation
Integrated photonic resonators are widely used to manipulate light propagation in an evanescently-coupled
waveguide. While the evanescent coupling scheme works well for planar optical systems that are naturally
waveguide based, many optical applications are free-space based, such as imaging, display, holographics,
metrology and remote sensing. Here we demonstrate an active dielectric antenna as the interface device that
allows the large-scale integration capability of silicon photonics to serve the free-space applications. We
show a novel perturbation-base diffractive coupling scheme that allows a high-Q planer resonator to directly
interact with and manipulate free-space waves. Using a silicon-based photonic crystal cavity whose
resonance can be rapidly tuned with a p-i-n junction, a compact spatial light modulator with an extinction
ratio of 9.5 dB and a modulation speed of 150 MHz is demonstrated. Method to improve the modulation
speed is discussed.Air Force Office of Scientific Research (AFOSR grant FA9550-12-1-0261
Development of lumped element kinetic inductance detectors for mm-wave astronomy at the IRAM 30 m telescope
This thesis studies the development of LEKID arrays for the use in a mm-wave camera for the IRAM 30m telescope. This includes the design and fabrication of the superconducting microresonators, the modeling and optimization of the mm-wave coupling to the detector and the characterization of the arrays at low temperatures. The results obtained brought IRAM to test a prototype instrument at the telescope, where first astronomical results have been achieved, which are also presented in this work
A study of secondary winding designs for the two-coil Tesla transformer
The multi-order response of the tuned secondary circuit of a Tesla
transformer, following impulse excitation from its tuned primary circuit, is presented and analysed at the fundamental resonant
frequency and at higher-order mode frequencies. A novel way
of modifying the frequency response of the secondary coil is then investigated by utilising a technique normally applied to the design of a certain type of filter known as a helical filter. In general,
these are used in radio and microwave frequency circuits in order to pass certain frequencies with little attenuation whilst significantly attenuating other frequencies. Design techniques, developed over
several decades, modify and optimise the performance of such filters. The frequency response of the helical filter is modified by
altering the geometry of the helical resonator component therein, which is typically in the form of an air-cored single-layer solenoid.
A Tesla transformer whose secondary is constructed to be some form of single-layer solenoidal winding resonates at its designed frequency - its fundamental mode - but also at non-integer harmonics (higher-order anharmonic frequencies, also known as overtones).
Those multi-order oscillatory voltages and currents energised in the
secondary circuit have been identified and measured and research has
determined the fundamental and higher-order mode frequencies and amplitudes for various experimental secondary winding configurations derived from helical filter design techniques. Applied to the Tesla transformer secondary winding, such techniques lead to a new design with a performance that is improved by the suppression of higher-
order anharmonic frequencies whilst imparting little change to the fundamental response. It is anticipated that this feature will lead to
Tesla transformers which exhibit enhanced spectral purity and which will be better suited to use in certain pulsed power applications than conventionally wound designs
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