Photonic signal processing offers the prospect of realizing extremely high multigigahertz sampling frequencies, overcoming inherent electronic limitations. This stems from the intrinsic excellent delay properties of optical delay lines. These processors provide new capabilities for realizing high time-bandwidth operation and high-resolution performance. In-fiber signal processors are inherently compatible with fiber-optic microwave systems and can provide connectivity with built-in signal conditioning. Fundamental principles of photonic signal processing, including sampling, tuning, and noise, are discussed. Structures that can extend the performance of photonic signal processors are presented, including methods for improving the filter shape characteristics of interference mitigation filters, techniques to increase the stopband attenuation of bandpass filters, and methods to achieve large free spectral range. Several photonic signal processors, including high-resolution microwave filters, widely tunable filters, arbitrary waveform generators, and fast signal correlators, are discussed. Techniques to solve the fundamental noise problem in photonic signal processors are described, and coherence-free structures for few-tap notch filters are discussed. Finally, a new concept for realizing multiple-tap coherence-free processor filters, based on a new frequency-shifting technique, is presented. The structure not only eliminates the phase-induced intensity noise limitation, but can also generate a large number of taps to enable the achievement of processors with high performance and high resolution.

Photonic signal processing of microwave signals

Mounting of the acute inflammatory response is crucial for host defense and pivotal to the development of chronic inflammation, fibrosis, or abscess formation versus the protective response and the need of the host tissues to return to homeostasis. Within self-limited acute inflammatory exudates, novel families of lipid mediators are identified, named resolvins (Rv), protectins, and maresins, which actively stimulate cardinal signs of resolution, namely, cessation of leukocytic infiltration, counterregulation of proinflammatory mediators, and the uptake of apoptotic neutrophils and cellular debris. The biosynthesis of these resolution-phase mediators in sensu stricto is initiated during lipid-mediator class switching, in which the classic initiators of acute inflammation, prostaglandins and leukotrienes (LTs), switch to produce specialized proresolving mediators (SPMs). In this work, we review recent evidence on the structure and functional roles of these novel lipid mediators of resolution. Together, these show that leukocyte trafficking and temporal spatial signals govern the resolution of self-limited inflammation and stimulate homeostasis.

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Lipid Mediators in the Resolution of Inflammation

Amplifiers are ubiquitous in electronics and play a fundamental role in a wide range of scientific measurements. From a user's perspective, an ideal amplifier has very low noise, operates over a broad frequency range, and has a high dynamic range - it is capable of handling strong signals with little distortion. Unfortunately, it is difficult to obtain all of these characteristics simultaneously. For example, modern transistor amplifiers offer multi-octave bandwidths and excellent dynamic range. However, their noise remains far above the fundamental limit set by the uncertainty principle of quantum mechanics. Parametric amplifiers, which predate transistor amplifiers and are widely used in optics, exploit a nonlinear response to transfer power from a strong pump tone to a weak signal. If the nonlinearity is purely reactive, ie. nondissipative, in theory the amplifier noise can reach the quantum-mechanical limit. Indeed, microwave frequency superconducting Josephson parametric amplifiers do approach the quantum limit, but generally are narrow band and have very limited dynamic range. In this paper, we describe a superconducting parametric amplifier that overcomes these limitations. The amplifier is very simple, consisting only of a patterned metal film on a dielectric substrate, and relies on the nonlinear kinetic inductance of a superconducting transmission line. We measure gain extending over 2 GHz on either side of an 11.56 GHz pump tone, and we place an upper limit on the added noise of the amplifier of 3.4 photons at 9.4 GHz. Furthermore, the dynamic range is very large, comparable to microwave transistor amplifiers, and the concept can be applied throughout the microwave, millimeter-wave and submillimeter-wave bands.

/pdf/a-wideband-low-noise-superconducting-amplifier-with-high-5gmsu34n36.pdf

A wideband, low-noise superconducting amplifier with high dynamic range

Stereolithography is a solid freeform technique (SFF) that was introduced in the late 1980s Although many other techniques have been developed since then, stereolithography remains one of the most powerful and versatile of all SFF techniques It has the highest fabrication accuracy and an increasing number of materials that can be processed is becoming available In this paper we discuss the characteristic features of the stereolithography technique and compare it to other SFF techniques The biomedical applications of stereolithography are reviewed, as well as the biodegradable resin materials that have been developed for use with stereolithography Finally, an overview of the application of stereolithography in preparing porous structures for tissue engineering is given

A review on stereolithography and its applications in biomedical engineering

Diameter-controlled Growth of Single-crystalline In2O3 Nanowires and Their Electronic Properties

In this article, a novel design approach for designing $4\times 4$ and $8\times 8$ filtering Butler matrices is proposed. The matrices, composed of combined 90° couplers and 180° filtering couplers as well as phase shifters, provide incremental phase shifts and a bandpass filter performance. The detailed design process and synthesis method for the Butler matrices are presented. A three-layer symmetrical stripline structure is used to realize the Butler matrix, allowing a fully planar structure without interlayer connections. For experimental verification, two prototype $4\times 4$ and $8\times 8$ filtering Butler matrices, operating at the center frequency of 2.4 GHz with a bandpass response, are devised, manufactured, and tested. The test results match well with the simulation ones. Based on the measurements, array factors have been calculated, which further indicate the acceptance of the measured results.

Design of 4 × 4 and 8 × 8 Filtering Butler Matrices Utilizing Combined 90° and 180° Couplers

A microwave SIW sensor loaded with CSRR for wireless pressure detection in high-temperature environments

This paper proposes two methods to improve the spurious-free stopband range for high-quality-factor spherical resonators and a new family of shaped spherical resonators are presented. Geometrical shaping of the proposed resonators is realized by symmetrically squeezing a spherical cavity and further opening a rectangular slot in each squeezed area. The higher order modes of the resonator are first tuned spectrally farther away from the dominant mode by the squeezing, and then are suppressed by the slotting. X-band resonator prototypes are designed, and 3-D printed by using a metallic selective laser melting technique. Quality factors of the fabricated resonators are further improved by vibration grinding process. The experiment validates effective suppression of the first higher order mode and indicates potential applications of the proposed resonators in bandpass filters to extend the spurious-free stopband bandwidths.

Shaping and Slotting High-Q Spherical Resonators for Suppression of Higher Order Modes

This paper provides a systematic review of the technical issues of SU8 fabrication for millimeter-wave and terahertz components based on research carried out at the University of Birmingham in the past decade. A design-for-manufacturability approach is followed. The flexibility of the SU8 process enables many device structures. Challenges and problems during fabrication will be discussed and demonstrated with examples. The measurement of the devices is also a significant challenge when the critical dimensions of the device shrink and special testing fixtures are needed in some cases. Finally, a brief overview of the issues discussed above is given for future guidance.

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Investigation of SU8 as a structural material for fabricating passive millimeter-wave and terahertz components

This paper presents a center-feed parasitic circular patch antenna with continuously tuning linear polarization performance. Eutectic gallium-indium (EGaIn) liquid metal alloy is employed to tune the angle of linear polarization continuously. The antenna is feed at the center of a circular patch with a ring slot. The rotational symmetry of the antenna helps maintain the impedance and radiation pattern at different polarization angles. The liquid metal is contained in a 1mm × 1mm channel etched in a polymethyl methacrylate (PMMA) cylinder. The polarization angle is tuned by controlling the location of a short bar of EGaln. The center resonant frequency of the demonstrated antenna is 5.19 GHz with a -10dB impedance bandwidth of 0.24 GHz.

/pdf/parasitic-circular-patch-antenna-with-continuously-tunable-4lvyg68vbu.pdf

Yi Wang

Papers

Design of 4 × 4 and 8 × 8 Filtering Butler Matrices Utilizing Combined 90° and 180° Couplers

A microwave SIW sensor loaded with CSRR for wireless pressure detection in high-temperature environments

Shaping and Slotting High-Q Spherical Resonators for Suppression of Higher Order Modes

Investigation of SU8 as a structural material for fabricating passive millimeter-wave and terahertz components

Parasitic circular patch antenna with continuously tunable linear polarization using liquid metal alloy