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.

/pdf/lipid-mediators-in-the-resolution-of-inflammation-16p8f9iuvq.pdf

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

Passband flatness and band-edge selectivity in microwave filters with finite quality-factor resonators can be improved by the synthesis of lossy filters. This paper demonstrates the extension of this technique to a lossy diplexer by means of resistive coupling. A dual-mode stub-loaded resonator (SLR) junction and a fork-like feedline are used in the diplexer to address the challenge of independently controlling the external coupling from the common port to the two channel filters and therefore enable flexible realization of the channel bandwidth. The coupling matrices with resistive couplings for the lossy diplexer are generated. For verification, a microstrip lossy diplexer operating at 1.91 and 2.6 GHz was designed and tested. The flatness of the passband has been significantly improved, with a reduction of the passband insertion loss variation from 1.4/1.2 dB to 0.66/0.63 dB for the low/high band. The measured results are in good agreement with the simulations as well as the theoretical responses from the coupling matrix. This was also experimentally compared with a reference diplexer without resistive couplings.

/pdf/a-microstrip-lossy-diplexer-with-flat-channel-passbands-rloyu9y9ph.pdf

A Microstrip Lossy Diplexer with Flat Channel Passbands

It is widely accepted that the unwanted radiation from some feeding networks could degrade the performance of the antenna array. However, this interfering effect was not seen to be characterized in the open literature. This paper investigated this effect by a comparative study on a microstrip 4 × 4 Butler matrix fed linear patch antenna array at 2 GHz. The designs and measurement of the Butler matrix and the array are presented.

Investigation on the interfering effect of feeding network on the performance of a beamforming antenna array

This article presents a <inline-formula> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula>-band <inline-formula> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula>-plane 90° filtering coupler and a <inline-formula> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula>-band six-port junction (SPJ), both working at 150 GHz. The coupler is formed by ten resonators, having a fourth-order Chebyshev response. Two of the couplers were combined with a 90° 3-dB branch-line coupler to build the filtering SPJ with 20 resonators in total. Inheriting from the filtering coupler, the SPJ also has a fourth-order Chebyshev response. A coupling matrix (CM) consisting of both resonant and nonresonant nodes, based on the coupling topology, was constructed to predict the theoretical responses. Guided by this CM, the coupler and the SPJ were designed and modeled. In addition, two silicon-based absorber chips were designed and implemented as two matched loads in the filtering SPJ. The SPJ was optimized, fabricated, and tested. The center frequency of the SPJ is 150 GHz and the bandwidthis 4 GHz. Simulation shows 0.5–0.7-dB insertion loss at 150 GHz and a maximum 3° phase error in the working band. The measurement gives the same center frequency andbandwidth. The response shows 0.7–2.0-dB insertion loss at 150 GHz and a maximum 15° phase error in the working band.

Subterahertz Filtering Six-Port Junction

This paper proposes a new pole-generating resonant iris structure for the design of iris-coupled cavity filters. By replacing the conventional reactive iris with a resonant iris, extra transmission pole can be generated without increasing the number of resonant cavities. This leads to several design advantages: (i) a more compact filter structure; and (ii) ability to realize wide bandwidth and to improve out-of-band rejection. To demonstrate these, a third-order Chebyshev filter is designed and implemented, occupying the same footprint as a second-order filter. To facilitate the formation of the intricate resonant iris structures, the filter was printed monolithically using selective laser melting (SLM) technique. Very good agreement between the measurements and simulations has been achieved.

Yi Wang

Papers

A Microstrip Lossy Diplexer with Flat Channel Passbands

Investigation on the interfering effect of feeding network on the performance of a beamforming antenna array

Subterahertz Filtering Six-Port Junction

Compact Monolithic SLM 3D-Printed Filters using Pole-Generating Resonant Irises

Corrigendum to “Total synthesis of resolvin E1” [Tetrahedron Lett. 52 (2011) 2623–2626]