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

A 4-pole interdigital filter has been demonstrated at 60 GHz with a bandwidth of 10%, it is made using micromachining and a multi-layer bonding. The filter is an airfilled three-dimensional structure. It is formed of five layers which are bonded together. Each layer is micromachined SU-8 based, 200-μm thick, and finished with 1.5 μm gold coating. The resonators are thick stripline-like and enclosed in a cavity. The input and output are transitions from a coplanar structure to a rectangular coaxial line, which are then coupled into the cavity. The filter is only 3.7 mm by 2.0 mm in size and 1.0 mm in height. The measured insertion loss is 1.1 dB and the return loss is below -9 dB. The bandwidth of the tested filter is broadened due to fabrication imperfections, which have been identified by modelling and discussed in the paper.

/pdf/micromachined-60-ghz-air-filled-interdigital-bandpass-filter-pifdrsv7di.pdf

Micromachined 60 GHz Air-filled Interdigital Bandpass Filter

A novel compact filtering rat-race hybrid coupler with improved upper stopband is presented in this letter. Four coupled-resonator pairs are utilized to replace the λ/4- and 3λ/4-transmission lines in the conventional hybrid. Each coupled-resonator pair exhibits a bandpass filtering response and acts as a K-inverter. Eight resistors are placed at the center of the λ/2-resonators to suppress the 2nd-harmonic. For verification, a filtering rat-race hybrid is implemented with a center frequency of 1.27 GHz and 20-dB rejection band of 2.73 f0. Good in-phase and out-of-phase characteristics are obtained. The proposed device has a simple circuit topology, compact size and good performance.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/el.2016.2225

Design of compact filtering rat-race hybrid with λ/2-resonators

An all-resonator based triplexer is presented using a double-stub-loaded resonator (DSLR) that acts as a common resonator at the junction of the three channels. The open stub DSLR has been analysed using even and odd-mode method to reveal the relationship between the three resonant modes. The design offers flexibility of frequency selection. The DSLR resonator is coupled with three sets of hairpin resonators to form the triplexer at 1.8, 2.1, and 2.6 GHz for mobile communication applications. The measurement results are in very good agreement with the simulations.

/pdf/microstrip-triplexer-using-a-common-triple-mode-resonator-11tecbfclz.pdf

Microstrip Triplexer using a common triple-mode resonator

Making accurate and reliable measurements at WR-3 band is challenging. This is made more so when a T/R-T based test configuration is used. This paper compared the calibrations and measurements between a T/R-T and a full T/R-T/R configuration. The shortfall of load matching in the T/R-T configuration has been identified and described using signal flow analyses. The effects of both the device performance and the load match on the measurement uncertainty have been studied. The insertion of an attenuator at the T-module test port has been used to overcome the poor load matching, and significant improvements have been achieved on the measurements of micromachined waveguide devices.

Measurements of micromachined waveguide devices at WR-3 band using a T/R-T module based network analyzer

This paper proposes the use of asynchronously coupled resonator junctions in the design of diplexers. This is to ease the control and implementation of the external couplings at the common port of an all-resonator-based diplexer. A comparison study has been performed between a conventional diplexer and the proposed diplexer. To further explore the possibilities of the proposed junction technique, a four-port multi-port filtering networks was proposed and designed to function as a double diplexer. Good agreements have been achieved between the measurements of the prototype devices and the simulations.

/pdf/asynchronously-coupled-resonant-junctions-for-diplexers-and-15sk0reund.pdf

Yi Wang

Papers

Micromachined 60 GHz Air-filled Interdigital Bandpass Filter

Design of compact filtering rat-race hybrid with λ/2-resonators

Microstrip Triplexer using a common triple-mode resonator

Measurements of micromachined waveguide devices at WR-3 band using a T/R-T module based network analyzer

Asynchronously coupled resonant junctions for diplexers and multiport filtering networks