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

This letter presents a high-gain 32 × 32-element full corporate-feed array antenna using a simplified assembly of only two split blocks. This is made possible by a new feeding configuration which eliminates the cavity-backed layer used in conventional designs. E-plane T-junctions, as well as the single-ridge waveguide output structure, are used in the full corporate-feed network to reduce its size. This helps to realize the one-to-one corresponding excitation between the output port of the feed network and the radiation slots. In addition, a transition structure from single-ridge waveguide to double-ridge waveguide is employed to improve the impedance matching bandwidth of the radiation part. For demonstration, a prototype is designed, fabricated, and measured. Experimental results show that the array antenna achieves an impedance bandwidth of 19% (71–86 GHz) with input reflection coefficient better than −13 dB, the antenna efficiency of over 76.4%, and peak gain of better than 38.4 dBi over the entire operating band.

/pdf/e-band-full-corporate-feed-32-32-slot-array-antenna-with-3rttp4j5gg.pdf

E-Band Full Corporate-Feed 32 × 32 Slot Array Antenna With Simplified Assembly

This paper presented a microwave resonator-based dielectric metrology technique using a new unified analytical model to extract complex permittivity of low-loss liquid materials. The main design drive of the modified re-entrant cavity is to confine the electric field and therefore enhance the interaction with the material under test while maintaining high quality factor of the cavity. This enables high sensitivity when measuring complex permittivity of low loss materials. The fabrication of the resonator was made easy by using stereo-lithography (SLA) 3D printing. The measured resonance frequency of the fabricated cavity is 2.09 GHz and the quality factor is 5250. The device was first validated using several common solvents. A unified analytical perturbation model based on simulations is developed for the extraction of the complex permittivity. The influence of the dielectric constant on the loss-tangent model has been fully taken into account. Results obtained agree very well with literature values. The device has subsequently been used in the measurement of crude oil samples and the correlation between permittivity measurement and crude oil category has been established.

3D printed re-entrant cavity resonator for complex permittivity measurement of crude oils

This article explored the use of high-precision metal three-dimensional printing in subterahertz waveguide devices and demonstrated a 300 GHz waveguide bandpass filter made by micro laser sintering (MLS) process. The filter structure is composed of five rectangular waveguide cavities (fundamental TE101 mode), two back-to-back right-angle bends and WR-03 waveguide sections. It is made of two identical blocks of stainless steel and two brass plates were used to clamp them together and achieve secure contact in the E plane cut. The measured response of the as fabricated stainless-steel filter showed minimum passband insertion loss of 4.7 dB due to the degraded effective conductivity of the stainless steel and surface roughness. To reduce the insertion loss, the filter was gold plated using an electro-less process with nickel undercoat layer. Plating the filter significantly improved the passband insertion loss, measured to be between 1.1 and 2.7 dB. Inspection of the filter using an Alicona optical system showed that dimensional accuracy within ± 15 μm on average has been achieved by the MLS printer. The investigative study tested the boundary of the technology in subterahertz device applications.

A 3-D Printed 300 GHz Waveguide Cavity Filter by Micro Laser Sintering

Tuning of a superconducting microwave resonator, operating at 77 K, is demonstrated using a silicon micro-machined comb-drive actuator. Thermal expansion coefficient differences between the silicon actuator and the MgO substrate are accommodated by the use of stress absorbing springs. A tuning range of 4.6% is demonstrated for a superconducting microwave resonator with a frequency just below 6 GHz.

Silicon comb-drive actuators for low-temperature tuning of superconducting microwave circuits

This paper presents a new implementation technique of transmission zeros in an in-line coupled filter. Neither cross couplings between non-adjacent resonators nor separate side-line resonators have been used. Instead a mixture of single-mode hairpin resonators and dual-mode patch resonators have been adopted in a bandpass filter with one asymmetric transmission zero. The introduction of the patch led to an improved frequency selectivity through an independently controllable transmission zero. This approach has been verified by a three-pole filter at 2.6 GHz with 8% bandwidth and a transmission zero at 2.4 GHz. Good agreement has been shown between the measurements and the simulation.

https://www.jpier.org/pierc/pierc59/11.15072905.pdf

Yi Wang

Papers

E-Band Full Corporate-Feed 32 × 32 Slot Array Antenna With Simplified Assembly

3D printed re-entrant cavity resonator for complex permittivity measurement of crude oils

A 3-D Printed 300 GHz Waveguide Cavity Filter by Micro Laser Sintering

Silicon comb-drive actuators for low-temperature tuning of superconducting microwave circuits

Bandpass Filters with Mixed Hairpin and Patch Resonators