Rapid prototyping of waveguide and horn antennas

In this paper we review how fused deposition modelling (FDM) can be deployed for the rapid prototyping of microwave waveguide componentry and antennas. Additive manufacture of such objects allows new, novel and complex structures to be fabricated with lower impact on the environment relative to current manufacturing processes, plus the fast turnaround of design to manufacture and test. Additionally while the resulting physical antenna properties may not be perfect compared to the design or what can be machined, their RF/microwave performance can be quite forgiving thereby allowing the antenna design engineer to fully exploit the rapid prototyping concept

Additively manufactured profiled conical horn antenna with dielectric loading

The world's first additively manufactured dielectric loaded profiled conical horn antenna is presented in this letter. With a smooth profiled flare and two loaded dielectric core materials, this horn offers symmetrical patterns, wideband gain, low sidelobe level, and low cross polarization. Additive manufacturing, including electroplating, has been employed to address the fabrication challenges. The measurement results show that the fabrication process produces a horn antenna with reduced mass and volume (<;200 g with three-dimensional-printed flange) and high antenna performance with realized gain 16-20 dBi, sidelobe level -22 to -19 dB across the frequency range from 9 to 15 GHz

Fused deposition modelling for microwave circuits & antennas

Additive Manufacturing, or 3D printing, is moving from the research labs and into both consumer and commercial manufacturing markets. As the systems, processes and materials available are becoming more mature we are seeing them being tested for new application areas such as electronics. In this paper we review how fused deposition modelling (FDM) is being explored for creating microwave circuits and componentry, their RF performance and the materials challenges faced. In recent years such microwave circuits and components have included antennas, lenses, antireflective coatings, transmission lines and planar circuits, waveguide terminations, performing at frequencies ranging from low GHz up to tens of GHz. Additive manufacture of such objects allows new, novel and complex structures to be fabricated with lower impact on the environment relative to current manufacturing processes, plus the rapid prototyping of circuits. Additionally it currently offers reasonable RF performance that can be competitive through further advances in manufacturing processes and materials

Wearable and meshed wideband monopole antennas and their interactions with the human body

This study considers a wideband monopole antenna and its interactions with different separations from the human body phantom over a wide frequency. A meshed alternative version has also been developed which has similar performance to the circular wideband monopole antenna but requires less material. The specific absorption rate and efficiency of this antenna have been analysed as a function of separation distance and frequency. The mesh design has been fabricated by using embroidery and 3D printing techniques

First Results from the CHARA Array. II. A Description of the Instrument

The CHARA Array is a six 1-m telescope optical/IR interferometric array located on Mount Wilson California, designed and built by the Center for High Angular Resolution Astronomy of Georgia State University. In this paper we describe the main elements of the Array hardware and software control systems as well as the data reduction methods currently being used. Our plans for upgrades in the near future are also described

Performance of the Xpert HPV assay in women attending for cervical screening

© 2015 The Authors. Objectives: This study evaluated the Xpert HPV Assay in women attending screening in general practice by comparing Xpert with two established HPV tests, cytology and histology. Methods: A prospective study in women aged 20-60 years attending screening in Bristol, Edinburgh and London using residual Preservcyt cytology samples. Sample order was randomised between Roche cobas4800 and Cepheid Xpert assays with Qiagen hc2 third. Results: 3408 cases were included in the primary analysis. Positivity for Xpert was 19.6%, cobas 19.2% and hc2 19.9% with high concordance (kappa=86.8% vs cobas, 81.55 vs hc2). Xpert, cobas and hc2 showed similar sensitivity (98.7%, 97.5%, 98.7%) for CIN2+. All pairwise comparisons had high concordance (Kappa ≥0.78 with any abnormal cytology. Xpert and hc2 were positive for all cases of ≥moderate dyskaryosis ( N=63)), cobas was negative in two. Histology was available for 172 participants. 79 reported CIN2+, 47 CIN3+. All CIN3+ was positive on Xpert and hc2 and one case negative for cobas. One case of CIN2 was negative for all assays. Conclusions: The performance of Xpert HPV Assay in a general screening population is comparable to established HPV tests. It offers simplicity of testing, flexibility with non-batching of individual samples and rapid turnaround time

Evidence for a three-nucleon-force effect in proton-deuteron elastic scattering

Developments in spin-polarized internal targets for storage rings have permitted measurements of 197 MeV polarized protons scattering from vector polarized deuterons. This work presents measurements of the polarization observables A_y, iT_11, and C_y,y in proton-deuteron elastic scattering. When compared to calculations with and without three-nucleon forces, the measurements indicate that three-nucleon forces make a significant contribution to the observables. This work indicates that three-body forces derived from static nuclear properties appear to be crucial to the description of dynamical properties.Comment: 8 pages 2 figures Latex, submitted to Phys. Rev. Letter

Complex permittivity measurement system for solid materials using complementary frequency selective surfaces

This paper describes a novel method of characterizing complex permittivity using a complementary frequency selective surface (CFSS). The CFSS provides a passband behavior and the change in the passband when a material under test (MUT) is placed adjacent to the CFSS has been used for retrieving of the complex permittivity of the MUT. The complex permittivity of the MUT are determined based on the measured bandpass resonant frequency and insertion loss of the CFSS with the MUT. This is an amplitudeonly method where phase measurements are not required. This technique offers a convenient, fast, low-cost and nondestructive measurement that is not restricted by the sample size or shap

3-D printed bandpass filters with coupled vertically extruded split ring resonators

The additive manufacturing process of multimaterial extrusion offers performance advantages using functional materials including conductors while making accessible the third dimension in the design of electronics. In this work we show that the additional geometrical freedom offered by this technique can be exploited for the design and realisation of filters made of three- dimensional (3D) resonators that exhibit enhanced characteristics. The coupling properties of 3D grounded square split ring resonators (SRRs) are initially explored. We demonstrate by simulations and experiments that SRRs with finite height display significantly stronger coupling compared to equivalent thin printed circuit structures. The observed trend can be exploited for designing filters with wider operational bandwidths for a given footprint, or miniaturized layouts and enhanced compatibility with fabrication limits for minimum feature size and spacing without performance degradation. This concept is demonstrated by presenting results of full-wave simulations for sample bandpass filters with identical footprint but formed by coupled 3D square SRRs of different heights, showing that filters with taller resonators exhibit increasingly wider bandwidths. Two filter prototypes with centre frequencies at 1.6 GHz and 2.45 GHz are manufactured by multimaterial 3D printing. The measured characteristics of these prototypes are found to be in good agreement with numerical simulations taking into account the effect of the lossier metallic and dielectric materials used in 3D printing and confirm the predicted larger bandwidth of the filters made of 3D SRRs with marginally higher insertion losses

Cold-sintered temperature stable Na0.5Bi0.5MoO4−Li2MoO4 microwave composite ceramics

A cold sintering process (150 °C, 30 min and 200 MPa) was employed to fabricate Na0.5Bi0.5MoO4−Li2MoO4 (NBMO-LMO) composites with up to 96.4% relative density. X-ray diffraction traces, backscattered electron images and Raman spectra indicated the coexistence of NBMO and LMO phases in all composites with no detectable secondary phases. The pemittivity (εr) and temperature coefficient of resonant frequency (TCF) decreased, whereas microwave quality factor (Q × f) increased, with increasing weight % LMO. Near-zero TCF was obtained for NBMO-20 wt %LMO with εr ∼ 17.4 and Q × f ∼7470 GHz. Functionally graded ceramics were also fabricated with 5 ≤ εr ≤ 24. To illustrate the potential of these cold sintered composites to create new substrates and device architecture, a dielectric graded radial index lens was designed and simulated based on the range of εr facilitated by the NBMO-LMO system, which suggested a 78% aperture efficiency at 34 GHz