Evaluating the Effect of Using Precision Alignment Dowels on Connection Repeatability of Waveguide Devices at Frequencies from 750 GHz to 1.1 THz

This paper describes an investigation into the effects of using additional precision alignment dowel pins on the connection repeatability performance of waveguide interfaces at submillimeter-wave frequencies. The waveguide interface type that was used for this investigation is an adapted version of the `precision' UG-387 (i.e. based on the MIL-DTL-3922/67 design), manufactured by Virginia Diodes, Inc. The investigation was undertaken in the WM-250 waveguide band (i.e. at frequencies ranging from 750 GHz to 1.1 THz). Connection performance is compared with and without the use of added precision dowel pins in the inner dowel holes of this flange type. The repeatability of the measurements is assessed using statistical techniques, in terms of the experimental standard deviation in both the real and imaginary components of the complex-valued linear reflection coefficient

An intra-laboratory investigation of on-wafer measurement reproducibility at millimeter-wave frequencies

Understanding the relative contribution of contact repeatability and overall reproducibility for on-wafer measurements provides useful insight into the significance of measurement comparisons. We report on an intra-laboratory investigation into contact repeatability and the variation that may be anticipated when measurements are reproduced in different laboratories using different equipment. We pay particular attention to the dispersion in measurement results arising from the use of on-wafer and off-wafer calibration. Experimental results are reported for measurements in the frequency range 140 GHz to 220 GHz, together with preliminary estimates of the repeatability limits for this type of measurement

‘Mind the Gap’ . . . Establishing Measurement Capability in the Terahertz Gap Region – from 0.1 THz to 1.1 THz

This paper reviews the current state-of-the-art of measurements made using vector network analysers operating in the 0.1 THz to 1.1 THz frequency range. The paper concentrates on the development of three types of measurement capability: (i) in rectangular metallic waveguides; (ii) on-wafer planar circuits; (iii) bulk material characterisations. The paper describes progress to date with establishing this measurement capability and reviews the remaining challenges facing this measurement community

3D printed waveguides: A revolution in low volume manufacturing for the 21st century

3D printing is a disruptive technology, offering the inherent capabilities for creating truly arbitrary 3D structures, with low manufacturing costs associated with low volume production runs. This paper provides an overv iew of the current progress in 3D printing of metal - pipe rectangular waveguide (MPRWG) components, from 10 GHz to 1 THz, at Imperial College London. First, measurements performed at the UK National Physical Laboratory demonstrate that 3D printed MPRWG perf ormance is comparable to standard commercial waveguides at X - band and W - band. Then, a fully 3D printed X - band dielectric flap tuneable phase shifter and W - band 6th - order inductive iris bandpass filter are demonstrated experimentally. Finally, an optically - controlled 500 GHz IQ vector modulator will also be presented; packaged laser diodes and high resistivity silicon implants are integrated within a hybrid 3D printed split - block module, representing a paradigm shift in additive manufacturing for realizing t uneable THz applications

Metrology State-of-the-Art and Challenges in Broadband Phase-Sensitive Terahertz Measurements

The two main modalities for making broadband phase-sensitive measurements at terahertz (THz) frequencies are vector network analyzers (VNA) and time-domain spectrometers (TDS). These measuring instruments have separate and fundamentally different operating principles and methodologies, and they serve very different application spaces. The different architectures give rise to different measurement challenges and metrological solutions. This article reviews these two measurement techniques and discusses the different issues involved in making measurements using these systems. Calibration, verification, and measurement traceability issues are reviewed, along with other major challenges facing these instrument architectures in the years to come. The differences in, and similarities between, the two measurement methods are discussed and analyzed. Finally, the operating principles of electro-optic sampling (EOS) are briefly discussed. This technique has some similarities to TDS and shares application space with the VNA

An interlaboratory study of the reproducibility of on-wafer S-parameter measurements from 140 GHz to 220 GHz

The development, modelling and characterization of millimeter-wave semiconductor devices calls for accurate and reproducible on-wafer measurements. We report on an interlaboratory study involving on-wafer S-parameter measurements in the 140 GHz to 220 GHz band, conducted by three well-established measurement laboratories. The measurements can be used to form typical reproducibility limits for these measurements when conducted in different laboratories using different equipment and calibration methods

Strategies for Traceable Submillimeter-Wave Vector Network Analyzer

This paper presents a strategy for achieving metrological traceability using vector network analyzers (VNAs) at submillimeter-wave frequencies (300-3000 GHz). The strategy includes the use of traceable calibration techniques designed for operation at these frequencies. Slight, but significant, physical differences between the waveguide line standards, used during calibration, are accommodated by applying a weighting technique to combine results using different calibration lines. Measurement uncertainty is assessed by analyzing replicate measurement data, to take account of the different waveguide interface interactions that occur when the line standards are connected to the VNA. The strategy is illustrated using measurements made in the WM-250 (750-1100 GHz) waveguide band

Determination of the Permittivity of Transmission Lines at Milli-kelvin Temperatures

Many quantum technologies rely heavily on propagation of RF and microwave signals through devices at cryogenic temperatures, and detailed understanding of materials and signal propagation is therefore key to improving the performance of quantum circuits. The properties of dielectric substrate materials used for transmission lines (TLs) such as their permittivity need to be precisely determined to design high performance quantum integrated circuits. In this paper, we discuss a measurement technique for determining the effective permittivity of a TL at mK temperatures. The technique utilizes S-parameter measurements of multiple TLs to reliably extract the effective permittivity of the TL implemented in a substrate material. The technique is demonstrated using measured S-parameters of grounded co-planar waveguide (GCPW) at 296 K and 15 mK. The effective permittivity of the TL at 296 K and 15 mK are determined from measurements and compared. We observed the effective permittivity determinations at 15 mK to be approximately frequency independent and calculated the relative permittivity of Rogers RO4350B material at 15 mK to be 3.64. There is no significant deviation from this relative permittivity value with respect to manufacturer data and from measured data at 296 K

Lesion detection in demoscopy images with novel density-based and active contour approaches

<p>Abstract</p> <p>Background</p> <p>Dermoscopy is one of the major imaging modalities used in the diagnosis of melanoma and other pigmented skin lesions. Automated assessment tools for dermoscopy images have become an important field of research mainly because of inter- and intra-observer variations in human interpretation. One of the most important steps in dermoscopy image analysis is the detection of lesion borders, since many other features, such as asymmetry, border irregularity, and abrupt border cutoff, rely on the boundary of the lesion. </p> <p>Results</p> <p>To automate the process of delineating the lesions, we employed Active Contour Model (ACM) and boundary-driven density-based clustering (BD-DBSCAN) algorithms on 50 dermoscopy images, which also have ground truths to be used for quantitative comparison. We have observed that ACM and BD-DBSCAN have the same border error of 6.6% on all images. To address noisy images, BD-DBSCAN can perform better delineation than ACM. However, when used with optimum parameters, ACM outperforms BD-DBSCAN, since ACM has a higher recall ratio.</p> <p>Conclusion</p> <p>We successfully proposed two new frameworks to delineate suspicious lesions with i) an ACM integrated approach with sharpening and ii) a fast boundary-driven density-based clustering technique. ACM shrinks a curve toward the boundary of the lesion. To guide the evolution, the model employs the exact solution <abbrgrp><abbr bid="B27">27</abbr></abbrgrp> of a specific form of the Geometric Heat Partial Differential Equation <abbrgrp><abbr bid="B28">28</abbr></abbrgrp>. To make ACM advance through noisy images, an improvement of the model’s boundary condition is under consideration. BD-DBSCAN improves regular density-based algorithm to select query points intelligently.</p