Ultra-Wideband 90 degrees Waveguide Twist for THz applications

We report on the design, fabrication, and characterization of a novel 90\uba waveguide step twist with 56% fractional bandwidth. The proposed twist provides 90\uba field rotation in the frequency range 210-375 GHz. The experimental results are in good agreement with the electromagnetic simulations showing an insertion loss below 0.3 dB and a return loss better than 20 dB over most of the band. The ultra-wideband performance, tolerance to fabrication inaccuracies and compactness makes the proposed design attractive for various mm and sub-millimeter applications. The twist geometry is optimized for simple fabrication through direct milling. Furthermore, the design remains highly compact since both steps are fabricated on a single washer

Waveguide-to-substrate transition based on unilateral substrateless finline structure: Design, fabrication, and characterization

We report on a novel waveguide-to-substrate transition with prospective use for broadband mixer design. The transition employs a substrateless finline, i.e., a unilateral finline structure with the substrate removed between the fins. This distinctive feature diminishes the overall insertion loss and facilitates matching with the waveguide. The transition is designed on a thin silicon substrate covered by a superconducting niobium thin layer. An auxiliary Au layer situated on top of the Nb layer provides grounding for the fins and facilitates the mounting process in the split-block waveguide mount. Aiming to compare simulations with measurements, a back-to-back transition arrangement for the 211-373 GHz frequency band was designed, fabricated, and characterized at cryogenic temperatures. The simulation results for the back-to-back structure show an insertion loss of less than 0.6 dB in the whole band, i.e., 0.3 dB per transition. Furthermore, a remarkable fractional bandwidth of 55% with a return loss better than 15 dB is predicted. Experimental verification shows consistent results with simulations

Millimeter-Wave Wideband Waveguide Power Divider with Improved Isolation between Output Ports

We present a novel compact wideband waveguide T-junction power divider especially suited for mm-wave and THz frequencies. It incorporates substrate-based elements into a waveguide structure to provide the output port\u27s isolation and matching. The internal port is introduced at the apex of the T-junction formed as an E-probe on a substrate. This facilitates efficient coupling of the reflected energy from the output port to a novel thin-film-based resistive termination integrated with the E-probe onto the same substrate and fabricated by means of thin-film technology. A power divider was designed, simulated, and fabricated for the frequency band 150-220 GHz, to experimentally verify the theoretical and simulated performance. The results showed excellent agreement between the simulations and measurements with the devices demonstrating a remarkable return loss of 20 dB for both the input and output ports for a three-port device with equal split and isolation better than 17 dB between the output ports. Furthermore, the measured insertion loss is less than 0.3 dB and the amplitude and phase imbalance are 0.15 dB and 0\ub0, respectively. Moreover, the divider\u27s remarkable tolerance to the dimensions and sheet resistance of the resistive material of the built-in absorbing load, makes the device a very practical component for mm-wave and THz systems, in particular radio-astronomy receivers

Wideband Slotline-to-Microstrip Transition for 210-375 GHz based on Marchand Baluns

This paper describes the design and cryogenic measurement of a novel slotline-to-microstrip transition based on Marchand baluns. The proposed transition is an attractive solution for numerous THz applications due to its remarkable broadband performance and compactness. For instance, such transition could be considered for wideband devices covering the frequency band 210-375 GHz. The suggested transition is designed on a thin silicon substrate and employs superconducting Nb as the electrode for the slotline and microstrip lines. In order to verify the performance of the designed transition, we fabricated a dedicated test structure consisting of two transitions connected back-to-back and integrated with E-probes at the waveguide interfaces. Due to the inherent bandwidth limitation of the E-probes, two different test structures for 210-295 GHz and 295-375 GHz were employed to characterize the proposed transition over the whole frequency band. The experimental verification performed at cryogenic temperatures showed results consistent with the simulation. Moreover, the cryogenic measurements indicated a remarkable 56% fractional bandwidth with an insertion loss as low as 0.3 dB for the fabricated slotline-to-microstrip transition

SEPIA345: A 345 GHz dual polarization heterodyne receiver channel for SEPIA at the APEX telescope

Context. We describe the new SEPIA345 heterodyne receiver channel installed at the Atacama Pathfinder EXperiment (APEX) telescope, including details of its configuration, characteristics, and test results on sky. SEPIA345 is designed and built to be a part of the Swedish ESO PI Instrument for the APEX telescope (SEPIA). This new receiver channel is suitable for very high-resolution spectroscopy and covers the frequency range 272- 376 GHz. It utilizes a dual polarization sideband separating (2SB) receiver architecture, employing superconductor-isolator-superconductor mixers (SIS), and provides an intermediate frequency (IF) band of 4- 12 GHz for each sideband and polarization, thus covering a total instantaneous IF bandwidth of 4 \uc3\uc2 - 8 = 32 GHz. Aims. This paper provides a description of the new receiver in terms of its hardware design, performance, and commissioning results. Methods. The methods of design, construction, and testing of the new receiver are presented. Results. The achieved receiver performance in terms of noise temperature, sideband rejection, stability, and other parameters are described. Conclusions. SEPIA345 is a commissioned APEX facility instrument with state-of-the-art wideband IF performance. It has been available on the APEX telescope for science observations since July 2021

Access and utilisation of maternity care for disabled women who experience domestic abuse:a systematic review

BACKGROUND: Although disabled women are significantly more likely to experience domestic abuse during pregnancy than non-disabled women, very little is known about how maternity care access and utilisation is affected by the co-existence of disability and domestic abuse. This systematic review of the literature explored how domestic abuse impacts upon disabled women’s access to maternity services. METHODS: Eleven articles were identified through a search of six electronic databases and data were analysed to identify: the factors that facilitate or compromise access to care; the consequences of inadequate care for pregnant women’s health and wellbeing; and the effectiveness of existing strategies for improvement. RESULTS: Findings indicate that a mental health diagnosis, poor relationships with health professionals and environmental barriers can compromise women’s utilisation of maternity services. Domestic abuse can both compromise, and catalyse, access to services and social support is a positive factor when accessing care. Delayed and inadequate care has adverse effects on women’s physical and psychological health, however further research is required to fully explore the nature and extent of these consequences. Only one study identified strategies currently being used to improve access to services for disabled women experiencing abuse. CONCLUSIONS: Based upon the barriers and facilitators identified within the review, we suggest that future strategies for improvement should focus on: understanding women’s reasons for accessing care; fostering positive relationships; being women-centred; promoting environmental accessibility; and improving the strength of the evidence base

ALMA Band 5 receiver cartridge. Design, performance, and commissioning

We describe the design, performance, and commissioning results for the new ALMA Band 5 receiver channel, 163–211 GHz, which is in the final stage of full deployment and expected to be available for observations in 2018. This manuscript provides the description of the new ALMA Band 5 receiver cartridge and serves as a reference for observers using the ALMA Band 5 receiver for observations. At the time of writing this paper, the ALMA Band 5 Production Consortium consisting of NOVA Instrumentation group, based in Groningen, NL, and GARD in Sweden have produced and delivered to ALMA Observatory over 60 receiver cartridges. All 60 cartridges fulfil the new more stringent specifications for Band 5 and demonstrate excellent noise temperatures, typically below 45 K single sideband (SSB) at 4 K detector physical temperature and below 35 K SSB at 3.5 K (typical for operation at the ALMA Frontend), providing the average sideband rejection better than 15 dB, and the integrated cross-polarization level better than –25 dB. The 70 warm cartridge assemblies, hosting Band 5 local oscillator and DC bias electronics, have been produced and delivered to ALMA by NRAO. The commissioning results confirm the excellent performance of the receivers

Broadband Waveguide-to-Substrate Transition Using a Unilateral Etched Finline Structure

We present a novel broadband waveguide-tosubstrate transition that aims to be used for broadband mixer design. The transition consists of a unilateral finline structure with etched substrate between the fins. This particular feature reduces the overall insertion loss and facilitates matching with the waveguide. The transition is designed of a thin silicon substrate covered by a superconducting niobium thin layer. An auxiliary gold layer situated on top of the Nb-layer provides grounding for the fins and facilitates a simple mounting process in the split-block waveguide mount. In order to compare simulations with measurements, a back-to-back arrangement was designed and simulated using HFSS in the 211-373 GHz frequency band. The back-to-back simulation results show an insertion loss of less than 0.3 dB in the whole band. Furthermore, a fractional bandwidth of 55% with a return loss better than 15 dB is achieve

Design and Implementation of a Compact 90 degrees Waveguide Twist With Machining Tolerant Layout

We report on a novel compact wideband 90 degrees twist with performance tolerant to small geometry variation and hence improved manufacturability through direct milling. The experimental verification shows 44% fractional bandwidth with return loss better than 20 dB over the 140-220 GHz band. The performance, compactness, and tolerance to manufacturing inaccuracy make it very suitable for use in various waveguide systems from microwave to millimeter-wave range