Microstrip broadband thin-film attenuators without via-hole-ground at millimeter wave frequencies

A comprehensive design methodology for microstrip broadband attenuators is presented. Closed-form design equations are given for two types of distributed attenuators. The attenuators are based on a cascade connection of thin-film resistors and microstrip line sections. The structure provides maximally flat attenuation and wideband performance without the need of plated via holes to ground, facilitating manufacture as well as achieving proper performance at millimeter wave frequencies. Experimental results demonstrate the validity of the technique applied to 3 dB and 13 dB broadband attenuators on aluminasubstrate up to 67 GHz. The proposed topology can be applied not only to MIC, but also to MMIC designs at the highest frequencies.This work was supported by the Spanish Ministry of Economy and Competitiveness mainly under Grant ESP2015-70646-C2-2-R and additionally under Grant TEC2017-83343-C4-1-R, and Ministry of Science, Innovation and Universities under Grant AYA2017-92153-EXP. The authors thank Eva Cuerno for her assistance during the attenuators assembly

Noise conversion of Schottky diodes in mm-wave detectors under different nonlinear regimes: modeling and simulation versus measurement

This paper presents and discusses several methods for predicting the low-frequency (LF) noise at the output of a mm-wave detector. These methods are based on the extraction of LF noise source parameters from the single diode under a specific set of bias conditions and the transfer or conversion of these noise sources, under different operating conditions including cyclostationary regime, to the quasi-dc output of a mm-wave detector constructed with the same model of diode. The noise analysis is based on a conversion-matrix type formulation, which relates the carrier noisy sidebands of the input signal with the detector output spectrum through a pair of transfer functions obtained in commercial software. Measurements of detectors in individual and differential setups will be presented and compared with predictions.The authors would like to thank the Spanish Ministry of Science and Innovation (MICINN) for the financial support provided through projects TEC2011-29264-C03-01, CONSOLIDER-INGENIO CSD2008-00068 (TERASENSE), TEC2014-58341-C4-1-R, FEDER co-funding, CONSOLIDER-INGENIO CSD2010-00064 and the University of Cantabria Industrial Doctorate programme 2014, project: “Estudio y Desarrollo de Tecnologías para Sistemas de Telecomunicación a Frecuencias Milimétricas y de Terahercios con Aplicación a Sistemas de Imaging en la Banda 90–100 GHz”

Performance assessment of W-Band radiometers: direct versus heterodyne detections

W-Band radiometers using intermediate frequency down-conversion (super-heterodyne) and direct detection are compared. Both receivers consist of two W-band low noise amplifiers and an 80-to-101 GHz filter, which conforms to the reception frequency band, in the front-end module. The back-end module of the first receiver comprises a subharmonic mixer, intermediate frequency (IF) amplification and a square-law detector. For direct detection, a W-Band detector replaces the mixer and the intermediate frequency detection stages. The performance of the whole receivers has been simulated requiring special techniques, based on data from the experimental characterization of each subsystem. In the super-heterodyne implementation a local oscillator at 27.1 GHz (with 8 dBm) with a x3 frequency multiplier is used, exhibiting an overall conversion gain around 48 dB, a noise figure around 4 dB, and an effective bandwidth over 10 GHz. In the direct detection scheme, slightly better noise performance is obtained, with a wider bandwidth, around 20 GHz, since there is no IF bandwidth limitation (~15 GHz), and even using the same 80-to-101 GHz filter, the detector can operate through the whole W-band. Moreover, W-band detector has higher sensitivity than the IF detector, increasing slightly the gain. In both cases, the receiver performance is characterized when a broadband noise input signal is applied. The radiometer characteristics have been obtained working as a total power radiometer and as a Dicke radiometer when an optical chopper is used to modulate the incoming signal. Combining this particular super-heterodyne or direct detection topologies and total power or Dicke modes of operation, four different cases are compared and discussed, achieving similar sensitivities, but better performances in terms of equivalent bandwidth and noise for the direct detection radiometer. It should be noted that this conclusion comes from a particular set of components, which we could consider as typical, but we cannot exclude other conclusions for different components, particularly for different mixers and detectors.This research was funded by the Spanish Ministry of Science and Innovation through the grant: PID2019-110610RB-C22 and by the Spanish Ministry of Economy and Competitiveness, Program CONSOLIDER-INGENIO reference CSD2010-00064, CONSOLIDER-SPATEK Network of Excellence and University of Cantabria, Industrial Doctorate reference 12.DI05.648

Amplificador de bajo ruido MMIC en la banda Ka a temperatura criogénica

The cryogenic performance of a Ka-Band MMIC LNA (Low Noise Amplifier) is presented. The amplifier has four self-biased stages based on GaAs technology. At room temperature the amplifier gain is 18 dB and with a noise temperature of 300 K at 30 GHz and a power consumption of 97 mW. When it is cooled to 37 K a noise temperature of 70 K is obtained with an associated gain of 23 dB at 30 GHz. The noise temperature test has been carried out using the cold attenuator method

Radiómetro en banda W para aplicaciones de radioastronomía

A W-band radiometer with intermediate frequency down-conversion for radio astronomy applications is presented. The receiver consists of two W-band low noise amplifiers followed by a subharmonic mixer, intermediate frequency amplification and a square-law detector. The performance of the receiver subsystems is characterized experimentally. The receiver works in the 82 to 96 GHz frequency band, and using a local oscillator of 27.1 GHz with 8 dBm of available power, it exhibits an overall conversion gain around 48 dB, a noise figure of 4.5 dB, and an effective bandwidth of 10 GHz. The receiver performance is characterized when a broadband noise input signal is applied. The radiometer characteristic has been obtained working as a total power radiometer and as a Dicke radiometer when an optical chopper is used to modulate the incoming signal.Este trabajo ha sido financiado por el Ministerio de Economía y Competitividad bajo el programa CONSOLIDER-INGENIO 2010 referencia CSD2010-00064, Red de excelencia CONSOLIDER-SPATEK y Universidad de Cantabria, Doctorado Industrial 2014 referencia 12.DI05.648

The Canfranc Axion Detection Experiment (CADEx): Search for axions at 90 GHz with Kinetic Inductance Detectors

We propose a novel experiment, the Canfranc Axion Detection Experiment (CADEx), to probe dark matter axions with masses in the range 330-460 $\mu$eV, within the W-band (80-110 GHz), an unexplored parameter space in the well-motivated dark matter window of Quantum ChromoDynamics (QCD) axions. The experimental design consists of a microwave resonant cavity haloscope in a high static magnetic field coupled to a highly sensitive detecting system based on Kinetic Inductance Detectors via optimized quasi-optics (horns and mirrors). The experiment is in preparation and will be installed in the dilution refrigerator of the Canfranc Underground Laboratory. Sensitivity forecasts for axion detection with CADEx, together with the potential of the experiment to search for dark photons, are presented.Comment: 23 pages, 10 figure

Patients awaiting surgery for neurosurgical diseases during the first wave of the COVID-19 pandemic in Spain: a multicentre cohort study.

The large number of infected patients requiring mechanical ventilation has led to the postponement of scheduled neurosurgical procedures during the first wave of the COVID-19 pandemic. The aims of this study were to investigate the factors that influence the decision to postpone scheduled neurosurgical procedures and to evaluate the effect of the restriction in scheduled surgery adopted to deal with the first outbreak of the COVID-19 pandemic in Spain on the outcome of patients awaiting surgery. This was an observational retrospective study. A tertiary-level multicentre study of neurosurgery activity between 1 March and 30 June 2020. A total of 680 patients awaiting any scheduled neurosurgical procedure were enrolled. 470 patients (69.1%) were awaiting surgery because of spine degenerative disease, 86 patients (12.6%) due to functional disorders, 58 patients (8.5%) due to brain or spine tumours, 25 patients (3.7%) due to cerebrospinal fluid (CSF) disorders and 17 patients (2.5%) due to cerebrovascular disease. The primary outcome was mortality due to any reason and any deterioration of the specific neurosurgical condition. Second, we analysed the rate of confirmed SARS-CoV-2 infection. More than one-quarter of patients experienced clinical or radiological deterioration. The rate of worsening was higher among patients with functional (39.5%) or CSF disorders (40%). Two patients died (0.4%) during the waiting period, both because of a concurrent disease. We performed a multivariate logistic regression analysis to determine independent covariates associated with maintaining the surgical indication. We found that community SARS-CoV-2 incidence (OR=1.011, p Patients awaiting neurosurgery experienced significant collateral damage even when they were considered for scheduled procedures