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Lumped-element superconducting resonators are a promising technology for their use in millimeter-wave observations and quantum computing applications that require large arrays of extremely sensitive detectors. Among them, lumped-element kinetic inductance detectors (LEKIDs) have shown good performance in the submillimeter band in several earth-based telescopes. In this work, LEKIDs for their use as millimeter-wave receivers of astronomical applications are presented. LEKID arrays using a thin bilayer of superconducting titanium/aluminum (Ti/Al), deposited on the silicon substrate, have been designed and fabricated. The design of a dual-polarization LEKID with the goal of detection at the $W$ -band for two orthogonal polarizations is described and a fabricated array has demonstrated absorption at ambient temperature. Also, an approximate design methodology of the coupling parameter for LEKIDs’ readout, essential for dynamic range optimization of the detector under millimeter-wave radiation, is proposed. In addition, the resonance characteristics and coupling factor of the fabricated superconducting resonators using high-quality internal factor $Q_{i}$ under cryogenic temperatures have been analyzed. The design guidelines in this work are applicable to other LEKID arrays, and the presented superconducting Ti/Al thin-film LEKIDs can be used in future receiver arrays in the millimeter bands. [ABSTRACT FROM AUTHOR]

Thermal capacitances are required to describe the fast dynamic thermal behavior in the silicon-on-insulator (SOI) devices. This article presents a physical model based on the ac technique, together with the characteristic thermal frequency determination through the frequency response of the output conductance, for calculating the thermal capacitance of single-finger and multi-finger SOI-MOSFETs. The model accounts for the total gate width and substrate temperature, making evident the augmented thermal coupling when multi-fingers are used. The thermal capacitances and the corresponding time constants, extracted from a variety of gate widths and number of fingers, are correctly predicted up to a substrate temperature of 150 °C. [ABSTRACT FROM AUTHOR]

A novel full-band square waveguide coupler design based on directional couplers which couple the TE10 and TE01 orthogonal modes in a square waveguide is presented. This waveguide coupler is aimed at the calibration of polarization receivers. This is composed of a pair of rectangular waveguide directional couplers, which are rotated 90° between them and both are coupled to the main square waveguide through each one of the square section walls. The coupler covers the full frequency band from 10 to 18.9 GHz. It has inherent low cross-polarization, which allows obtaining any known elliptically polarized wave at a square waveguide when a signal is applied to the couplers. The fabricated prototype of this coupler exhibits 31 dB of coupling, with flatness of ±3.8 dB and excellent cross polarization better than 50 dB over the whole band. [ABSTRACT FROM AUTHOR]

A novel full-band (40% relative bandwidth) waveguide polar modulator (WPM) design based on a new architecture with two turnstile junctions and a nearly frequency-independent differential 180° phase shift between orthogonal arms is presented. The use of suitably designed turnstile junctions together with antiphase waveguide-coaxial-waveguide transitions in reduced-height waveguide technology enables the improvement of bandwidth over previous WPMs with a very compact and simple solution. This design enables continuous rotation about its central axis at 40 revolutions/s, which makes the modulator suitable for receivers with significant $1/f$ noise such as cryogenic radiometers. The polar modulator presented in this paper is designed to be cooled down to cryogenic temperatures in order to reduce its contribution to the receiver noise. This design is suitable for radio astronomy applications due to its cost-effective, compact design, and high quality performance as well as being readily scalable. A polar modulator in the Ka-band (26.5–40 GHz) has been designed to show a reflection better than −20 dB, an insertion loss around 0.3 dB, and a cross-coupling near −35 dB measured at room temperature ( $T = 298$ K). This insertion loss is reduced by 30%, while the phase difference and cross-coupling maintain similar values when the polar modulator is cooled to approximately $T = 80$ K. [ABSTRACT FROM AUTHOR]

A wideband (30% relative bandwidth) correlation and detection module based on substrate-integrated waveguide (SIW) technology intended for a radio astronomy polarimeter is presented. The SIW circuit is a six-port network with two input ports that are correlated in two hybrid couplers and their corresponding output signals are routed to Schottky diode detectors, which are designed using microstrip technology and assembled within the same system. The designed SIW structure includes hybrid couplers, power dividers, a 90° phase shifter, and 90° bends, providing a real implementation of a functional system with improved bandwidth performance from 35 to 47 GHz. Experimental results are in concordance with simulations, and they validate the module operation for the proposed application. [ABSTRACT FROM AUTHOR]

A novel four-state full Q-band waveguide phase shifter based on smooth-ridged sections is presented. The waveguide structure combines differential 90° and 180° phase shifters, whose combination provides the four-phase states (0°, 90°, 180°, and 270°) by appropriately controlling a set of millimeter-wave switches. Each differential phase shifter is performed using an E-plane continuous profile ridge to reach the 90° or 180° phase shift, respectively. The phase shifter module provides outstanding performance covering the full Q-band (33–50 GHz) with average phase results of 93.5°, 182.8°, and 270.6°. [ABSTRACT FROM PUBLISHER]

In this paper, monolithic microwave integrated circuit (MMIC) broadband low-noise amplifiers (LNAs) for cryogenic applications based on a 100-nm metamorphic high-electron mobility transistor (mHEMT) technology in combination with grounded coplanar waveguide are reported. A three-stage LNA, operating in 4–12 GHz and cooled to 15 K exhibits an associated gain of 31.5 dB \pm 1.8 dB and average noise temperature of 5.3 K (NF=0.079\ \ dB) with a low power dissipation of 8 mW. Additionally another three-stage LNA 25–34 GHz cooled to 15 K has demonstrated a flat gain of 24.2 dB \pm 0.4 dB with 15.2 K (NF=0.22\ \ dB), average noise temperature, with a very low power dissipation of 2.8 mW on chip. The mHEMT-based LNA MMICs have demonstrated excellent noise characteristics at cryogenic temperatures for their use in radio-astronomy applications. [ABSTRACT FROM AUTHOR]

This work describes the principle of operation, assembly and performance of one branch of the 44 GHz back end module (REM) for the Planck low frequency instrument (LFI). This subsystem constitutes a fully rep representative branch of the qualification-model version (QM). It includes waveguide to microstrip transition, GaAs pseudomorphic high electron mobility transistor (PHEMT) low noise amplifiers (LNA), bandpass filter, square-law detector and dc amplifier. The fundamentals of the design of the RF part are described and all of the components have been tested individually before integration. Using single tone and wideband noise stimuli, the output voltage has been measured for several input powers, in order to obtain the sensitivity factor of the complete BEM. The effective bandwidth and the equivalent noise temperature have been calculated from the measurements, taking into account the frequency dependence on the noise source and the BEM. Finally the low frequency output power spectrum has been obtained and a maximum 1/f knee frequency around 200 Hz has been measured with a 3 dB output signal video bandwidth above 50 KHz. [ABSTRACT FROM AUTHOR]

The PLANCK mission of the European Space Agency is devoted to produce sky maps of the cosmic microwave back- ground radiation. The low-frequency instrument is a wide-hand cryogenic microwave radiometer array operating at 30, 44, and 70 GHz. The design, test techniques, and performance of the complete differential radiometer at 30 GHz are presented. This elegant breadboard 30-GHz radiometer is composed of a front-end module (FEM) assembled at the Jodrell Bank Observatory, Cheshire, U.K., and a back-end module assembled at the Universidad de Cantabria, Cantabria, Spain, and Telecomunicació, Universitat Politécnica de Catalunya, Barcelona, Spain. The system noise temperature was excellent, mainly due to the very low noise performance of the FEM amplifiers, which achieved an average noise temperature of 9.4 K. [ABSTRACT FROM AUTHOR]

A Ka-band hybrid 0/180^\circ phase switch working at cryogenic temperature is presented. The circuit is designed on an alumina substrate using uniplanar hybrid technology, combining air-bridged coplanar waveguides and slotlines. Schottky diodes are used as switching elements, taking advantage of their cryogenic behavior, with low equivalent series resistance and low capacitance. Cryogenic performance at 15 K shows a phase difference response of 177 \pm 2^\circ, average insertion losses of 1 dB and amplitude imbalance of less than 0.2 dB between states in the frequency range from 24 to 37 GHz (40% relative bandwidth) with a low-power consumption of 10.5 mW. The low insertion loss and small phase error make the designed phase switch suitable to be used on radioastronomy receivers (QUIJOTE experiment 26–36 GHz band) minimizing the total system noise temperature. [ABSTRACT FROM PUBLISHER]

Based on frequency-domain system-identification techniques combined with an optimal model-order selection, this modeling method efficiently simulates microwave radiometers. A broadband microwave receiver (with astronomical applications) is modeled and simulated to illustrate the technique. This particular receiver is a challenging case because it samples cosmic microwave background (CMB) low-power broadband (10-gigahertz) signals over a long period. [ABSTRACT FROM PUBLISHER]