Coherent polarimeter modules for the QUIET experiment

The Q/U Imaging Experiment (QUIET) is an experimental program to make very sensitive measurements of the Cosmic Background Radiation (CMB) polarization from the ground. A key component of this project is the ability to produce large numbers of detectors in order to achieve the required sensitivity. Using a breakthrough in mm-wave packaging at JPL, a polarimeter-on-a-chip has been developed which lends itself to the mass-production techniques used in the semiconductor industry. We describe the design, implementation and performance of these polarimeter modules for QUIET Phase I and briefly discuss the plans for further module development

Coherent Arrays for Astronomy and Remote Sensing - Final Report

The Coherent Arrays for Astronomy and Remote Sensing Program sponsored by the Keck Institute for Space Studies has had a profound impact on astronomy at Caltech – both at JPL and on campus – and worldwide. It provided funds for the establishment of a world-class coherent detector laboratory – the Cahill Radio Astronomy Laboratory (CRAL) that, in collaboration with JPL and Northrop Grumman, now sets the global standard in coherent detectors in the centimeter-millimeter wavelength range – as shown by three key highlights: (i) NRAO’s recent selection of CRAL MMIC detectors over its own in house MIC detectors for the upgrade of the ALMA Band 2 receivers; (ii) NSF’s funding of a 16-element 85 GHz – 115 GHz focal plane array (ARGUS) for the Green Bank Telescope ($1M); and (iii) NSF’s funding of the 26 GHz – 34 GHz CO Mapping Array Pathfinder (COMAP$2.5M). The funding of COMAP was particularly important since it demonstrated in the wake of the NSF decline of the CARMA proposal (2014) that the US astronomy community and the NSF were prepared to fund large new projects at the Owens Valley Radio Observatory (OVRO), enabling the OVRO to re-establish itself as a world-class radio observatory and convincing Caltech to continue its funding of the OVRO. It is no exaggeration that the KISS coherent detector program played THE major role in saving the OVRO. The position of the CRAL and of the OVRO is now very strong and the staff, decimated by the CARMA decline, is being rebuilt and is once more at a robust strength. Two new multi-national partnerships – the Radio Astronomy Partnership (RAP) and the MMIC Partnership (MMICP) have been established at Caltech as a direct result of the KISS investment in creating the CRAL, and these are providing independent funding to OVRO and the CRAL. There are now eight agency-funded programs at the OVRO and we are optimistic about the prospects of having two more programs funded in the next year, in view of important science breakthroughs at OVRO over the last 6 months

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization

125 - 211 GHz low noise MMIC amplifier design for radio astronomy

To achieve the low noise and wide bandwidth required for millimeter wavelength astronomy applications, superconductor-insulator-superconductor (SIS) mixer based receiver systems have typically been used. This paper investigates the performance of high electron mobility transistor (HEMT) based low noise amplifiers (LNAs) as an alternative approach for systems operating in the 125 — 211 GHz frequency range. A four-stage, common-source, unconditionally stable monolithic microwave integrated circuit (MMIC) design is presented using the state-of-the-art 35 nm indium phosphide HEMT process from Northrop Grumman Corporation. The simulated MMIC achieves noise temperature (T_e) lower than 58 K across the operational bandwidth, with average T_e of 38.8 K (corresponding to less than 5 times the quantum limit (hf/k) at 170 GHz) and forward transmission of 20.5 ± 0.85 dB. Input and output reflection coefficients are better than -6 and -12 dB, respectively, across the desired bandwidth. To the authors knowledge, no LNA currently operates across the entirety of this frequency range. Successful fabrication and implementation of this LNA would challenge the dominance SIS mixers have on sub-THz receivers

A Physical Model for Drain Noise in High Electron Mobility Transistors: Theory and Experiment

We report the on-wafer characterization of $S$-parameters and microwave noise temperature ($T_{50}$) of discrete metamorphic GaAs high electron mobility transistors (HEMTs) at 40 K and 300 K over a range of drain-source voltages ($V_{DS}$). From these data, we extract a small-signal model and the drain noise temperature ($T_{d}$) at each bias and temperature. We find that $T_d$ follows a superlinear trend with $V_{DS}$ at both temperatures. These trends are interpreted by attributing drain noise to a thermal component associated with the channel resistance and a component due to real-space transfer (RST) of electrons from the channel to the barrier [1]. In the present devices at the minimum $T_{50}$, RST contributes $\sim 10$% of the drain noise at cryogenic temperatures. At 300 K, the contribution increases to over $\sim 60$% of the total drain noise. This finding indicates that improving the confinement of electrons in the quantum well could enable room-temperature receivers with up to $\sim 50$% lower noise temperatures by decreasing the contribution of RST to drain noise.Comment: 6 pages, 6 figure

Investigation of Cryogenic Current-Voltage Anomalies in SiGe HBTs: Role of Base-Emitter Junction Inhomogeneities

The anomalous current-voltage characteristics of cryogenic SiGe heterojunction bipolar transistors (HBTs) have been a topic of investigation for many years. Proposed explanations include quasiballistic transport of electrons across the base or tunneling from the emitter to the collector, but inconsistencies exist with these hypotheses. Although similar behavior occurs in Schottky junctions and has been attributed to spatial inhomogeneities in the base-emitter junction potential, this explanation has not been considered for SiGe HBTs. Here, we experimentally investigate this hypothesis by characterizing the base-emitter junction ideality factor and built-in potential of a SiGe HBT versus temperature using a cryogenic probe station. The temperature-dependence of the ideality factor and the relation between the built-in potential as measured by capacitance-voltage and current-voltage characteristics are in good qualitative agreement with the predictions of a theory of electrical transport across a junction with a Gaussian distribution of potential barrier heights. These observations support the origin of cryogenic electrical anomalies in SiGe HBTs as arising from lateral inhomogeneities in the base-emitter junction potential. This work helps to identify the physical mechanisms limiting the cryogenic microwave noise performance of SiGe HBTs

Coherent Arrays for Astronomy and Remote Sensing - Final Report

The Coherent Arrays for Astronomy and Remote Sensing Program sponsored by the Keck Institute for Space Studies has had a profound impact on astronomy at Caltech – both at JPL and on campus – and worldwide. It provided funds for the establishment of a world-class coherent detector laboratory – the Cahill Radio Astronomy Laboratory (CRAL) that, in collaboration with JPL and Northrop Grumman, now sets the global standard in coherent detectors in the centimeter-millimeter wavelength range – as shown by three key highlights: (i) NRAO’s recent selection of CRAL MMIC detectors over its own in house MIC detectors for the upgrade of the ALMA Band 2 receivers; (ii) NSF’s funding of a 16-element 85 GHz – 115 GHz focal plane array (ARGUS) for the Green Bank Telescope ($1M); and (iii) NSF’s funding of the 26 GHz – 34 GHz CO Mapping Array Pathfinder (COMAP$2.5M). The funding of COMAP was particularly important since it demonstrated in the wake of the NSF decline of the CARMA proposal (2014) that the US astronomy community and the NSF were prepared to fund large new projects at the Owens Valley Radio Observatory (OVRO), enabling the OVRO to re-establish itself as a world-class radio observatory and convincing Caltech to continue its funding of the OVRO. It is no exaggeration that the KISS coherent detector program played THE major role in saving the OVRO. The position of the CRAL and of the OVRO is now very strong and the staff, decimated by the CARMA decline, is being rebuilt and is once more at a robust strength. Two new multi-national partnerships – the Radio Astronomy Partnership (RAP) and the MMIC Partnership (MMICP) have been established at Caltech as a direct result of the KISS investment in creating the CRAL, and these are providing independent funding to OVRO and the CRAL. There are now eight agency-funded programs at the OVRO and we are optimistic about the prospects of having two more programs funded in the next year, in view of important science breakthroughs at OVRO over the last 6 months

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization

125 - 211 GHz low noise MMIC amplifier design for radio astronomy

To achieve the low noise and wide bandwidth required for millimeter wavelength astronomy applications, superconductor-insulator-superconductor (SIS) mixer based receiver systems have typically been used. This paper investigates the performance of high electron mobility transistor (HEMT) based low noise amplifiers (LNAs) as an alternative approach for systems operating in the 125 — 211 GHz frequency range. A four-stage, common-source, unconditionally stable monolithic microwave integrated circuit (MMIC) design is presented using the state-of-the-art 35 nm indium phosphide HEMT process from Northrop Grumman Corporation. The simulated MMIC achieves noise temperature (T_e) lower than 58 K across the operational bandwidth, with average T_e of 38.8 K (corresponding to less than 5 times the quantum limit (hf/k) at 170 GHz) and forward transmission of 20.5 ± 0.85 dB. Input and output reflection coefficients are better than -6 and -12 dB, respectively, across the desired bandwidth. To the authors knowledge, no LNA currently operates across the entirety of this frequency range. Successful fabrication and implementation of this LNA would challenge the dominance SIS mixers have on sub-THz receivers