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Register a new userCold-Source Noise Measurement of a Differential Input Single-Ended Output Low-Noise Amplifier Connected to a Low-Frequency Radio Astronomy Antenna
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We present two methods for measuring the noise temperature of a differential input single-ended output (DISO) Low-Noise Amplifier (LNA) connected to an antenna. The first method is direct measurement of the DISO LNA and antenna in an anechoic chamber at ambient temperature. The second is a simple and low-cost noise parameter extraction of the DISO device using a coaxial long cable. The reconstruction of the DISO noise parameter from the noise wave measurements of the DISO LNA with one terminated input port is discussed in detail. We successfully applied these methods to the Murchison Widefield Array LNA and antenna.
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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 (Te) lower than 58 K across the operational bandwidth, with average Te 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.
We report on the detection of source noise in the time domain at 162MHz with the Murchison Widefield Array. During the observation the flux of our target source Virgo A (M87) contributes only $sim$1% to the total power detected by any single antenna, thus this source noise detection is made in an intermediate regime, where the source flux detected by the entire array is comparable with the noise from a single antenna. The magnitude of source noise detected is precisely in line with predictions. We consider the implications of source noise in this moderately strong regime on observations with current and future instruments.
MASER (Measurements, Analysis, and Simulation of Emission in the Radio range) is a comprehensive infrastructure dedicated to time-dependent low frequency radio astronomy (up to about 50 MHz). The main radio sources observed in this spectral range are the Sun, the magnetized planets (Earth, Jupiter, Saturn), and our Galaxy, which are observed either from ground or space. Ground observatories can capture high resolution data streams with a high sensitivity. Conversely, space-borne instruments can observe below the ionospheric cut-off (at about 10 MHz) and can be placed closer to the studied object. Several tools have been developed in the last decade for sharing space physics data. Data visualization tools developed by various institutes are available to share, display and analyse space physics time series and spectrograms. The MASER team has selected a sub-set of those tools and applied them to low frequency radio astronomy. MASER also includes a Python software library for reading raw data from agency archives.
We present a heralded single-photon source with a much lower level of unwanted background photons in the output channel by using the herald photon to control a shutter in the heralded channel. The shutter is implemented using a simple field programable gate array controlled optical switch.
We present the design and characterisation of a low-noise, resonant input transimpedance amplified photodetector. The device operates at a resonance frequency of $90 ,textrm{MHz}$ and exhibits an input referred current noise of $1.2,textrm{pA}/sqrt{textrm{Hz}}$---marginally above the the theoretical limit of $1.0,textrm{pA}/sqrt{textrm{Hz}}$ set by the room temperature Johnson noise of the detectors $16,textrm{k}Omega$ transimpedance. As a result, the photodetector allows for shot-noise limited operation for input powers exceeding $14,mutextrm{W}$ at $461,textrm{nm}$ corresponding to a noise equivalent power of $3.5,textrm{pW}/sqrt{textrm{Hz}}$. The key design feature which enables this performance is a low-noise, common-source JFET amplifier at the input which helps to reduce the input referred noise contribution of the following amplification stages.
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