Minimum Noise Temperature Research Articles

Design and Development of SIS Mixers for ALMA Band 8

In this paper, we report on the design and experimental results of a fix-tuned Superconductor-Insulator-Superconductor (SIS) mixer for Atacama Large Millimeter/submillimeter Array (ALMA) band 8 (385-500 GHz) receivers. Nb-based SIS junctions of a current density of 10 kA/cm/sup 2/ and one micrometer size (fabricated with a two-step lift-off process) are employed to accomplish the ALMA receiver specification, which requires wide frequency coverage as well as low noise temperature. Parallel-connected twin junctions (PCTJ) are designed to resonate at the band center to tune out the junction geometric capacitance. A waveguide-microstrip probe is optimized to have nearly frequency-independent impedance at the probe's feed point, thereby making it much easier to match the low-impedance PCTJ over a wide frequency band. In addition, a superconducting magnet fixed onto the compact mixer block to provide efficient magnetic field coupling is designed. The SIS mixer demonstrates a minimum double-sideband receiver noise temperature of 108 K at the band center and temperatures of less than 167 K over the whole band (for an intermediate-frequency range of 4-8 GHz).

Ultrasensitive radio-frequency pseudomorphic high-electron-mobility-transistor readout for quantum devices

Two versions of a cryogenic multistage pseudomorphic high-electron-mobility field-effect transistor amplifier (based on the AlGaAs/InGaAs/GaAs heterostructure) have been designed for quantum device readout and tested at an ambient temperature ∼380mK. The minimum noise temperature of the first amplifier version is below 110±25mK(∼80±20hf∕kB) at 28.6 MHz, estimated from the noise of input 10 kΩ resistance and coupled input tank circuit with an active resistance at the resonant frequency RS(f0)≈17.9kΩ. Its minimum voltage spectral noise density, with respect to the input, is about 200pV∕(Hz)1∕2 and the corner frequency of the 1∕f noise is close to 300 kHz. For the amplifier with the lowest designed back action, the minimum noise temperature below 130±30mK(∼100±25hf∕kB) at 26.8 MHz was estimated when coupled to an input tank circuit with RS(f0)≈61.8kΩ. The power consumption of the amplifiers is in the range of 100–600 μW.

Accurate charge‐control model for analysis of noise properties for AlGaAs/GaAs hemt and AlGaAs/InGaAs phemt at microwave frequencies

AbstractAn accurate charge‐control approach to analytical noise modeling of a high electron mobility transistor, which provides excellent results in agreement with the experimental data, is presented. The small‐signal parameters, and the drain and gate‐noise sources are calculated to determine the noise coefficients, minimum noise figure Fmin and minimum noise temperature Tmin. The influence of drain current, frequency, and device parameters upon Fmin and Tmin for AlGaAs/GaAs HEMT and AlGaAs/InGaAs/GaAs PHEMT is presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 489–494, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20346

Noise sources and dissipation mechanisms of a 120 ℏ SQUID amplifier

A two-stage superconducting quantum interference device (SQUID), based on a commercial sensor, is strongly coupled to an electrical resonator at 11 kHz with a quality factor Q=600 000 and operated in the temperature range 1.33–4.17 K. From the analysis of the noise generated by this system, the back action noise of the SQUID amplifier is estimated. The minimum noise temperature, calculated from back action and additive noise measurements, is 63 μK at 1.33 K, and corresponds to 120 times the quantum-limited noise temperature. We discuss and experimentally verify a mechanism, which can limit the noise temperature and add losses to the system.

Low noise, low power consumption high electron mobility transistors amplifier, for temperatures below 1 K

Low noise three-stage pseudomorphic high electron mobility field-effect transistors amplifier were designed for the temperature range below 1 K. A minimum noise temperature TN≈100 mK was measured at an ambient temperature of about 380 mK at frequencies between 1 and 4 MHz for a source resistance of 10 kΩ. The gain of the amplifier was 50 at a power consumption of about 200 μW. The noise parameters of the amplifier are stable to within 30%, for a power consumption in the range of 100–300 μW. Minimum voltage spectral noise density of the amplifier with respect to the input is about 200 pV/Hz1/2 and the corner frequency of the 1/f noise is close to 300 kHz.

A submillimetre-wave SIS mixer using NbN/MgO/NbN trilayers grown epitaxially on an MgO substrate

We have designed, fabricated and tested a quasi-optical superconductor–insulator–superconductor (SIS) mixer employing distributed NbN/MgO/NbN tunnel junctions and NbN/MgO/NbN microstriplines at submillimetre-wave frequencies. These trilayers were fabricated by dc- and rf-magnetron sputtering on an MgO substrate at ambient temperature so that the NbN and MgO films were grown epitaxially. Our SIS mixer consists of an MgO hyperhemispherical lens with an antireflection cap and a self-complementary log-periodic antenna made of a single-crystal NbN film, on which the distributed SIS junctions and the two-section impedance transformers were mirror-symmetrically placed at the feed point of the antenna. As designed, the junctions are 0.6 μm wide and 15.5 μm long, which is sufficient to absorb the incoming signal along this lossy transmission line, assuming a current density of 10 kA cm−2. The mixer showed good I–V characteristics, with subgap-to-normal resistance ratios of about 13, although weak-link breaks were observed above the gap voltage. The minimum double side band receiver noise temperature was 334 K at 678 GHz, including the input noise of about 200 K as estimated by the standard technique. The noise temperature gradually rose to 672 K at 820 GHz. This behaviour may be caused by RF losses from the weak-link parts, due to the steps between the distributed junctions and the microstriplines being less than 1 μm wide.

A 350 GHz SIS Receiver on the Nobeyama 10 m Submillimeter Telescope

Abstract We have developed a low-noise submillimeter-wave SIS receiver (320–360 GHz) for a 10 m submillimeter telescope, which was installed at Nobeyama in 2000 February. This receiver and a millimeter-wave SIS receiver are mounted on the ceiling of the Cassegrain receiver cabin of the 10 m telescope. Two curved mirrors couple a shaped Cassegrain beam from the subreflector to mixer horns. The minimum noise temperature measured in front of the receiver was 52 K in double sideband (DSB) at a local oscillator (LO) frequency of 354 GHz, which corresponds to three-times quantum limits ($3h\nu/k_{\mathrm{B}}$). This noise temperature contributions are resolved into the optics, mixer, and IF parts. The temperature ripple of a two-stage Gifford–McMahon cryocooler has been reduced to be 2 mK peak-to-peak at the mixer block with a helium pot temperature stabilizer. Mechanical vibration (30 ${\mu \mathrm {m}}$ peak-to-peak) of the cold head degrades the receiver stability.

Low-noise S-band DC SQUID based amplifier

A low-noise rf amplifier based on a dc SQUID (SQA) is tested in the frequency range 3.3-4.1 GHz. A new signal launching system for the SQA rf coupling has been developed and successfully implemented. The following parameters have been measured at 3.65 GHz using a band-pass filter at the input of a single-stage SQA: gain (11.0/spl plusmn/1.0) dB, 3 dB bandwidth of 300 MHz and noise temperature (4.0/spl plusmn/1.0)K. This figure corresponds to a flux noise S/sub /spl Phi///sup 1/2 /=0.6 /spl mu//spl Phi//sub 0//Hz/sup 1/2 / and an energy sensitivity /spl epsi//sub i//spl ap/75 h. The input saturation power, P/sub s/, (1 dB gain compression) is measured for different bandwidths of the input band-pass filter, A corresponding input signal saturation temperature (normalized for a 1 GHz bandwidth) T/sub SAT//sup 1GHZ/=P/sub SAT//k/sub B/ is estimated to be 11.5 K GHz at an SQA bias voltage 27 /spl mu/V (condition for minimum noise temperature). The dependencies of the SQA gain, noise temperature and saturation level on the operation point are studied. The reason for the SQA saturation is discussed.

A three photon noise SIS heterodyne receiver at submillimeter wavelength

An ultra-low noise single sideband SIS receiver has been prepared for radio astronomy at the sub millimeter wavelength /spl lambda//spl ap/0.85 mm. The minimum single sideband receiver noise temperature of 48 K corresponds to 3 h/spl omega//k or equivalent number of 3 photon of noise. The minimum single sideband SIS mixer noise temperature is about 20 K, close to 1.2 h/spl omega//k, or one photon of noise. The Nb/AlOx/Nb junctions with a Josephson critical current density of 9 KA/cm/sup 2/ and with the area of about 0.9 /spl mu/m/sup 2/ were used. The receiver has been tested at the 30 meter IRAM radio telescope in the winter seasons of 1997 and 1998. The observations at the radio telescope are speeded up by a factor of two to three with the new receiver.

Investigation of NbN phonon-cooled HEB mixers at 2.5 THz

The development of superconducting hot electron bolometric (HEB) mixers has been a big step forward in the direction of quantum noise limited mixer performance at THz frequencies. Such mixers are crucial for the upcoming generation of airborne and spaceborne THz heterodyne receivers. In this paper we report on new results on a phonon-cooled NbN HEB mixer using e-beam lithography. The superconducting film is 3 nm thick. The mixer is 0.2 /spl mu/m long and 1.5 /spl mu/m wide and it is integrated in a spiral antenna on a Si substrate. The device is quasi-optically coupled through a Si lens and a dielectric beam combiner to the radiation of an optically pumped FIR ring gas laser cavity. The performance of the mixer at different THz frequencies from 0.69 to 2.55 THz with an emphasis on 2.52 THz is demonstrated. At 2.52 THz minimum DSB noise temperatures of 4200 K have been achieved at an IF of 1.5 GHz and a bandwidth of 40 MHz with the mixer mounted in a cryostat and a 0.8 m long signal path in air.

4 GHz cryogenic low noise IF amplifiers for OSO imaging receiver

We present the design and realization of 4 GHz cryogenic low noise amplifiers used as IF amplifiers in a radio-camera receiver (SISYFOS project) which is to be installed in the Onsala 20 m millimetre wave telescope. We show that a very simple and compact input design provides good matching over a broad bandwidth while ensuring the stability of the amplifier. The minimum noise temperature and the gain of the amplifier measured at cryogenic ambient temperature over the specified bandwidth are 7 K and 28 dB respectively.

A Low-Noise 230 GHz SIS Receiver for Radio Astronomy Employing Untuned Nb/AlOx/Nb Tunnel Junctions

A heterodyne receiver based on a ∼1/3 reduced height rectangular waveguide SIS mixer with two mechanical tuners has been built for astronomical observations of molecular transitions in the 230 GHz frequency band. The mixer used an untuned array (ωRnCj≈3, Rn≈70 Ω) of four Nb/AIOx/Nb tunnel junctions in series as a nonlinear mixing element. A reasonable balance between the input and output coupling efficiencies has been obtained by choosing the junction number N=4. The receiver exhibits DSB (Double Side Band) noise temperature around 50 K over a frequency range of more than 10 GHz centered at 230 GHz. The lowest system noise temperature of 38 K has been recorded at 232.5 GHz. Mainly by adjusting the subwaveguide backshort, the SSB (Single Side Band) operation with image rejection of ≥ 15 dB is obtained with the noise temperature as low as 50 K. In addition, the noise contribution from each receiver component has been studied further. The minimum SIS mixer noise temperature is estimated as 15 K, pretty close to the quantum limit ħv/k∼11 K at 230 GHz. It is believed that the receiver noise temperatures presented are the lowest yet reported for a 230 GHz receiver using untuned junctions.

A new noise measurement method of noise parameters at microwave frequencies

This paper proposes a new method for noise parameter measurement of microwave devices. Instead of measuring the noise figure, the optimum source impedance /spl Gamma//sub opt/ is determined by measuring the noise powers corresponding to cold impedances, then, the minimum noise figure F/sub min/ (or minimum effective noise temperature T/sub min/) and noise conductance G/sub n/ are determined by connecting a calibrated hot noise source. Measurements with highly mismatched impedances (magnitude of the reflection coefficient close to one |/spl Gamma/|/spl ap/1) are possible, which is not the case with the classical method. Automatic tuner and isolators used in the classical method are no longer necessary. Using the method described, noise measurement system cost can be reduced and measurement time minimized.

Fabrication and mixer performance of Nb/Al double-barrier junctions

Specific difficulties of the fabrication of Nb/Al double-barrier junctions with high current density (10 kA/cm/sup 2/) and small area (1-3 /spl mu/m/sup 2/) are discussed and possible solutions are presented. The problem of nonuniform areas of the two superposed junctions was circumvented by introducing a loading effect in the etching process. Strong backbending of the I/V-curve was reduced by increasing the thickness of the Nb layer between the two superposed junctions. In a mixer experiment in the 100 GHz frequency band a broad-band response of the double-barrier device was obtained with a minimum receiver noise temperature of 45 K at 115 GHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Four photons sensitivity heterodyne detection of submillimeter radiation with superconducting tunnel junctions

An ultra low noise SIS receiver has been prepared for radio astronomy. The minimum double sideband receiver noise temperature is about 30 K which corresponds to 2 /spl planck//spl omega//k or an equivalent number of 4 photons of noise. The minimum measured double sideband mixer noise temperature is about 10 K which corresponds to 0.6 /spl planck//spl omega//k or approximately to 1 photon of noise. The fixed tuned SIS mixer operates in the 290-370 GHz frequency range. The submicron niobium junctions mere fabricated using photoresist lines for junction definition. The receiver has been used at the 30 m IRAM radio telescope in Spain in winter 1994. Telescope system noise temperature of 500 K single sideband has been achieved when the sky opacity was about 0.17.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical displacement sensor with frequency-selective squeezing of the vacuum noise

Electromechanical analogies are used to derive expressions for the electromechanical Z parameters and for the energy spectra of Langevin sources of noise in an lf equivalent of an optical displacement sensor with frequency-selective squeezing of the vacuum noise. The minimum noise temperature of the sensor is estimated. The use of squeezed vacuum fluctuations can improve the noise matching of the sensor and help to achieve the minimum noise temperature even for nonoptimal parameters of the system.

Noise performance of Si/Si/sub 1-x/Ge/sub x/ FETs

Noise characteristics are evaluated for SiGe/Si based n-channel MODFETs and p-channel MOSFETs. The analysis is based on a self-consistent solution of Schrodinger and Poisson's equations. The model predicts a superior minimum noise figure for an n-channel MODFET at 77 K. P-channel MOSFETs behave similar to n-channel devices operating at 300 K. Minimum noise figure decreases with increasing quantum well (QW) width for both n- and p-channel devices. However, the p-channel devices are less sensitive to QW width variation. Minimum noise temperature behaves similarly. As observed, a range of doped epilayer thickness exists where minimum noise figure is a minimum for both n- and p-channel FETs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimization of a schottky barrier mixer diode in the submillimeter wave region

We have designed a mixer Schottky barrier diode (SBD) for use in the submillimeter wave region with a structure optimized for minimum noise temperature. The dependence of mixer noise temperature upon thickness and doping density of the epitaxial layer and diode diameter of SBDs was simulated within the framework of existing theories. Special care was taken to formulate the SBD current-voltage and capacitance-voltage relations in a way that correctly describes the behavior of real SBDs.

Modeling the performance of high temperature superconductor based sin and sis quasiparticle mixers

Abstract The Tucker model has been used to simulate the performance of high-Tc based, SIN and SIS quasiparticle mixers, operating as photon detectors in the THz regime. The realistic numerical simulations utilipe experimentally measured, current vs voltage (I-V) tunneling characteristics from point contact junctions on HgBa2CuO4, (Tc = 95 K) phich have displaped BCS-like characteristics. An optimipation algorithm has been developed to determine the parameter range phere maximum conversion efficiencp and minimum noise temperature (TM) for the mixer are found. It is shopn that infinite gain is achievable at 4.2 K for the SIS mixer in both the single-side band (SSB) and double-side-band (DSB) mode and also for the SIN mixer in the DSB mode. Noise temperatures approaching the puantum limit are found for the SIN mixer in the range 1–5 THp. Thus it is possible to develop a heterodpne detector in this Frequency range operating at 4.2 K phich utilipes simpler SIN thin film junctions on HgBa2CuO4. Simulations on SIS junctions operating at temperatures of closed-cycle refrigerators (T = 12 K) also display quantum limited noise performance.

Noise temperature modeling of AlGaAs/GaAs and AlGaAs/InGaAs/GaAs HEMTs

An accurate modeling of noise temperature for AlGaAs/GaAs HEMTs and AlGaAs/InGaAs/GaAs Pseudomorphic HEMTs (PHEMTs) is presented. The analysis is based on a self-consistent solution of Schrödinger and Poisson's equations. Pseudomorphic HEMTs have a lower noise temperature as compared to normal AlGaAs/GaAs HEMTs. The minimum noise temperature in pseudomorphic HEMTs decreases with increasing quantum-well (QW) width. Noise temperature in general increases with increasing gate length.