GaAs HEMT low-noise cryogenic amplifiers from C-band to X-band with 0.7-K/GHz noise temperature

Cryogenic low-noise two-stage amplifiers were developed for frequency bands of 3.4-4.6 GHz, 4-8 GHz, and 8-9 GHz using commercial GaAs high electron mobility transistor. The performances are in very good agreement with simulations, and at a cryogenic temperature of 12 K, input noise temperatures get as low as 0.6 K/GHz (2.8 K for the 3.4-4.6 GHz LNA and 5 K for the 4-8 GHz and 8-9 GHz LNAs). Gain ranges from 25 to 28 dB. Ultralow noise temperature, low-power consumption, high reliability, and reproducibility make these devices adequate for series production and receiver arrays in, e.g., telescopes.     

Low-noise 320?360 GHz cryogenically cooled waveguide Schottky diode mixer

Construction details and results of noise measurements on a cryogenically cooled Schottky diode mixer for the 320?360 GHz range are given. Critical mixer parts are electro-formed or machined on a precision lathe. The system double-sideband noise temperature is close to 400 K over a 30 GHz range with a lowest temperature of 385 K at 335 GHz. The mixer uses a tunable contacting backshort and has a total RF/IF double-sideband conversion loss of about 6dB, including input lens and diplexer losses. Corrected for input losses and second-stage contribution, a mixer double-sideband noise temperature of 271 K has been calculated at 335 GHz. This mixer has shown reliable and reproducible performance during five cooldowns to 15 K.     

180–425 GHz low noise SIS waveguide receivers employing tuned Nb/AIO x /Nb tunnel junctions

We report recent results on a 20% reduced height 270–425 GHz SIS waveguide receiver employing a 0.49 µm² Nb/AlO _x /Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an “end-loaded” tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0–2 dB of conversion gain and 50–80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is ≈ 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270–425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200–300 GHz. Best operation is again achieved with the mixer tuned for 0.5–1.5 dB conversion loss which at 258 GHz resulted in receiver and mixer noise temperature of 34K and 27K respectively.     

低噪声1.21.8GHz致冷FET放大器

本文介绍了低噪声1.21.8 GHz致冷FET放大器的研制工作。在20K环境温度下,带宽1.21.7GHz范围内,放大器噪声温度低于10K,最佳为4K。增益约30dB。设计了一个噪声温度自动测试系统。另外对输入电缆的噪声和总测量误差作了分析。测试总误差为2K。     

A low noise SIS array receiver for radioastronomical applications in the 35–50 GHz band

Arrays of six superconducting tunnel junctions have been used in a heterodyne receiver over the frequency range 35–50 GHz. The mixer array and a 3.7–4.2 GHz parametric amplifier used as the if amplifier are immersed in liquid helium and operated at 2 K. The high if allows single sideband operation with a system noise temperature varying rather smoothly from 220 K at 35 GHz to 140 K at 50 GHz. Mixer noise temperatures between 11 and 21 K were measured over the band indicating that the use of arrays to enhance the dynamic range does not seriously affect the mixer noise performance in this frequency range. The receiver is used for radio astronomical observations in the Onsala 20 m telescope in Sweden.     

A low-noise 1.2–1.8 GHz cooled GaAs FET amplifier

A low-noise 1.2–1.8 GHz cooled GaAs FET amplifier with mixer bias circuit is reported. The amplifier noise temperature obtained at an ambient temperature of 20 K in the frequency range of 1.2–1.7 GHz is 10K. The lowest noise temperature is 4K. The gain is about 30 dB. An automatic measuring instrument for noise temperature was designed. The noise effect of the input cable and the error analysis of the total measurement were made. The total measurement error is 2 K.     

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 (ωR_nC_j≈3, R_n≈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 ?v/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 Fixed Tuned Low Noise 600-700 GHz SIS Receiver

We have designed and fabricated a fixed tuned low noise 600-700 GHz SIS mixer. Twin junctions connected in parallel was employed in the mixer design. A short microstrip tuning structure was used to minimize the RF signal loss at frequency above the energy gap. A receiver noise temperature below 200 K (without any loss correction) in the frequency range of 630 to 660 GHz was recorded. The lowest noise temperature of the receiver was 181 K (without any loss correction) at 656 GHz.     

The Development of a Dual Channel SIS Receiver of Trao Telescope

We developed a low noise dual channel receiver with 100GHz and 150GHz band, which is used to make the simultaneous observation with two bands. The SIS mixers are used in both bands. The constructed dewar for the receiver has a performance with a vacuum of 10^?8torr and a temperature of 4.2K. The receiver noise temperature is 50K(DSB) for 100GHz band and 80K(DSB) for 150GHz band, respectively. In order to achieve the simultaneous observations, the quasioptical system is precisely designed, and also evaluated by measurements in the laboratory. The relative pointing offset between two bands is 3″. We have observed the various sources using the receiver since October 1998.     

Ultra-low-noise cryogenic high-electron-mobility transistors

Quarter-micrometer gate-length high-electron-mobility transistors (HEMTs) for cryogenic low-noise application with very low light sensitivity have been developed. At room temperature, these exhibit a noise figure of 0.4 dB with associated gain of 15 dB at 8 GHz. At a temperature of 12.5 K the minimum noise temperature of 5.3±1.5 K has been measured at 8.5 GHz, which is the best noise performance observed to date for any microwave transistors. The results clearly demonstrate the potential for low-temperature low-noise applications     

Cryogenic cooling of mixers for millimeter and centimeter wavelengths

It is shown theoretically that cryogenically cooling a Schottky-barrier mixer only slightly increases the conversion loss while giving a considerable reduction in mixer noise. The d.c. bias and local oscillator drive must be appropriately scaled. Experimental results indicate that in conjunction with a cooled paramp IF amplifier, single-sideband (SSB) receiver noise temperatures of ~350 K at 85 GHz, and ~260 K at 33 GHz are presently obtainable-an improvement by a factor of 6 at 85 GHz and 4 at 33 GHz over current room-temperature mixer receivers. An unexplained source of noise within the diodes has been observed and if this can be eliminated a further factor of 2 improvement in noise temperature will be obtained.     

Low-noise room-temperature wideband parametric amplifiers

Two room-temperature parametric amplifiers are described which have gains of 26 dB. One has an excess noise temperature of between 74 and 85 K across the band 3.7?4.2 GHz, and the other has an excess noise temperature of between 85 and 99 K across the band 7.25?7.75 GHz.     

A low noise receiver for millimeter and submillimeter wavelengths

A broadband, low noise heterodyne receiver, suitable for astronomical use, has been built using a Pb alloy superconducting tunnel junction (SIS). The RF coupling is quasioptical via a bowtie antenna on a quartz lens and is accomplished without any tuning elements. In this preliminary version the double sideband receiver noise temperature rises from 205 K at 116 GHz to 375 K at 349 Ghz, and to 815 K at 466 GHz. This is the most versatile and sensitive receiver yet reported for sub-mm wavelengths.     

125–170 GHz SIS-receiver with closed cycle refrigeration system

A mechanically tunable SIS receiver covering the frequency range from 125 to 170 GHz is described. For cooling at 2.8 K, a closed cycle refrigeration system has been developed that has a cooling power of 350 mW at 2.8 K. The IF is centered at 1.4 GHz with a bandwidth of 600 MHz. For preamplification, a cryogenic 2-stage HEMT amplifier has been developed that has a noise temperature of about 7 K. The best narrow-band spot noise temperature of the receiver is 28 K (DSB) at 133 GHz. Typical broadband (600MHz) values are between 50 and 200 K depending on the frequency. The receiver is used for radioastronomical measurements at the Cologne 3-m radiotelescope.     

Noise performance at cryogenic temperatures at AlGaAs/InGaAs HEMT'swith 0.15-μm T-shaped WSix gates

T-shaped 0.15-μm WSi_x gate HEMTs have been fabricated on AlGaAs/InGaAs MBE wafers. Their S-parameters, output noise spectral density P_no, and noise temperatures T _e at cryogenic temperatures, were measured. The current gain cutoff frequency f_T increases from 61 GHz at 295 K to 87 GHz at 90 K. P_no and T_e measurements indicate that the hot-electron effect is noticeable at low temperatures at high drain current. At 30 GHz, the noise temperature is 19±3 K with an associated gain of 10.4 dB at the physical temperature of 20 K. The results demonstrate the great potential of AlGaAs/InGaAs HEMTs for low-temperature applications     

Precision measurement method for cryogenic amplifier noise temperatures below 5 K

We report precision measurements of the effective input noise temperature of a cryogenic (liquid-helium temperature) monolithic-microwave integrated-circuit amplifier at the amplifier reference planes within the cryostat. A method is given for characterizing and removing the effect of the transmission lines between the amplifier reference planes and the input and output connectors of the cryostat. In conjunction with careful noise measurements, this method enables us to measure amplifier noise temperatures below 5 K with an uncertainty of 0.3 K. The particular amplifier that was measured exhibits a noise temperature below 5.5 K from 1 to 11 GHz, attaining a minimum value of 2.3 K/spl plusmn/0.3 K at 7 GHz. This corresponds to a noise figure of 0.034 dB/spl plusmn/0.004 dB. The measured amplifier gain is between 33.4 dB/spl plusmn/0.3 dB and 35.8 dB/spl plusmn/0.3 dB over the 1-12-GHz range.     

A low noise SIS receiver covering the frequency range 215–250 GHz

We have developed a heterodyne receiver incorporating an SIS mixer for use on a radiotelescope operating at 1.3 mm wavelength. The mixer has a minimum conversion loss of <2 dB and contributes less than 60 K to a total double side band receiver noise temperature of about 80 K at 220 GHz and 230 GHz. To our knowledge this represents the lowest receiver noise ever reported in this frequency range.     

Investigation of a heterodyne receiver with open structure mixer at 324 GHz and 693 GHz

The performance of a submillimeter heterodyne receiver using an HCOOH laser local oscillator and an open structure mixer with a Schottky barrier diode has been optimized for 693 GHz. Working at room temperature a single sideband (SSB) system noise temperature of 7,300 K, a mixer noise temperature of 6,100 K and a conversion loss of 12 dB has been achieved. The same receiver system has been investigated at 324 GHz using an HCOOD laser local oscillator yielding a noise temperature of 3,100 K (SSB), a mixer noise temperature of 2,400 K (SSB) and a conversion loss of 10 dB (SSB). An acousto-optical spectrometer has also been constructed, with 1024 channels and a channel-bandwidth of 250 kHz. The system NEP per channel was 2.5×10^?17 W/Hz^1/2 at 324 GHz and 5.0×10^?17 W/Hz^1/2 at 693 GHz.     

A low-noise SIS receiver measured from 480 GHz to 650 GHz using Nb junctions with integrated RF tuning circuits

A heterodyne receiver using an SIS waveguide mixer with two mechanical tuners has been characterized from 480 GHz to 650 GHz. The mixer uses either a single 0.5 × 0.5 µm² Nb/AlO_x/Nb SIS tunnel junction or a series array of two 1 µm² Nb tunnel junctions. These junctions have a high current density, in the range 8 – 13 kA/cm². Superconductive RF circuits are employed to tune the junction capacitance. DSB receiver noise temperatures as low as 200 ± 17 K at 540 GHz, 271 K ± 22 K at 572 GHz and 362 ± 33 K at 626 GHz have been obtained with the single SIS junctions. The series arrays gave DSB receiver noise temperatures as low as 328 ± 26 K at 490 GHz and 336 ± 25 K at 545 GHz. A comparison of the performances of series arrays and single junctions is presented. In addition, negative differential resistance has been observed in the DC I–V curve near 490, 545 and 570 GHz. Correlations between the frequencies for minimum noise temperature, negative differential resistance, and tuning circuit resonances are found. A detailed model to calculate the properties of the tuning circuits is discussed, and the junction capacitance as well as the London penetration depth of niobium are determined by fitting the model to the measured circuit resonances.     

A 210–280 GHz sis heterodyne receiver for the James Clerk Maxwell Telescope part I: Design and performance

We describe the design and performance of a 210–280 GHz SIS heterodyne receiver built for use on the Maxwell Telescope. The mixer utilises a lead alloy SIS tunnel junction, mounted in 4∶1 reduced height rectangular waveguide, and is tuned with a backshort in 2∶1 reduced height guide. The receiver has a receiver noise temperature of <200K (DSB) across the RF band from 210–270 GHz, with a best noise temperature measured in the laboratory of 113K (DSB) at 231 GHz. A prototype version of this receiver was successfully operated on the telescope in May 1989. By direct intercalibration with a Schottky diode receiver we deduced a best receiver noise temperature of 140K (DSB) at 245 GHz. Discrepancies between this figure and that derived from broad band thermal load calibration are discussed in the accompanying paper (Little et al., 1992, this issue).