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Author Tong, C.-Y. E.; Meledin, D.; Loudkov, D.; Blundell, R.; Erickson, N.; Kawamura, J.; Mehdi, I.; Gol’tsman, G.
Title A 1.5 THz Hot-Electron Bolometer mixer operated by a planar diode based local oscillator Type Conference Article
Year 2003 Publication IEEE MTT-S Int. Microwave Symp. Digest Abbreviated Journal IEEE MTT-S Int. Microwave Symp. Digest
Volume 2 Issue Pages 751-754
Keywords (down) waveguide NbN HEB mixers
Abstract We have developed a 1.5 THz superconducting NbN Hot-Electron Bolometer mixer. It is operated by an all-solid-state Local Oscillator comprising of a cascade of 4 planar doublers following an MMIC based W-band power amplifier. The threshold available pump power is estimated to be 1 /spl mu/W.
Address Philadelphia, PA, USA
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Call Number Serial 1516
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Author Lobanov, Y.; Tong, E.; Blundell, R.; Hedden, A.; Voronov, B.; Gol'tsman, G.
Title Large-signal frequency response of an HEB mixer: from 300 MHz to terahertz Type Journal Article
Year 2011 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal
Volume 21 Issue 3 Pages 628-631
Keywords (down) waveguide NbN HEB mixers
Abstract We present a study of the large signal frequency response of an HEB mixer over a wide frequency range. In our experiments, we have subjected the HEB mixer to incident electromagnetic radiation from 0.3 GHz to 1 THz. The mixer element is an NbN film deposited on crystalline quartz. The mixer chip is mounted in a waveguide cavity, coupled to free space with a diagonal horn. At microwave frequencies, electromagnetic radiation is applied through the coaxial bias port of the mixer block. At higher frequencies the input signal passes via the diagonal horn feed. At each frequency, the incident power is varied and a family of I-V curves is recorded. From the curves we identify 3 distinct regimes of operation of the mixer separated by the phonon relaxation frequency and the superconducting energy gap frequency observed at about 3 GHz and 660 GHz respectively. In this paper, we will present observed curves and discuss the results of our experiment.
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Call Number RPLAB @ gujma @ Serial 719
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Author Lobanov, Y.V.; Tong, C.-Y.E.; Hedden, A.S.; Blundell, R.; Voronov, B.M.; Gol'tsman, G.N.
Title Direct measurement of the gain and noise bandwidths of HEB mixers Type Journal Article
Year 2011 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 21 Issue 3 Pages 645-648
Keywords (down) waveguide NbN HEB mixers
Abstract The intermediate frequency (IF) bandwidth of a hot electron bolometer (HEB) mixer is an important parameter of the mixer, in that it helps to determine its suitability for a given application. With the availability of wideband low noise amplifiers, it is simple to measure the performance of an HEB mixer over a wide range of IF at a fixed LO frequency using the standard Y-factor method. This in-situ method allows us to measure both the gain and noise bandwidths simultaneously. We have also measured mixer output impedance with a vector network analyser. Intrinsic time constant has been extracted from the impedance data and compared to the mixer's bandwidths determined from receiver Y-factor measurement.
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Call Number RPLAB @ gujma @ Serial 720
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Author Tong, C. Edward; Trifonov, Andrey; Blundell, Raymond; Shurakov, Alexander; Gol’tsman, Gregory
Title A digital terahertz power meter based on an NbN thin film Type Abstract
Year 2014 Publication Proc. 25th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 25th Int. Symp. Space Terahertz Technol.
Volume Issue Pages 170
Keywords (down) waveguide NbN HEB mixers
Abstract We have further studied the effect of subjecting a superconducting Hot Electron Bolometer (HEB) element made from an NbN thin film to microwave radiation. Since the photon energy is weak, the microwave radiation does not simply heat the film, but generates a bi-static state, switching between the superconducting and normal states, upon the application of a small voltage bias. Indeed, a relaxation oscillation of a few MHz has previously been reported in this regime [1]. Switching between the superconducting and normal states modulates the reflected microwave pump power from the device. A simple homodyne setup readily recovers the spontaneous switching waveform in the time domain. The switching frequency is a function of both the bias voltage (DC heating) and the applied microwave power. In this work, we use a 0.8 THz HEB waveguide mixer for the purpose of demonstration. The applied microwave pump, coupled through a directional coupler, is at 1 GHz. Since the pump power is of the order of a few μW, a room temperature amplifier is sufficient to amplify the reflected pump power from the HEB mixer, which beats with the microwave source in a homodyne set-up. After further amplification, the switching waveform is passed onto a frequency counter. The typical frequency of the switching pulses is 3-5 MHz. It is found that the digital frequency count increases with higher microwave pump power. When the HEB mixer is subjected to additional optical power at 0.8 THz, the frequency count also increases. When we vary the incident optical power by using a wire grid attenuator, a linear relationship is observed between the frequency count and the applied optical power, over at least an order of magnitude of power. This phenomenon can be exploited to develop a digital power meter, using a very simple electronics setup. Further experiments are under way to determine the range of linearity and the accuracy of calibration transfer from the microwave to the THz regime. References 1. Y. Zhuang, and S. Yngvesson, “Detection and interpretation of bistatic effects in NbN HEB devices,” Proc. 13 th Int. Symp. Space THz Tech., 2002, pp. 463–472.
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Call Number Serial 1366
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Author Loudkov, D.; Tong, C.-Y. E.; Blundell, R.; Kaurova, N.; Grishina, E.; Voronov, B.; Gol’tsman, G.
Title An investigation of the performance of the superconducting HEB mixer as a function of its RF embedding impedance Type Journal Article
Year 2005 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 15 Issue 2 Pages 472-475
Keywords (down) waveguide NbN HEB mixers
Abstract We have conducted an investigation of the optimal embedding impedance for a waveguide superconducting hot-electron bolometric (HEB) mixer. Three mixer chip designs for 800 GHz, offering nominal embedding resistances of 70 /spl Omega/, 35 /spl Omega/, and 15 /spl Omega/, have been developed. We used both High Frequency Structure Simulator (HFSS) software and scale model impedance measurements in the design process. We subsequently fabricated HEB mixers to these designs using 3-4 nm thick NbN thin film. Receiver noise temperature measurements and Fourier Transform Spectrometer (FTS) scans were performed to determine the optimal combination of embedding impedance and normal-state resistance for a 50 Ohm IF load impedance. A receiver noise temperature of 440 K was measured at a local oscillator frequency 850 GHz for a mixer with normal state resistance of 62 /spl Omega/ incorporated into a circuit offering a nominal embedding impedance of 70 /spl Omega/. We conclude from our data that, for low noise operation, the normal state resistance of the HEB mixer element should be close to the embedding impedance of the mixer mount.
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Call Number 1439677 Serial 1464
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