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| Author |
Lobanov, Y.; Tong, C.; Blundell, R.; Gol'tsman, G. |
| Title |
A study of direct detection effect on the linearity of hot electron bolometer mixers |
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Conference Article |
| Year |
2009 |
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Proc. 20th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 20th ISSTT |
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282-287 |
| Keywords |
HEB mixer, direct detection effect |
| Abstract |
We have performed a study of how direct detection affects the linearity and hence the calibration of an HEB mixer. Two types of waveguide HEB devices have been used: a 0.8 THz HEB mixer and a 1.0 THz HEB mixer which is ~5 times smaller than the former. Two independent experimental approaches were used. In the ΔG/G method, the conversion gain of the HEB mixer is first measured as a function of the bias current for a number of bias voltages. At each bias setting, we carefully measure the change in the operating current when the input loads are switched. From the measured data, we can derive the expected difference in gain between the hot and cold loads. In the second method (injection method [1]), the linearity of the HEB mixer is independently measured by injecting a modulated signal for different input load temperatures. The results of both approaches confirm that there is gain compression in the operation of HEB mixers. Based on the results of our measurements, we discuss the impact of direct detection effects on the operation of HEB mixers. |
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RPLAB @ gujma @ |
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724 |
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Lobanov, Y. V.; Tong, Cheuk-Yu E.; Hedden, A. S.; Blundell, R.; Gol'tsman, G. N. |
| Title |
Microwave-assisted슠measurement슠of the슠frequency슠response슠of슠terahertz슠HEB슠mixers슠with a슠fourier슠transform슠spectrometer |
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Conference Article |
| Year |
2010 |
Publication |
21st International Symposium on Space Terahertz Technology |
Abbreviated Journal |
21st ISSTT |
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420-423 |
| Keywords |
HEB mixer |
| Abstract |
We describe a novel method of operation of the HEB direct detector for use with a Fourier Transform Spectrometer. Instead of elevating the bath temperature, we have measured the RF response of waveguide HEB mixers by applying microwave radiation to select appropriate bias conditions. In our experiment, a microwave signal is injected into the HEB mixer via its IF port. By choosing an appropriate injection level, the device can be operated close to the desired operating point. Furthermore, we have shown that both thermal biasing and microwave injection can reproduce the same spectral response of the HEB mixer. However, with the use of microwave injection, there is no need to wait for the mixer to reach thermal equilibrium, so characterisation can be done in less time. Also, the liquid helium consumption for our wet cryostat is also reduced. We have demonstrated that the signalto-noise ratio of the FTS measurements can be improved with microwave injection. |
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RPLAB @ gujma @ |
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725 |
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Ожегов, Р.В.; Окунев, О.В.; Гольцман, Г.Н. |
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Флуктуационная чувствительность сверхпроводящего болометрического смесителя на эффекте разогрева электронного газа |
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Journal Article |
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2009 |
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Радиотехника |
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3 |
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120-124 |
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смеситель на горячих электронах; флуктуационная чувствительность; тепловизор терагерцевого диапазона частот; hot-electron bolometer mixer; Imaging system; Noise equivalent temperature difference; Heterodyne receiver; Terahertz range |
| Abstract |
Interest in research in the terahertz range is driven by a great number of various applications, where terahertz instruments may play a leading role. To name just a few, such applications include study of the cosmic microwave background radiation and the distribution of the dark matter, medicine, navigation, fire alarm, security systems and environmental monitoring. The paper discusses the possibility of using a receiver based on the hot-electron effect in superconducting films as an imaging system. We present the results of the noise equivalent temperature difference (NETD) measurements performed with a hot-electron bolometer mixer made from a thin superconducting film. The receiver with a noise temperature of ~ 3800 K at a local oscillator frequency of 300 GHz a bandwidth of 500 MHz and an integration time of 1 s has offered an NETD of 0.5 K. We have also developed a technique that enabled us to reduce the contribution of the mixer gain fluctuations to the overall system instability. As of this writing, the above value of the NETD is the lowest value offered for this type of receiver, which indicates the possibility to use such receivers in real-time imaging systems. The technique offered in the paper for achieving the limiting value of the NETD offers an alternative to the phase-locking scheme.
Представены результаты измерения флуктуационной чувствительности (NETD – noise equivalent temperature difference) болометрического смесителя на эффекте разогрева электронного газа в тонких сверхпроводящих пленках. Получено предельное значение NETD, равное 0,5 К, при шумовой температуре приемника 3800 К, ширине полосы преобразования 500 МГц, постоянной времени 1 с и частоте гетеродина 300 ГГц. Разработана методика достижения предельной флуктуационной чувствительности, позволяющая избежать влияния нестабильности коэффициента преобразования смесителя. |
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RPLAB @ gujma @ |
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728 |
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| Author |
Ожегов, Роман Викторович |
| Title |
Флуктуационная чувствительность и стабильность приемников с СИС и HEB смесителями для терагерцового тепловидения |
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2011 |
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Радиофизика |
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135 |
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HEB |
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RPLAB @ gujma @ |
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731 |
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| Author |
Shurakov, Alexander; Tong, Edward; Blundell, Raymond; Gol'tsman, Gregory |
| Title |
Microwave stabilization of HEB mixer by a microchip controller |
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2012 |
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IEEE MTT-S international microwave symposium digest |
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1-3 |
| Keywords |
HEB mixer stability, microwave injection, Allan variance, Allan time |
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The stability of a Hot Electron Bolometer (HEB) mixer can be improved by the use of microwave injection. In this article we report a refinement of this approach. We introduce a microchip controller to facilitate the implementation of the stabilization scheme, and demonstrate that the feedback loop effectively suppresses drifts in the HEB bias current, leading to an improvement in the receiver stability. The measured Allan time of the mixer's IF output power is increased to > 10 s. |
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Montreal, QC, Canada |
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