Gol'tsman, G., Maslennikov, S., Finkel, M., Antipov, S., Kaurova, N., Grishina, E., et al. (2006). Nanostructured ultrathin NbN film as a terahertz hot-electron bolometer mixer. In Proc. MRS (Vol. 935, 210 (1 to 6)).
Abstract: Planar spiral antenna coupled and directly lens coupled NbN HEB mixer structures are studied. An additional MgO buffer layer between the superconducting film and Si substrate is introduced. The buffer layer enables us to increase the gain bandwidth of a HEB mixer due to better acoustic transparency. The gain bandwidth is widened as NbN film thickness decreases and amounts to 5.2 GHz. The noise temperature of antenna coupled mixer is 1300 and 3100 K at 2.5 and 3.8 THz respectively. The structure and composition of NbN films is investigated by X-ray diffraction spectroscopy methods. Noise performance degradation at LO frequencies more than 3 THz is due to the use of a planar antenna and signal loss in contacts between the antenna and the sensitive NbN bridge. The mixer is reconfigured for operation at higher frequencies in a manner that receiver’s noise temperature is only 2300 K (3 times of quantum limit) at LO frequency of 30 THz.
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Vachtomin, Y. B., Antipov, S. V., Maslennikov, S. N., Smirnov, K. V., Polyakov, S. L., Zhang, W., et al. (2006). Quasioptical hot electron bolometer mixers based on thin NBN films for terahertz region. In Proc. 16th Int. Crimean Microwave and Telecommunication Technology (Vol. 2, pp. 688–689).
Abstract: Presented in this paper are the performances of HEB mixers based on 2-3.5 nm thick NbN films integrated with log-periodic spiral antenna. Double side-band receiver noise temperature values are 1300 K and 3100 K at 2.5 THz and at 3.8 THz, respectively. Mixer gain bandwidth is 5.2 GHz. Local oscillator power is 1-3 muW for mixers with different active area
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Jiang, L., Miao, W., Zhang, W., Li, N., Lin, Z. H., Yao, Q. J., et al. (2006). Characterization of a quasi-optical NbN superconducting HEB mixer. IEEE Trans. Microwave Theory Techn., 54(7), 2944–2948.
Abstract: In this paper, the performance of a quasi-optical NbN superconducting hot-electron bolometer (HEB) mixer, cryogenically cooled by a close-cycled 4-K refrigerator, is thoroughly investigated at 300, 500, and 850 GHz. The lowest receiver noise temperatures measured at the respective three frequencies are 1400, 900, and 1350 K, which can go down to 659, 413, and 529 K, respectively, after correcting the loss and associated noise contribution of the quasi-optical system before the measured superconducting HEB mixer. The stability of the quasi-optical superconducting HEB mixer is also investigated here. The Allan variance time measured with a local oscillator pumping at 500 GHz and an IF bandwidth of 110 MHz is 1.5 s at the dc-bias voltage exhibiting the lowest noise temperature and increases to 2.5 s at a dc bias twice that voltage.
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Zhang, W., Jiang, L., Lin, Z. H., Yao, Q. J., Li, J., Shi, S. C., et al. (2005). Development of a quasi-optical NbN superconducting HEB mixer. In Proc. 16th Int. Symp. Space Terahertz Technol. (pp. 209–213).
Abstract: In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolometer) mixer measured at 500 and 850GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled by a 4-K close-cycled refrigerator. Measured receiver noise temperature at 850 and 500GHz are 3000K and 2500K respectively with wire grid as beamsplitter, while the lowest receiver noise temperature is found to be approximately 1200K with Mylar film. The theoretical receiver noise temperature (taking into account the elliptical polarization of log-spiral antenna) is consistent with measured one. The receiver noise temperature and conversion gain with 15-μm Mylar film as the beamsplitter at 500GHz are thoroughly investigated for different LO pumping levels and dc biases. The stability of the mixer’s IF output power is also demonstrated.
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Jiang, L., Zhang, W., Yao, Q. J., Lin, Z. H., Li, J., Shi, S. C., et al. (2005). Characterization of a quasi-optical NbN superconducting hot-electron bolometer mixer. In Proc. PIERS (Vol. 1, pp. 587–590).
Abstract: In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolome-ter) mixer measured at 500 GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled bya 4-K close-cycled refrigerator. Its receiver noise temperature and conversion gain are thoroughly investigatedfor different LO pumping levels and dc biases. The lowest receiver noise temperature is found to be approxi-mately 1200 K, and reduced to about 445 K after correcting theloss of the measurement system. The stabilityof the mixer’s IF output power is also demonstrated.
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