ORCID Profile
0000-0002-6108-2551
Current Organisation
Beijing Institute of Technology
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Publisher: IEEE
Date: 15-11-2021
Publisher: IOP Publishing
Date: 04-06-2019
Publisher: IEEE
Date: 09-2016
Publisher: AIP Publishing
Date: 05-11-2021
DOI: 10.1063/5.0064416
Abstract: This paper presents systematic modeling and performance analyses of a 340-GHz dual-polarized antenna-coupled single-sideband (SSB) high-Tc superconducting (HTS) mixer for terahertz (THz) communication systems. The mixer features a fully monolithic-integrated circuit layout, which enables both sensitive heterodyne detection and high image rejection by appropriate polarization-manipulating operation. To predict the comprehensive performance of such a HTS mixer with relatively complicated network architecture and polarization relationships, an innovative modified three-port modeling approach is presented and developed by theoretical derivations. Using the measured Josephson junction parameters of our previous experimentally demonstrated HTS mixer module at the same band, the best conversion gain and SSB noise temperature of the presented mixer are predicted to be around −5 dB and 1200 K at the operating temperature of 40 K, respectively. In addition, the mixer exhibits a flat frequency response over a wide intermediate-frequency range from 15 to 25 GHz and high image rejection of more than 17 dB over the radio frequency operation range. The SSB HTS Josephson mixer will be useful for THz wireless communication applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2015
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2012
Publisher: IOP Publishing
Date: 2015
Publisher: IEEE
Date: 09-2013
Publisher: AIP Publishing
Date: 20-01-2022
DOI: 10.1063/5.0077776
Abstract: High-Tc superconducting (HTS) receivers are promising candidates for terahertz (THz) communication applications due to their superior sensitivity and the cooling attainability with a miniature cryogenic system. Nevertheless, currently reported HTS mixers are mostly single-junction devices, and a more complicated architecture like the balanced configuration has not been investigated. This paper presents the design of a 600-GHz single-balanced HTS mixer, where detailed electromagnetic simulations are carried out to optimize the coupling efficiency and port isolation, as well as desired litude and phase relationship. To predict the noise and conversion performance, we present an innovative multiport network interleaving-based modeling method that enables powerful simulation verifications for single-balanced HTS Josephson mixers. Simulation results show that the presented device exhibits very good HTS mixer performance at the 600-GHz band, which validates the effectiveness of the design and the potential of the mixer for THz communication applications.
Publisher: IEEE
Date: 09-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2022
Publisher: IEEE
Date: 29-08-2021
Publisher: China Science Publishing & Media Ltd.
Date: 10-09-2012
Publisher: IOP Publishing
Date: 14-08-2017
Publisher: Springer Science and Business Media LLC
Date: 08-09-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2015
Publisher: IEEE
Date: 14-05-2023
Publisher: IEEE
Date: 07-2015
Publisher: IEEE
Date: 09-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2023
Publisher: IOP Publishing
Date: 18-11-2020
Abstract: Sensitive high- T c superconducting (HTS) heterodyne receivers are envisioned as promising technologies for terahertz (THz) communication and sensing applications due to the lack of power efficient sources in the band. HTS device properties, particularly the noise temperature, are dependent on complicated factors that include multiple noise sources as well as the interaction between Josephson junction and radio-frequency (RF) networks. We report investigations on the device properties of an HTS THz mixer in the presence of nonlinear thermal fluctuation and series junction array. By using the three-port analysis method, it is observed that the Planck and quantum noises representing nonlinear thermal fluctuation plays a significant role in the cases of smaller fluctuation parameters and higher signal frequencies. The influence of series junction array on mixer performance is also studied, which shows that there is an optimum junction number dependent on the normalized RF source impedance. The measured results of a broadband antenna-coupled HTS single-junction mixer agree well with that obtained by numerical simulation. The results predict that noise performance, conversion gain and operating bandwidth would be considerably improved if a series junction array with a suitable junction number is used for heterodyne mixing.
Publisher: Oxford University Press (OUP)
Date: 14-01-2020
Abstract: We explore deep rest-frame UV to FIR data in the COSMOS field to measure the in idual spectral energy distributions (SED) of the ∼4000 SC4K (Sobral et al.) Lyman α (Ly α) emitters (LAEs) at z ∼ 2–6. We find typical stellar masses of 109.3 ± 0.6 M⊙ and star formation rates (SFR) of SFR$_{\\rm SED}=4.4^{+10.5}_{-2.4}$ M⊙ yr−1 and SFR$_{\\rm Ly\\,\\alpha }=5.9^{+6.3}_{-2.6}$ M⊙ yr−1, combined with very blue UV slopes of $\\beta =-2.1^{+0.5}_{-0.4}$, but with significant variations within the population. MUV and β are correlated in a similar way to UV-selected sources, but LAEs are consistently bluer. This suggests that LAEs are the youngest and/or most dust-poor subset of the UV-selected population. We also study the Ly α rest-frame equivalent width (EW0) and find 45 ‘extreme’ LAEs with EW0 & 240 Å (3σ), implying a low number density of (7 ± 1) × 10−7 Mpc−3. Overall, we measure little to no evolution of the Ly α EW0 and scale length parameter (w0), which are consistently high (EW$_0=140^{+280}_{-70}$ Å, $w_0=129^{+11}_{-11}$ Å) from z ∼ 6 to z ∼ 2 and below. However, w0 is anticorrelated with MUV and stellar mass. Our results imply that sources selected as LAEs have a high Ly α escape fraction (fesc,Ly α) irrespective of cosmic time, but fesc,Ly α is still higher for UV-fainter and lower mass LAEs. The least massive LAEs (& .5 M⊙) are typically located above the star formation ‘main sequence’ (MS), but the offset from the MS decreases towards z ∼ 6 and towards 1010 M⊙. Our results imply a lack of evolution in the properties of LAEs across time and reveals the increasing overlap in properties of LAEs and UV-continuum selected galaxies as typical star-forming galaxies at high redshift effectively become LAEs.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2023
Publisher: IOP Publishing
Date: 06-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Publisher: IOP Publishing
Date: 02-2014
Publisher: Springer Science and Business Media LLC
Date: 20-08-2022
DOI: 10.1038/S43246-022-00279-7
Abstract: Reconfigurable terahertz electronics devices with high tuneability are pivotal for next-generation high speed wireless communication and sensing technologies. Significant challenges exist for realizing these devices, particularly on the design of smart metastructures that can manipulate electromagnetic radiation at the terahertz frequencies and the fabrication of devices with effective tuneability and reconfigurability. Here, we incorporate graphene into a graphene/gold bilayer superimposed metamaterial structure, which enables efficient electrical tuning of terahertz waves. A 0.2 THz frequency-selective absorber is designed and experimentally developed using this graphene/gold bilayer metamaterial approach. The device demonstrates 16 dB litude tuning at 0.2 THz resonance and over 95% broadband modulation at just 6 V bias voltage while maintaining a benchmark high-quality factor resonance performance. The design and fabrication methods presented can be readily applied to produce a myriad of tuneable terahertz devices required for high-speed, reconfigurable THz wireless communication and sensing technologies.
Publisher: IOP Publishing
Date: 29-10-2021
Abstract: This paper presents a W-band high- T c superconducting (HTS) Josephson-junction fundamental mixer which is coupled using a dual-beam lens-free slot-array antenna. The antenna features a uniplanar six-element slot array fed by an ungrounded coplanar waveguide line, of which each element is a long slot loaded by four rectangular loops. Highly directional radiation is therefore realized by utilizing the long slots and array synthesis to form a relatively large antenna aperture. The antenna also enables asymmetric dual-beam radiation in opposite directions, which not only reduces the RF coupling losses but greatly facilitates the quasi-optics design for the integration of the HTS mixer into a cryocooler. The electromagnetic simulations show that a coupling efficiency as high as −2.2 dB, a realized gain of 13 dB and a front-to-back ratio of 10 dB are achieved at the frequency of 84 GHz. Using this on-chip antenna, a W-band HTS fundamental mixer module is experimentally developed and characterized for different operating temperatures. The measured conversion gain is −10 dB at 20 K and −14.6 dB at 40 K, respectively. The mixer noise temperature is predicted to be around 780 K at 20 K and 1600 K at 40 K, respectively. It is also analyzed that the mixer performance can be further improved if the Josephson junction parameters were optimized.
Publisher: Springer Science and Business Media LLC
Date: 09-2022
Publisher: Optica Publishing Group
Date: 13-09-2022
DOI: 10.1364/OE.467809
Abstract: In this paper, we present a quasi-optically coupled 600-GHz high-temperature superconducting (HTS) sub-harmonic mixer for communication and sensing applications. The mixer features an innovative double-Y-type slot integrated lens antenna, which can efficiently couple the radio frequency (RF) and local oscillator (LO) signals with a small frequency ratio by exciting the half-wave and full-wave resonant current modes on the slot, respectively. Considering the low impedance characteristics of HTS Josephson junctions, a coplanar-waveguide stepped impedance transformer is utilized for minimizing the mismatching loss. A cascaded filter network is designed to prevent the high-frequency signal leakage at both bands while coupling the intermediate-frequency (IF) signal output efficiently. Based on this antenna design and an established HTS step-edge junction technology, a 600-GHz mixer prototype was designed, fabricated and measured, which was compared with the simulation results. The achieved conversion gain and noise temperature are the best performance specs as reported to date for HTS harmonic mixers at comparable frequencies and operating temperatures.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2017
Publisher: The Optical Society
Date: 15-01-2016
DOI: 10.1364/OL.41.000424
Publisher: Shanghai Institute of Optics and Fine Mechanics
Date: 2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2019
Publisher: IOP Publishing
Date: 12-10-2018
Publisher: IEEE
Date: 15-11-2021
Publisher: IEEE
Date: 08-11-2020
Publisher: The Optical Society
Date: 31-05-2013
Publisher: IEEE
Date: 07-12-2020
Publisher: IEEE
Date: 09-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2016
Publisher: IEEE
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 07-10-2022
DOI: 10.1038/S41598-022-20895-0
Abstract: Earthquakes, forest fires, mudslides and other natural disasters occur frequently in recent years. They usually occur in the mountainous and dense forests, where local communication facilities do not exist or have been destroyed by the disasters. Adverse geographical environment poses a huge challenge to emergency communications and rescue. This paper presents comparative studies on multi-carrier transmission schemes in the mountainous and dense forest environment. The comprehensive communication performance for various multi-carrier waveform schemes, has been extensively analyzed by using the Stanford University Interim channel model. Simulation results show that the pruned discrete Fourier transform spread filter bank multi-carrier scheme exhibits generally the best performance in terms of transmission rate and distance for most operation modes.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: MDPI AG
Date: 13-12-2022
DOI: 10.3390/APP122412813
Abstract: Ordinary mixers can hardly meet the requirements in terahertz (THz) communications due to the low-power and expensive THz sources. Sensitive harmonic mixers have been widely studied to avoid this problem, owing to the fact that the higher the number of harmonics, the lower the local oscillator (LO) frequency, and the lower the cost. High-Tc superconducting (HTS) Josephson junction (JJ) mixers are performing candidates for THz receiver frontends because of the advantages of excellent sensitivity, wide bandwidth, high harmonic number and low LO power requirement. However, the normal-state resistance of HTS JJ is so low that traditional antennas are difficult to match it. In other words, it is quite a challenge to match the input impedance to a low input impedance for traditional antennas, especially for antennas fed by coplanar striplines (CPSs). In this work, based on the structure of bowtie, two types of stub tuners were integrated to decrease the impedance of the bowtie antenna so as to improve the coupling efficiency between the traditional bowtie antenna and the JJ. Furthermore, HTS YBa2Cu3O7-δ (YBCO) JJ harmonic mixers coupled with the proposed structures and fed by CPSs are fabricated and measured. The measurements show that the JJ mixer coupled with a pair of open-end stubs of the bowtie antenna achieves up to 88 harmonics, with a conversion efficiency of −69.6 dB. In contrast, the JJ mixer coupled with a pair of lumped-element stubs of the bowtie antenna only attains to 30 harmonics, with a conversion efficiency of −73.4 dB. Additional numerical simulations indicate that the coupling efficiency is enhanced when the complex impedance of the antenna is explicitly considered. Compared with other coupled traditional antennas, the JJ mixer with bowtie antenna has the largest harmonic number. This work paves the way for the future application of low-frequency and low-cost LO for THz communications.
Publisher: Institution of Engineering and Technology (IET)
Date: 03-2014
DOI: 10.1049/EL.2014.0085
Publisher: Springer Science and Business Media LLC
Date: 13-07-2017
Publisher: IEEE
Date: 09-2013
Publisher: AIP Publishing
Date: 06-11-2017
DOI: 10.1063/1.5004733
Abstract: This letter presents both theoretical and experimental investigations on the noise and conversion performance of a high-Tc superconducting (HTS) step-edge Josephson-junction mixer at the frequency of 0.6 THz and operating temperatures of 20–40 K. Based on the Y-factor and U-factor methods, a double-sideband noise temperature of around 1000 K and a conversion gain of −3.5 dB were experimentally obtained at 20 K. At the temperature of 40 K, the measured mixer noise and conversion efficiency are around 2100 K and −10 dB, respectively. The experimental data are in good agreement with the numerical analysis results using the three-port model. A detailed performance comparison with other reported HTS terahertz mixers has confirmed the superior performance of our presented mixer device.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2021
Publisher: IEEE
Date: 09-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Publisher: IEEE
Date: 09-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2013
Publisher: IOP Publishing
Date: 30-11-2016
Publisher: IEEE
Date: 17-10-2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2023
Publisher: IEEE
Date: 09-2019
Publisher: IEEE
Date: 29-08-2021
Publisher: IEEE
Date: 09-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2023
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2017
Location: China
Location: Australia
No related grants have been discovered for Xiang Gao.