研究目的
To develop and characterize a high-Tc superconducting Josephson-junction sub-terahertz fourth-harmonic mixer with a dual-band on-chip antenna for improved coupling efficiency and performance in terahertz wireless applications.
研究成果
The dual-band on-chip antenna achieves high coupling efficiencies of -4 dB at 160 GHz and -3.5 dB at 640 GHz. The HTS fourth-harmonic mixer demonstrates a conversion gain of -18 dB at 20 K and -22 dB at 40 K, with an IF bandwidth exceeding 23 GHz and low LO power requirement of around 50 nW. These results represent the best performance for HTS harmonic mixers in comparable sub-THz bands, offering a cost-effective solution for terahertz wireless communication and sensing applications. Future work could focus on extending the operating range and improving integration with other system components.
研究不足
The study is limited to specific frequency bands (160 GHz and 640 GHz) and operating temperatures (20 K to 77 K). The fabrication process involves specialized techniques like step-edge junction technology, which may not be easily scalable. The quasi-optical link and measurement tolerances could introduce uncertainties in results. Further optimization is needed for broader bandwidth and higher temperature operation.
1：Experimental Design and Method Selection:
The study involves designing a dual-band on-chip antenna with twin-slots and a CPW network for high coupling efficiency, followed by fabricating and testing an HTS Josephson-junction mixer. Electromagnetic simulations using CST Microwave Studio are employed for antenna design and analysis.
2：Sample Selection and Data Sources:
The mixer is fabricated using YBa2Cu3O7-x (YBCO) step-edge junction technology on an MgO substrate with a high-resistivity silicon lens. Measurements are conducted in a cryocooler at temperatures from 20 K to 77 K.
3：List of Experimental Equipment and Materials:
Equipment includes a cryocooler, solid-state sources (AMCs from VDI and Millitech), off-axis parabolic mirror, Teflon plano-convex lens, beam splitter, quasi-optical attenuator, rotatable wire-grid polarizer, low noise amplifier (LNA), Agilent E4407B spectrum analyzer, battery-operated current source, and vector network analyzer (VNA). Materials include MgO substrate, high-resistivity silicon lens, gold thin-film, YBCO film, and Ar-ion beam etching tools.
4：Experimental Procedures and Operational Workflow:
The antenna is designed and simulated for impedance and radiation patterns. The mixer is fabricated, packaged, and mounted in a cryocooler. RF and LO signals are generated, combined, and coupled to the mixer. DC biasing is applied, and IF output is amplified and measured. Linearity, frequency response, conversion gain, and noise temperature are characterized.
5：Data Analysis Methods:
Data analysis includes calculating coupling efficiency, conversion gain using PIF / (PRF ? GIF), and noise temperature using numerical simulations based on junction parameters. Statistical analysis of measurement results is performed to assess performance.
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