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IEEE Transactions on Applied Superconductivity

Performance Improvements of a Microwave Oscillator Using High Temperature Superconducting Harmonic Mixer

Weiwei Xu, Y.F. Zhang, X.K. Jiang, K.. Ling, J.. Chen, Peiheng Wu

Published Jun 1, 2007• 3 citations
Publisher

Abstract

Based on YBa2Cu3O7Josephson junction mounted on a pulse tube cryocooler, a compact superconducting harmonic mixer is used to phase-lock a microwave source at 3 mm waveband to a reference of high precision at much lower frequency, thus greatly improving the performances of the former. Currently the highest harmonic number at which phase locking can be realized is 60. The experimental system, main results, and the problem of how to increase the harmonic number are discussed in details.

DOI
10.1109/tasc.2007.898610

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Based on YBa2Cu3O7Josephson junction mounted on a pulse tube cryocooler, a compact superconducting harmonic mixer is used to phase-lock a microwave source at 3 mm waveband to a reference of high precision at much lower frequency, thus greatly improving the performances of the former. Currently the highest harmonic number at which phase locking can be realized is 60. The experimental system, main results, and the problem of how to increase the harmonic number are discussed in details.
Using a high Tc superconducting grain boundary Josephson junction, harmonic mixing experiments in the mm waveband were carried out, aiming at as large a harmonic number and as high a signal frequency as possible. The dependencies of intermediate frequency output on dc bias, harmonic number, frequency of local oscillator (LO), and other parameters were carefully studied. Until now, our best result was the mixing between the signal at 95 GHz and the 105th harmonic of LO at about 900 MHz. Preliminary experiments using a high Tc harmonic mixer and phase-locking loop were tried to stabilize the frequency of a mm wave source.
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1 Introduction Compared with its semiconductor counterpart, Josephson junction (J. J.) usually has larger nonlinearity, lower noise temperature, wider operating waveband and less microwave loss, thus making itself a good candidate for applications at submillimeter and far-infrared wavebands. Some harmonic mixing experiments were done previously using N_b point-contact junctions, with the highest signal frequency being about 4.25 THz and the largest harmonic number being 851. However, because of the requirement of liquid