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Externally Phase Locked Submm-Wave Flux Flow Oscillator for Integrated Receiver

Authors:
V.P. Koshelets, A.B. Ermakov, S.V. Shitov, P.N. Dmitriev, L.V. Filippenko, A.M. Baryshev, W. Luinge, J. Mygind, V.L. Vaks, D.G. Pavel
Abstract:
The combination of narrow linewidth and wide-band tunability makes the Josephson Flux Flow Oscillator (FFO) a perfect on-chip local oscillator for integrated submm -wave receivers. A noise temperature of about 100 K (DSB) has been achieved for the integrated receiver with the FF0 operating near 500 GHz. An instantaneous bandwidth of 15 — 20 % is estimated from Fourier transform spectroscopy (FTS) and heterodyne measurements. The far-field antenna beam is measured as [approx. equal] f/l0 with sidelobes below -16 dB which is suitable for coupling to a telescope antenna. For application in spectral radio astronomy, besides low noise temperature and good beam pattern, also a local oscillator with narrow-linewidth and long-term stability is required. Recently the feasibility of phase locking of the FFO to an external reference oscillator was demonstrated experimentally. A spectral linewidth as low as 1 Hz (determined by the resolution of the spectrum analyzer) has been measured in the frequency range 270 - 440 GHz relative to a reference oscillator. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. A new technique for linewidth measurements and FFO phase locking has been devised and put to use. This method employs an off-chip harmonic multiplier that considerably simplifies the design of the chip for a fully superconductive integrated phase-locked receiver. The linewidth of Nb-A10x-Nb FFOs has been carefully studied in the frequency range 250 - 600 GHz. Based on frequency measurements the 1-T0 I-V curve has been reconstructed with an accuracy better than 1 nV. Finally, the results of FFO phase noise measurements are also presented and discussed.
Categories:
High TC
Year:
2000
Session:
9
Full-text:
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Page Number(s):
523-532