Ultra-low Phase Noise Oscillators and Synthesizers for Managing and Relieving Spectral Congestion: A Tutorial Introduction

D.A. Howe, A. Hati, C.W. Nelson

Abstract:	Precise timing in shared-user, wireless data communications systems directly affects the growing concern in establishing and managing ‘spectrum harmony’. For shared spectrum, an efficient and widely accepted modulation type is orthogonal frequency division multiplexing (OFDM). The main advantage of OFDM to other modulation protocols is its efficient use of spectrum and substantial resistance to multipath effects and fading. This report discusses how ultra-low -phase noise (ULPN) oscillators from stabilized optical frequency dividers (OFD’s) might be used to improve the efficiency in shared-user, wireless data communications systems. In particular, spectral congestion might be alleviated by simply increasing the number of sub-carriers. This can only be done by lowering phase noise, especially near the carrier, in the local oscillators (LOs) used throughout a particular network of users. We find that the number of users in wireless communications systems can be increased by using new low-phase noise oscillators that are being developed for other applications. The improved long-term (>1s) phase stability can significantly narrow the bandwidth (BW) to 1 Hz in the clock (tracking) used in the receiver. This BW further increases resistance to other shared users and jammers, multipath fading, and eavesdropping, thus increasing range. How much advantage depends on a multitude of factors and is beyond the scope of this overview. Our intent is to show how ULPN-OFD technology can and should be a part of the roadmap toward improved spectrum management.
Published in:	Proceedings of the 45th Annual Precise Time and Time Interval Systems and Applications Meeting December 2 - 5, 2013 Hyatt Regency Bellevue Bellevue, Washington
Pages:	263 - 264
Cite this article:	Howe, D.A., Hati, A., Nelson, C.W., "Ultra-low Phase Noise Oscillators and Synthesizers for Managing and Relieving Spectral Congestion: A Tutorial Introduction," Proceedings of the 45th Annual Precise Time and Time Interval Systems and Applications Meeting, Bellevue, Washington, December 2013, pp. 263-264.
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