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New Improved System for WWVB Broadcast

Published

Author(s)

John P. Lowe, Matthew J. Deutch, Glenn K. Nelson, Douglas D. Sutton, William C. Yates, Peder Hansen, Oren Eliezer, Tom Jung, Stephen Morrison, Yingsi Liang, Dinesh Rajan, Sidharth Balasubramanian, Arun Ramasami, Waleed Khalil

Abstract

The WWVB broadcast of the time-code signal has not undergone major changes in its communications protocol and modulation scheme since its introduction in 1963. Its amplitude-modulation (AM) and pulse-width based representations of its digital symbols were designed to allow for a simple low-cost realization of a receiver based on envelope detection, widely used with AM audio broadcasting at the time, whereas present day technology allows much more efficient methods for modulation/demodulation to be realized at low cost. Over a decade ago, the station’s power was significantly increased, allowing the broadcast from Colorado to effectively cover most of North America. This has spurred the popularity of radio-controlled clocks and watches, more commonly known as “atomic clocks”. However, electromagnetic interference (EMI) experienced in typical residential and office environments can make it difficult to receive the WWVB signal in various locations, and particularly on the East Coast, where on-frequency interference from the MSF station in the UK, is received at relatively high levels. The new protocol and modulation scheme being introduced by NIST effectively addresses these problems, and will enable greatly improved reception of the WWVB broadcast without impacting the existing devices. This backward-compatibility is achieved by maintaining the existing AM characteristics while adding various new features through phase modulation (PM). While the new protocol can provide improved timing resolution, it was designed primarily to enhance the system’s robustness by reducing the signal-to-interference-and-noise-ratio (SINR) required for reception, to provide much improved coverage, and to enable new applications. Although the demodulation of the signal’s phase involves greater complexity, today’s technology allows for such implementation to be realized in a low-cost integrated circuit. Analyses are presented, including simulated and measured results, to illustrat
Proceedings Title
Proceedings of 43rd Annual PTTI Meeting
Conference Dates
November 14-17, 2011
Conference Location
Long Beach, CA
Conference Title
43rd Annual PTTI Meeting

Keywords

phase modulation, radio controlled clocks, WWVB
Created November 14, 2011, Updated December 13, 2017