An enhanced broadcast format and multi-mode receiver for WWVB time signal radio.

摘要

WWVB is a broadcast station, operated by the National Institute of Standards and Technology, which has been broadcasting time information to radio-controlled clocks (RCC) throughout the continental US since 1965. The transmitted information includes the year (excluding the century), day, hour, minute, and notifications for leap seconds and for daylight saving time (DST) transitions. By receiving this information from WWVB, RCCs can acquire and maintain accurate timing and automatically adjust for DST transitions and leap seconds. The legacy amplitude modulation (AM)-based broadcast format, introduced in the 1960s, while allowing for a simple implementation of a receiver with the technology of that era, exhibits low efficiency. Consequently, RCCs based on it often fail to receive reliably, particularly in locations that are distant from the station. To improve the station's coverage, an enhanced broadcast format, based on the addition of phase modulation (PM), was deployed in 2012. The new broadcast format has enhanced features including modulation schemes, source coding, channel coding, and various transmission modes. These features enable more reliable receiver performance and greater time-keeping accuracy at reduced power consumption. Analysis and simulations show that the new broadcast can achieve as much as 41 dB performance gain compared with the legacy broadcast format.;Various challenges with the design of receivers for the enhanced WWVB broadcast are presented. A new architecture and algorithms for the multi-mode receivers that overcome these challenges are proposed. The trade-off between performance and energy consumption of the receiver are also quantified. The performance of the receiver based on Normal mode and Medium mode of the WWVB broadcast is presented. In Normal mode, the proposed receiver demonstrates a 12 dB performance gain provided by the improved modulation, and additional 3 dB to 4 dB performance gains achieved by the algorithms used in a different reception operating mode, compared with the RCC for the legacy broadcast. In Medium mode, a sequential synchronizer that is robust against variations in channel gain is proposed to overcome the time-varying reception conditions and the demanding constraint on reception energy. The proposed receiver in Medium mode can offer 31 dB performance gain compared with the conventional receiver based on envelope detection.