Biphase mark encoding is a commonly used format for transmitting data. Using biphase mark encoded data, synchronization or clock data may be extracted from the data without requiring separate transmission of a clock signal.
Several standards use biphase mark encoding. For example, the Audio Engineering Society (AES) has set forth a standard format for biphase mark encoding of digital audio signals often referred to as AES-3. This standard is defined in a document called “AES Recommended practice for digital audio engineering—Serial transmission format for two channel linearly represented digital audio data.” An example form of an AES-3 signal is described in more detail below. The AES-3 specification applies to signals sent over balanced twisted-pair cabling. A similar encoding of digital audio signals is used in SPDIF (Sony Philips Digital Interface).
Under AES-3, actual data rates may be variable. Different systems may have different fixed data rates and one system may use multiple data rates over time. Therefore, conventional designs for AES-3 receivers use analog phase-locked loops to recover clock, data and audio sample synchronization signals. Less expensive digital designs for AES-3 receivers generally have been limited to a receiving input signals having a single, fixed frequency, making them inapplicable to environments in which variable data rates are actually used.
As with most clocked data signals that are transmitted, jitter may arise due to a variety of factors. This prospect of jitter introduction limits, for example, the length or other characteristics of a transmission medium that may be used. Any clock and data recovery scheme should take into account the possibility of jitter that has been introduced in the received signal.
USPTO Backgrounds
USPTO Backgrounds