Abstract: The invention provides an improved method and apparatus for detecting the phase difference between a digital data signal and a clock signal. By ensuring that no pulse in the output phase signal is narrow enough to introduce a non-linearity, the present invention avoids a source of non-linearity exhibited in existing phase detectors.In addition, by ensuring that critical timing paths through the circuit contain similar circuit blocks, with similar propagation delays, relative time relationships are preserved from clock and data inputs to XOR inputs. The circuit is therefore largely insensitive to changes in the characteristics of the components so long as they all move together, as they would in an integrated circuit implementation.

Abstract: The invention seeks to provide an improved, bandwidth-efficient method and apparatus for acquiring and tracking bursts of data, or continuous data, of varying and unpredictable amplitude, extinction ratio, and phase.The system avoids the use of digital signal processing which is not practical at high data signal rates. The system also obviates encoding of the data signal using a line code, thereby extending the existing technology to give a significant increase in data throughput for the same available bandwidth.The system may treat acquisition of each data burst, comprising alternate synchronisation parts and data parts, ab initio.