1
David C Chu: Time interval measuring apparatus and method. Hewlett Packard Company, Edward Y Wong, September 23, 1986: US04613951 (62 worldwide citation)

A time interval measuring apparatus is provided for measuring the time interval between two signals. The two signals are successively brought to synchronization by delaying one of the two signals as they pass through a series of time shift cells connected in tandem. These delays are accumulated in a ...


2
David C Chu: Double vernier time interval measurement using triggered phase-locked oscillators. Hewlett Packard Company, David A Boone, August 14, 1979: US04164648 (40 worldwide citation)

Measurement of a time interval between a start and a stop event is made by activating a start oscillator in response to the start event and activating a stop oscillator in response to the stop event. The number of cycles of each respective oscillator signal which occur between the activation of each ...


3
David C Chu, Thomas A Knotts: Picosecond event timer. Hewlett Packard Company, November 24, 1992: US05166959 (33 worldwide citation)

A circuit for time stamping event signals, e.g. zero-crossings, using coarse and fine timers. The fine timer is a circuit section which subdivides a period from a phase-locked ring-oscillator into 2N subparts. An event signal is timed by latching a digital representation of a particular subpart. The ...


4
David C Chu, Michael J Ward: Data capture in an uninterrupted counter. Hewlett Packard Company, Edward Y Wong, May 21, 1985: US04519091 (20 worldwide citation)

A method of sampling accurately the instantaneous content of a high speed counter without interrupting the counting process is provided. The method is applicable even when the higher order digits of the counter are constructed by slower switching circuits configured in either a synchronous or ripple ...


5
David C Chu: System and method for interferometer non-linearity compensation. Agilent Technologies, May 18, 2004: US06738143 (20 worldwide citation)

A system and method for non-linearity compensating interferometer position data includes receiving a plurality of groups of digital position values. A first group of the digital position values are digitally processed to generate a plurality of data values. The plurality of data values are digitally ...


6
David C Chu, Alistair D Black: Precision timed delay measurement using phaselocked CW technique. Hewlett Packard Company, January 24, 1995: US05384541 (16 worldwide citation)

A method and apparatus for the measuring of a delay in a delay circuit by making a continuous frequency measurement is proposed. The phase-locking of a variable frequency signal applied to the delay circuit allows the user to significantly improve the precision and accuracy of the time delay measure ...


7
David C Chu: Frequency measurement using phase continuous frequency switching. Hewlett Packard Company, David A Boone, October 5, 1976: US03984770 (12 worldwide citation)

An automatic transfer oscillator system for frequency measurement using a single sampler is described. Two signals, of frequencies f.sub.1 and f.sub.2, are alternately used to drive the sampler. The two frequencies are sufficiently close by design so that the intermediate frequency signals generated ...


8
David C Chu: System for highly repeatable clock parameter recovery from data modulated signals. Hewlett Packard Company, November 21, 1995: US05469466 (11 worldwide citation)

A system for recovering parameters of an underlying clock signal from data modulated signals includes a time digitizer, or time stamping device, for sampling and locating edges of the data modulated signals, thereby selectively providing time stamp readings identifying incoming edges of the data sig ...


9
David C Chu, Jeremy S Sommer: Digital phase detector. Hewlett Packard Company, Pamela Lau Kee, September 2, 1997: US05663666 (8 worldwide citation)

In the present embodiment, digital phase detection of digital telecommunications signals is based on heterodyning. The frequency of two signals are scaled to different nominal values that are separated by a typically small but finite difference. The two frequencies are then mixed to generate a finit ...


10
David C Chu, Robert W Offermann: Automatic echo-chamber for measuring single time intervals by replication and averaging. Hewlett Packard Company, Edward Y Wong, May 10, 1983: US04383166 (7 worldwide citation)

A method is provided for measuring a single-shot time interval using startable oscillators to replicate indefinitely the time interval for averaging. Also provided is a circuit for automatically selecting a proper ratio of division to ensure that the interval being measured is less than the period o ...