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CMOS TIME-TO-DIGITAL CONVERTER STRUCTURES FORTHE INTEGRATED RECEIVER OFA PULSED TIME-OF-FLIGHT LASER RANGEFINDER, ACTA UNIVERSITATIS OULUENSIS C Technica 390

ISBN-13:	978-951-42-9546-1
Kieli:	englanti
Kustantaja:	Oulun yliopisto
Oppiaine:	Tekniikka, matematiikka
Painosvuosi:	2011
Sidosasu:	pehmeäkantinen
Sijainti:	Print Tietotalo
Sivumäärä:	178
Tekijät:	NISSINEN ILKKA

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The aim of this thesis was to develop time-to-digital converters (TDC) for the integrated receiverof a pulsed time-of-flight (TOF) laser rangefinder aiming at cm-level accuracy over an input rangeof 10 m–15 m. A simple structure, a high integration level and low power consumption are thedesired features for such a TDC. From the pulsed TOF laser rangefinder point of view anintegrated receiver consisting of both the TDC and the receiver channel on the same die offers thepossibility of manufacturing these laser rangefinders with a high integration level and at a lowprice to fulfil the needs of mass industrial markets. The heart of the TDC is a CMOS ring oscillator, the clock frequency of which is used tocalculate the full clock cycles between timing signals, the positions of the timing signals inside theclock period being determined by storing the state of the phase of the ring oscillator for each timingsignal. This will improve the resolution of the TDC. Also, additional delay lines are used togenerate multiple timing signals, each having a time difference of a fraction of that of the ringoscillator. This will further improve the resolution of the whole TDC. To achieve stable resultsregardless of temperature and supply voltage variations, the TDC is locked to an on-chip referencevoltage, or the resolution of the TDC is calibrated before the actual time interval measurement.The systematic walk error in the receiver channel caused by amplitude variation in the receivedpulse is compensated for by the TDC measuring the slew rate of the received pulse. This timedomain compensation method is not affected by the low supply voltage range of modern CMOStechnologies. Three TDC prototypes were tested. A single-shot precision standard deviation of 16 ps(2.4mm) and a power consumption of 5.3mW/channel were achieved at best over an input rangeof 100 ns (15 m). The temperature drifts of an on-chip voltage reference-locked TDC and a TDCbased on the calibration method were 90 ppm/°C and 0.27 ps/°C, respectively. The results alsoshowed that a pulsed TOF laser rangefinder with cm-level accuracy over a 0–15 m input rangecan be realized using the integrated receiver with the time domain walk error compensationdescribed here.

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