Integrated chip set for a pulsed time-of-flight laser radar

The pulsed time-of-flight laser range finding techniques based on laser diode transmitter enables one to realize a mm-level accuracy to non-cooperative targets in a distance measurement range of several tens of meters in industrial applications such as the measurement of level heights in silos, positioning of tools and vehicles, velocity measurement, anti-collision radars, proximity sensors, etc. In this work the basic pulsed time-of-flight laser radar functions, the receiver channel and the time interval measurement unit, have been realized in the form of high-performance full-custom integrated circuits, which should pave the way for realizing a laser radar eventually as a component-like micro system thus increasing the number of possible applications for the developed techniques. The integrated BiCMOS receiver channel produces a logic level output pulse for the time interval measurement from the received laser echo. Two versions were realized, one detecting the leading edge of the received pulse and achieving an accuracy of +/-35mm in a dynamic range of 1:4000. In the other version gain control and constant fraction type of timing detection techniques are used to enhance the accuracy. With this circuit an input dynamic range of 1:650 (SNR > 10) can be achieved with a timing accuracy of about +/-3mm. The developed fully integrated CMOS time-to-digital converter realization is based on a counter and a novel parallel two-step interpolation method. The single-shot precision and measurement range of the unit are 50ps and 2 mus, respectively. In averaging mode the linearity is better than +/-5ps. Even better single-shot precision can be realized with analog interpolation techniques, however, at the expense of reduced stability.