Integrated receiver channel and timing discrimination circuits for a pulsed time-of-flight laser rangefinder

In this thesis integrated receiver channel techniques and circuit implementations for a pulsed timeof-flight (TOF) laser rangefinder are developed with the aim to achieve centimetre level accuracy within the dynamic range of > 1:10 000 of the input pulse amplitudes. The receiver channel converts the input current pulses produced by the photo detector to voltage pulses and produces a logic-level timing pulse for the time interval measurement. In addition to the minimization of noise, the main design challenge is the minimization of the timing walk error resulting from the varying amplitude of the received optical echo. In automotive perception laser radar application, which was the target application of this work, the input amplitude of the received echo varies in a range of 1:10 000 or even more due to changes in the measured distance and reflectivity and orientation of the target. Two receiver channel and timing discriminator architectures were developed and realized as integrated circuits in 0.35 μm BiCMOS technology, and finally verified by measurements. One of the receiver channels is based on the detection of the zero-crossing of the timing pulse produced with a unipolar-to-bipolar conversion at the input of the receiver. It achieved a timing walk error of ±8 mm in a dynamic range of 1:3000. Another receiver channel is based on the leading edge timing discrimination, in which the timing walk error is being compensated for in time domain by measuring the width of the timing pulse simultaneously with its leading edge time position. An important feature of this technique, suggested in this thesis, is that it is operative also beyond the linear range of the receiver channel, which is typically limited to 1:10 000 taking into consideration the varying reflectivity of the target materials used.