Integrated receiver channel circuits and structures for a pulsed time-of-flight laser radar

Abstract This thesis describes the development of integrated structures and circuit implementations for the receiver channel of portable pulsed time-of-flight laser rangefinders for industrial measurement applications where the measurement range is from ∼1 m to ∼100 m to noncooperative targets and the required measurement accuracy is from a few millimetres to a few centimetres. The receiver channel is used to convert the current pulse from a photodetector to a voltage pulse, amplify it, discriminate the timing point and produce an accurately timed logic-level pulse for a time-to-digital converter. Since the length of the laser pulse, typically 5 ns, is large compared to the required accuracy, a specific point in the pulses has to be discriminated. The amplitude of the input pulses varies widely as a function of measurement range and the reflectivity of the target, typically from 1 to 100 ... 1000, so that the gain of the amplifier channel needs to be controlled and the discrimination scheme should be insensitive to the amplitude variation of the input signal. Furthermore, the amplifier channel should have low noise in order to minimize timing jitter. Alternative circuit structures are discussed, the treatment concentrating on the preamplifier, gain control circuitry and timing discriminator, which are the key circuit blocks from the performance point of view. New circuit techniques and structures, such as a fully differential transimpedance preamplifier and a current mode gain control scheme, have been developed. Several circuit implementations for different applications are presented together with experimental results, one of them being a differential BiCMOS receiver channel with a bandwidth of 170 MHz, input referred noise of 6 pA/√Hz and maximum transimpedance of 260 kW. It has an accuracy of about +/- 7 mm (average of 10000 measurements), taking into account walk error with an input signal range of 1:624 and jitter (3s). The achievable performance level using integrated circuit technology is comparable or superior to that of the previously developed commercially available discrete component implementations, and the significantly reduced size and power consumption open up new application areas

A low noise, wide dynamic range TOF laser radar receiver based on pulse shaping techniques

Abstract A time of flight (TOF) laser radar receiver based on unipolar-to-bipolar pulse shaping at its input is presented. The pulse shaping and the non-linear feedback of the transimpedance preamplifier give low timing error and jitter over a wide input pulse amplitude range. This receiver is realized in a 0.35μm CMOS technology and intended to be used in laser ranging with laser pulses of width ~1ns. Post-layout simulations show a dynamic range of more than 1:200000, a trans-impedance gain of 117dbΩ, a bandwidth of 260MHz and an input-referred equivalent current noise of 70nA. These results are achieved while keeping the walk error less than ±55ps (9mm) without any need for complicated calibration methods