Sami Kurtti

An Integrated Laser Radar Receiver Channel Utilizing a Time-Domain Walk Error Compensation Scheme

An integrated receiver channel for a pulsed time-of-flight (TOF) laser rangefinder has been designed and fabricated in a 0.35-μm SiGe BiCMOS process. The receiver channel generates a timing mark for the TDC by means of a leading-edge timing discriminator that detects the crossover of the received pulse with respect to a set reference level. The walk error generated by the amplitude variation is compensated in the time domain on the basis of the measured dependence of the walk on the length of the received pulse. The measurement accuracy is ±15 ps with compensation within a dynamic range of 1:100000, and the single-shot precision and power consumption are 120 ps for a minimum detectable signal of ~1 μA and 115 mW, respectively.

A quadrature charge-domain sampler with embedded FIR and IIR filtering functions

A circuit technique for integrating built-in complex finite-impulse-response (FIR) and infinite-impulse-response (IIR) filtering functions into operation of a subsampler is presented. Based on integrative multiple sampling in the charge domain, the complex FIR filtering function of the sampler provides internal anti-aliasing and image band suppression prior to quadrature downconversion by subsampling. The complex IIR filtering function, taking place at the output sampling rate of the sampler, performs further first-order channel selection filtering on the downconverted signal. An example 50-MHz IF-sampler implementation in 0.8-/spl mu/m BiCMOS demonstrating the feasibility of the technique is presented in the paper.

Laser Radar Receiver Channel With Timing Detector Based on Front End Unipolar-to-Bipolar Pulse Shaping

An integrated receiver channel for a pulsed time-of-flight laser range finder is presented based on a timing discrimination principle in which the incoming unipolar detector current pulse is converted to a bipolar pulse at the front end of the receiver channel. Thus no optical or electrical gain control is needed within the dynamic range of the receiver, which according to measurements is 1:3000 with a timing walk error of plusmn 55 ps (plusmn 8 mm in distance). The minimum detectable input signal current is about 1.3 muA at an SNR of 10 with a bandwidth of 200 MHz. The circuit is realized in a 0.35 mum SiGe BiCMOS process and consumes 220 mW of power.

An integrated optical receiver with wide-range timing discrimination characteristics

An integrated receiver channel with a wide dynamic range for a pulsed time-of-flight laser rangefinder was designed and tested. The timing discriminator is realized so that the received unipolar pulse is converted to a bipolar signal at the front-end of the receiver channel, thus gain control and off-chip components are not needed. The walk error is 110 ps, or 16 mm in distance, over the dynamic range 1:1600. The minimum detectable signal is 1.52 /spl mu/A with the required SNR of 10. The circuit was implemented in a 0.35-/spl mu/m SiGe BiCMOS process.

Pulse width time walk compensation method for a pulsed time-of-flight laser rangefinder

A new walk compensation method for a pulsed time-of-flight rangefinder is suggested. The receiver channel operates without gain control using leading edge timing discrimination principle. The generated walk error is compensated for by measuring the pulse length and knowing the relation between the walk error and pulse length. The walk compensation is possible also at the range where the signal is clipped and where the compensation method by amplitude measurement is impossible. Based on the simulations walk error can be compensated within the dynamic range of 1:30 000.

An integrated receiver channel for a laser scanner

An integrated receiver channel for a compact scanning automotive LIDAR sensor is presented. It is designed to meet the requirements of the traffic application, such as a very wide dynamic range of the input signal, accurate timing detection and the possibility for detecting several successive pulses that may be caused by rain or mirror reflections, for example. The receiver operates on the leading edge timing discrimination principle. The input amplitude-dependent timing error is compensated for by measuring the pulse length with a multi-channel TDC and knowing the relation between the error and the pulse length. A timing accuracy of ± 10ps (±1.5mm in distance) within a dynamic range of 1:2 000 was achieved.

On the minimization of timing walk in industrial pulsed time-of-flight laser radars

Pulsed time-of-flight laser ranging is based on measuring the transit time of a short laser pulse to an optically visible target and back to the receiver. These techniques are gaining in popularity for industrial distance measurement applications. The laser pulse length typically used is in the range of 3 ns, which corresponds to about 1 m in air. This pulse length poses a challenge for detection of the echo from the target since the accuracy aimed at in a single shot is typically at the level of a few centimetres or even better with a dynamic range of more than 1:10 000. This paper studies the possibility of realizing the timing detection of the laser pulses with a straight-forward leading edge type of receiver that detects the cross-over of the received pulse with respect to a set reference level. Without any other measures the timing walk error that would be produced with this kind of receiver, would be at the level of nanoseconds. However, by measuring either the width or the slew rate of the rising edge of the received pulse, timing walk can be compensated for based on the measured dependence of the walk on the respective parameter. The advantage of these methods is that they are effective even when the optoelectronic receiver is saturated, thus enabling one to achieve wide dynamic operating range. Using these time-domain walk compensation methods we have constructed fully integrated CMOS and BiCMOS laser radar receivers that achieve timing walk error of less than +/-30ps in dynamic range of 1:10 000 -100 000.

A 50-MHz BiCMOS quadrature charge sampler and complex bandpass SC filter for narrowband applications

An implementation of a quadrature charge sampler and a complex bandpass switched-capacitor (SC) filter in 0.8 /spl mu/m BiCMOS applicable to narrowband low-IF receivers is presented. The circuit quadrature downconverts a 49.85-MHz IF input signal to a low IF of 15 kHz by charge-mode subsampling and performs further complex narrowband filtering on the signal. The measured image rejection is more than 44 dB on the 26.3 kHz -3 dB bandwidth.

A Laser Scanner Chip Set for Accurate Perception Systems

This paper presents an integrated receiver channel and an integrated time-to-digital (TDC) converter fabricated in a 0.35 μm SiGe BiCMOS and in 0.35 μm CMOS technologies, respectively, that give the required performance for a pulsed time-of-flight (TOF) laser radar to be used in a laser scanner in automotive applications. The receiver-TDC chip set is capable to measure the positions and widths of three separate successive timing pulses with sub-ns level precision in a wide dynamic amplitude range of more than 1:10.000.