P. Palojarvi

A wide dynamic range receiver channel for a pulsed time-of-flight laser radar

An integrated receiver channel for a pulsed time-of-flight (TOF) laser rangefinder has been designed and tested. The bandwidth of the receiver channel is 170 MHz, the transimpedance can be controlled in the range from 1.1 k/spl Omega/ to 260 k/spl Omega/, and the input-referred noise is /spl sim/6 pA//spl radic/Hz. The distance measurement accuracy is /spl plusmn/4.7 mm (average of 10000 measurements), taking into account walk error (input signal amplitude varies in the range 1:624) and jitter. A considerable increase in the input dynamic range of the receiver has been achieved by placing an integrated current buffer with variable attenuation between the external photodetector and the transimpedance preamplifier. Integrated electronic gain control structures together with the small size and low power consumption achieved by the use of full custom integrated technology considerably simplifies rangefinding devices for many applications. The circuit was implemented in an 0.8-/spl mu/m BiCMOS process.

Integrated time-of-flight laser radar

A small, hand-held pulsed time-of-flight (TOF) laser radar device has been designed and tested. The aim was to implement the receiver channel and time-to-digital converter (TDC) with application-specific integrated circuits (ASICs) in order to reduce power consumption, cost, weight, and size. The measurement range of the device is from 1 m to 30 m to a noncooperative target, and an accuracy of 35 mm is achieved with a measuring time of 200 ms between temperatures of -10/spl deg/C and +30/spl deg/C. Power consumption during continuous measurement is 0.84 W.

A 250-MHz BiCMOS receiver channel with leading edge timing discriminator for a pulsed time-of-flight laser rangefinder

An integrated receiver channel of a pulsed time-of-flight (TOF) laser rangefinder for fast industrial measurement applications with the measurement accuracy of a few centimeters in the measurement range from /spl sim/1 m to /spl sim/30 m to noncooperative targets was developed. The receiver channel consists of a fully differential transimpedance amplifier channel, a peak detector, an rms meter and a timing discriminator. In this particular application there is no time to measure the received signal strength beforehand and it is not predictable from previous measurements, so a leading edge timing discriminator with a constant threshold voltage was used. The amplitude of the received pulse is measured with a peak detector and the amplitude information is used to compensate for the resulting walk error. The measured bandwidth of the receiver channel is 250 MHz, the maximum transimpedance 40k/spl Omega/ and the input-referred noise /spl sim/7pA//spl radic/Hz (C/sub photodiode/=2 pF). The timing detection accuracy of the receiver is better than /spl plusmn/35 mm in a single-shot measurement in a dynamic range of 1:4000 and a temperature range of 0/spl deg/C to +50/spl deg/C.

A current-mode gain-control scheme with constant bandwidth and propagation delay for a transimpedance preamplifier

This paper presents a current-mode gain-control scheme that significantly increases the input dynamic range of a wideband optoelectronic receiver without affecting its bandwidth or delay or deteriorating its noise properties. A current buffer with variable attenuation is placed between the photodetector and the transimpedance preamplifier. In this way, the input dynamic range of the receiver can be increased, or alternatively, the signal dynamics can be reduced, by over 20 dB. A BiCMOS test circuit designed for a pulsed time-of-flight laser rangefinder has a measured bandwidth of 170 MHz and an input dynamic range of /spl sim/80 dB. The delay varies only /spl plusmn/5 ps when the gain is varied by 24 dB (1:15).

Pulsed time-of-flight laser radar module with millimeter-level accuracy using full custom receiver and TDC ASICs

A laser rangefinding device based on a pulsed time-of-flight distance measurement technique was constructed and tested. The aim, millimeter-level measurement accuracy with low power consumption, cost, and size, were achieved using full-custom application-specific integrated circuits in significant parts of the device, the receiver channel, and the time-to-digital converter. The accuracy of the device with a measurement time of one second and of the optomechanical head used in the measurements is at the mm-level in the case of a noncooperative target at a measurement range from 4 to 34 m and at a temperature between -10/spl deg/C and +50/spl deg/C.

Receiver channel with resonance-based timing detection for a laser range finder

An integrated receiver channel for a pulsed time-of-flight laser range finder is presented. The receiver operates in a wide dynamic range without gain control. This is achieved by converting the received unipolar pulse to a bipolar waveform already after the optical detector before the signal is fed to amplifier blocks. Thus the nonlinearities of the amplifiers have the minimum effect on the timing point, which is located in the zero crossing of the bipolar pulse. A parallel resonant circuit is used to shape the pulse in the input of the channel, which consists of a cascade of limiting voltage amplifiers followed by a comparator. The measurements show that the receiver has a walk error of 74 ps in the dynamic range of 1:1280. This corresponds to 11 mm in distance. The minimum usable input signal is limited by the noise of the receiver and equals 1.9 muA

A CMOS receiver for a pulsed time-of-flight laser rangefinder

An integrated CMOS 0.35/spl mu/m receiver channel with a wide dynamic range for a pulsed time-of-flight laser rangefinder was designed and tested. The circuit uses a leading edge timing discrimination technique. The measured bandwidth, transimpedance and an input referred noise current are 80 MHz, 122 k/spl Omega/ and 6.1 pA//spl radic/Hz. The measured walk error is 0.6 ns in 1:1000 dynamic range. The time-to-digital converter (TDC) is also implemented on the same chip.

A 4 GHz differential transimpedance amplifier channel for a pulsed time-of-flight laser radar

A wideband differential transimpedance amplifier channel was designed for the receiver of a pulsed time-of-flight (TOF) laser radar using a high frequency bipolar analog array. The measured maximum total transimpedance is /spl sim/11 k/spl Omega/ the bandwidth /spl sim/2.5 GHz (limited by the buffer amplifier used for test purposes only, corresponding to an internal bandwidth of /spl sim/4 GHz) and the input-referred noise current density /spl sim/8 pA//spl radic/(Hz). The amplifier channel has a current mode gain control cell in front of the transimpedance preamplifier to reduce the dynamic range of the output signal.

BiCMOS and CMOS timing detectors for the receiver of a portable laser rangefinding device

Integrated CMOS and BiCMOS timing detectors have been designed for the receiver of a portable laser radar. The timing detectors produce accurately timed logic level pulses from noisy analog pulses, whose amplitude varies in a wide range. The distance measurement result of the designed BiCMOS (CMOS) detector varies +/-4 mm (+/-9 mm) with an input amplitude range of 55 mV-3.3 V (0.5 V-2.2 V). The single shot resolution with SNR=250 is better than 6 mm (10.5 mm).

Electronic gain control with constant propagation delay for integrated transimpedance preamplifiers

This paper presents an electronic gain control scheme which significantly increases the dynamic range of an optoelectronic receiver without deteriorating the noise properties or affecting the propagation delay or bandwidth. A current buffer with variable attenuation is placed between the photodetector and the transimpedance preamplifier. The simulated dynamic range of the proposed front-end is 80 dB. A test circuit was designed for a pulsed time-of-flight laser rangefinder to verify the feasibility of the scheme. According to measurement results, the timing point varies /spl plusmn/5 ps when the gain is varied 24 dB (1:15).