Tarmo Ruotsalainen

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.

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).

CMOS-compatible position-sensitive devices (PSDs) based on photodetector arrays

Abstract This paper reports five different constructions of optical position-sensitive devices (PSDs) implemented using standard CMOS technology. It is found that despite the non-idealities of CMOS-compatible photodetectors, CMOS technology provides a means of implementing PSDs with relatively high performance. This can be achieved, for example, by using an array of discrete photodetectors instead of the continuous single element structure used in conventional lateral effect PSDs (LEPs). The results show that, relative to a conventional LEP manufactured with dedicated technology, the linearity of an array-type two-axis CMOS PSD can be two to eight times better, and that its precision in low bandwidth (

CMOS position-sensitive photodetectors (PSDs) for integrated sensor systems

Implementations and test results of one single-axis and 2- axis CMOS PSDs as well as a BiCMOS integrated receiver channel are presented. The single-axis PSD has a conventional LEP structure. It uses the well-substrate junction as a photodetector and pinched well as current dividing layer. An interelectrode resistance, NEP and position sensing accuracy of 152 k(Omega) , 1.6 pW/(root)Hz (850 nm) and 0.1%rms are achieved with the detector measuring 5 X 0.2 mm2. The first 2-axis PSD is a tetralateral LEP but instead of having strip-like continuous edge-electrodes it has electrodes composed of 100 discrete contacts, each of which is connected to the output current line using MOS switches. Linear position response is provided by disconnecting one opposite pair of the electrodes from preamplifier inputs and measuring one dimension at a time. An interelectrode resistance, NEP and accuracy of 4.5 k(Omega) , 10 pW/(root)Hz and 0.07%rms were achieved with this PSD using the alternate measurement mode. The second 2-axis PSD has an operating principle similar to a basic LEP but is composed of an array of phototransistors and polysilicon resistors. The NEP and position sensing nonlinearity of the sensor were 0.5 pW/(root)Hz and 0.04%rms, respectively. The third 2-axis PSD has the same construction as the second one but the phototransistors and polysilicon resistors were replaced with well-substrate photodiodes and pmos transistors, respectively. By driving one or more adjacent transistors in off-state the LEP mode can be changed to a segmented PSD mode providing the means to combine the high lateral sensitivity of the segmented mode with the large and linear measurement fields of the LEP. The BiCMOS receiver channel is composed of a transimpedance preamplifier, voltage amplifiers, gain control and offset cancellation blocks and a synchronous detector. The transimpedance at four different gains for a signal frequency ranging typically from 5 kHz to 10 kHz were 7 M(Omega) , 33 M(Omega) , 143 M(Omega) and 488 M(Omega) . The measured noise current density was lower than 0.3 pA(root)Hz, and the area and power consumption were 2.9 X 0.45 mm2 and 37 mW, respectively. As the achieved results fulfill the demands set for a typical signal conditioning channel of a PSD sensor system, the properties appear to be suitable for integrated PSD systems.

Photodiodes for high-frequency applications implemented in CMOS and BiCMOS processes

In this paper the high frequency behavior of integrated pn- photodiodes is discussed and measurement results of two different types of photodiodes, one implemented in a standard 1.2 micrometers BiCMOS process and the other in a 0.8 micrometers CMOS process are presented. The rise times and responsivities of the photodiodes are under 5 ns and 0.26 A/W in the CMOS process and about 30 ns and 0.23 A/W in the BiCMOS process, respectively. Furthermore, the suitability of the technique for 3D vision has been investigated by designing an array of photodetectors and measuring the isolation between detector blocks.

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.

Systems on chips design: system manufacturer point of view

This paper discusses the design, packaging and testing of complex systems used for cellular mobile applications. The design process starting from requirements and ending to production ICs and systems, especially as the design time, size, cost and power consumption need to be minimized without sacrificing reliability.

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 +/- 35 mm 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 +/- 3 mm. 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 50 ps and 2 microseconds, respectively. In averaging mode the linearity is better than +/- 5 ps. Even better single-shot precision can be realized with analog interpolation techniques, however, at the expense of reduced stability.

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).