Michael Hofbauer

Pulse Shape Measurements by On-Chip Sense Amplifiers of Single Event Transients Propagating Through a 90 nm Bulk CMOS Inverter Chain

Single event transient (SET) pulse shapes caused by Au ions with an energy of 946 MeV were measured at the microprobe facility at GSI in Darmstadt. Using on-chip sense amplifiers, our novel approach allows observing SET pulse shapes at any interesting circuit node with negligible distortion. We were hence able to accurately trace the propagation of SET pulses through a 90 nm CMOS inverter chain.

A Monolithic Silicon Quantum Random Number Generator Based on Measurement of Photon Detection Time

In this paper, a nondeterministic random number generator based on detection of the single photons emitted by an Si-CMOS-LED light source integrated for the first time on the detector chip is presented and experimentally demonstrated. We use a ring-shaped single-photon avalanche diode (SPAD) around the Si-CMOS-LED fabricated in 0.35-μm HV-CMOS technology to generate random events. The time intervals between single-photon events are independent quantum random variables. A field-programmable gate array (FPGA) digitizes the time variables to the stream of random bits. Bias in the raw data due to the nonuniform distribution of the time intervals is removed by postprocessing in a special configuration of xor gates to improve the randomness of the generated random bits. The quantum random numbers in 1-Gb streams with bit generation rate of 1 Mb/s were directly delivered to a personal computer (PC) and passed all statistical tests from ENT, STS, and DIEHARD, as well as for more accuracy correlation and bias tests applied on these streams.

Design and Implementation of an Integrated Reconfigurable Silicon Photonics Switch Matrix in IRIS Project

This paper aims to present the design and the achieved results on a CMOS electronic and photonic integrated device for low cost, low power, transparent, mass-manufacturable optical switching. An unprecedented number of integrated photonic components (more than 1000), each individually electronically controlled, allows for the realization of a transponder aggregator device which interconnects up to eight transponders to a four direction colorless-directionless-contentionless ROADM. Each direction supports 12 200-GHz spaced wavelengths, which can be independently added or dropped from the network. An electronic ASIC, 3-D integrated on top of the photonic chip, controls the switch fabrics to allow a complete and microsecond fast reconfigurability.

High dynamic range background light suppression for a TOF distance measurement sensor in 180nm CMOS

In this paper an integrated background light (BGL) immune single-pixel range finding sensor based on the time-of-flight (TOF) principle is presented. The sensor is fabricated in a standard 180 nm 1P6M CMOS process, reaching 40 × 40 µm2 total pixel area, at a fill factor of ∼ 67%. As a key element for the BGL suppression a current-sample-and-hold circuit is introduced. A resulting distance variation as a function of BGL remained in a 1.5 cm range for applied dc light of 180 klx, which is, to our best knowledge, the highest BGL immunity reported so far. Measurement results are carried out at 100 fps, showing a standard deviation of 8 mm at 1 m and ∼ 4 cm for distances up to 3.2 m.

FPGA based time-of-flight 3D camera characterization system

In this paper we present an FPGA based characterization system for our 3D TOF distance sensors supporting up to 128 × 128 pixels. The system is capable of flexibly generating all control signals required for a typical TOF measurement. Their properties can be changed within a very broad range. The cycle-to-cycle jitter of those signals was reduced to 1 ps by ECL circuitry. This is equivalent to a standard deviation of the measured distance of 0.15 mm. Furthermore, the system is able to preprocess the distance information before transferring the data to a terminal PC, which reduces the data load on the USB interface. The system includes an averaging function with a maximum of 256 elements to reduce the standard deviation of precision distance measurement sensors. A novel fiber based setup is introduced to systemize the characterization process. By means of averaging a standard deviation of 2 mm could be achieved with one of our 3D TOF distance sensors.

Supply Voltage Dependent On-Chip Single-Event Transient Pulse Shape Measurements in 90-nm Bulk CMOS Under Alpha Irradiation

Direct on-chip pulse shape measurements of single-event transients (SETs) in a single inverter in 90-nm bulk CMOS have been performed at the microbeam facility at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. Alpha particles with an energy of 8 MeV were used as projectiles, and the supply voltage dependence of the arising SETs was investigated. A strong dependence of the resulting pulse heights, widths, and shapes on the supply voltage could be observed.

Correction of the temperature induced error of the illumination source in a time-of-flight distance measurement setup

A systematic investigation of the combination of a reference path and a reference pixel as correction method for a systematic error induced by the light source of a time-of-flight (TOF) distance measurement sensor is presented. A change of the bandwidth of the light source, e.g. caused by drifting temperature of the used LEDs results in a bandwidth dependent distance error. The presented method allows reducing this error over a large operating range by ~97 %, i.e. to 3 %.

Investigation of the distance error induced by cycle-to-cycle jitter in a correlating time-of-flight distance measurement system

Abstract. Time-of-flight (TOF) range sensors acquire distances by means of an optical signal delay measurement. As the signal travels at the speed of light, distance resolutions in the subcentimeters range require a time measurement resolution that is in the picoseconds range. However, typical clock synthesizers and digital buffers possess cycle-to-cycle jitter values of up to hundreds of picoseconds, which can potentially have a noticeable impact on the TOF system performances. In this publication, we investigate the influence of two common types of cycle-to-cycle jitter distributions on the measured distance. This includes a random Gaussian distribution, which is caused by, e.g., stochastic noise sources, and a discrete jitter distribution, which is found when timing constraints fail in synchronous digital designs. It was demonstrated that a Gaussian cycle-to-cycle jitter has only a negligible impact on the performance of the TOF distance sensors up to a standard deviation of 1 ns of the Gaussian jitter distribution. However, even the discrete cycle-to-cycle jitter investigated in its simplest form lowers the distance precision of the TOF sensor by a factor of 2.86, i.e., the standard deviation increases from 2.9 to 8.3 mm.

Correction of a phase dependent error in a time-of-flight range sensor

Time-of-Flight (TOF) 3D cameras determine the distance information by means of a propagation delay measurement. The delay value is acquired by correlating the sent and received continuous wave signals in discrete phase delay steps. To reduce the measurement time as well as the resources required for signal processing, the number of phase steps can be decreased. However, such a change results in the arising of a crucial systematic distance dependent distance error. In the present publication we investigate this phase dependent error systematically by means of a fiber based measurement setup. Furthermore, the phase shift is varied with an electrical delay line device rather than by moving an object in front of the camera. This procedure allows investigating the above mentioned phase dependent error isolated from other error sources, as, e.g., the amplitude dependent error. In other publications this error is corrected by means of a look-up table stored in a memory device. In our paper we demonstrate an analytical correction method that dramatically minimizes the demanded memory size. For four phase steps, this approach reduces the error dramatically by 89.4 % to 13.5 mm at a modulation frequency of 12.5 MHz. For 20.0 MHz, a reduction of 86.8 % to 11.5 mm could be achieved.

Integrated fiber optical receiver reducing the gap to the quantum limit

Experimental results of a single-photon avalanche diode (SPAD) based optical fiber receiver integrated in 0.35 µm PIN-photodiode CMOS technology are presented. To cope with the parasitic effects of SPADs an array of four receivers is implemented. The SPADs consist of a multiplication zone and a separate thick absorption zone to achieve a high photon detection probability (PDP). In addition cascoded quenchers allow to use a quenching voltage of twice the usual supply voltage, i.e. 6.6 V instead of 3.3 V, in order to increase the PDP further. Measurements result in sensitivities of −55.7 dBm at a data rate of 50 Mbit/s and −51.6 dBm at 100 Mbit/s for a wavelength of 635 nm and a bit-error ratio of 2 × 10−3, which is sufficient to perform error correction. These sensitivities are better than those of linear-mode APD receivers integrated in the same CMOS technology. These results are a major advance towards direct detection optical receivers working close to the quantum limit.