Juha Kostamovaara

A CMOS time-to-digital converter with better than 10 ps single-shot precision

A high-precision CMOS time-to-digital converter IC has been designed. Time interval measurement is based on a counter and two-level interpolation realized with stabilized delay lines. Reference recycling in the delay line improves the integral nonlinearity of the interpolator and enables the use of a low frequency reference clock. Multi-level interpolation reduces the number of delay elements and registers and lowers the power consumption. The load capacitor scaled parallel structure in the delay line permits very high resolution. An INL look-up table reduces the effect of the remaining nonlinearity. The digitizer measures time intervals from 0 to 204 /spl mu/s with 8.1 ps rms single-shot precision. The resolution of 12.2 ps from a 5-MHz external reference clock is divided by means of only 20 delay elements.

The use of stabilized CMOS delay lines for the digitization of short time intervals

The basic advantages and limitations of using integrated digital CMOS delay lines for the digitization of short time intervals are discussed. Accuracies of 6-7 b and single-shot resolutions from 0.1 to 10 ns are demonstrated to be realizable using fully integrated, tapped, and voltage-controlled CMOS delay lines as a time base for the measurement. >

A low-power CMOS time-to-digital converter

A time-to-digital converter, TDC, with 780 ps lsb and 10-/spl mu/s input range has been integrated in a 1.2-/spl mu/m CMOS technology. The circuit is based on the interpolation time interval measurement principle and contains an amplitude regulated crystal oscillator, a counter, two pulse-shrinking delay lines, and a delay-locked loop for stabilization of the delay. The TDC is designed for a portable, low-power laser range-finding device. The supply voltage is 5/spl plusmn/0.5 V, and the operating temperature range is -40 to +60/spl deg/C. Single-shot accuracy is 3 ns and accuracy after averaging is /spl plusmn/120 ps with input time intervals 5-500 ns. In the total input range of 10 /spl mu/s, the final accuracy after averaging is /spl plusmn/200 ps. Current consumption is 3 mA, and the chip size is 2.9 mm/spl times/2.5 mm. >

A CMOS Time-to-Digital Converter (TDC) Based On a Cyclic Time Domain Successive Approximation Interpolation Method

This paper describes a time-to-digital converter (TDC) with ~1.2 ps resolution and ~327 mus dynamic range suitable for laser range-finding application for example. The resolution of ~1.2 ps is achieved with interpolation based on a cyclic time domain successive approximation (CTDSA) method that resolves the time difference between two non-repetitive signals using binary search. The method utilizes a pair of digital-to-time converters (DTC), the propagation delay difference between which is implemented by digitally controlling the unit load capacitors of their delay cells, thus enabling sub-gate delay timing resolution. The rms single-shot precision, i.e., standard deviation sigma-value of the TDC is 3.2 ps, which is achieved by using an external integral nonlinearity look-up table (INL-LUT) for the interpolators. The power consumption is 33 mW at 100 MHz with a 3.3 V operating voltage. The prototypes were fabricated in a 0.35 mum CMOS process.

An integrated time-to-digital converter with 30-ps single-shot precision

A time-to-digital converter (TDC) with 32-ps resolution and 2.5-/spl mu/s measurement range has been integrated in a 0.8-/spl mu/m BiCMOS process. The TDC is based on a counter with a 100-MHz clock. Two separate time digitizers improve the time resolution by interpolating within the clock period. These interpolators are based on analog dual-slope conversion. According to test results, the single-shot precision of the TDC is better than 30 ps (/spl sigma/-value) and the nonlinearity is less than /spl plusmn/5 ps when input time intervals range from 10 ns to 2.5 /spl mu/s. The conversion time is /spl les/6.3 /spl mu/s. Temperature drift, excluding the temperature dependence of the oscillator, is below /spl plusmn/40 ps in the temperature range of -40 to 60/spl deg/C. The size of this chip, including pads, is 3.5/spl times/3.4 mm/sup 2/ and its power consumption is 350 mW.

A high-precision time-to-digital converter for pulsed time-of-flight laser radar applications

A time-to-digital converter (TDC) has been designed, and six units have been constructed and tested. It consists of integrated digital time-interval measurement electronics with a /spl plusmn/10-ns resolution that can be improved to /spl plusmn/10 ps by an analog interpolation method. Identical construction of the interpolation electronics leads to stable performance of the TDC. The drifts of all six TDC units remain within /spl plusmn/10 ps over a temperature range from -10/spl deg/C to +50/spl deg/C. The stability can be improved further by a real-time calibration procedure developed here. The single-shot precision of the TDC is better than 15 ps (standard deviation), but precision can be improved to below 0.1 ps by averaging about 10 000 measurements at the maximum measurement speed of 100 kHz. The time range of the TDC is currently 2.55 /spl mu/s, but this can be increased by adding an external digital counter. The TDC suffers from a periodic nonlinearity over the measured time range from 0 to 1.3 /spl mu/s, the amplitude and period of the nonlinearity being /spl plusmn/20 ps and 40 ns, respectively. The reason lies in the integrated digital part of the electronics. The linearity of interpolation in the 10-ns time range improves, however, as more results are averaged.

Profiling of hot surfaces by pulsed time-of-flight laser range finder techniques.

The possibilities for using the pulsed time-of-flight (TOF) laser radar technique for hot refractory lining measurements are examined, and formulas are presented for calculating the background radiation collected, the achievable signal-to-noise ratio (SNR), and the measurement resolution. An experimental laser radar device is presented based on the use of a laser diode as a transmitter. Results obtained under real industrial conditions show that a SNR of 10 can be achieved at measurement distances of up to 15-20 m if the temperature of the converter is 1400 °C and the peak power of the laser diode used is 10 W. The single-shot resolution is about 60 mm (sigma value), but it can be improved to millimeter range by averaging techniques over a measurement time of 0.5 s. A commercial laser radar profiler based on the experimental laser radar device is also presented, and results obtained with it in real measurement situations are shown. These measurements indicate that it is possible to use the pulsed TOF laser radar technique in demanding measurement applications of this kind to obtain reliable data on the lining wear rate of a hot converter in a steel works.

A low noise quadrature subsampling mixer

Noise analysis of a subsampling mixer structure based on current signal sampling is performed. The calculations show that a promisingly low noise figure can be obtained. The results of the analysis are verified by high-level simulations and measurements of a test circuit designed for quadrature downconversion from a 1st IF of 44.87 MHz to a low IF of 13 kHz.

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.

Precise pulsed time-of-flight laser range finder for industrial distance measurements

A pulsed time-of-flight laser range finder with a 1 GHz avalanche photo diode (APD) receiver and a laser pulser with ∼35 ps pulse width has been developed and tested. The receiver channel is constructed using a silicon ASIC chip and a commercially available silicon APD placed on a hybrid ceramic susbstrate. The laser pulser utilizes a single heterostructure laser operating in Q-switching mode. It is shown that the single-shot precision of the complete laser range finder is ∼2.1 mm (σ value) at best. The nonaccuracy in the distance range of 0.5–34.5 m was ∼±2 mm excluding errors caused by the statistical variations and long-term instability. The single-shot precision is clearly better than the single-shot precision of the earlier laser range finders with ∼100–200 MHz bandwidths. Also, two types of optics, coaxial and paraxial, were tested. The linearity of the coaxial optics was better, especially with a long (4 m) receiver fiber. Some possible applications of the laser range finder utilizing ps level puls...