Ryszard Pelka

Single-chip interpolating time counter with 200-ps resolution and 43-s range

In this paper, we present a design and test results of the interpolating time counter implemented on a single field programmable gate array (FPGA) chip. The counter contains two 6-bit time-to-digital converters (TDCs), each having 200-ps resolution (LSB) within 10 ns range, and the 32-bit, 100-MHz real-time counter, which is also used for frequency measurement. The utilization of the logic cells on the FPGA chip is 93%. The software correction of the TDCs nonlinearity errors resulted in lowering the random error of the counter to 0.65 LSB or 129 ps (RMS).

Error analysis and design of the Nutt time-interval digitiser with picosecond resolution

Several sources of errors related to the Nutt time-interval digitiser are discussed, including the quantisation process, time jitter, non-linearity of time stretchers and phase noise of the reference clock. A model of the total measurement uncertainty is formulated. The authors also describe the main circuitry and test results of a microprocessor-controlled digitiser which has been developed to achieve a negligible quantisation error (1 ps resolution) and 1 ms range.

Nonlinearity correction of the integrated time-to-digital converter with direct coding

A method is presented for automated identification and correction of the nonlinearity error of the time-to-digital converter (TDC) with delay-line coding and 200 ps resolution, integrated on a single Field Programmable Gate Array (FPGA) device. The nonlinearity error is estimated using a statistical method based on a sufficiently large number N of measurements of random input time intervals having a uniform distribution within the input range of TDC. Then, the resulting estimate of the error function is used for training a two-layer neural network (NN) designed for correction of the nonlinearity error. Training of the NN is based on the fast Levenberg-Marquardt (LM) learning rule and the goal is to minimize the maximum nonlinearity error of the TDC. Experimental tests have shown, that using a relatively small number of N=5/spl times/10/sup 4/ identification measurements the maximum nonlinearity error of a TDC may be reduced from 1.37 LSB (least significant bit) to about 0.12 LSB (24 ps).

PRECISION TIME COUNTER FOR LASER RANGING TO SATELLITES

A new design of the precision time counter for satellite laser ranging is described. The instrument features 3 ps incremental resolution within the measuring range up to 21.47 s, the short‐term rms error below 30 ps, and the time drift within ±5 ps. To reject unwanted noise and other disturbing signals the programmable window discriminator has been employed. In order to achieve high accuracy and good long‐term stability we used an automatic calibration based on the adaptive prediction. Further significant reduction of the measurement error has been achieved by self‐correction of the nonlinearity error and robust estimation. Results from experimental tests are presented to demonstrate the performance of the instrument.

A method for autocalibration of the interpolation time interval digitiser with picosecond resolution

A calibration method is described which allows precise determination of the stretch factors of the time stretchers used in the interpolation time interval digitiser with 1 ps incremental resolution. The method is based on analysis of statistical phenomena related to time jitter close to the threshold level of the phase detectors contained in the interpolators. The bias error inherent in the method is analysed and compensation of that error is discussed. A detailed description of a microprocessor procedure to perform automatic calibration is given. The usefulness of the method is proved by numerical examples and experimental results.

A 7.5 ps single-shot precision integrated time counter with segmented delay line

This paper describes the design and test results of time interval counter featuring the single-shot precision of 7.5 ps root mean square (rms) and measurement range of 1 ms. These parameters have been achieved by combining direct counting method with a two-stage interpolation within a single clock period. Both stages of interpolation are based on the use of tapped delay lines stabilized by delay locked loop mechanism. In the first stage, a coarse resolution is obtained with the aid of high frequency multiphase clock, while in the second stage a sub-gate delay resolution is achieved with the use of differential delay line. To reduce the nonlinearities of conversion and to improve the precision of measurement, a novel segmented delay line is proposed. An important feature of this segmented delay line is partial overlapping of measurement range and resulting enhancement of both resolution and precision of time interval counter. The maximum integral nonlinearity error of the fine-stage interpolators does not exceed 16 ps and 14 ps in START and STOP interpolators, respectively. These errors have been identified by statistical calibration procedure and corrected to achieve single-shot precision better than 7.5 ps (rms). The time counter is integrated in a single ASIC (Application Specific Integrated Circuit) chip using a standard cost-effective 0.35 μm CMOS (Complementary Metal Oxide Semiconductor) process.

Improved time-interval counting techniques for laser ranging systems

Recent improvements in precision time-interval counting techniques are presented. Real-time autocalibration using an adaptive method for setting the optimum calibration rate, robust estimation of counter parameters, and input data filtering are discussed. The techniques described were evaluated during the development of time-interval counter T-1810B for satellite LRS in the Polish Academy of Sciences. Two adaptive calibration algorithms were tested, and results are presented. >

Adaptive calibration of time interval digitizer with picosecond resolution

An adaptive method is presented for real-time calibration of the interpolation time-interval digitizer (TID) with picosecond res- olution. Reduction of calibration uncertainty to the level of &4 ps has been achieved. Experimental results and comparison with some exist- ing methods for TID calibration are also presented. The method may also be used in any other measurement system where intermittent self- calibration interrupts the measurements.

An adaptive method for automatic calibration of interpolation time interval digitizer with picosecond resolution

An adaptive method is presented for real-time calibration of an interpolation time-interval digitizer (TID) with picosecond resolution. Reduction of calibration uncertainty to the level of 3 ps (RMS) has been achieved. Experimental results and comparison with some existing methods for TID calibration are also presented. The adaptive method was developed to solve a calibration problem that emerged in the course of developing an advanced TID for a satellite laser ranging systems.<<ETX>>

AN AUTOMATIC CORRECTION OF QUANTIZATION ERROR FOR PICOSECOND TIME COUNTING

ABSTRACT A method for automatic correction of the quantization error in time-interval counters is presented. A detailed analysis for Gaussian time-intervals is given for synchronous and asynchronous counting mode, considering the time jitter as well as the bias error inherent in the counter. The usefulness of the method is proved by numerical examples and experimental results.