Pasquale Arpaia, Nello Polese
UNCERTAINTY REDUCTION IN MEASUREMENT SYSTEMS BY STATISTICAL PARAMETER DESIGN

In measurement system design, uncertainty is usually reduced by a cost increase: more accurate components are selected and narrower variations to influence parameters are imposed. In this paper, an alternative cost-saving approach is proposed: suitable values of design parameters capable of minimizing the measurement uncertainty due both to component’s uncertainty and to influence parameters are identified without any loss in other metrological performances. With this aim, a general method based on statistical parameter design is proposed. The method effectiveness is highlighted by an experimental case study related to the design of a pass-band passive filter.

Antonio Moschitta, Dario Petri
PERFORMANCE REQUIREMENTS OF BANDPASS SIGMA-DELTA CONVERTERS IN OFDM SYSTEMS

This paper analyzes the effect of analog-to-digital bandpass Sigma-Delta conversion on the performance of Orthogonal Frequency Division Multiplexing (OFDM) systems. A brief description of both OFDM systems and the related simulation model is given. The nonlinear effects of quantization overload on overall OFDM performance are evaluated in terms of quantization noise power and bit error rate. It is shown how minimizing quantization noise power can lead to suboptimal results. Moreover a set of minimum performance requirements for Sigma-Delta converters is established.

Cristian Zet, Marinel Temneanu, Cristian Fosalau, Mihai Cretu
SAMPLE AUTO-RANGING DATA ACQUISITION USING NATIONAL INSTRUMENTS SUPPORT

In the process of data acquisition the analogic gain is usually determined by the peak value of the input signal. For all samples the quantization error is theoretically less than 1/2 LSB. However for samples having small value, the relative error due to the quantization is high, and it goes higher with the decreasing of the sample value. The relative measuring error can be reduced by dynamically setting the proper gain. This is usually achieved with a supplementary hardware arrangement. The solution proposed in this paper consists in a numeric algorithm, developed in LabView, which replaces the hardware. The idea is to measure the same signal with many channels, set up with different gains, and to rebuild the signals, choosing the samples measured with the maximum accuracy. Sample translation must be performed due to the inter-channel delay.

L. Angrisani, A. Baccigalupi, A. Di Meo
JITTER MEASUREMENT IN PDH/SDH-BASED TELECOMMUNICATION NETWORKS: OPTIMISATION AND PERFORMANCE ASSESSMENT OF A DIGITAL SIGNAL PROCESSING METHOD

The paper deals with jitter measurement in PDH/SDH-based telecommunication networks. The attention is mostly paid to the accuracy assured by any PDH/SDH analyser compliant the ITU-T recommendations, which seems to be unsatisfying for both designers and manufacturers. Trying to give an answer to this problem, a digital signal-processing method was already proposed by the authors; it avoids the use of a timing recovery circuitry, which strongly degrades the aforementioned accuracy. The method is here optimised with the aim both of further enhancing the accuracy on jitter estimates and testing, in an automatic way, jitter performance of network elements operating at the PDH bit rate of 140 Mbit/s and the SDH bit rate of 155 Mbit/s. In particular, an innovative procedure for automatically recovering the binary information conveyed by the jittered signal under analysis and a proper strategy for carrying out instantaneous jitter measurements at uniform time intervals are developed. After a brief outline of the old version of the method, the proposed modifications are described in detail. Then, the performance of the optimised method is assessed through many laboratory tests on emulated signals, the results of which are given and discussed. At the end, the outcomes of real automatic tests, conducted on PDH/SDH-based equipment produced by Marconi Sud S.p.A., are also presented.

D. R. Larson, N. G. Paulter
USING THE NOSE-TO-NOSE SAMPLER CALIBRATION METHOD IN PULSE METROLOGY

We present our analysis of the nose-to-nose (ntn) method for use as an accurate sampler calibration method. The variations in the measurement of the sampler impulse response using the ntn method are described and the assertion that the kick-out pulse is identical to the sampler impulse response is assessed. Temperature effects on the ntn method are also examined. Finally, the effect of uncertainties in the ntn calibration method on the uncertainties in reported pulse parameters is examined.