Development of a Digital Calibration Test System for Flickermeter

Over last few decades, there has been deterioration in the power quality due to the increase in non-linear domestic and industrial loads usage. There may be a systematic low frequency variation of the voltage envelope or a series of random voltage changes, which the magnitude may not normally exceed the voltage regulations laid down by the supply authority. These phenomena known as voltage flicker have severe effect on power quality. Flickermeter is the power analyzer for measuring the voltage flicker, flicker sensation and flicker severity index. International Electrotechnical Commission (IEC) has published IEC 61000-4-15 standard describing the functional and design specifications for flickermeter. Most of the flickermeter and flickermeter calibration test systems presented in the literature are based on analog signal processing techniques. In this thesis, a digital calibration test system for flickermeter based on digital signal processor (DSP) is presented. The system has been developed around DSP TMS320 and test signals required as per IEC 61000-4-15 standard to test a flickermeter is generated. A DSP based waveform generator, which can give sine, square, triangular waveform with frequency of operation from 0.01 Hz to 24 kHz has been described in this thesis. The DSP starter kit (DSK) TMS320C6713DSK with Code Composer Studio and C programming language had been used in obtaining the desired signal. Amplitude modulated test signals with different modulation index as per IEC 61000-4-15 standard had been generated using DSP based waveform generator. A measurement system was developed to capture the analog signals generated by DSP starter kit. LabVIEW had been used to perform the data analysis and from which voltage fluctuation for P and Pst measurement was obtained. For the voltage fluctuation of P measurement, it was found that the percent modulation of test signals measured by the oscilloscope is from 2.15% to 8.20% for sinusoidal modulating frequency; and 0.67% to 7.65% for rectangular modulating frequency. The average of the difference between the test signals generated and IEC standard value was 4.6% for sinusoidal voltage fluctuation; and 3.9% for the rectangular voltage fluctuation. For the voltage fluctuation of Pst measurement, it was found out that test signals generated are 2.8% deviated from IEC standard. The digital calibration test system developed was able to generate test conditions which were within 5% from the standard values required for testing

Modeling and Compensation of Nonlinear Distortion in Horn Loudspeakers

Horn loaded compression drivers are widely used in the area where high sound pressure levels together with good directivity characteristics are needed. Major disadvantage of this kind of drivers is the considerable amount of nonlinear distortion. Due to the quite high air pressures in the driver the air is driven into its nonlinear range. This paper describes a technique to reduce the distortion caused by this phenomenon. Using a Digital Signal Processor (DSP), a feedforward compensation technique, based on an equivalent lumped parameter circuit, is implemented and tested in real–time in series with the loudspeaker. Measurement and simulation results are given. The overall conclusion is that a distortion reduction is obtained in the frequency span from 600 to 1050 Hz

A Software-Defined Channel Sounder for Industrial Environments with Fast Time Variance

Novel industrial wireless applications require wideband, real-time channel characterization due to complex multipath propagation. Rapid machine motion leads to fast time variance of the channel's reflective behavior, which must be captured for radio channel characterization. Additionally, inhomogeneous radio channels demand highly flexible measurements. Existing approaches for radio channel measurements either lack flexibility or wide-band, real-time performance with fast time variance. In this paper, we propose a correlative channel sounding approach utilizing a software-defined architecture. The approach enables real-time, wide-band measurements with fast time variance immune to active interference. The desired performance is validated with a demanding industrial application example.Comment: Submitted to the 15th International Symposium on Wireless Communication Systems (ISWCS 2018

Design and Implementation of a FPGA and DSP Based MIMO Radar Imaging System

The work presented in this paper is aimed at the implementation of a real-time multiple-input multiple-output (MIMO) imaging radar used for area surveillance. In this radar, the equivalent virtual array method and time-division technique are applied to make 16 virtual elements synthesized from the MIMO antenna array. The chirp signal generater is based on a combination of direct digital synthesizer (DDS) and phase locked loop (PLL). A signal conditioning circuit is used to deal with the coupling effect within the array. The signal processing platform is based on an efficient field programmable gates array (FPGA) and digital signal processor (DSP) pipeline where a robust beamforming imaging algorithm is running on. The radar system was evaluated through a real field experiment. Imaging capability and real-time performance shown in the results demonstrate the practical feasibility of the implementation

Hardware for digitally controlled scanned probe microscopes

The design and implementation of a flexible and modular digital control and data acquisition system for scanned probe microscopes (SPMs) is presented. The measured performance of the system shows it to be capable of 14-bit data acquisition at a 100-kHz rate and a full 18-bit output resolution resulting in less than 0.02-Å rms position noise while maintaining a scan range in excess of 1 µm in both the X and Y dimensions. This level of performance achieves the goal of making the noise of the microscope control system an insignificant factor for most experiments. The adaptation of the system to various types of SPM experiments is discussed. Advances in audio electronics and digital signal processors have made the construction of such high performance systems possible at low cost

Analysis and application of digital spectral warping in analog and mixed-signal testing

Spectral warping is a digital signal processing transform which shifts the frequencies contained within a signal along the frequency axis. The Fourier transform coefficients of a warped signal correspond to frequency-domain 'samples' of the original signal which are unevenly spaced along the frequency axis. This property allows the technique to be efficiently used for DSP-based analog and mixed-signal testing. The analysis and application of spectral warping for test signal generation, response analysis, filter design, frequency response evaluation, etc. are discussed in this paper along with examples of the software and hardware implementation