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Journal Details
Format
Journal
eISSN
1335-8871
First Published
07 Mar 2008
Publication timeframe
6 times per year
Languages
English

Search

Volume 11 (2011): Issue 1 (February 2011)

Journal Details
Format
Journal
eISSN
1335-8871
First Published
07 Mar 2008
Publication timeframe
6 times per year
Languages
English

Search

6 Articles
Open Access

A New Digital Signal Processing Method for Spectrum Interference Monitoring

Published Online: 08 Apr 2011
Page range: 1 - 8

Abstract

A New Digital Signal Processing Method for Spectrum Interference Monitoring

Frequency spectrum is a limited shared resource, nowadays interested by an ever growing number of different applications. Generally, the companies providing such services pay to the governments the right of using a limited portion of the spectrum, consequently they would be assured that the licensed radio spectrum resource is not interested by significant external interferences. At the same time, they have to guarantee that their devices make an efficient use of the spectrum and meet the electromagnetic compatibility regulations. Therefore the competent authorities are called to control the access to the spectrum adopting suitable management and monitoring policies, as well as the manufacturers have to periodically verify the correct working of their apparatuses. Several measurement solutions are present on the market. They generally refer to real-time spectrum analyzers and measurement receivers. Both of them are characterized by good metrological accuracies but show costs, dimensions and weights that make no possible a use "on the field". The paper presents a first step in realizing a digital signal processing based measurement instrument able to suitably accomplish for the above mentioned needs. In particular the attention has been given to the DSP based measurement section of the instrument. To these aims an innovative measurement method for spectrum monitoring and management is proposed in this paper. It performs an efficient sequential analysis based on a sample by sample digital processing. Three main issues are in particular pursued: (i) measurement performance comparable to that exhibited by other methods proposed in literature; (ii) fast measurement time, (iii) easy implementation on cost-effective measurement hardware.

Keywords

  • Spectrum monitoring
  • spectrum management
  • spectrogram
  • digital signal processing
  • RF measurement
Open Access

Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

Published Online: 08 Apr 2011
Page range: 9 - 14

Abstract

Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

We studied the effects of slight Sm-Ba non-stoichiometry in Sm-Ba-Cu-O superconducting compounds on their transition, structural, and magnetic properties. Two series of single-phase samples of Sm1+xBa2-xCu3O7+Δ and Sm1+xBa2-xCu3O7+Δ with composition deviation from stoichiometry x from 0 to 0.1 were synthesized by the solid-state reaction method from Sm2O3, BaCO3 and CuO precursors and sintered at the temperature of ~ 1060 °C in flowing oxygen. All samples showed the values of Tc > 90 K and the volume density, p, 6.45 g cm-3 < p ≤ 6.73 g cm-3. The effect of the composite deviation of x on Tc, ΔTc, and volume magnetization M was studied. For Sm1+xBa2-xCu3O7+Δ compounds, optimal values of x were determined to maximize the width of the magnetization hysteresis at higher values of the applied magnetic field, corresponding mainly to the grain contribution. We also prepared the Sm1+xBa2-xCu3O7+Δ samples with x from 0 to 0.1 using the same processing conditions as in the case of A and B series. For the Sm1+xBa2-xCu3O7+Δ samples, values of x = 0.02 - 0.03 optimize Tc, ΔTc, Hp1 as well as M.

Keywords

  • Superconductors
  • Sm-123
  • cation non-stoichiometry
  • critical temperature
  • magnetization
Open Access

Correction of ADC Errors by Additive Iterative Method with Dithering

Published Online: 08 Apr 2011
Page range: 15 - 18

Abstract

Correction of ADC Errors by Additive Iterative Method with Dithering

The iterative method could be used for automatic accuracy improvement of a measurement system. In its application for analog-to-digital converter (ADC) a quantization error represents a limitation for the correction process. Therefore, combination of correction methods is common for ADC error correction. Combination of the additive iterative method (AIM) with nonsubtractive dithering (ND) has been proposed for slow measurement based on ADC where errors could change in time. The principle of combination of both techniques is described in the paper. AIM is based on precise inverse element (IE). In the designed system the IE output signal is created by pulse width modulation and low-pass filtering. A technique similar to deterministic dithering is employed to achieve precise processing of signal from IE. Analysis of influence of stochastic dither upon the results of correction is performed with the aim to find optimal parameters of ND. Finally, dependency of the root mean squared error and error dispersion on the measured value is drawn to show how AIM corrects the nonlinear deterministic error but slightly increases system noise.

Keywords

  • Iterative Correction
  • Dithering
  • ADC error
Open Access

A Simple Procedure to Determine Complex Permittivity of Moist Materials Using Standard Commercial Coaxial Sensor

Published Online: 08 Apr 2011
Page range: 19 - 22

Abstract

A Simple Procedure to Determine Complex Permittivity of Moist Materials Using Standard Commercial Coaxial Sensor

A simple procedure was developed to determine complex permittivity of moist materials for known percentage of moisture content at any frequency based using a standard commercial coaxial sensor. Polynomial fitting and Gaussian elimination method were applied to obtain a single equation of complex permittivity as a function of frequency and moisture content. The empirical equation was tested for new samples and was found to have mean error percentage of 5.14 % and 10.22 % for dielectric constant and loss factor, respectively, when compared to a commercial probe.

Keywords

  • Open ended coaxial line
  • permittivity
  • maize
  • empirical modelM
Open Access

Critical Aspects in Calibration of ESD Generators

Published Online: 08 Apr 2011
Page range: 23 - 28

Abstract

Critical Aspects in Calibration of ESD Generators

Electrostatic discharge (ESD) immunity tests are widely carried out in order to assess the immunity level of electrical and electronic equipment. ESD is a severe source of interference which can produce damage, upset or failures in any electronic system. A careful calibration procedure is required to assure that the ESD generator parameters fulfill the standard specifications. In this paper, tationhe main critical aspects involved in the calibr measurement setup are dealt with and a simple modeling support is given. On the basuis of the obtained reslts, some usefuln. conclusions and practical suggestions are finally drawn.

Keywords

  • Electrostatic discharges
  • calibration
  • electromagnetic compatibility
  • electromagnetic measurements
  • modeling
  • immunity
Open Access

Synthesis and Transport Properties of Nanostructured VO2 by Mechanochemical Processing

Published Online: 08 Apr 2011
Page range: 29 - 33

Abstract

Synthesis and Transport Properties of Nanostructured VO<sub>2</sub> by Mechanochemical Processing

The high-energy milling of the V2O5-Na2SO3 mixture in the range of 5 - 100 min leads to a synthesis of monoclinic VO2. The starting and minimum (at 220 °C) values of electric resistance R of the 100 min milled and pressed VO2-Na2SO4 mixture were 13.9 MΩ and 91.5 kΩ, respectively. The subsequent washing of the as-milled powder partially leads to the development of VO2 nanostructures with tube-like, sheet-like and rod-like morphology, besides VO2 (B) belt-like morphology, depending on the milling times.

Keywords

  • Nanostructures
  • chemical synthesis
  • transmission electron microscopy (TEM)
  • electrical resistivity
6 Articles
Open Access

A New Digital Signal Processing Method for Spectrum Interference Monitoring

Published Online: 08 Apr 2011
Page range: 1 - 8

Abstract

A New Digital Signal Processing Method for Spectrum Interference Monitoring

Frequency spectrum is a limited shared resource, nowadays interested by an ever growing number of different applications. Generally, the companies providing such services pay to the governments the right of using a limited portion of the spectrum, consequently they would be assured that the licensed radio spectrum resource is not interested by significant external interferences. At the same time, they have to guarantee that their devices make an efficient use of the spectrum and meet the electromagnetic compatibility regulations. Therefore the competent authorities are called to control the access to the spectrum adopting suitable management and monitoring policies, as well as the manufacturers have to periodically verify the correct working of their apparatuses. Several measurement solutions are present on the market. They generally refer to real-time spectrum analyzers and measurement receivers. Both of them are characterized by good metrological accuracies but show costs, dimensions and weights that make no possible a use "on the field". The paper presents a first step in realizing a digital signal processing based measurement instrument able to suitably accomplish for the above mentioned needs. In particular the attention has been given to the DSP based measurement section of the instrument. To these aims an innovative measurement method for spectrum monitoring and management is proposed in this paper. It performs an efficient sequential analysis based on a sample by sample digital processing. Three main issues are in particular pursued: (i) measurement performance comparable to that exhibited by other methods proposed in literature; (ii) fast measurement time, (iii) easy implementation on cost-effective measurement hardware.

Keywords

  • Spectrum monitoring
  • spectrum management
  • spectrogram
  • digital signal processing
  • RF measurement
Open Access

Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

Published Online: 08 Apr 2011
Page range: 9 - 14

Abstract

Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

We studied the effects of slight Sm-Ba non-stoichiometry in Sm-Ba-Cu-O superconducting compounds on their transition, structural, and magnetic properties. Two series of single-phase samples of Sm1+xBa2-xCu3O7+Δ and Sm1+xBa2-xCu3O7+Δ with composition deviation from stoichiometry x from 0 to 0.1 were synthesized by the solid-state reaction method from Sm2O3, BaCO3 and CuO precursors and sintered at the temperature of ~ 1060 °C in flowing oxygen. All samples showed the values of Tc > 90 K and the volume density, p, 6.45 g cm-3 < p ≤ 6.73 g cm-3. The effect of the composite deviation of x on Tc, ΔTc, and volume magnetization M was studied. For Sm1+xBa2-xCu3O7+Δ compounds, optimal values of x were determined to maximize the width of the magnetization hysteresis at higher values of the applied magnetic field, corresponding mainly to the grain contribution. We also prepared the Sm1+xBa2-xCu3O7+Δ samples with x from 0 to 0.1 using the same processing conditions as in the case of A and B series. For the Sm1+xBa2-xCu3O7+Δ samples, values of x = 0.02 - 0.03 optimize Tc, ΔTc, Hp1 as well as M.

Keywords

  • Superconductors
  • Sm-123
  • cation non-stoichiometry
  • critical temperature
  • magnetization
Open Access

Correction of ADC Errors by Additive Iterative Method with Dithering

Published Online: 08 Apr 2011
Page range: 15 - 18

Abstract

Correction of ADC Errors by Additive Iterative Method with Dithering

The iterative method could be used for automatic accuracy improvement of a measurement system. In its application for analog-to-digital converter (ADC) a quantization error represents a limitation for the correction process. Therefore, combination of correction methods is common for ADC error correction. Combination of the additive iterative method (AIM) with nonsubtractive dithering (ND) has been proposed for slow measurement based on ADC where errors could change in time. The principle of combination of both techniques is described in the paper. AIM is based on precise inverse element (IE). In the designed system the IE output signal is created by pulse width modulation and low-pass filtering. A technique similar to deterministic dithering is employed to achieve precise processing of signal from IE. Analysis of influence of stochastic dither upon the results of correction is performed with the aim to find optimal parameters of ND. Finally, dependency of the root mean squared error and error dispersion on the measured value is drawn to show how AIM corrects the nonlinear deterministic error but slightly increases system noise.

Keywords

  • Iterative Correction
  • Dithering
  • ADC error
Open Access

A Simple Procedure to Determine Complex Permittivity of Moist Materials Using Standard Commercial Coaxial Sensor

Published Online: 08 Apr 2011
Page range: 19 - 22

Abstract

A Simple Procedure to Determine Complex Permittivity of Moist Materials Using Standard Commercial Coaxial Sensor

A simple procedure was developed to determine complex permittivity of moist materials for known percentage of moisture content at any frequency based using a standard commercial coaxial sensor. Polynomial fitting and Gaussian elimination method were applied to obtain a single equation of complex permittivity as a function of frequency and moisture content. The empirical equation was tested for new samples and was found to have mean error percentage of 5.14 % and 10.22 % for dielectric constant and loss factor, respectively, when compared to a commercial probe.

Keywords

  • Open ended coaxial line
  • permittivity
  • maize
  • empirical modelM
Open Access

Critical Aspects in Calibration of ESD Generators

Published Online: 08 Apr 2011
Page range: 23 - 28

Abstract

Critical Aspects in Calibration of ESD Generators

Electrostatic discharge (ESD) immunity tests are widely carried out in order to assess the immunity level of electrical and electronic equipment. ESD is a severe source of interference which can produce damage, upset or failures in any electronic system. A careful calibration procedure is required to assure that the ESD generator parameters fulfill the standard specifications. In this paper, tationhe main critical aspects involved in the calibr measurement setup are dealt with and a simple modeling support is given. On the basuis of the obtained reslts, some usefuln. conclusions and practical suggestions are finally drawn.

Keywords

  • Electrostatic discharges
  • calibration
  • electromagnetic compatibility
  • electromagnetic measurements
  • modeling
  • immunity
Open Access

Synthesis and Transport Properties of Nanostructured VO2 by Mechanochemical Processing

Published Online: 08 Apr 2011
Page range: 29 - 33

Abstract

Synthesis and Transport Properties of Nanostructured VO<sub>2</sub> by Mechanochemical Processing

The high-energy milling of the V2O5-Na2SO3 mixture in the range of 5 - 100 min leads to a synthesis of monoclinic VO2. The starting and minimum (at 220 °C) values of electric resistance R of the 100 min milled and pressed VO2-Na2SO4 mixture were 13.9 MΩ and 91.5 kΩ, respectively. The subsequent washing of the as-milled powder partially leads to the development of VO2 nanostructures with tube-like, sheet-like and rod-like morphology, besides VO2 (B) belt-like morphology, depending on the milling times.

Keywords

  • Nanostructures
  • chemical synthesis
  • transmission electron microscopy (TEM)
  • electrical resistivity

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