Large scale spectrum survey in rural and urban environments within the 50 MHz–6 GHz bands

In-depth spectrum measurement was conducted in rural and urban locations, covering 50 MHz–6 GHz bands, during the weekdays and weekends. A modified duty cycle metric is presented by introducing a space variable into the existing metrics available today. An adaptive energy detection threshold technique was employed, the results indicate the average spectral occupancy of 0.18%, and 5.08% in rural and urban locations respectively during weekdays and 1.45% on weekends for urban locations. Furthermore, short and long term temporal variations of the duty cycle for each of the bands were studied, and it was found that GSM 900 shows significant temporal variation when compared with GSM 1800. It was also found that the choice of the detection threshold would significantly affect the duty cycle as GSM 900 and 1800 give exponential decay with increase in detection threshold while TV band shows very sharp exponential decay which becomes invariant after −85 dBm.     

Mobile measurement of radiofrequency electromagnetic field exposure level and statistical analysis

In this study, radiofrequency electromagnetic field exposure levels were measured as mobile on the main streets of Diyarbakır during a week. The measurements were carried out using high precision spectrum analyzer with an isotropic antenna mounted on the top of a car. With this mobile measurement, large areas were measured in a short time and information about characteristics of electromagnetic environment was obtained quickly. Measurement results showed that measurement values were not in normal distribution and variances between independent variables were not homogeneous. According to Spearman’s rho correlation coefficient, there was no strong correlation between measurement days. In terms of mean electric field values, contribution of each band to total band was arranged as UMTS DL, GSM900 DL, GSM1800 DL, TV4-5, FM, and TV3 band, respectively. It was determined that all measurement values were below the reference levels of the International Commission on Non-Ionizing Radiation Protection.     

Medium wave DRM field trials in Brazil – Some daytime and nighttime results in urban environment

The Digital Radio Mondiale (DRM) system broadcasts audio in the frequency band below 174 MHz  and . In this experiment in urban areas in Brazil, a hybrid signal composed of an analog AM signal and a digital DRM30 signal, with the same content, were broadcasted in diurnal and nocturnal transmissions. This paper describes the experimental setup, which employs the spectral shaping technique in simulcast transmission [14], and presents some results of medium wave propagation measurements campaigns that are being carried out in Brazil. The experiment is part of a series of field trials that are being conducted by the Brazilian Government which includes campaigns at MW, HF and VHF frequency bands.     

Spectral occupation of TV broadcast bands: Measurement and analysis

The findings of a TV broadcast spectrum measurement campaign, performed at six different locations on the Hatfield campus of the University of Pretoria, are presented. Since the use of television white spaces (TVWS) could help to alleviate the impending spectrum crunch, the motivation for the study was to identify possibly unused bands for use by emerging technologies, such as cognitive radio, and also to address the hidden node problem associated with spectrum sensing (SS). This was achieved by comparing measured data to both actual TV channel allocations and a geo-location database (GLDB) for the Tshwane metropolitan area (city of Pretoria). Localised measurements indicated that a number of TVWS opportunities existed, with between 216 and 376 MHz of spectrum found to be potentially available for secondary usage. However, a comparison with TV channel allocations (256 MHz free) and the GLDB (96 MHz free) highlighted the effect of the hidden node problem.     

The application of a channel-individualized method for assessing long-term,realistic exposure to radiofrequency radiation emitted by mobile communication base station antennas

Human exposure to radiofrequency signals emitted by Global System for Mobile communications (GSM) base station antennas is still of interest from health and environmental protection perspectives, mainly in the long-term. With the technological advancement of real-time vector signal analyzers, a more precise exposure evaluation has become achievable. By using an original procedure based on tandem-in-time- and frequency-domain measurements and by experimental weighting to obtain a realistic field strength, we succeeded in expressing actual exposure in an urban, indoor location in the long run. The work covers two stages: one characterizes specificities of channels in the GSM900 downlink band, in order to improve experimental measurement capabilities, and the other assesses the exposure level inside the whole downlink band with best precision during 24 h. The results confirm traffic load impact on exposure level and the importance of the experimental procedure for gaining accurate results and prediction capabilities.     

基于复合左／右手传输线的双频功分器

本文介绍了一种新型的基于复合左／右手（CRLH）传输线理论的双频功分器设计方法,该功分器工作于900MHz和1800MHz。用集总电感和电容元件构成的复合左／右手传输线在900MHz和1800MHz的相移分别是超前和滞后90°。完全可以替代传统功分器中的四分之一波长阻抗变换传输线,且具有占用面积小和可设计工作于任意两个频率的优点。在双频工作的现代无线通信系统中有很广阔的应用前景。     

Effect of molybdenum tri-oxide molar ratio on the optical and some physical properties of tellurite-vanadate-molybdate glasses

Glasses with composition (60 − x)V₂O₅-40TeO₂ − x MoO₃ with 20 ? x ? 60 (in mol%) have been prepared using the usual melt quenching method. The optical absorption spectra of the glasses have been recorded in the wavelength range 300-800 nm. The position of the absorption edge and therefore the optical band gap values were found to be depend on the glass composition. For these glasses, the optical band gap was found to be in the range 2.03-2.86 eV with increasing of MoO₃ concentration. The absorption spectrum fitting method was employed to obtain the energy gap. In this method, only the measurement of the absorbance spectrum of the glass is needed. For each sample, the width of the band tail was determined. Also, the density and glass transition temperature values indicate that the rigidity and packing of the samples increase with increase in MoO₃ concentration as a network former.     

Noise floor and dynamic range analysis of a microwave attenuation measurement receiver from 50 MHz to 26.5 GHz

The noise floor and dynamic range of a proposed voltage-ratio based microwave attenuation measurement receiver are analysed. The thermal noise and phase noise effect on attenuation measurement is studied. For frequencies higher than 1 GHz, the receiver employs a lock-in amplifier with a coherent frequency reference to minimize the phase noise effect and achieve very wide dynamic range of attenuation measurement. The equivalent noise floor at the receiver mixer output port is found to be around −172 dBm. The dynamic range of the receiver is 181-175 dB from 50 MHz to 26.5 GHz. Measurement results of a 0-170 dB synthesized step attenuator at 26 GHz is given to verify the performance of the proposed receiver.     

Vibration effect on hardness measurement

In this paper, the effect of ground vibration on hardness measurement, Rockwell scale C hardness, Vickers scale HV1 hardness and Leeb hardness is studied. The hardness machines were placed on the vibration table. The vibration signal is single frequency sinusoidal wave, which frequency and amplitude of vibration can be controlled. The hardness value at free from vibration state is used as a reference to calculate the error of each hardness measurement at certain frequency and amplitude. Two Rockwell hardness testing machines are used to measure hardness blocks: 20, 40, and 60 HRC. Both machines give the same tendency. Significant negative errors occur around frequency 5–15 Hz. Moreover, ground vibration has more impact on the soft range of hardness than hard range. The result from this paper can be used as guideline for laboratory to control environmental vibration amplitude to be less than 0.01 m/s² for frequency (10 ± 5) Hz and 0.05 m/s² for other in Rockwell scale C hardness measurement. Effect of vibration on Vickers and Leeb hardness measurement is preliminarily studied. Results on 200 HV1 and 900 HV1 measurement show that vibration creates peak of error at frequency 20 Hz of amplitude more than 0.01 m/s² and the effect can be observable at all frequency for amplitude of 0.04 m/s². Different from Rockwell and Vickers, Leeb hardness measurement is not influenced by vibration in this experiment.     

Modified uncertainty estimation of antenna factor measurement by standard site method

The standard site method was used to measure antenna factor. Based on calculation of antenna factor uncertainty, ways of more precise estimation of uncertainty, leading to uncertainty reduction, are presented. Using uncertainty standards together with known approaches to radiated emission measurement uncertainty calculation, a model of antenna factor measurement and an equation for calculation of its uncertainty were derived. Possible steps to reduce resultant measurement uncertainty are described, including an analysis of correlation, and acknowledgment of frequency dependence. The uncertainty was calculated in 25 frequency points in the range from 30 MHz to 1000 MHz. Furthermore, various calculations of uncertainty are executed to examine the suggested effects on the uncertainty value.     

Signal amplification and frequency-conversion units for radioastronomical receivers

Broadband amplification and signal-frequency-conversion units with built-in heterodynes have been developed for radioastronomical receivers in wavelengths ranges of 3.5/13 and 6 cm. The use of such units allows extension of the reception band to 900 MHz and 2 GHz in the 6- and 3.5-cm wavelength bands, respectively, an increase in the dynamic ranges of the receivers by 12–15 dB, an increase in the noise immunity in the 13-cm band, and an improvement of a number of parameters that affect the quality of data acquired in radioastronomical observations. The units that were installed in the radio telescopes of the Quasar-KVO complex made it possible to increase the reliability and reduce the set of receiving equipment.     

The GIF Quantum,a next generation post-column imaging energy filter

We describe a new post-column imaging energy filter for (scanning) transmission electron microscopy from 60 to 300 kV operating voltage. The completely redesigned GIF quantum has a gradient magnetic prism, dodecapole optics, a 10-times faster 40 Mpixel/sec CCD camera, a 1 μs electrostatic shutter, and new user interface, control, and auto-alignment software. An 8 dodecapole lens system, performs full 2nd and 3rd, and partial 4th and 5th order aberration correction. The improved aberration correction has allowed the size of the entrance aperture to be nearly doubled to 9.0 mm compared to current generation post-column designs. The electrostatic shutter provides exposure control down to 1 μs, extending the exposure time range to over 7 orders of magnitude. Spectroscopy operation has been improved with a larger 2 keV field of view at 200 kV, and a maximum acquisition rate of 1000 spectra per second. A high-speed DualEELS mode simultaneously acquires core- and low-loss spectra up to 2 keV apart. A more intuitive user interface includes new capabilities such as automated exposure control and optimized full spectrum acquisition. The auto-alignment software has been significantly enhanced to use the full flexibility of the dodecapole lens system.     

基于RFID的药品管理系统

为了实现药品的防伪和追踪,基于射频识别(RFID)技术开发了一个药品管理系统。利用UHF900MLow Level Operation类封装了900 MHz读写器,方便地进行900 MHz读写器打开或关闭、寻卡、读卡、写卡等操作。基于Qt进行药品管理系统中标签初始化、药品流通各个环节信息记录的界面设计,并通过信号/槽这种异步方式进行读写器事件的处理,实现有效的药品管理和追溯。     

Complex permittivity measurement using capacitance method from 300 kHz to 50 MHz

Complex permittivity measurement has been performed using a parallel plate capacitor and a vector network analyzer (VNA) from 300 kHz to 50 MHz. The material under test (MUT) is a flat and thin sample clamped between the capacitor plates and connected to the VNA to obtain its two port S parameters. The S parameter is converted into impedance to calculate the complex permittivity using Matlab program. Techniques used to overcome the air gap and stray capacitance was described. Measurement obtained using the proposed method was compared with the free space method to validate its accuracy. The percent difference is less than 5%.     

Inhomogeneity correction in calibration of electrical conductivity standards

The method for inhomogeneity investigation of measurement standards for electrical conductivity has been studied in the conductivity range from 2 MS/m to 14 MS/m. For this purpose a planar spiral coil has been developed and characterized. The impedance values of the coil are measured in the air and with a conducting plate above the coil at discrete frequencies from 2 kHz to 70 kHz. By selecting the corresponding operating frequency, relative changes in the conductivity value throughout the sample thicknesses have been measured. It was revealed that inhomogeneity of measurement standards has an effect on further measurements with calibrated conductivity meters. The relative conductivity changes of 0.1% due to inhomogeneity can be detected with the measurement uncertainty (k = 2) of less than 0.3% of the measured value.     

Lattice constant measurement from electron backscatter diffraction patterns

Kikuchi bands in election backscattered diffraction patterns (EBSP) contain information about lattice constants of crystallographic samples that can be extracted via the Bragg equation. An advantage of lattice constant measurement from EBSPs over diffraction (XRD) is the ability to perform local analysis. In this study, lattice constants of cubic STN and cubic YSZ in the pure materials and in co‐sintered composites were measured from their EBSPs acquired at 10 kV using a silicon single crystal as a calibration reference. The EBSP distortion was corrected by spherical back projection and Kikuchi band analysis was made using in‐house software. The error of the lattice constant measurement was determined to be in the range of 0.09–1.12% compared to values determined by XRD and from literature. The confidence level of the method is indicated by the standard deviation of the measurement, which is approximately 0.04 Å. Studying Kikuchi band size dependence of the measurement precision shows that the measurement error decays with increasing band size (i.e. decreasing lattice constant). However, in practice, the sharpness of wide bands tends to be low due to their low intensity, thus limiting the measurement precision. Possible methods to improve measurement precision are suggested.     

A system for gas sensing employing correlation spectroscopy and wavelength modulation techniques with a multimode diode laser

A tunable multi-mode diode laser system based on correlation spectroscopy and wavelength modulation spectroscopy (TMDL–COSPEC–WMS) is designed and demonstrated for the concentration measurements of oxygen using A-band absorption lines of oxygen around 760 nm. The O₂ concentrations are conversed from the relation between the normalized WMS-2f signal peak heights of the measurement and reference signals which selected based on high signal to noise ratio and correlation coefficient. The correlation and the fitted slope between the measured and actual O₂ concentration are 0.9987 and of 1.025 ± 0.012 respectively over the tested range, which indicate the high linearity and accuracy of the system. A sensitivity of 350 ppm m is approved using 30 successive measurements with each measurement time taking ∼20 s during 30 min. A continuous measurement for oxygen in ambient air during approximately 200 min confirms the stability and the capability of the system.     

Evaluation of moment arm length and fulcrum sensitivity limit in a 10 N·m dead weight torque standard machine

Many torque tools, such as torque wrenches and torque screwdrivers, as well as torque measuring devices (TMDs) with a rated capacity of less than 5 N·m are being widely used in industry. Thus, a small-rated-capacity torque standard has to be established as soon as possible. A 10 N·m dead weight torque standard machine (10 N·m DWTSM) has been under development since 2006 at the National Metrology Institute of Japan (NMIJ), part of the National Institute of Advanced Industrial Science and Technology (AIST). Characteristically, the main parts of the moment arm are made of low thermal-expansion alloy (Super INVAR), and an aerostatic bearing is employed as the fulcrum supporting the moment arm to minimize rotational friction. The moment arm was evaluated with regard to the coefficient of thermal expansion (CTE), the lengths measured by a 3D coordinate measurement machine (CMM), and temperature correction realized by measuring the moment arm temperature. The sensitivity limit of the fulcrum in the 10 N·m DWTSM was also estimated. As a result, the apparent overall CTE of the moment arm was 1.06 × 10⁻⁶ K⁻¹, and the expanded uncertainty was 2.24 × 10⁻⁹ K⁻¹ (k = 2). The results of the CMM measurement were a right-hand side length of 510.2773 mm and a left-hand side length of 510.2657 mm, with a relative expanded uncertainty of 4.0 × 10⁻⁵ (k = 2). The moment arm temperature increased by approximately 0.6 K during the ordinary calibration process. The corresponding change in the lengths of the moment arm was estimated to be approximately 0.3 μm, which is considered to be sufficiently small compared with the expanded uncertainty of the lengths of the moment arm. The fulcrum of the 10 N·m DWTSM was found to have sufficient sensitivity under three conditions: without the weight loading components, with the weight loading components, and with loaded weights. In particular, the fulcrum had sufficient sensitivity of at least 0.5 mg when weights of 100 g were loaded on both 5th stages in the weight loading components to generate a radial load equivalent to 1 N·m.     

Miniature low-power IR monitor for methane detection

A portable methane gas monitor based on an infrared spectrum absorption principle has been developed using a dual-channel and dual-wavelength pyroelectric infrared detector, active filters around the overtone absorption lines of methane at 3.31 μm, reference filters around the non-absorption lines of methane at 3.93 μm, mid-IR LEDs, a miniature gold-filled cell structure, temperature sensors for gas concentration calibration and compensation, an electrical modulation source, and a highly integrated intelligent controller. A detailed investigation has been carried out to design a low-cost portable IR optical sensor for methane detection that can operate in harsh environments with temperature variations between −10 °C and 40 °C. The infrared detection optics principle used in developing this system is mainly analyzed. A prototype based on this design showed an accuracy of ±0.05%, which meets the technology requirements of lower-power consumption, reduced volume, and wide measurement range.     

Accurate measurement of millimeter-wave attenuation from 75 GHz to 110 GHz using a dual-channel heterodyne receiver

A dual-channel millimeter-wave attenuation measurement system from 75 GHz to 110 GHz using a heterodyne receiver is described. The millimeter-wave attenuation is derived from the voltage ratio at 5.02 kHz using an inductive voltage divider as a reference standard. The measurement uncertainties are estimated to be 0.015–0.030 dB for attenuation ranging from 0 dB to 70 dB at 110 GHz. Measurement results of a waveguide rotary vane attenuator with 0–70 dB attenuation steps at 110 GHz are presented.