Polarization response of asymmetric-spiral infrared antennas

We present measurements on the polarization response of Ni-NiO-Ni diodes coupled to asymmetric spiral antennas. Our data are for the wavelength dependence of the orientation of the major axis of the polarization ellipse over the wavelength range 10.2-10.7 mum. The data are well fit by a two-wire antenna model. We find that the modes excited on the antenna are a combination of the balanced and unbalanced modes of a two-wire lossy transmission line.     

Stability of the spectral responsivity of cryogenically cooled InSb infrared detectors

The spectral responsivity of two cryogenically cooled InSb detectors was observed to drift slowly with time. The origin of these drifts was investigated and was shown to occur due to a water-ice thin film that was deposited onto the active areas of the cold detectors. The presence of the ice film (which is itself a dielectric film) modifies the transmission characteristics of the antireflection coatings deposited on the active areas of the detectors, thus giving rise to the observed drifts. The magnitude of the drifts was drastically reduced by evacuating the detector dewars while baking them at 50 degrees C for approximately 48 h. All InSb detectors have antireflection coatings to reduce the Fresnel reflections and therefore enhance their spectral responsivity. This work demonstrates that InSb infrared detectors should be evacuated and baked at least annually and in some cases (depending on the quality of the dewar and the measurement uncertainty required) more frequently. These observations are particularly relevant to InSb detectors mounted in dewars that use rubber O rings since the ingress of moisture was found to be particularly serious in this type of dewar.     

Modeling the responsivity and self-emission of a double-beam Fourier-transform infrared interferometer

A modeling study aimed at characterizing the radiometric properties of a double-beam Fourier-transform infrared interferometer is presented. Measurements showed that the two responsivities associated with each interferometer channel are different in certain spectral regions. This anomaly was attributed to a dissymmetry between the optical transmissions of the two plates that form the beam splitter. This dissymmetry is primarily responsible for the instrument residual emission. A secondary cause of residual emission is attributed to the relative alignment of the two input optics. Both effects were taken into account in a model that gives the instrument residual emission in terms of the beam splitter temperature. Actual results indicate that in the 7-14-mum window the instrument residual emission can be modeled with an absolute radiometric error smaller than 0.5 K (blackbody at 290 K). The model was used to develop an automatic calibration procedure that yields radiance errors smaller than 0.05 muW/cm(2) sr cm(-1) in the 7-14-mum band. The radiometric stability of the interferometer was analyzed.     

Nontraditional antennas in complex dielectric-constant measurement

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 22–24, November, 1990.     

Spatial impulse response of lithographic infrared antennas

We present measurements of the spatial response of infrared dipole and bow-tie lithographic antennas. Focused 10.6-mum radiation was scanned in two dimensions across the receiving area of each antenna. Deconvolution of the beam profile allowed the spatial response to be measured. The in-plane width of the antenna's spatial response extends approximately one dielectric wavelength beyond the metallic structure. Determination of an antenna's spatial response is important for several reasons. The power collected by the antenna can be calculated, if the collection area and the input irradiance (watts per square centimeter) are known. The actual power collected by the antenna is required for computation of responsivity and noise-equivalent power. In addition, the spatial response provides insight into the current-wave modes that propagate on an antenna and the nature of the fringe fields that exist in the adjacent dielectric.     

大尺寸测量的温度误差修正的不确定度分析

文章着重讨论了大尺寸测量中影响温度误差修正精度的主要因素并深入分析了温度误差修正后的不确定度为满足大尺寸高精度的测量要求,提出了精确测定材料膨胀系数的方法,有效降低了温度误差修正后的不确定度,确保了大尺寸的高精度测量的实现。     

Influence of dielectric substrate on the responsivity of microstrip dipole-antenna-coupled infrared microbolometers

We report on the influence of the dielectric substrate on the performance of microstrip dipole-antenna-coupled microbolometers. The location, the width, and the magnitude of the resonance of a printed dipole are altered when the dielectric substrate is backed by a ground plane. A thicker dielectric substrate shifts the antenna resonance toward shorter dipole lengths and leads to a stronger and slower detector response. The incorporation of an air layer into the antenna substrate further increases thermal impedance, leading to an even stronger response and shifting the antenna resonance toward longer dipole lengths.     

水听器法的医用超声声场参数测量不确定度分析

提出了一种基于水听器法测量医用超声声场参数的测量装置,可通过扫描声场获取IEC 61157国际标准所要求的声场中峰值负声压等医用超声诊断设备的声输出参数.同时以一种B型超声诊断仪为例,对声场中声压的测量不确定度进行分析,分别给出A类、B类测量不确定度及标准不确定度,并对影响测量结果的主要因素进行了评定,得出当声压测定结果为1.456 4MHz时,其最小扩展不确定度可为0.215 0MHz.     

An investigation into measurement of handset antennas

This paper describes the investigation into the effects of signal cables on the operating frequencies, radiation patterns, and gains of handset antennas under test by using a proposed testing scheme. In this simple testing method, a coaxial signal cable feeds the handset antenna under test through a microstrip transmission-line etched onto a printed circuit board. The studies of the influences of different feeding schemes and cable arrangements on two commonly used handset antennas are carried out experimentally and numerically. Also, the distributions of the fields close to the antenna, handset chassis, and the cable are measured and simulated to explore the cable-related influences.     

半电波暗室中的EMI辐射骚扰试验测量不确定度分析与评定

半电波暗室能模拟理想的开阔场情况,符合电磁波在自由空间中的传播规律,在此特定环境中测量EMC一个重要技术指标——辐射骚扰场强,简单介绍测量不确定度理论,详细分析辐射骚扰场强的测量不确定度来源与评定,并给出评定结果,为实验室的电磁兼容检测提供指导。     

Uncertainty analysis of absolute concentration measurement with continuous-wave cavity ringdown spectroscopy

To evaluate the uncertainty of concentration measurement using cavity ringdown spectroscopy, we analytically derived expressions for uncertainty for parameters, such as temperature, laser frequency, and ringdown time deviation, from the model equation. The uncertainties that are due to systematic errors in a practical cavity ringdown system were assessed through an experimental study of the PQ(35) transition in an A band of molecular oxygen. We found that, except for the line strength that is regarded as a reference value independent of the measurement, the laser frequency jitter is the largest uncertainty source in the system. Some practical requirements for minimizing the uncertainty in concentration measurements are discussed. We also demonstrated determination of the line strength of the PQ(35) transition line of oxygen to be 8.63(3) x 10(-27) cm(-1) with a relative uncertainty of less than 0.4%.     

Deconvolution method for two-dimensional spatial-response mapping of lithographic infrared antennas

The spatial impulse response of antenna-coupled infrared detectors with dimensions comparable with the wavelength is obtained from a two-dimensional scan of a tightly focused CO(2)-laser beam. The method uses an experimental setup with submicrometer resolution and an iterative deconvolution algorithm. The measured spatial response is compared with numerically computed near-field distributions of a dipole antenna, with good agreement.     

Comparison of absolute spectral irradiance responsivity measurement techniques using wavelength-tunable lasers

Independent methods for measuring the absolute spectral irradiance responsivity of detectors have been compared between the calibration facilities at two national metrology institutes, the Helsinki University of Technology (TKK), Finland, and the National Institute of Standards and Technology (NIST). The emphasis is on the comparison of two different techniques for generating a uniform irradiance at a reference plane using wavelength-tunable lasers. At TKK's Laser Scanning Facility (LSF) the irradiance is generated by raster scanning a single collimated laser beam, while at the NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (SIRCUS), lasers are introduced into integrating spheres to generate a uniform irradiance at a reference plane. The laser-based irradiance responsivity results are compared to a traditional lamp-monochromator-based irradiance responsivity calibration obtained at the NIST Spectral Comparator Facility (SCF). A narrowband filter radiometer with a 24 nm bandwidth and an effective band-center wavelength of 801 nm was used as the artifact. The results of the comparison between the different facilities, reported for the first time in the near-infrared wavelength range, demonstrate agreement at the uncertainty level of less than 0.1%. This result has significant implications in radiation thermometry and in photometry as well as in radiometry.     

Uncertainty of measurement results in various scales

The relationship between the concepts of “error” and “uncertainty” of measurement results is examined. The concepts of “standard uncertainty,” “combined standard uncertainty,” and “expanded uncertainty” are shown to be inapplicable in nonmetric scales of quantities and properties, in which the general concept of “uncertainty” in the broad sense is recommended. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–30, May, 2000.     

Spectral reflectance and responsivity of Ge- and InGaAs-photodiodes in the near-infrared: measurement and model

The spectral reflectance and responsivity of Ge- and InGaAs-photodiodes at (nearly) normal and oblique incidence (45 degrees) were investigated. The derived data allow a calculation of the photodiodes responsivities for any incident angle. The measurements were carried out with s- and p-polarized radiation in the wavelength range from 1260 to 1640 nm. The spectral reflectance of the photodiodes was modeled by using the matrix approach developed for thin-film optical assemblies. The comparison between the calculated and measured reflectance shows a difference of less than 2% for the Ge-photodiode. For the InGaAs-photodiode, the differences between measured and calculated reflectance are larger, i.e., up to 6% for wavelengths between 1380 and 1580 nm. Despite the larger differences between calculated and measured spectral reflectances for the InGaAs-photodiode, the difference between calculated and measured spectral responsivity is even smaller for the InGaAs-photodiode than for the Ge-photodiode, i.e., < or =1.2% for the InGaAs-photodiode compared to < or =2.2% for the Ge-photodiode. This is because the difference in responsivity is strongly correlated to the absolute spectral reflectance level, which is much lower for the InGaAs-photodiode. This observation also shows the importance of having small reflectances, i.e., appropriate antireflection coatings for the photodiodes. The relative standard uncertainty associated with the modeled spectral responsivity is about 2.2% for the Ge-photodiode and about 1.2% for the InGaAs-photodiode for any incident angle over the whole spectral range measured. The data obtained for the photodiodes allow the calculation of the spectral responsivity of Ge- and InGaAs-trap detectors and the comparison with experimental results.     

空气焓值法测量空调制冷量的不确定度评定

基于空气焓值法数学模型，对某空调机组制冷量测试结果的不确定度进行分析，讨论影响制冷量不确定度的主要因素，为改善测试系统的精度提供参考。     

红外测温仪检定误差原因剖析及对策

介绍黑体炉及红外测温仪的基本工作原理。分析红外测温仪检定时测量误差产生的原因,并提出了减小误差的措施和方法。     

A method of determining the spatial position of the phase center of log-periodic antennas

A method of estimating the position of the phase center of log-periodic antennas from the phase radiation pattern in the intermediate zone is proposed. __________ Translated from Metrologiya, No. 4, pp. 39–43, April, 2008.     

Differential spectral responsivity measurement of photovoltaic detectors with a light-emitting-diode-based integrating sphere source

We present an experimental realization of differential spectral responsivity measurement by using a light-emitting diode (LED)-based integrating sphere source. The spectral irradiance responsivity is measured by a Lambertian-like radiation field with a diameter of 40 mm at the peak wavelengths of the 35 selectable LEDs covering a range from 280 to 1550 nm. The systematic errors and uncertainties due to lock-in detection, spatial irradiance distribution, and reflection from the test detector are experimentally corrected or considered. In addition, we implemented a numerical procedure to correct the error due to the broad spectral bandwidth of the LEDs. The overall uncertainty of the DSR measurement is evaluated to be 2.2% (k = 2) for Si detectors. To demonstrate its application, we present the measurement results of two Si photovoltaic detectors at different bias irradiance levels up to 120 mW/cm(2).     

Uncertainty in measurement: Definition and calculation methods

The concept of uncertainty is discussed. A refined, more-correct definition of the term “uncertainty” is offered. Methods for calculation of expanded uncertainty are proposed. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 26–27, May, 2000.