天线的测量校准方法

天线是测量电波辐射强度的必备工具．天线系数是用于场强测量和DEMI测量天线的重要参数。人们利用测量接收机读数、天线系数来计算电波辐射场强。在难以用理论计算的方法精确获得天线系数时．需要对天线的天线系数进行测量校准。本文介绍了常用的天线系数的校准方法．讨论了在天线校准中引起测量误差的各种因素．并总结了各种校准方法的适用范围及特点。     

天线系数的校准和使用

天线系数是一项重要参数。然而 ,天线生产者提供的天线系数都是在一定前提下进行校准的 ,如果直接用于测量现场就会带来误差。但若在测量现场先求得天线实际增益 ,便可计算出精度更高、实用而有效的天线系数。     

天线系统的校准和使用

天线系统是一项重要参数。然而，天线生产者提供的天线系数都是在一定前提下进行校准的，如果直接用于测量现场就会带来误差。但若在测量现场先求得天线实际增益，便可计算出精度更高、实用而有效的天线系数。     

辐射发射测量天线的校准方法

文章介绍了辐射发射测量所用宽带天线天线系数的校准方法,并对影响测试结果的因素进行分析.     

单极子天线系数的CST仿真和试验结果对比

根据相关标准选择双天线法校准单极子天线.运用CST软件建模仿真,得到两个天线之间6 GHz以下的传输系数S21,同时制作和仿真模型同样的实物装置并测量两天线之间的传输系数S21.结果表明,仿真结果和实测结果吻合得比较好.通过传输系数S21,可以进一步计算出天线系数,从而实现对单极子天线的校准.     

宽带天线系数的校准

天线系数校准是一个重要的计量课题 ,也是电磁兼容工作者们极为关注的问题。本文介绍互易法校准宽带天线系数及应注意的一些问题。     

GB/T6113.106工作组会议在北京召开

GB／T6113．106《无线电骚扰和抗扰度测量设备和测量方法规范第1-6部分无线电骚扰和测量设备电磁兼容天线校准》规定了确定天线系数时的天线校准程序并给出了相关信息,适用于电磁兼容测量辐射骚扰的测量天线。     

基于控制电路编码算法的相控阵天线快速测量

为了解决相控阵天线快速测量和校准问题,提出了换相测量法和编码矩阵相结合的快速测量相控阵天线的新方法。测试中相控阵天线和测试探头均不动,利用编码系数矩阵对相控阵天线中各移相器的移相状态进行控制,然后解码复原各单元移相位的信号和各通道的激励,并可进行单元的故障诊断。为了验证该方法的正确性和有效性,对一相控阵天线模型的测量全过程进行模拟,从模拟结果可以看出,该测量方法是行之有效的。     

多组阵列天线相位校准方法

提出了利用多次幅度测量实现多组阵列天线相位校准的方法,解决了多组阵列在天线辐射方向需要同相位合成的难题,保证了多组阵列实现高效率合成。介绍了校准方法的工作原理,给出了多组阵列天线进行相位校准的工作过程。对校准前后的天线测试结果进行对比分析,得出校准精度符合工程设计要求,且无需调试,易于实现远场自动校准,适用于多组阵列天线研制过程中的相位校准工作。     

基于三天线外推法的微波天线增益精确校准技术

三天线外推法是目前国际上公认的增益测量最准确的方法之一,简要介绍三天线外推法增益测量基本理论,并结合中国计量科学研究院的外推法天线测量标准装置,分析天线增益精确校准及相关不确定度评估技术.     

An A.C magnetic field calibration system for SLF magnetic antenna Feng Shimin(冯士民), Zhou Suihua(周穗华), Chen Zhiyi(陈志毅),

Calibrating the super low frequency （SLF） magnetic antenna in magnetic free space or an outdoor environment is difficult and complicated due to the large size calibration instruments and lots of measurement times. Aiming to calibrate the SLF magnetic antenna simply and efficiently, a calibration system comprised of a multi-frequency source, an A.C constant-current source and a solenoid is proposed according to the characteristic of an SLF magnetic antenna. The static magnetic transfer coefficient of the designed solenoid is calibrated. The measurement of the frequency response characteristics suggests the transfer coefficient remains unchanged in the range of the SLF band and is unaffected by the magnetic antenna internally installed. The CORDIC algorithm implemented in an FPGA is realized to generate a linear evenly-spaced multi-frequency signal with equal energy at each frequency. An A.C constant weak current source circuit is designed in order to avoid the impact on the magnetic induction intensity of a calibration system affected by impedance variation when frequency changing, linearity and the precision of the source are measured. The frequency characteristic of a magnetic antenna calibrated by the proposed calibration system agrees with the theoretical result and the standard Glass ring calibration result. The calibration precision satisfies the experimental requirement.     

Environmental-adaptive indoor radio path loss model for wireless sensor networks localization

In the received signal strength indicator (RSSI) based indoor wireless sensor networks localization system, RSSI measurements are very susceptible to multipath fading, anisotropy of antenna, low supply voltage of node and so on, which will cause the system failure to achieve a high location accuracy. This paper presents an environmental-adaptive path loss model. In the process of localization, the calibrated coefficient LSV of low supply voltage, which can be determined by monitoring the supply voltage of the sender, is used to calibrate ranging errors caused by its low supply voltage. The blind node utilizes the absolute value of RSSI to generate the phase of the corresponding receiver's location so as to determine the correction coefficient of indoor multipath fading R_i. Furthermore, in order to improve the accuracy of RSSI measurements, we also take full consideration of the effect of antenna to accurately determine the corresponding path loss model of the two communication nodes. The proposed path loss model is suitable for the majority of wireless location systems that are on the basis of RSSI-based ranging techniques. Experiment results show that the estimation accuracy and adaptability of the proposed path loss model are significantly higher than that of the traditional one.     

天线特性测量中极化基失配的影响及校准

对一部待测、待评估的天线,其交叉极化特性实际上是依赖于极化基的,极化基匹配或失配情况下,得到的交叉极化性能评估结果也不一样.文中首先建立了天线极化特性测最模型,推导了交叉极化测量校准约束模型,给出了该约束下的最佳收发极化基.并针对实际的雷达天线进行了外场测量实验,实测处理结果验证了上述结论.利用约束模型可对实测的极化方向图实现有效的校准.     

Dielectric spectroscopy using monopole antennas of general electrical length

A procedure is developed for measuring the complex dielectric permittivity of a material over a broad range of frequencies using a monopole antenna. No restrictions are placed on the electrical size of the antenna. The antenna is calibrated one time by measuring the input admittance in a standard medium with known permittivity, such as air. Next, the admittance is measured with the antenna immersed in a material with unknown permittivity. These two sets of admittances are then used to determine the permittivity of the material. As an application of the procedure, the complex permittivity of the alcohol 1-butanol and saline solutions were measured using a cylindrical monopole antenna. The measured permittivities are in good agreement with those determined by previous investigators.     

External Calibration of SIR-B Imagery with Area-Extended and Point Targets

Data takes on two ascending orbits of the Shuttle Imaging Radar-B (SIR-B) over an agricultural test site in west-central Illinois were used to establish end-to-end transfer functions for conversion of the digital numbers on the 8-bit image to values of the radar backscattering coefficient ?0 (m2/m2) in dB. The transfer function for each data take was defined by the SIR-B response to an array of six calibrated point targets of known radar cross section (transponders) and to a large number of area-extended targets also with known radar cross section as measured by externally calibrated, truck-mounted scatterometers. The radar cross section of each transponder at the SIR-B center frequency was measured on an antenna range as a function of the local angle of incidence. Two truck-mounted scatterometers observed 20-80 agricultural fields daily at 1.6 GHz with HH-polarization and at azimuth viewing angles and incidence angles equivalent to those of the SIR-B. The form of the transfer function is completely defined by the SIR-B receiver and the incoherent averaging procedure incorporated into production of the standard SIR-B image product. Assuming that the processing properly accounts for the antenna gain, all transfer function coefficients are known except for the thermal noise power and a system " constant" that has been shown to vary as a function of uncommanded changes in the effective SIR-B transmit power.     

阵列天线近场校准方法及在波束形成中的应用

大型相控阵天线阵列由于天线口径很大,给天线远场测试带来很多困难,天线近场测试方法可以有效解决这类问题。本文在实际工程中利用天线近场测试方法对大型天线阵列的幅相误差进行了测试及校准。试验结果表明,此方法可以用于评估阵列天线的一致性。波束形成后,相对于接收机闭环校准,天线误差校准可以明显降低旁瓣,并且测角偏差明显减少,在短波低频段表现尤为突出。     

紧缩场静区校准用超宽带天线性能的分析

紧缩场是天线天线罩辐射特性、目标散射特性测试的重要设备,在使用前需要对其静区平面波幅度锥削、幅度波 纹及相位变化等电磁性能参数进行校准。紧缩场的静区性能校准离不开全频段的探头接收天线,校准天线的性能会影响紧缩 场静区电磁参数的校准结果。文中阐述了校准紧缩场静区性能的扫描法原理,利用本单位研制的紧缩场校准系统,在某研究 所的紧缩场环境内,比较了标准增益喇叭天线与超宽带双脊喇叭天线分别作为接收探头的差异。实验证明,设计完成的超宽 带双脊喇叭天线具有驻波低、增益适中、更换方便、频带宽等优点,完全可以替代六个波段标准增益喇叭天线的功能。     

Short-Range Ultra-Broadband Terahertz Communications: Concepts and Perspectives

We propose the concept of ultra-broadband terahertz communication, based on directed non-line-of-sight (NLOS) transmissions. Potential applications of such a system supporting multi-gigabit data rates are given, and put into the context of currently emerging WLANs/WPANs. The technology and propagation constraints serve as boundary conditions for the determination of the required antenna gain to support ultra-broadband communication. Resulting high-gain antenna requirements will necessitate highly directed transmissions. We propose the use of omni-directional dielectric mirrors to support directed NLOS paths. Their performance is investigated with ray-tracing simulations of a terahertz propagation channel in a dynamic office environment, which is calibrated with measured building-material and mirror parameters. We demonstrate that a directed NLOS path scheme will make a terahertz communication system robust to shadowing. Furthermore, we show that dielectric mirrors covering only parts of the walls will significantly enhance the signal coverage in a typical indoor scenario.     

3D autocorrelation coefficients of dipole antenna

An analytical expression is given for the 3D autocorrelation coefficient of a half-wavelength dipole antenna as a function of spatial separation in an isotropic scattering environment. Results are verified experimentally through measurements conducted in antenna anechoic chambers. The results closely match previously published work based upon measurements collected in a typical indoor mobile communication environment. It is recommended that the 3D autocorrelation coefficient model be used to gauge diversity antenna measurement systems.