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A technique to diagnose faulty elements present in patch antenna array from either measured far field radiation pattern or return loss characteristic is suggested. A linear array consisting of eight square patch elements with uniform excitation and ./2 spacing between them is considered. A method is developed using Artificial Neural Networks to detect one or two faulty elements present in the array. A neural network is trained with one third of the possible faulty radiation patterns and tested with two thirds of faulty patterns. ANN is implemented with Radial Basis Function neural network (RBF) and Probabilistic neural network and their performance is compared.
Compact test ranges are worldwide used for real-time measurements of antenna and payload systems. The Compensated Compact Range CCR 75/60 and 120/100 of Astrium represent a standard for measurement of satellite antenna pattern and gain as well as payload parameter due to its extremely outstanding cross-polar behavior and excellent plane wave field quality in the test zone. The plane wave performance in the test zone of a compact test range is mainly dependent on the facilities reflector system and applied edge treatment as well as on the RF performance of the range feed. To provide efficient and economic testing and maintaining the needed measurement accuracy the existing standard set of high performance single linear feeds covering the frequency range from 1 - 40 GHz had been extended to operate simultaneously in dual linear polarization. In addition several customer specific range feeds had been developed and manufactured and validated. More detailed information and achieved test results for the new high performance range feeds will be presented.
The 18 terms technique, for the evaluation of the measurement error, was used to justify the differences between the measurement data obtained from the three facilities. In Addition a general description of the test setup and the principle error sources found during the finalization of the test setup are given.
ORBIT/FR has recently delivered several high performance millimeter wave antenna systems for use in compact range and direct illumination chambers. These systems utilize the latest Agilent Technologies millimeter wave modules used in conjunction with the PNA-X vector network analyzer. These systems offer the following features: . Integration of the transmit and receive modules at the AUT and source/feed antenna for a low loss implementation . Integral range reversibility for AUT transmit or receive capability . Full integration with a baseline 2-50 GHz system capability . Full and automatic harmonic selection for all measurement bands . Optimized RF equipment placement in the chamber The systems are integrated with the 959Spectrum Antenna Measurement Software to provide a fully automatic antenna measurement capability from 2-110 GHz. Patch panels were used to avoid any re-cabling form the microwave bands to millimeter wave bands. Greater than 70dB dynamic range was demonstrated at W band. Performance results are shown, and optimized layout considerations are discussed that demonstrate a design that results in high performance as well as operator convenience is setting up measurements over all the microwave and millimeter wave bands.
The Ohio State University ElectroScience Laboratory in partnership with Syntonics Corporation has been developing a new type of programmable antenna over the past 4 years. The antenna is made of an array of small pistons where the top of the piston is conductive, followed by a dielectric layer and then a conductive remainder. When all of the pistons are in the down position, they form a ground plane. When a row or a region of pistons are in the up position, microstrip transmission lines and patch or rampart antenna elements can be created. We have several years of theoretical and experimental data showing the effectiveness of the transmission lines and antennas thus created. Small hand-emplaced elements have been used in the past, but at this time, a prototype programmable antenna system has been built and tested. We will show examples of array beam formation and beam steering. Now that the prototype is available, we are testing an automatic array generation software system that creates the radiating elements and the transmission line system so as to form the array at the desired frequency and pointing in the desired direction. This is particularly interesting because of the need to design the beam former feed based on only discrete increments but with the flexibility to shift the location of the radiating elements. This paper will show examples of the operation of the system and the resulting beam patterns. .
The Ohio State University ElectroScience Laboratory has been developing a small zero power wireless sensor for sensing temperature and strain of turbine blades in a jet engine. The RF propagation environment has considerable multipath and is dynamic. The sensor must be very small and very thin. Our solution is to use a 10 mil thick patch antenna feeding a surface acoustic wave (SAW) delay chip. The SAW chip is a special design with two (at least) reflectors fed by a deposited interdigital transducer. A transponder transmits a burst of RF into the running jet engine and measures the change in differential delay between the two return signals. The multipath ringdown time establishes the chip delay time. The size of the openings between the turbine or compressor blades establishes the lower frequency limit of the RF because of waveguide cutoff effects. The 5 GHz cutoff frequency implies the interdigital line spacing must be less than 100 nm. Since this is smaller than a wavelength of light, the deposited lines must be created using electron beam deposition. We will show the internal multipath propagation in a jet engine, and show results of wireless measurements of strain and temperature.
Measuring the radiation pattern of passive ultra-high frequency (UHF) radio frequency identification (RFID) tags is challenging due to the special characteristics of RFID systems. In this paper we presented a comparison of radiation pattern measurement techniques for passive UHF RFID tags. Intermodulation-based, backscattered power-based and threshold power-based techniques are used to measure the E and H plane radiation patterns of a dipole-type and slot-type tags. In this study, we have measured the radiation pattern of RFID tags in active mode, i.e. when the tag is characterized in operation with the microchip.
An accurate and efficient numerical model is developed to simulate the far field of an antenna under test (AUT) measured in a Compact Antenna Test Range (CATR), on the basis of the known quiet zone field and the theoretical aperture field distribution of the AUT. The comparison with the theoretical far-field pattern of the AUT shows the expected measurement accuracy. The numerical model takes into account the relative movement of the AUT within the quiet zone and is valid for any CATR and AUT of which the quiet zone and aperture field, respectively, are known. The antenna under test is the Validation Standard Antenna (VAST12), especially designed in the past for antenna test ranges validations. Simulated results as well as real measurements data are provided.
ABSTRACT In this work, a probe compensated near-field – far-field transformation technique with spherical spiral scanning suitable to deal with elongated antennas is developed by properly applying the unified theory of spiral scans for nonspherical antennas. A very flexible source modelling, formed by a cylinder ended in two half-spheres, is considered as surface enclosing the antenna under test. It is so possible to obtain a remarkable reduction of the number of data to be acquired, thus significantly reducing the required measurement time. Some numerical tests, assessing the accuracy of the technique and its stability with respect to random errors affecting the data, are reported.
This contribution deals with guided radar distance measurements in the .eld of industrial tank level control. The aim is to achieve a submillimeter gauging accuracy even when conducting the measurement within thehighlydispersive environment of large and thus overmoded cylindrical waveguides. In this case normally multimode propagation causes a decrease in measurement precision. Therefore, the effects of intermodal dispersion are fundamentally reviewed and based on these results, two different approaches for overcoming the drawbacks of this measurement scenario are derived. On the one hand a prototype of a novel concept for compact mode-preserving waveguide transitions is presented, ef.ciently avoiding the excitation of higher order modes. By applying this concept, free-space optimized signalprocessing algorithms canbe used advantageously. On the other hand, an alternative correlation-based signal processing method is presented. The method is able to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition. Finally, the trade-off between the signal processing’s and waveguide transition’s complexity is highlighted and discussed. Measurement results in a frequency range of 8.5 to 10.5 GHz are provided for different kinds of waveguide transitions proving the capability of both approaches.
The gain-transfer technique is the most commonly used antenna gain measurement method and involves the comparison of the AUT gain to that of another antenna with known gain. At microwave frequencies and above, special pyramidal horn antennas known as standard-gain horns are universally accepted as the gain standard of choice. A design method and gain curves for these horns were developed by the US Naval Research Laboratory in 1954. This paper examines the ability of modern numerical electromagnetic modeling to predict the gain of these horns and possibly achieve greater accuracy than with the NRL approach. Similar computational electromagnetic modeling is applied to predict the gain and pattern of open-ended waveguide probes which are used in near-field antenna measurements. This approach provides data for probes that are not available in the literature.
The NIST 18 Term Error Analysis Technique uses a combination of mathematical analysis, computer simulation and near-field measurements to estimate the uncertainty for near-field range results on a given antenna and frequency range. A subset of these error terms is considered for alignment accuracy of an antenna’s RF main beam. Of the 18 terms, several have no applicable influence on determining the beam pointing or the terms have a minor effect and when an RSS estimate is performed they are rendered inconsequential. The remainder become the dominant terms for identifying the alignment accuracy. There are six terms that can be evaluated to determine the main beam pointing uncertainty of an antenna with respect to dual band performance. Analysis of the near-field measurements is performed to identify the alignment uncertainty of the main beam with respect to a specified mechanical position as well as to the main beam of the second band.
Small size ultra-wideband (UWB) antennas are attractive for aircraft and ground vehicle communication systems. In this paper, we presented a novel compact low-profile Inverted-Hat Antenna (IHA) to work from low VHF frequencies up to 2GHz. Such a large bandwidth is achieved via excitation of traveling waves between the ground plane and the top portion of the antenna. As one UWB radiator, the IHA is designed to have frequency-independent behavior by introducing a moderate number of elliptical segments. In particular, an 11-ellipse IHA is fabricated and tested to validate the concept. Fairly good impedance matching and radiation properties are achieved. In addition, quad-blade IHA is investigated to show the flexibility of both impedance and pattern control. The proposed antenna is simple and rugged for various UWB applications.
The accurate measurement of the infinite ground plane antenna patterns are needed in different applications as discussed in [1–12]. The comprehensive performance of a general antenna in a complex environment including interaction can be evaluated fast and accurately using ray tracing techniques [1,2]. This approach requires a reliable representation of the local source behaviour either through measurements or simulation. A good source approximation for this method is the infinite ground plane pattern assuming a perfectly conducting plane. The infinite ground plane condition can be achieved easily in simulation using full-wave computational tools but is very difficult to measure on a general antenna due to the finite dimensions of the measurement systems. Different measurements and post processing approaches have been investigated in the past to determine the infinite ground plane pattern of a general antenna. Spherical mode truncation/filtering have been used as means to eliminate edge diffraction from finite ground plane measurements. This method suffers from the dependence on the selection of filtering parameters as discussed in [3]. Time-gating can give some information about the isolated antenna pattern in most directions as discussed in [4-6] but is not completely general and require special equipment and setup for the measurement. Other approaches to eliminate the edge diffraction by special design of the ground plane shape have also been pursued as discussed in [7-10]. This paper introduces a simple formulation to accurately determine the infinite ground plane pattern of any antenna from measurements on a small finite ground plane. The theory of the method is presented and its accuracy and suitability demonstrated with measured examples.
This paper describes measurements performed at the National Physical Laboratory (NPL) and Near Field Systems Inc (NSI) on Open Ended Waveguide (OEWG) probes that are typically used for near-field measurements. The effect of the size and location of the absorber collar placed behind the probe was studied. It was found that for some configurations, the absorber collar could cause noticeable ripples in the far-field patterns of the probe and this in turn could affect the probe correction process when the probe was used in near-field measurements. General guidelines were developed to select an absorber configuration that would have minimal effect on the patterns, polarization and gain of the probes.
Measurements of RCS of targets in measurement facilities which are not Faraday cages may be strongly corrupted by eventual outside transmissions which fill the spectral band of measurement. In the case where the construction of a Faraday cage is not considered, it is then indispensable to reduce these not cooperative interferences thanks to specific proceeding, in order to be able to give correct values of RCS on the polluted band of frequencies. This article deals with this proceeding, while giving theoretic methods which allow limiting the influence of interferences on the measured value of RCS. Then these methods are applied in a concrete way on a given example.
Measurements of a conical micro-strip Wraparound™ antenna array mounted on a portion of the entry vehicle for NASA’s Mars Science Laboratory mission were completed at Nearfield Systems, Inc.’s new spherical near-field range facility. The Wraparound™ antenna, designed and manufactured by Haigh-Farr, Inc., provides nearly full spherical coverage and operates in the UHF frequency band for telecommunications to orbiting assets at Mars. A summary of the measurements techniques and results are presented, along with a comparison of the measured and calculated patterns.
This measurement paper presents the procedures used for the quick characterization of WiFi and WiMax commercially available antennas. Measurements were done in the 2.3 GHz to 2.6 GHz region using a short 101” spacing to measure the gain function of the antennas at boresight. Gain was measured against a Standard Gain Horn (made by IFI). The Agilent Vector Network Analyzer was used to perform the measurements and Microsoft Excel was used to plot the data and results. Results seem to indicate most commercially available antennas do not meet the advertised gain parameters and they normally fall short by as much as 50%. The paper shows all the antennas measured results, a comparison against the manufacturer’s advertised gain and their return loss as function of frequency. The measurements were conducted in a few hours per antenna and without the use of complex anechoic chamber.
A 3-D radiation pattern measurement system using an ultra light phantom is proposed for the evaluation of handset antennas in mobile communication systems. The problem of phantom imitating human electrical characteristics is its heavy weight to mount on the 3-D pattern measurement system for the conical or great circle cut method. This difficulty is removed by a light-weight phantom. This paper presents a novel phantom consisting of a plastic shell and wave absorbers whose electrical parameters are optimized to obtain electrically equivalent performance with the human head and body. Single and double layered absorbers are used for the phantom in the frequency range of 800 to 2000 MHz. The weight is less than 7 kg for an upper body phantom with an arm and a hand holding handset under test. This light weight phantom is easily installed on the rotating table of great circle cut measurement facility. This paper presents a design method of ultra light phantom, the characteristics of the phantom and 3-D antenna pattern measurement system in detail.