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A new 3-dimensional measurement method for the determination of the radiated power of mobile phones is presented. In contrast to usual 2D cut plane measurements, the 3D method gives the whole 3D radiation pattern. From this, insight into the detailed angular dependent radiation characteristics can be derived, which is very useful for mobile phone manufacturers and antenna developers. Furthermore, the overall radiated power as well as the directivity of the mobile phone can be post processed from the measured data. A very interesting feature is the ability of the measurement set up to carry a phantom head. With it, measurements of the whole system user and mobile phone can be performed to study the user's influence. The measurements are carried out in an EMC anechoic chamber, which has been specially optimized regarding reflection absorption. Some examples demonstrate the comprehensive measurement capabilities of the presented method.
In this paper, a three-covered monopole array antenna with 155o phase-shift and 0.1 ë spacing was suggested to give a minimum power radiation in the direction of the mobile user’s head, consequently the hazard that may the EMW inflects on the human health can be considerably reduced. Several experiments were conducted in this work to measure the power radiation pattern of the monopole, as a common antenna used in mobile telephones, and the three-element array antenna in free-space and with human head adjacent to the antenna. The frequencies were chosen to be 1800 MHz and 1985 MHz, for uncovered and covered designs, respectively, to cover the GSM-1800, PCS-1900, and DECT frequencies. A dielectric material with år = 2.33 , tanä = 0.0005 , and thickness equal to the radius of the monopole was used to cover each array element. It was found that the length of the covered monopole is about 90% of the uncovered length. A practical method was suggested in this work for attaching the adopted array to the mobile telephone.
Compensated Compact Ranges (CCR) represent a high standard of state-of-the-art test facilities with a fast and real time measurement capability up to the submm wave range. Future scientific and earth observation instruments of ESA/ESTEC such as MASTER, PLANCK and HERSCHEL are working within this frequency ranges and require a high measurement accuracy for large antenna apertures. Within the ADMIRALS study for ESA/ESTEC, transmit and receive modules up to 500 GHz and an appropriate large offset reflector antenna with precise surface accuracy in form of a Representative Test Object (RTO) were applied. Related tests in the CCR 75/60 of Astrium were performed in order to qualify the test facility and verify the antenna measurements with theoretical pattern calculations. The present paper shows measurement results with the highly accurate Plane Wave Scanner (PWS) of Astrium GmbH and the RTO. Through the measurements performed, the accuracy of the plane wave field as well as pattern accuracy in the quiet zone of the CCR 75/60 have been qualified up to 500 GHz.
Two ways of modelling a compact range design are presented, and the coupling to a given antenna under test (AUT) is determined and compared to the AUT far field. The compact range models are both based on physical optics (PO). The first model applies a simple presentation of the serrations of the range reflector while the second model is based on a new feature of GRASP8, which allows a detailed description of the triangles of the range serrations. The AUT measurement is modelled by an accurate coupling analysis between the current elements on the compact range reflector and the antenna under test. This coupling pattern is compared to the real far-field pattern and the differences are discussed. By including known range imperfections in the AUT-torange coupling a better agreement to the measured patterns may be obtained. All computations are carried out by GRASP8.
CAMELIA is a large RCS measurements facility (45m.12m.13m in dimensions) that is operated at both SHF and V/UHF frequencies. In the V/UHF band, coupling between the target and the walls can be exhibited, due to non directive transmitting/receiving antenna, and low efficiency absorbers, that must be eliminated to derive the intrinsic response of the target To this aim, we have first developed a 1:10 small scale model of the chamber, that is operated in the SHF band. It enables the experimental simulation of RCS measurements in the V/UHF band, and confirmed the interpretation of the electromagnetic phenomena in the large scale facility ([l]). Then, two theoretical algorithms were developed, modeling these coupling phenomena. The first one is a simple ray tracing model, requiring as input data the measured reflection coefficient of the walls, the radiation pattern of the transmitting/ receiving antenna and the bistatic RCS of the target. The second one introduces an analytical model for the antenna and its images with respect to the walls, and calculates the near field scattered by the target. The measurement of several targets bas been modeled, and a good agreement bas been obtained. The advantages and drawbacks of each method are discussed.
A method is presented for calculating the gain of corrugated conical horns. It is based on basic symmetry conditions of circular or conical waveguide mode fields. This formulation allows to derive the radiation pattern over a complete sphere form two principal polarization patterns (E- and H-plane patterns). This method can be applied for both theoretical or experimental patterns, respectively. The theory has been verified experimentally with measurements carried out on two different ranges. The results agreed within 0.05 dB or less in all situations.
Log Periodic Dipole Arrays (LPDAs) are widely used for certain metrology applications including site attenuation measurements. To accurately make such measurements, the location of the phase center of the antenna is required. However, the LPDA does not, in the strictest sense, exhibit a phase center. Approximate phase centers can be defined by computing the local curvature of a far-field constant-phase surface on the antenna’s principal lobe. However, because the E- and H-plane patterns are different, the phase centers computed from each pattern (or any two-dimensional cut) are not co-located at a given frequency and, moreover, track differently with frequency. An H-plane array of LPDAs with an appropriate taper can be made to exhibit very similar E and H plane patterns over a very broad frequency range. Such an antenna exhibits a much better defined phase center (the phase center still moves as a function of frequency) and is therefore much better suited for metrology applications. Here we present phase center calculations and measurements for two different H-plane arrays of LPDAs. One array is composed of two highly compressed LPDAs (ô=.88, ó=.05) fed with a corporate feed network, while the other is composed of two high gain LPDAs using the so-called “optimum” parameters (ô=.88, ó=.16) and fed with a hybrid feed network. Numerically predicted and experimentally measured results for the phase center loci are presented and compared with those of the component LPDAs.
A method is presented for correcting for range measurement errors resulting from non-uniform quiet zone illumination in indoor tapered antenna chambers. The interaction of the source antenna with the throat of the chamber causes undesirable amplitude and phase variations over the quiet zone, the region where the antenna under test (AUT) is located. These variations can impact the accuracy of the antenna pattern measurements, especially when the AUT has a significant aperture. These quiet-zone anomalies can be measured and removed from the antenna patterns by quiet-zone probing. The quiet zone can be probed planar, cylindrical, or spherical quiet zone probe configurations. A planar quiet-zone probe is used here. This process of calibrating the antenna pattern measurements for quiet-zone range errors is called quietzone synthesis (QZS) and is implemented here using MATLAB [1].
A transmitting multi-beam frequency-reuse antenna on an orbiting satellite has N co-polarized spot-beams with each beam driven by a separate transmitter (all transmitters sharing a common band) and each pointed in a different azimuth and elevation direction. The interference effect of N-1 beam side-lobes falling simultaneously on any receiving ground user in a satellite main beam can be estimated by combining the N-1 radiation pattern side-lobe levels which coincide on each user. To predict this effect, the radiation pattern of each beam can be measured in a near field pattern range (NFR) on the ground. When this is done, the measurement error (uncertainty) of each side-lobe falling in the direction of a given main beam ground terminal can also be obtained by a series of special error measurements. The measured error terms for a given side-lobe can be combined in an NFR error table to obtain the measurement error for that side-lobe in the direction of the given terminal location. This process can be repeated for each of the N-1 side-lobes. In this paper we present a method for combining the measured errors of the N-1 side-lobes to yield a combined uncertainty for the combined interference level of the N-1 side-lobes. This process can be repeated for each main beam terminal location. Several tables are presented showing how the combined side-lobe error varies as a function of the levels of the individual side-lobes and the measurement uncertainty of each side-lobe.
Earlier (AMTA'97, AMTA'98), we have proposed a new low-cost laboratory method named the quasi-optical waveguide modeling (QWM) method to study power and amplitude-phase scattering characteristics of objects, in particular the RCS of targets or their scale models, in the near millimeter (NMM) and submillimeter (SMM) wave regions. A specific feature of this technique in that an investigated object (or its scale model) is mounted inside a quasi-optical waveguide structure in the form of a hollow dielectric waveguide (HDW), in which the scattering characteristics of the waveguide dominant HE11 mode are determined. These characteristics are related to the wanted scattering characteristics of the test object in free space by definite relationships. At the same time the HDW serves several functions: it forms a quasiplane incident wave within the scattering area where test object is placed, performs the low-loss and low-distortion transmission of the scattered wave carrying information of the object being tested to the receiver, effectively filters the unwanted modes arising at the scattering on the test object, and insulates the measurement area from the ambient conditions containing parasitic sources. In this paper we consider the possibility of using the QWM method to study polarization backward scattering characteristics of physical objects, in particular the complex elements of the scattering matrix with relative phase (SMR). A quasi-optical polarimetric micro-compact range (PMCR) based on the circular HDW and quasi-optical devices has been developed and built. The measurement results of the SMR and backward scattering patterns of a reference object as a square metallic cylinder obtained in the PMCR for the different linear polarization basic sets at the 4-mm wave band are presented. The comparison between the experimental results for the reference object and the theoretical data calculated by the geometrical theory of diffraction have shown a good agreement, and demonstrated the possibilities of the QWM method, and its good perspectives for backward scattering polarization characteristics modeling in the NMM and SMM wave regions.
A prototype broadband ground reflection range, to be used for measuring antenna patterns on full sized aircraft, was built and evaluated. The range was designed to evaluate an antenna at several arbitrary VHF/UHF frequencies simultaneously. This is a follow on to two previous papers that explored the design of such a range using numerical modeling and optimization by the use of genetic algorithms.
We present a preliminary evaluation of a microwave measurement system that has been designed to determine electromagnetic fields in the quiet-zone of an antenna measurement range and to produce an image of the sources, intended and unintended, of the incident radiation. This information is of potential value in the processes of improving range perfor mance, correcting pattern results for non-ideal illumination , and evaluating measurement uncertainty.
This paper describes error analysis and measurement techniques that have been developed specifically for cylindrical near-field measurements. A combination of analysis and computer simulation is used to show the comparison between planar and cylindrical probe correction. Error estimates are derived for both the pattern and probe polarization terms. The analysis is also extended to estimate the effect of position errors. The cylindrical measurement geometry is very useful for evaluating the effect of room scattering from very wide angles since scans can cover 360 degrees in azimuth. Using a broad beam AUT and scanning over a large y-range provides almost full spherical coverage. Comparison with planar measurements with similar accuracy is presented.
In this paper, a versatile indoor antenna measu rement facility in Nokia Resea rch Center is presented Two measurement systems have been implemented into a rectangular, shielded anechoic chamber having dimensions of 10 m * 7 m * 7 m. The first configuration is an in-house developed 3D radiation pattern measurement system that uses a rotating elevation arm. The primary application of this system is characterization of terminal antennas including the effect of a test person or a human body phantom. The elevation arm can be easily removed and the chamber then used as a conventional 5-m far-field range. This configuration is applied mainly for directive antennas. The facility has been found out to be very useful in research and development of wireless com munications antennas. The 3D spherical scanning system opens up a much wider perspective than before on how the human body interacts with different kinds of terminal antennas and what are the radiation and receiving performance characteristics under realistic usage conditions.
The automobile antenna industry is facing a rapidly growing trend leading to the incorporation of effective, low cost, conformal antenna designs. There are many situations where an omnidirectional azimuth pattern is desired for a conformal antenna on a vehicle. Conformal antennas, however, are typically restricted to mounting locations on the side of vehicles where the vehicle itself obstructs the signal. It is very difficult to obtain omnidirectional performance in these cases. A technique to substantially improve omnidirectionality of automotive conformal antennas is described. This technique is based on the use of dual symmetric antennas connected to a common junction point using equal length cables. Experimental results of implementing this technique using a dual sideUte film antenna on a commercial vehicle in the FM frequency band are presented. It is shown that the dual sidelite conformal antenna is an effective, low cost solution for achieving omnidirectional performance in FM automotive applications.
The design of hybrid-mode dielectrically-loaded horns [1][2] for antenna test range illumination is described. These horns have a wide operating bandwidth of 5:1 or greater and were designed to replace conventional corrugated- or smooth-walled illumination horns that, typically, have a bandwidth of 2:1or less. Dielectrically-loaded horns have the radiation characteristics desirable for test range illumination: principal plane pattern symmetry, reasonably low cross-polarization and low sidelobes, low reflection coefficient and relatively constant beamwidth. At CSIRO we have developed software and manufacturing techniques to design and make these horns accurately. Measured results, that show close agreement with predicted values, are presented for a horn made for the frequency range, 7 to 40 GHz.
An accurate determination of the radiation pattern coverage is necessary for Flight Termination and Safety (FTS) systems. Vehicles such as the X-34 are physically large and can be difficult to handle and mount for full spherical characterization of the patterns. The question addressed here is "can a partial, full-scale mockup be used for FTS measurement purposes?" Simulations were performed to determine the percent spherical coverage for three candidate X-34 full-scale configurations: 1) Complete mockup, 2) full-length mockup without wings or tail and 3) a partial-length model without wings or tail. The radiation patterns were computed using NEC-BSC and post processing was done to determine the coverage. The FTS UHF percent spherical coverage calculations varied by less than 0.5 dB. For the three configurations, the level at 95% spherical coverage varied from -20.55 to -21.0 dBi for LHCP. Subsequent measurements of case 3) were within 0.5 dB of the values predicted.
Composite Optics Inc (COI) has designed and constructed a Portable Far-Field Antenna Test Chamber to complement their Large Compact Range. The need for this chamber arose after COI won a contract to design, build, and test hundreds of small broadband antenna elements. Because of the portability requirement, COI chose to procure and modify an industrial container, suitable for transportation on a standard flatbed trailer. This paper discusses the design, fabrication, and installation of a chamber, suitable for pattern measurements of small (<2 feet) antennas in the 6-18 GHz frequency range.
For greatest efficiency and accuracy in measuring patterns of a circularly polarized antenna on a planar near field range (NFR), a recommended procedure is to use a fast switched, dual circularly polarized probe. With such equipment one obtains complete pattern and polarization data from a single scan of the antenna aperture. For our task of measuring high gain shaped beam apertures, measurement efficiency is further improved by using a moderately high gain (about 12 dBi) probe that has been accurately calibrated for patterns, polarization, and gain over the test frequency band. Such a probe allows scan data point spacing to be typically at least one wavelength, thus keeping scan time minimized with acceptably small aliasing (data spacing) error. The measured near field amplitude and phase data is transformed via computer to produce the angular spectrum that is further processed to remove the effect of the probe patterns, i.e. probe correction. The final output is a set of (principal and cross) circular polarized far field patterns. However on one occasion, due to fast breaking changes in requirements, we were unable to obtain a calibrated circular polarized probe in the available time. For this test we used an available calibrated 12 dBi fast-switched dual linear-polarized probe with software capable of processing principal and cross circular-polarized far field patterns. As anticipated, we found from preliminary tests that the predicted low cross-polarized shaped beam pattern was not achieved when using the calibrated fast Ku band probe switch. Further tests showed the problem to be due to small errors in calibration of the probe switch. This paper will discuss test and analysis details of this problem and methods of solution.
When mounted on spacecraft , pattern of some antennas are perturbed by the presence of satellite body. The prediction of antenna performances including satellite structure effect is generally done at early stage of antenna design but is limited in terms of model complexity. The test on full spacecraft & in far field condition is then necessary. This solution is very expensive as it means for test at satellite level to use Compact antenna Test Range in order to satisfy cleanliness aspects. For the Meteosat Second Generation (MSG) program test on the toroidal antennas need to be performed on different model including a flight model. A good compromise was to use the external omnidirectional antenna range and a part of satellite structure representing the major contributor for the antenna pattern as identified via numerical analysis. The external range offer possibilities that cannot be reached in Compact range, e.g. low cost, full sphere pattern, low frequency range.