Welcome to the AMTA paper archive. Select a category, publication date or search by author.
(Note: Papers will always be listed by categories. To see ALL of the papers meeting your search criteria select the "AMTA Paper Archive" category after performing your search.)
Two types of cellular handset testing are presented. The first studies models of a cellular handset near the human head. A comparative analysis is done between simulation and measurement of an inexpensive head mockup compared to a more expensive head mockup. Peak gain values have good agreement within about 1 dB. The second type of cellular handset testing is for a PCS band PIFA antenna integrated to a cellular handset. This paper describes the design and experimental study of the radiation patterns of a PCS band (1850-1990MHz) cellular handset with an internal PIFA. The PIFA described in this paper has good gain, impedance matching, and reduced sensitivity to human body interaction. This PIFA is a good cellular internal antenna.
SATIMO has recently installed a spherical near-field antenna measurement system for ALLGON MOBILE COMMUNICATIONS, the market leader in the field of antennas for mobile telephones. This spherical near-field system, as shown in Figure 1, allows for real-time measurements of antennas and will among other be used for the measurements of the radiation characteristics of mobile telephones and satellite terminals in the presence of the human operator. The system consists of a circular of 4m diameter containing 64 dual polarized measurement which are electronically scanned giving a real-time near-field pattern cut over 310° in elevation. A full sphere measurement including near-field to far-field transformation is available in seconds with a single +/- 90° azimuth rotation. The paper will present the measurement system and the results of the final acceptance tests. The acceptance tests are based on both range inter comparisons and also by measurement of key terms in the overall error budget.
NPL has been providing antenna gain standards since the late 1970's, initially to service internal needs for microwave field strength standards. To meet the increasing industrial demand for the calibration of microwave antennas in areas such as satellite communications and radar, NPL has developed an antenna extrapolation range. The current facility, which is due to be replaced by the end of the year, is used to measure the gain of microwave antennas in the frequency range 1 to 60 GHz, often with a gain uncertainty as low as ± 0.04 dB. Axial ratio, tilt, sense of polarisation and pattern measurements can also be made in the same facility, while for larger antennas a planar near-field scanner is used. Of the many measurement techniques for determining the gain of an antenna, the most accurate is the three antenna extrapolation technique [1,2] which was developed at the National Institute of Standards and Technology (NIST) at Boulder, Colorado, and is the method used at NPL. This is an absolute method as it does not require a prior knowledge of the gain of any of the antennas used. Since calibration data is often required across a wide frequency band, the measurement techniques and software have been developed to allow measurements to be performed at a large number of frequencies simultaneously. This reduces the turn round time, the cost and the need for interpolation between measurement points.
The European Space Agency (ESA) began serious investigations into the implementation and exploitation of near field antenna testing techniques already in the early 1970s where all three near field measurement geometries were considered (1). Spherical near field scanning was selected by ESA as being the most promising alternative to even larger conventional outdoor ranges. In the meantime, work was underway at the Technical University of Denmark (TUD) on spherical wave theory and its application to near field antenna measurements (2,3). As work began under ESA contract to demonstrate the technique, the most important aspect, the transformation algorithm and software was developed allowing dual polarized probe pattern and polarization corrected spherical near field measurements to be implemented (4).
Antennas characteristics can be measured in two ways. lfrequency Domain Method (FDM) is more widely known. The main measuring instruments: Microwave Generator and Receiver. In Time Domain Method (TDM) measurements are fulfilled by using superwide band pulses. The main measuring instruments: Pulse Generator and Sampling Oscilloscope. TDM shows a number of advantages but for narrow-band antennas TDM is difficult to apply and FDM is required. At the testing polygons aimed to measure various antennas we set equipment allowing to use both measurement methods. For TDM we used a two channel sampling converter SD200 of Geozondas production with bandwidth 0-18 GHz. To unify measurements we developed a 3-channel sampling converter SD303 allowing besides pulse to measure sine wave amplitude and phase difference in dynamic range 100 dB. The third channel is used for synchronization. Thus the same instrument assures antenna measurements both in TDM and FDM. At 100 m distance the following characteristics are obtained in Time and Frequency Domains Measurements: Bandwidth 1- 18 GHz. Antenna pattern dynamic range 60 dB Gain measurement accuracy 0.5 dB Phase difference between 2 antennas error 0.5 - 3° (depends on frequency). Hardware, software and digital signal processing algorithms are considered.
Design optimization and measurement of the Luneburg lens antennas are the focus of this paper. One of the important design aspects of an optimal Luneburg lens antenna is to construct a high performance lens with as low number of spherical shells as possible. In a uniform Luneburg lens, the gain is decreased and unwanted grating lobes are generated by reducing the number of shells. This deficiency in the radiation performance of the uniform lens may be overcomed by designing a non uniform lens antenna. The optimized non-uniform spherical lens antenna is designed utilizing the dyadic Green's function of the multi-layered dielectric sphere integrated with a Genetic Algorithm (GA)/Adaptive Cost Function optimizer. Additionally, a novel 2-shell lens antenna is studied and its performance is compared to the Luneburg lens. Finally, measured results for far field patterns and holographic images are shown for the Luneburg lens antenna using the UCLA's bi-polar near field facility.
A simulation tool used during the design of near-field ranges for phased array antenna testing is presented. This tool allows the accurate determination of scanner size for testing phased array antennas under steered beam conditions. Estimates can be formed of measured antenna pointing accuracy, side lobe levels, polarization purity, and pattern performance for a chosen rectangular phased array of specified size and aperture distribution. This tool further allows for the accurate testing of software holographic capabilities.
Antenna measurement techniques historically have been dominated by an assumption that an antenna is a discrete component of the overall electronic system into which it is built. Under this assumption, the measurement technique is to remove the antenna from its host electronic system and place it in a generic test system to measure the gain, pattern, etc. Although this technique still applies to many antenna measurements, it does not work well in cellular/PCS handset measurement applications because cellular/PCS handsets exhibit significant electromagnetic coupling to the human holding the phone. Therefore, the antenna should be measured in situ with a person holding the phone or, for practical reasons, with a mannequin arranged such that it can hold the phone. The mannequin is placed on an azimuth positioner and a near-field probe is moved on a very accurate circular arch from zenith to a significant angle below the mobile phone horizon plane. A description of the chamber and system, and measured results are provided.
In this paper, a near-field time domain scattering measurement technique is described. Near-field measurements are typically performed for radiation applications but not scattering applications. This time domain measurement approach borrows from many of the principles developed in the frequency domain and is ideally suited for broadband scattering characterization. The goal of determining the scattered far-fields of a structure is accomplished by the transformation of near-field data collected over a planar sampling surface. The scattered near-fields were generated with a probe excited by a fast rise time step. In particular, the near-fields were sampled with a second probe and digitized using a digital sampling oscilloscope. The bandwidth of the excitation pulse was approximately 15 GHz. The overall accuracy of this approach is examined through a comparison of the transformed far-field pattern to a numerical calculation.
In-situ pattern measurement of JHU/APL's 60-foot parabolic reflector antenna (S-band), using a low-earth orbit satellite as the source is described. The signal strength and X and Y tracking error voltages are measured as the antenna dish sweeps a matrix of points around the position of the moving satellite. The swept region is approximately ±0.30° from the antenna's boresight. This technique was evaluated during April 1998. This measurement was used to baseline the current performance of the ground station before the feed underwent significant modifications. Before the new feed assembly was installed, the position of the current feed was translated to the new feed assembly. Once installed the performance of the reflector was verified. Misalignment of the feed broadens the main beam and increases the sidelobes. More importantly, the inclusion of new components inside the feed also has the potential to introduce phase errors onto the tracking signals. These phase errors will be translated by the auto-track electronics into pointing errors causing the antenna system to inaccurately follow a target. This paper describes the measurement of the reflector antenna pattern and tracking pattern before the new assembly was installed. Results of pattern measurements with the new assembly will be presented at the conference
The use of dual polarization in meteorological radars offers significant advantages over single polarization. Recently a standard single-polarization Cuband radar was upgraded to operate in dual-polarization mode. The antenna has a 4.2m diameter parabolic reflector with a prime-focus feed. A spherical Fresnel-zone holographic technique was used to obtain the radiation pattern for the upgraded antenna. The sidelobes were higher than predicted and so the data was analyzed to identify the relative contributions of shadowing from the feed crook and surface errors in the dish. This paper describes practical considerations in the measurement of this antenna and the analysis of the results.
Two normalized pattern functions appropriate to Ultra-Wideband (UWB) antennas were discussed at the 1992 AMTA meeting [1]. The normalized pattern spectrum is an image showing radiated signal intensity as a function of azimuth or elevation angle and frequency. The spectrum is complex, and thus requires both an amplitude spectrum image and a phase spectrum image to be complete. It is normalized by dividing by the complex radiated signal at the defined boresite angle for the designated antenna. Therefore, on boresite, the normalized pattern spectrum is unity. The normalized impulse response pattern function is the Fourier Transform of the normalized pattern spectrum. This image plots intensity(and polarity) of the real impulse response of the antenna vs time and angle. On boresite, it is a band-limited impulse corresponding to the normalized pattern spectrum. This paper will discuss measurements of seven UWB antennas, and present normalized pattern results of these antennas. The antennas include both off-the-shelf products and experimental prototypes. Included are antennas which have been used for wide-angle UWB SAR imaging, a coherent UWB application where both signal attenuation and dispersion vs angle are important. The results show how pattern behavior can be separated from boresite transfer function information, and how antennas compare in this compact image format.
Three common methods of measuring circularly antennas on a far-zone range are: using a spinning linear source antenna (SPIN-LIN), measuring the magnitude and with a linearly polarized source antenna in two orthogonal positions (MAG-PHS), and using a circularly polarized source antenna (CIRC-SRC). The MAG-PHS and CIRC-SRC methods are also used in a near-field or com pact range. The SPIN-LIN method is useful because an accur te measurement of the axial ratio and gain can be made without the need to measure phase. The MAG-PHS method is the most general method and can also completely characterize the polarization of the test antenna. The CIRC-SRC method is the simplest and least time-consuming measurement if the antenna response to only one polarization is needed. The choice of measurement method is dictated by schedule, accuracy requirements, and budget. An analysis is presented that provides errors in the measured gain, relative gain pattern, and phase of the test antenna depending on the polarization characteristics of the source and test antennas. These results are useful for deciding which measurement method is the most appropriate to use for a particular job. These results are also useful when constructing more complete error budgets.
Probe correction is required to accurately determine the far-field pattern of an antenna from near-field measurements. At Raytheon Primary Standards Laboratory (PSL) in El Segundo, CA, data acquisition hardware, instrument control software, and a mechanical positioning system have been developed and used with an HP Network Analyzer/Receiver system to perform these measurements. Using a three antenna technique, the on-axis and polarization parameters of a linearly (or circularly) polarized probe are calibrated. The relative far-field pattern of the probe is then measured utilizing the two nominal, orthogonal polarizations of the source antenna. All measurements are stepped in frequency and use a time domain gating technique. The probe and the source antenna are optically aligned to the interface and unique, kinematic designed interface flanges allow repeatable mounting of the antennas to the test station.
Practical antenna applications require accurate characterization of the antenna, including both the amplitude and phase performance. Recent advances in antenna measurement technologies allow the antenna to be measured in various indoor facilities with a well controlled environment. However, measurements that take a long time to complete can still suffer phase drift and variation due to the movement of RF cable as well as changes in the chamber environment. Without proper phase correction, the measured antenna pattern performance may not satisfy the desired requirement. Consequently, it is very important to have appropriate methods for phase correction in order to obtain more accurate results. In this paper, a simple procedure for phase correction of volumetric spherical near field antenna measurement is presented. In this method, only a few additional measurements are needed for correcting the phase variation observed in the original volumetric pattern. Application of the phase corrected pattern has been found to satisfy the desired antenna performance.
The Sirius 2 telcommunication satellite was build in France by Aerospatiale. As a subcontractor Saab Ericsson Space (SES) developed the telecommunication antenna for direct television broadcast. The satellite was successfully launched November 13, 1997. Three antennas were manufactured by SES: a quality model (QM), a flight model (FMl) and a flight spare (FM2). Each antennas consists of a 1.4 meter in diameter shaped main reflector fed by a shaped subreflector and a dual polarized feed horn. For the test of the antennas, spherical near-field antenna test ranges located at Ericsson Microwave System (EMW)/SES in Sweden and at the Technical University of Denmark (DTU) were used. Each of the three antennas was measured twice. Between the two measurements mechanical and thermal tests were performed. The paper presents the measurements on the satellite antennas together with a discussion of the advantages of using the spherical near-field technique for this type of measurements. Compared to a far-field range the advantages are evident: At both SES and DTU a measurement distance of ten and six meters respectively were used on the indoor ranges. On a far-field range a measurement distance in the excess of 250 meters must be applied. To decrease the measurement time the near fields were only measured in a certain region on the near field sphere. The influence of this truncation will be discussed. Coordinate systems for the antennas were defined using mirror cubes. The RF measurements as well as the optical measurements on the cubes were performed without dismounting the antenna from the antenna positioner. The radiation patterns are therefore precisely decined with respect to the coordinate systems of the cubes.
Hughes Space & Communications Group uses near field measurement systems for satellite antenna qualification tests on many of its commercial satellites. Hughes contracted with Nearfield Systems Inc. for delivery of several large horizontal planar near-field scanners for these tests. A 40' x 22' system was commissioned in early 1997 and has since been used for numerous commercial satellite tests. Prior to satellite antenna range testing, this range was characterized for gain measurements, co-polarized and cross-polarized pattern measurements, and measurement repeatability at C-band frequencies. This paper will highlight some of the findings from the characterization effort for this particular test facility.
This paper presents a new method of separating and evaluating the effects of each residual reflection caused by antenna measurement environment by distance changing technique. The effects represent radiation patterns caused by residual reflections (hereafter, error patterns). The key processes of this new method are to suppress sidelobes of a Fourier spectrum applying a window as a function of the distance with the purpose of obtaining an accurate spectrum of reflections and to separate error patterns each other using a gating technique at each angle. Using this method applying the above two processes, we can evaluate the error pattern for each reflection source with accuracy. The validity of this method is confirmed by a computer simulation. This method is especially useful to detect the position of each reflection source in a case of evaluation for antenna test range.
Properly designed elevated antenna ranges, that are to be used on aircraft sized structures, at VHF and UHF frequencies, are prohibitively large. Conventional ground reflection ranges can measure only one frequency at a time because the source antenna height must be set for each frequency. This paper describes a broadband antenna ground reflection range that has been designed for the purpose of making antenna pattern measurements at arbitrary frequencies between 30 MHz and 400 MHz on aircraft sized vehicles. This design uses multiple transmit antenna elements with the complex weighted excitation determined by the use of genetic algorithms.
This paper is concerned with the measurement and analysis of a circularly polarized, flat plate patch array receiving antenna at 12.5 GHz. Input impedance and far field pattern measurements of the antenna over the frequency band from 10 to 15 GHz were performed. The small Compact Range (CR) facility of the Ohio State University Electro Science Laboratory OSU/ESL was used to measure the gain pattern. Gain pattern measurement of the antenna was done by using the gain comparison method. A broadband (2-18 GHz), constant phase pyramidal horn antenna was used as a reference. The data were analyzed to determine the radiation efficiency of the antenna.