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.)
This paper will deal with basic rectangular chamber design and the choices that most affect the performance characteristics of a typical Rectangular Anechoic Chamber. The first and foremost criterion that needs to be addressed is “What is the chamber for”. The answer to this question is the primary driving factor regulating the overall chamber design. Is the chamber to be used to evaluate low gain, low frequency antennas? Is the chamber going to be used for RCS measurements of unique test bodies? Is the chamber going to be used to test high gain high frequency antennas? Is the chamber going to be used for far field measurements? Is the chamber going to be used for near field measurements? On and on. The answers to these very basic questions have a dramatic effect on the overall design of the anechoic chamber. Since there are so many preliminary criteria that have to be decided before we can even attempt a design I will make the following assumptions: 1) The chamber is to be a far field antenna measurement facility 2) The chamber is to operate from 2.0 Ghz to 18.0 Ghz 3) The chamber is to be of a rectangular design 4) The quiet zone is to be a 4’ diameter sphere 5) The range length is to be 20’ 6) The desired Quiet Zone performance is a. –30 dB @ 2.0 Ghz b. –40 dB @ 4.0 Ghz c. –50 dB @ 10.0 Ghz d. –50 dB @ 18.0 Ghz With these parameters we will first look at the effect that source antenna selection has on the chamber deign. The first design example will be with a low gain broadband antenna chosen as the source and the second case will be with a high gain antenna chosen as the source. This paper will detail the different design approaches that this choice has on the overall size and absorber placement in the chamber. These will have a dramatic effect on overall chamber size and cost.
From the earliest days of antenna development, the need for measurement of performance and function has been present. Some characteristics of antennas, such as radiation pattern, are measured by moving one antenna with respect to another. In early antenna testing, outdoor ranges were used to provide a close approximation to the pattern. However, due to the challenges of weather and other environmental effects, antenna testing moved indoors with a number of methods used to compensate for the lack of available space. This paper presents an overview of the history of testing at BATC, from the early days of outdoor testing to the transition to conventional anechoic chambers and nearfield probe facilities. During this time, a variety of techniques have been used to augment standard methods for special requirements, and this paper seeks to communicate some of these methods to the testing community as well as providing a general history of antenna measurement.
A system has been developed for acquiring an antenna’s complete (3D) radiation pattern and radar cross-section (RCS) measurements. The system consists of a motion controller, a network analyser and tower assembly. The tower assembly is in an anechoic chamber. The tower has a novel design. It uses three motors in a special configuration, thereby allowing 2 ½ degrees of freedom. This freedom gives the ability to run complete antenna or RCS measurements automatically. Another advantage stemming from the degrees of freedom is expansion of the range of measurements. This is enabled by a variety of possible positions inside the chamber. Tests have also been carried out on system performance. The data acquisition rate becomes crucial when dealing with 3D pattern measurements. The performance of an HP 8720 or 8753 network analyser series can be dramatically increased by using the power sweep mode for data acquisition. Together with the “external trigger-on-point” mode, this gives the best positioning accuracy. The six-month experience has demonstrated the flexibility and reliability of the set up and ideas.
It is a very common practice to over specify the Quiet Zone performance requirements for an anechoic chamber. Very often what is done is a person who is in need of a chamber contacts someone with a similar facility, often a supplier or a customer, and simply patterns their performance requirement after what the other guy has done. This often results in a chamber, which is specified to a tighter performance requirement than is actually needed to perform the particular measurements required and can cost thousands of dollars more than is necessary. Qualcomm had a requirement to build a chamber for the evaluation of various antenna designs for mobile communication equipment. Due to building and space limitations the “ideal” size for a chamber operating in the 800 Mhz to 6.0 Ghz was not available. Qualcomm worked with AEMI to define the performance parameters to provide them with the best performing chamber that could be built within the restricted space available. Once the design parameters were defined adequately the chamber deign was developed and the chamber was built. Once the chamber was built Qualcomm went about defining the best test methods and parameters that could be achieved given the performance limitations that were evident in the design due to the compromises that had to be made in the limited space available to accommodate the chamber. This paper will discuss the design process, the design limitations and the methods used to overcome the performance compromises made in the development of the chamber and its intended purpose.
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.
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.
This paper summarizes some results of a recent NIST measurement effort. The purpose of this effort was to use a NIST-developed ultrawideband measurement system to assess the time- and frequency-domain characteristics of selected ultrawideband (UWB) transmitting devices. Brief descriptions of NISTdeveloped measurement systems are provided. Highfidelity time-domain waveforms are shown, along with associated amplitude spectra for two devices. Excellent results are obtained for both conducted and radiated emissions from UWB devices. Keywords: amplitude spectrum, anechoic chamber, conducted emission, frequency domain, radiated emission, time domain, ultrawideband
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.
A novel, combined far-field and cylindrical near-field tapered anechoic chamber was designed for RACAL Antennas (UK). Advanced ElectroMagnetics Inc. (AEMI) and ORBIT/FR-Europe collaborated in the design and the facility was completed in April 2000. The far-field tapered chamber performance was verified by Shielding Integrity Services. The tapered chamber far field facility performance after construction is compared with the original design predictions at several cellular band frequencies. Near-field measurements, in the rectangular section, compare well with outdoor measurements. There is discussion of the installation of the shielded facility and the absorbers intended for engineers interested in the cellular antenna test and measu rement arena.
CAMELIA is a large RCS measurement facility (45m.12m. 13m in dimensions) whose compact range is optimized in the SHF band (1-18 GHz). Exploiting it at lower frequencies requires the modification of the absorbers and the use of huge broad band horns as RF sources (since the compact range is now not well adapted). To help understanding the radioelectric behavior of the large scale facility, we have developed a 1:10 small scale model as well as 1:10 scale horns, that are operated in the SHF band. It enables the experimental simulation of RCS measurements in the V/UHF band. Thus, all dimensions and frequencies are homothetic, only electromagnetic properties of materials are not. RCS measurements of several canonical targets have been performed in both facilities and compared. Due to non directive transmitting/receiving antenna, coupling between the targets and the wans has been exhibited. A simple ray tracing model, taking into account the measured reflection coefficient of the walls and the bistactic RCS of the target, shows good agreement with the measurements.
This paper will detail the implementation and results of a gain calculation performed on standard gain horns (SGHs) in the LS and XN microwave bands. The three-antenna method was used to ensure the highest accuracy possible, and extensive efforts were made to minimize the error budget. The measurement was performed in a large anechoic chamber, with the receive and transmit antennas placed 4.6 meters high in opposing corners. The resulting fifteen meters of aperture separation (approximately 10D2/l. for LS band and 15D2/l for XN band) eliminated all measurable aperture interactions and greatly reduced multipath interference from chamber reflections. Rigorous analysis of the error terms proved this method to be both accurate and reliable. Typical values of measured error terms will be presented.
TRW, working with several subcontractors, is building a Compact Antenna Test Range (CATR) in one of its existing buildings. This range will replace the function of a two mile long far-field range. Lehman Chambers Corp. provided the CATR Anechoic Chamber with Cuming Corp. Microwave Absorber. Mission Research Corp. provided the CATR Rolled Edge Reflector and feeds. M.I. Technologies is configuring TRW supplied positioners with new translators for AUT positioning. The system will operate with both the M.I. Technologies 3000 System software and TRW software. We will be using an existing S/A 1795 receiver for the RF portion of the system with HP sources. Completion of the range is scheduled by the beginning of the 4th quarter 2000. This paper will provide an overview of the system design and constraints. Individual portions of the CATR will be described in detail including decisions made to reduce the overall cost of the system and fit into an existing budget.
This paper summarizes a joint NIST-Industry measurement effort. The purpose of this effort was to use a NIST developed ultrawideband measurement system to assess the performance improvement of ferrite tile anechoic chamber after a partial retrofit. Measurements were performed in the 30-1200 MHz frequency range before and after treatments were applied and excellent results were obtained. The system exhibited good sensitivity and the results highlight the effects of various retrofitting treatments. The effort also demonstrates that the NIST ultra wideband system is an efficient tool for the evaluation for both current and proposed anechoic EMC compliance test chambers.
A reconstruction method that calculates bi-dimensional equivalent magnetic currents from the tangential electric field components over a hemispherical region is presented. The method is applied for diagnosis as well as for near field to far Field (NF-FF) transformation. The method is well suited for antenna radiation pattern measurement using a near-field spherical acquisition system in anechoic chamber.
This paper describes the alignment procedure for using a spherical near-field measurement facility to determine incident fields throughout a spherical volume. This information can be used, for example, to characterize an anechoic chamber or the quiet zone of a compact range. A probe is mounted on a standard roll-over-azimuth positioner and aligned looking out of the sphere so its aperture maps out the surface of a sphere. The probe measures the amplitude and phase of the fields incident on the sphere. This method differs from the standard spherical near-field measurement where the source antenna serves as the probe and is looking into a sphere containing the test antenna.
A compact range based measurement system for automotive radars is presented. The design driver for the system was production testing. Key characteristics of the system are: compact size, short test times, no need for an anechoic chamber, ease of operation, mobility and ruggedness. The measurement system is based on electronic equipment from Dornier GmbH, the company who developed the automotive radar for the new Mercedes S-Class. It uses a small rolled edge millimeter wave compact range from ORBIT/FR Europe GmbH. Some general characteristics of automotive radars are presented, followed by a more detailed description of the key subsystems of the measurement system: Simulator, Compact Range and Processing Control Unit. Finally some measurement results are presented and discussed.
The purpose for this advanced development program was to advance the flatness level on an RF/IR Beam combiner. The developed beam combiner minimized transmission losses for RF signals between 1 GHz and 40 GHz and maximized total transmission for RF signals between 8 GHz and 18 GHz. The combiner maximized IR reflectance for IR radiation (2µm to 13 tm). Two 12 inch units were delivered to NAWC-WPNS for evaluation. The combiners produced an average transmission losses in the range of 0.4 dB between 1 and 33 GHz and 0.8 dB between 33 GHz and 40 GHz. Reflectivity in the Infrared was measured at 87% with the use of a 3.39 µm laser source. The combiners were manufactured on PolyOxyMethyle (POM); they are highly crystalline structures, very flat (mold driven), with unique acetal resins structures. POMs are a variant of thermo plastics, are made by free radical polymerization initiated by a peroxide or azo catalyst, or by redox polymerization. Four basic polymerization processes may be used to produce good RF transmission acrylic resins. Using POM as the host material, a Frequency Selective Surface (FSS) using a low pass configuration, was Gold sputtered on the host material surface. The results produced a mirror like surface, highly visible and IR reflective, and very transmissive in the RF domain. These combiners are to be used for the anechoic chamber testing of dual mode missile seeker systems. The missile systems required in an anechoic chamber measurements, far field illumination from both IR signals and RF signals. The dual mode beam combiner allows spatially coherent signals to illuminate the missile seeker under test. Results of these development, seems to indicate that larger combiners can be fabricated on optically flat materials (e.g. fused silica) with flatness of 12 µm. This will allow the next generation seeker heads, operating with large focal plane arrays, to be stimulated in an anechoic chamber environment.
The growing need of ultra-wide band measurements has promoted the research on real time domain (TD) antenna measurements. Theory has been already established, but practices still under development until the measurement regime becomes fully operational. In the Delft University Chamber for Antenna Measurements (DUCAT) there have been already provided outstanding results in a TD far-field configuration. A TD far field model of the facility has been developed in order to provide a key to improve the range performance and accuracy. This paper presents the model and considerations for establishing TD error correction techniques.
The development and implementation of novel measurement systems for rapid electromagnetic (EM) field testing by using linear arrays of modulated scattering elements is presented and discussed. The measurement systems employ the Advanced Modulated Scattering Technique (A-MST) to accomplish rapid sampling of the incident electromagnetic field along the length of the linear probe array at rates that are faster than conventional mechanical scanning of a single probe by a factor of 10 to 1000 or more. The A-MST probe array may be located in the nea r-field (NF) or far-field (FF) of the EM sources.
We explore new methods for the evaluation of absorber-lined chambers in the 30-1000 MHz frequency range. Current domestic and international standards recommend chamber evaluations using CW site attenuation measurements. While these satisfy regulatory requirements, they are of little value in actually understanding a chamber environment. A technology, that circumvents the limitations of CW test methods, is currently under development at NIST. In order to explore the potential of this new methodology, we have developed a two-dimensional finite-difference time-domain model for a fully anechoic ferrite tile chamber. The results obtained are quite promising and demonstrate the potential of time-domain measu rements in chamber evaluations. A new chamber figure of merit is proposed that permits a more direct evaluation of the installed absorber system.