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The last published version of the IEEE Std 1128 is the 1998 edition. It is titled "Recommended Practice for RF Absorber Evaluation in the Range of 30 MHz to 5 GHz". Over the years, the document has been used widely for absorber evaluations in electromagnetic compatibility (EMC) applications as well as in antenna and microwave measurement applications. Besides the obvious frequency range which needs to be expanded to satisfy today's applications, several areas are in need of an update. The proposed document will change the upper frequency limit to 40 GHz (with provisions in the document to potentially extend above 40 GHz based on test methods). Measurement uncertainties were not discussed in the IEEE Std. 1128-1998. In the new edition, measurement instrumentation and test methods are expected to be updated with guidance on estimating measurement uncertainties. In the proposed document, a section on absorber evaluations for high power applications is planned, and fire properties and test methods will be included.
The publication of CISPR 16-1-6 [1] in 2107 marked a significant change in the CISPR documents, for the first time the consideration of how to perform antenna pattern measurements in and determine the associated estimate of the uncertainty of those measurement. This is a look at that technique and presentation of how that helps and relates to measurement traceability.
The characterization of antenna radiation patterns in the millimeter wave band are particularly challenging. This is due to the fact that a misalignment of just a few millimeters between the probe and the antenna can generate substantial measurement errors. This paper describes a strategy to reduce measurement errors by introducing a highly precise measurement system using a 6-axis small robotic arm to characterize the performance of a phased array antenna operating at 60 GHz. The position accuracy of the robotic arm itself is approximately 20 m and a maximum far field distance of approximately 380 mm can be achieved. The robot is programmed to perform a spherical trajectory around the array with stops every 0.5⁰ along the path to gather the measured gain. It operates continuously by communicating with a computer, which triggers the network analyzer at preprogrammed locations. The system is tested initially using two horn antennas as the antenna under test (AUT), and the results are presented.
Over-the-air (OTA) performance evaluation requires large investments in anechoic environments. The question of minimizing the test distance is hence critical, and even more in this time where millimeter-wave technologies are about to be largely deployed in 5G devices. A recent publication has identified that direct far-field measurements can be accurately carried out at a much shorter range length than the well-known Fraunhofer distance. This paper introduces a further validation of this reduced distance, by employing an innovative method to simulate spherical measurements with arbitrary DUT, test probes and range lengths. The studies carried out confirm the relevance of this shorter distance, not only for the evaluation of the peak equivalent istropic radiated power (EIRP) or sensitivity (EIS), but also for the total radiated power (TRP) or sensitivity (TIS). In addition, it is demonstrated that the usual assumption that the TRP or TIS measurement is almost independent from the range length is flawed. Two main reasons relating to the test antenna are established which create this dependence: (i) OTA test probes have a finite resolution, and (ii) the probe and instrumentation typically captures the magnitude of two components of the E-field, which are not straightforwardly related to the power density in the near-field.
Radar scattering is typically represented as the RCS of the test object. The term RCS evolved from the basic metric for radar scattering: the ratio of the power scattered from an object in units of power per solid angle (steradians) normalized to the plane-wave illumination in units of power per unit area. The RCS is thus given in units of area (or effective cross-sectional area of the target, hence the name). Note that the RCS of the test object is a property of the test object alone; it is neither a function of the radar system nor the distance between the radar and the test object, if the object is in the far field. Because the RCS of a target can have large amplitude variation in frequency and angle, it is expressed in units of decibels with respect to a square meter and is abbreviated as dBsm (sometimes DBSM or dBm2). In terms of this definition, the RCS of a radar target is a scalar ratio of powers. If the effects of polarization and phase are included, the scattering can be expressed as a complex polarimetric scattering (CPS) matrix. The measurement of the RCS of a test object requires the test object to be illuminated by an electromagnetic plane wave and the resultant scattered signal to be observed in the far field. After calibration, this process yields the RCS of the test object in units of area, or the full scattering matrix as a set of complex scattering coefficients. This paper describes the planned upgrades to the old IEEE Std 1502™-2007 IEEE Recommended Practice for Radar Cross-Section Test Procedures [1]. The new standard will reflect the recent improvements in numerical tools, measurement technology and uncertainty estimates in the past decade.
The aim of the paper is to address a relevant issue in the Near-Field (NF) measurements: the reduction of the measurement time. Generally speaking, for a given hardware, two main directions can be pursued. The first requires the adoption of an optimal field sampling strategy that reduces the number of sampling points, and the length of the scanning path, without impairing accuracy. The second strategy adopts an optimized control system able to exploit at the best the available hardware (scanning system and measurement instrument). Indeed, the latency of the instrument defines the maximum probe velocity during the field acquisition. Accordingly, unlike the conventional continuous scanning, an optimized controller can speed up the scanning by moving the probe along the measurement trajectory with a variable velocity, accelerating and decelerating between two consecutive sampling points, to increase the average speed. However, the use of an optimized controller is fruitful only when the optimized sampling scheme allows large distances between two consecutive sampling locations, to increase as much as possible the maximum probe speed. In this paper, by suitably using both the above strategies, it is proposed a fast NF system, implemented on a microcontroller Arduino Due, an extremely cheap and off the shelf hardware, that is able to handle the scanner and realize the synergy between the optimized sampling and the optimized control strategy. The simulation and experimental results show a dramatic reduction of the measurement time (up to one order of magnitude) with a high tracking precision (also in accordance with the proposed methodology), and of the costs with respect to standard solutions.
Measurement scenarios for 5G mobile communications are nowadays challenging the industry to define suitable turn-key solutions that allow Over the Air (OTA) testing of non-connectorized devices. In order to respond to the needs of an effective measurement solution, that allow measuring all the required OTA parameters at both sub6GHz and mm-Wave frequencies and that could be deployed in a very short time, the Compact Antenna Test Range (CATR) was chosen. In this paper, we will summarize the performance and the testing capabilities of a short focal-length, corner-fed CATR design, providing a 1.5 m x 1.5 m cylindrical Quiet Zone, operating from 1.7 GHz to 40 GHz and upgradeable to 110 GHz, allowing OTA measurements of Active Antenna System (AAS) Base Stations (BS), installed at Ericsson premises in Gothenburg, Sweden in 2017.
An algorithm is developed for the extraction of constitutive parameters from bi-layered uniaxial anisotropic materials backed by a conductive layer. A method of moments-based approach is used in conjunction with a previously-determined Green function. Possible challenges related to measurement diversity are highlighted and a possible mitigation path is proposed.
Specular reflectance data of indoor interior materials is a prerequisite to analysis of the channel characteristics for new millimeter and submillimeter indoor wireless communications. Antenna property such as gain and radiation pattern is one of the key measurement quantities in electromagnetic wave metrology. This paper describes a specular reflectance and antenna property measurement system and shows measurement results of the specular reflectance of an Acetal plate and the antenna property of a 24 dB horn antenna in 325-500 GHz frequency range.
This paper presents a time domain antenna measurement technique by using a low cost software defined radio receiver. The technique aims to resolve measurement challenges derived from antennas where the reference signal is not accessible. The phase reconstruction implemented in this work is based on calculating the Fast Fourier Transform of the time domain signal to estimate the power spectrum and the relative phase between measurement points. In order to do that a reference antenna is used to retrieve the phase, providing a full characterization in amplitude and phase of the electric field and allowing source reconstruction. The results demonstrate the potential of this technique for new antenna measurement systems and reveal some of the limitations of the technique to be optimized, like the undesired reflections due to the interactions between the probe and the reference antenna.
Prior literature in the subject area of far-field antenna measurements has demonstrated an extrapolation technique to isolate and correct the errors due to near-zone proximity effects as well as multi-path range reflections, thus allowing data to be collected at distances much less than the conventionally defined far-field criteria. This paper describes a modern, indoor, far-field antenna measurement range specifically designed to support this extrapolation technique. A multi-axis positioning system featuring a mobile horn tower capable of motion along the chamber Z-axis is emphasized. High-speed RF instrumentation and advanced software control support the full automation of the extrapolation method. This contemporary approach is demonstrated, and measurement examples are provided for an X-band slotted waveguide array. The resultant far-field gain calculations are also compared to similar data extracted using near-field scanning techniques.
The portable antenna measurement system PAMS was developed for arbitrary and irregular near-field scanning. The system utilizes a crane for positioning of the near-field probe. Inherent positioning inaccuracies of the crane mechanics are handled with precise knowledge of the probe location and a new transformation algorithm. The probe position and orientation is tracked by a laser while the near-field is being sampled. Far-field patterns are obtained by applying modern multi-level fast multipole techniques. The measurement process includes full probe pattern correction of both polarizations and takes into account channel imbalances. Because the system is designed for measuring large antennas the RF setup utilizes fiber optic links for all signals from the ground instrumentation up to the gondola, at which the probe is mounted. This paper presents results of the Ka-band test campaign in the scope of an ESA/ESTEC project. First, the new versatile approach of characterizing antennas in the near-field without precise positioning mechanics is briefly summarized. The setup inside the anechoic chamber at Airbus Ottobrunn, Germany is shown. Test object was a linearly polarized parabolic antenna with 33dBi gain at 33GHz. The near-fields were scanned on a plane with irregular variations of over a wavelength in wave propagation. Allowing these phase variations in combination with a non-equidistant grid gives more degree of freedom in scanning with less demanding mechanics at the cost of more complex data processing. The setup and the way of on-the-fly scanning are explained with respect to the crane speed and the receiver measurement time. Far-fields contours are compared to compact range measurements for both polarizations to verify the test results. The methodology of gain determination is also described under the uncommon near-field constraint of coarse positioning accuracy. Finally, the error level assessment is outlined on the basis of the classic 18-term near-field budgets. The assessment differs in the way the impact of the field transformation on the far-field pattern is evaluated. Evaluation is done by testing the sensitivity of the transformation with a combination of measured and synthetic data.
In this paper, an analysis of the intermodulation effects observed in radio communication signals measurement systems, placed in vicinity of highly congested FM stations sites is presented. This work is required due to intermodulation issues have been a widely-studied topic in frequency analysis for communication stations, nevertheless the perspective of those analysis is mainly focused on avoiding the generation of intermodulation products that represents real spectrum occupancy but there is no an analysis for the intermodulation caused by the susceptibility of monitoring devices that, due to the non-linear behavior of the electronic components, present intermodulation products like real signals. The causes of intermodulation phenomena are discussed, which are mainly due to the non-linear behavior of one or several components of the monitoring system, and due to the proximity between transmission sites or between the measurement system and the site of the transmission. As a complement, a review of technical specifications for different monitoring instrumentation like receptors, active and passive antenna system, amplifiers, and filters and its effects on unwanted Intermodulation generation is done. With the goal of suppressing or minimize the Intermodulation Distortion of the electronic devices used for monitoring, a procedure for identification, according ITU recommendations, based on attenuators for common spectrum analyzers and using passive antennas have been designed and tested in different sites in different countries. The measurements obtained with different active devices and passive devices in the measurement system are presented and compared, identifying with the procedure the spectral characteristics of the intermodulation products and the reduction or filtering of these effects analytically and graphically.
For high speed and high data-rate communications, operating frequency bands of wireless communication systems have been moving to submillimeter frequency range and their bandwidths have been broadening. IEEE 802.15 THz Interest Group (IEEE 802.15 IGthz) has been performing a channel characteristics study for future indoor millimeter and submillimeter wireless communications in the frequency range of 75 - 110 GHz and 270 - 320 GHz. Specular reflectance data of indoor interior materials is a prerequisite to analysis of the channel characteristics of new indoor millimeter and submillimeter wireless communications. Specular reflectiondescribed by the law of reflection states that the direction of the incident wave and the direction of the reflected wave make the same angle with respect to the surface normal, thus theangle of incidence is equal to that of reflection. This paper describes a specular reflectance measurement system and shows measurement result of dielectric plates in the frequency range from 110 GHz to 325 GHz. Specular reflectance measurement system consists of an S-parameters measurement system and a specular reflectance measurement apparatus. The S-parameters measurement system consists of a 67 GHz vector network analyzer used as the main frame and three frequency extenders which are operating at three frequency bands (D-band (110 -170 GHz), G-band (140-220 GHz) and J-band (220-325 GHz)), respectively. The specular reflectance measurement apparatus consists of a transmitting part, a receiving part, and a MUT holder which is positioned in the middle of the transmitting and receiving parts. During the specular reflectance measurement, the transmitting part is fixed while the MUT holder and receiving part are coaxial-rotating with 1:2 speed ratio. The transmitting and receiving frequency extenders are installed on the transmitting and receiving parts, respectively. For the specular reflectance measurement, one measures the transmission coefficient (S21_MUT) corresponding to the specular reflectance of an MUT mounted on the MUT holder. After replacing the MUT with a metal plate, one measures the transmission coefficient (S21_metal) corresponding to the specular reflectance of the metal plate, assumed to be -1. Specular reflectance of the MUT is obtained by taking the ratio (S21_MUT/S21_metal) of the respective transmission coefficients corresponding to the specular reflectance of the MUT and the metal plate. Multiple reflection effects between the transmitting and receiving antennas can be averaged out and minimized by averaging the transmission coefficients measured with changing the separation distances between the two antennas by ?/8 interval (i.e. initial distance + n·?/8, n=0,1,2,3). Specular reflectances of dielectric plates are measured in the 30° to 70° incident angle range with the developed measurement system in the frequency range from 110 GHz to 325 GHz. Description of the detailed measurement system and measurement result will be presented at the symposium.
Several instances in antenna design are known where an anisotropic material is useful ; however, finding a naturally occurring anisotropic material with the required dielectric tensor is often an impossibility. Therefore, artificially engineered anisotropic dielectric materials must be designed, tested, and implemented. In a previous paper by the authors [1], the design and initial measurement of an anisotropic material in Cartesian coordinates was presented along with predictions of how the material could be used to extend the bandwidth of a simple antenna structure. In this paper we shall present the final implementation of the anisotropic material (with a tensor implemented in cylindrical coordinates) along with data on the material properties, the resulting antenna bandwidth, and radiation pattern. Design considerations for implementation of this approach shall be discussed along with practical limitations. Data shall also be presented on an unexpected result showing that that a reduced volume of anisotropic material produces favorable results. Measured data shall be compared with values predicted using finite difference time domain (FDTD) software and applications of this new broadband antenna for range operations will be discussed. [1]. D. Tonn, S. Safford, M. Lanagan, E. Furman, S. Perini, “DESIGN AND TESTING OF LAYERED ANISOTROPIC DIELECTRIC MATERIALS”, AMTA 2015 Proceedings, Long Beach CA, October 2015.
Raytheon, El Segundo, CA chamber #2 is a dual reflector, indoor compact range that is the largest facility of its kind within the company. A series of tests were performed to characterize the measured transfer function of the chamber because of a recent capital upgrade of the range measurement system. The purpose of this paper is to document and discuss the results of the characterization testing, review how the measured transfer function of the range was determined, and compare the current results with both past data and analytical predictions, and demonstrate how this transfer function is used for antenna and radar cross section (RCS) measurement characterization. The measured transfer function of the range is used for both antenna and RCS measurement characterization. For antenna measurements, the transfer function is used in the Friis transmission equation to determine, for example, the expected power at the receiver given the transmit power and gain of both the transmit antenna and the antenna under test. Appropriate amplification and/or attenuation can determined as part of the test planning process saving time during test setup and test execution. For RCS measurements, the transfer function was recently utilized to study the benefits and challenges of relocating our instrumentation radar from a smaller compact range to this large compact range. The motivation for the study was enhanced measurement capability for larger targets and lower frequencies. This study utilized noise equivalent RCS (NERCS) as the metric and transmit power, pulse width, and pulse integration as the study parameters to find a practical solution for optimizing NERCS.
A multi-probe array (MPA) spherical near-field antenna measurement system, comprised of COTS equipment, has been developed for testing UHF antennas mounted in an aircraft rotodome. The spherical probe radius is 5 meters, which accommodates a 24 ft. diameter rotodome. The probe array, arranged in a circular arc about the test zone center, provides rapid time multiplexed samples of dual polarized spherical theta angle measurements. These measurements are collected at incremental steps of spherical phi angles, provided by a floor azimuth turntable. The rotodome is mounted on the azimuth turntable, and is rotated 360 degrees during a data collection. During one azimuth rotation, completed in a few minutes, a full set of 3D, dual polarized, multi-frequency near-field pattern data is collected. The data is transformed to full 3D far-field patterns in another few minutes, providing a complete rotodome test time within 15 minutes. The entire system is contained within a room 42’ x 42’ x 25’. This paper will describe the test requirements, physical requirements of the DUT, size constraints of the facility, and measurement speed goals. Alternate solutions and range geometries will be discussed, along with why the MPA solution is best given the requirements and size constraints. The system will be described in detail, including discussion of the room design, RF instrumentation, multi-probe array, positioning equipment, and controllers. Measurement results will be presented for test antennas of known pattern characteristics, along with other performance metrics, such as test times.
Several instances in antenna design are known where an anisotropic material is useful ; however, finding a naturally occurring anisotropic material with the required dielectric tensor is often an impossibility. Therefore, artificial anisotropic dielectric materials must be designed, tested, and implemented. In this paper we shall present a layered artificial anisotropic dielectric material with a biaxial permittivity tensor. This material is designed to be used in conjunction with an antenna in order to improve antenna bandwidth. The design motivation behind this material shall be discussed, along with its implementation, the measurement of its permittivity tensor, and testing characterization with a prototype antenna. Results from CST Microwave Studio® simulations and the mixing rules from dielectric material science will be compared with the measured data. Test fixture design and instrumentation will also be presented. Predictions on various types of artificial anisotropic dielectrics suitable for future applications will also be discussed.
This paper describes the mechanical design, control instrumentation and software for a precision model positioning system developed for use in the Experimental Test Range (ETR) electromagnetic test facility at NASA Langley Research Center. ADC has a contract to design, build, and install major components for an updated indoor antenna characterization and scattering measurement range at NASA Langley Research Center. State-of-the-art electromagnetic systems are driving a demand to increase the precision and repeatability of electromagnetic test ranges. Sophisticated motion control systems can help meet these demands by providing electromagnetic test engineers with a level of positioning fidelity and testing speed not possible with previous generation technology. The positioning system designed for the Experimental Test Range at NASA Langley Reseach Center consists of a rail positioning system and four rail positioning carriages: an antenna measurement positioner, scattering and RCS measurement pylon, an azimuth rotator to support foam columns, and an electric personnel lift for test article access. A switching station allows for rail positioning carriages to be quickly moved on and off of the rail system. Within the test chamber there is also a string reel positioning system capable of positioning test articles within a 40’ x 40’ x 25’ volume. Total length of the rail system is 112’ with laser position encoding for the final section of the rail system. Linear guide rails are used to support the carriages and each carriage is position with a rack and pinion drive. Rails mount to steel weldments that are supported with 8” diameter feet. Capacity of the rail system is 7,300 lbs. A switching station allows for positioning components to be moved off of and onto the rail system independently and a place to dock positioning components when they are not in use. A curved linear guide rail supports the switching station so that the platform can be rotated manually. Hardened tapered pins are used to align the switching station with mating rail segments. The scattering and radar cross section (RCS) measurement pylon is a 4:1 ratio ogive shape and has a 3,000 lb load capacity. A pitch rotator tip or spline driven azimuth tip can be mounted to the pylon. The spline drive shaft can be removed to allow for the pitch tip to be mounted to the end of the pylon. Total height of the pylon is 18’ from the floor to the pitch positioner mounting plate. Keywords: RCS, Scattering, Pylon, Positioner, Antenna Design, Rotator, Instrumentation, electromagnetic, Radio Frequency, Radar
Antenna measurement facilities face their physical limits with the growing size of today’s large and narrow packed antenna farms of telecom satellites but also of large unfurlable reflector antennas for low frequency telecom applications. The special operational constraints that come along when measuring such large future antennas demand for new measurement approaches, especially if the availability or realization of present measurement systems with large anechoic chambers is not an option. This paper presents a new system called PAMS (Portable Antenna Measurement System). The most characteristic part of PAMS is that the RF instrumentation is installed inside a gondola that is positioned by an overhead crane. The gondola is equipped with one or several probes to scan the near-fields of the antenna under test. With a modified crane control the gondola can be placed anywhere within the working space of the crane, which is considered as being giant in comparison to measurement volumes of existing large antenna test facilities. The whole system supports but is not limited to common classical near-field scanning techniques. Thanks to new near-field to far-field transformations the system can deal with arbitrary free form scanning surfaces and probe orientations allowing measurements that have been constrained by the classical near-field theory so far. The paper will explain the PAMS concept on system level and briefly on sub-system level. As proof of concept, study results of critical technologies are discussed. The paper will conclude with the status about on-going development activities.