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Hologram-based compact antenna test range (CATR) is a promising way to measure submm wave antennas. The hologram quality and the measurement accuracy of the hologram-based CATR is limited by the hologram manufacturing process. The measurement accuracy can be improved using pattern correction techniques. However, at submm wavelengths only the antenna pattern comparison (APC) technique is able to correct the effects of the spurious signals originating from the residual inaccuracies of the hologram pattern. A problem with the APC technique is that it is time consuming. This paper introduces a pattern correction technique for hologram-based CATRs. The technique is based on averaging in the frequency domain, and it is able to correct spurious signals originating from the hologram. Proposed technique is also faster than the APC technique. The proposed method is verified with a combination of measurements and simulations.
ABSTRACT The proposed system is aimed at offering a simple and cost-effective solution for antenna radiation pattern measurements coherently in the higher millimeter-wave range, particularly at the 77 GHz and 120 GHz frequency bands, using harmonic mixers and the multi-source option of the ordinary Vector Network Analyzers (VNAs). Within this paper, the detailed design procedures of every module of the harmonic mixers as well as the block diagram of the modified measurement setup are to be illustrated, in addition to the simulation and experimental results of every submodule in the system. Finally the link budget calculations of the whole arrangement will be demonstrated so as to show the relevant dynamic range of the measurements.
In previously reported work, the groundwave correction approach was presented for measurement of the gain of vertically polarized antennas in the presence of a seawater groundplane. This approach was limited to application in the commercial HF (2-30 MHz) band due to a variety of factors, including the geometry of the test range, and so can not always be applied at higher frequencies. This paper will discuss a method for measuring the gain and azimuthal pattern performance of antennas operating in the commercial VHF band (50-175 MHz) that has been developed at the NUWC Fishers Island Antenna Range, and will discuss its application and implementation.
The electromagnetic field as projected by a 12 ft. prime focus offset fed compact range reflector with r-card edge terminations located in an existing chamber 20 ft. high, 30 ft. wide and 66 ft. long was probed using a broadband antenna to sample the field at 12 inch increments from the center line to the anechoic chamber wall. The purpose of the test was to evaluate the field roll off in dB to see if a narrower room would significantly impact the performance of the existing reflector system. The new chamber is 20 ft. high, 20 ft. wide and 40 ft. long. The probe data at six frequencies from 2.1 to 17.8 GHz indicated that 10 ft. off the center line the measured field level was -20 dB or greater below the level of the test region, which was our maximum acceptable field level goal. It is expected that the sidewall absorber will provide over 20 dB of bistatic attenuation for a total reflected field level of -40 dB, and is sufficient for conducting antenna pattern measurements in an anechoic chamber. Key Words: Compact Range, R-Card Terminations, Absorber Performance
The present paper introduces a new antenna design to be used in anechoic chambers. When measuring 3D patterns the receiving antenna in the anechoic chamber must be able to sense the two orthogonal components of the field that exist in the far field. This can be accomplished by mechanically rotating the source horn in the chamber. A better and faster approach is to use a dual polarized antenna and electronically switch between polarizations. This new design is a broadband (2-18GHz) antenna with dual polarization. The antenna is a ridged guide horn. The novel part is that the sides have been omitted. Numerical analysis and measurements show that this open-sided or open-boundary horn provides a better and more stable pattern behavior for the entire band of operation as well as good directivity for its compact design. The radiation and input parameters of the antenna are analyzed in this paper for the novel design as well as for some of the early prototypes to show some of the ill effects of bounded quadridge horn designs for broadband applications. Mechanically the antenna is built so that it can be mounted onto the shield of an anechoic room without compromising the shield integrity of the chamber.
In this paper, we study the possibility to use an amplitude hologram as a reflection-type collimating element to produce a plane wave in the compact antenna test range (CATR). So far, we have used holograms as transmission-type elements only. The hologram studied here has a diameter of 600 mm and it operates at the frequency of 310 GHz. It is a computer-generated slot pattern etched on a thin metal-plated dielectric film. We have simulated and measured the plane wave field reflected from the hologram. The maximum measured ripples are only 1.6 dB and 20°, peak-to-peak. The reflection-type hologram has some advantages over the transmission-type one. For example, the power loss is about 4 dB lower for the reflection-type hologram. In addition, a CATR based on the reflection-type hologram can be situated in a much smaller space. To demonstrate the capability of the reflection-type hologram in actual antenna testing, the radiation pattern of a small reflector antenna was measured at 310 GHz.
A strong interest exists in the commercial and military sectors for small and broadband antennas. For instance, in the automotive industry there is a need for a single antenna operating in the frequency range of 825-2500 MHz (AMPS, DAB, GPS, PCS, SDARS). For military applications, there is also a need to have a single aperture which permits operation in different communication bands and can be also used for imaging and guidance applications. These needs require wide band antennas, such as the miniaturized spiral antenna. In this paper we present the implementation of a spiral antenna situated on a ground plane that is fully functional at the size of 0.16 wavelength onward. Low profile (0.05 wavelength) and broadband operation design goals bring unique challenges, which must be confronted with multiple-front techniques. A combination of antenna geometry design and material loading results in the desired miniaturization effect. Further techniques, including the use of distributed resistors ensure good axial ratio and VSWR. Pattern uniformity and phase linearity of the antenna was also improved. In addition, we also examine the effectiveness of broadband spiral antenna miniaturization as a function of loading material’s dielectric constant.
ABSTRACT We are in the era of wireless communications and devices. The antennas that enable these technologies are electrically small and can be challenging to test and analyze. Yet, the industry is becoming more standardized, and so too are the tests and certifications being adopted to validate these antennas. These antennas must undergo “antenna measurements” to characterize such information as far-field patterns and gain. Additionally, hand-held devices, such as cell phones, must satisfy requirements of the Over-the-Air (OTA) performance tests as specified by the Cellular Telecommunication and Internet Association (CTIA). These tests require a measurement system that can accurately collect data on a spherical surface enclosing the AUT. This system also has to provide the appropriate data analysis capabilities and has to be constructed from dielectric materials to minimize reflections.
Radiation efficiency is an inherent property of an antenna that relates the net power accepted by an antenna to the total radiated power. It is especially useful for handset antennas where the radiation patterns are often of less use for comparing competing antennas. Radiation patterns though not as useful for direct comparisons, still provide one method by which efficiency can be calculated. To accurately calculate the efficiency from patterns, it becomes necessary to obtain multiple pattern measurements (cuts). A larger number of cuts whilst yielding more accurate efficiency results, significantly increase measurement time. Thus an antenna designer is often forced to trade off accuracy against measurement time since both quick and accurate measurements are desired. The focus of this paper is to quantify this trade off, in order to provide guidelines on the number of pattern measurements required for accurate efficiency results. Simulated and measured far-field radiation patterns are used and various numbers of cuts are utilized to quantify the loss in accuracy with a reduced number of cuts. The techniques outlined are geared primarily towards cellular handset antennas.
This paper presents the methodology we use to measure radiation patterns of small terminal antennas. The in-house developed measuring system is capable to record radiation patterns on the entire sphere and recorded values are not corrupted due to proximity of a large dual-axis positioner. As a feed cable had been identified as a primary factor modifying electrical properties of small antennas, we eliminated the feed cable at all by use of a built-in generator. Such generator is mounted back-toback to the measured antenna. Most preferable the generator should be supplied with a battery, but use of a wired dc supply with a typical supplier is also acceptable in many instances. Such a concept of setup brings about many problems with providing a reference signal to an antenna receiver. Perhaps, firm operation of a reference channel is hard to accomplish without using advanced engineering means. Among them may be a switch with permanent power monitoring in its channels or an optoelectronic leg in the antenna microwave feed.
A method for detecting a single faulty element in a linear array using neural networks is presented. A feed forward back propagation neural network is trained to detect the faulty element. Given the error patterns due to the faulty array, the network can predict the number of faulty element. A linear array of 21 elements with uniform excitation and uniform spacing is considered. Indexing Terms: Array, Neural Networks, Feed Forward, Back Propagation.
Doing EIRP measurements in a nearfield facility is a known procedure. However, if the transmitted power is relative high, options are limited and care must be taken to prevent damage on equipment and absorbers. This paper describes how EIRP and pattern measurements for high power antennas and transmitters can be done in an indoor facility, and describes various considerations, choices and practical aspects. An example shows that even high power wide-band systems can be measured in near-field facilities.
The KRISS is in the process of completing the construction and installation of a planar near-field antenna test facility in the frequency range of 2 GHz to 50 GHz. This paper describes the planar near-field antenna test facility. Comparison of the far-field pattern, for verifying the antenna test facility, using a parabola antenna as artifact is also described. The patterns were measured by using the installed antenna test facility and a method developed by our group and showed good agreement.
In this paper two planar near-field scan plane reduction techniques are considered and results are presented. It is shown how truncation based on field intensity contours, instead of simple geometric truncation can in some cases improve the efficiency of the truncation process. Both techniques are applied to measured data sets and it is shown how these methods can be used to reduce data acquisition times while also assessing the impact of the total acquisition surface reduction on the far-field radiation pattern integrity.
At the Fraunhofer IIS many antenna design and measurement problems deal with electrically small antennas for different wireless communication links. Therefore we want to establish a meaningful procedure to measure the pattern and also the gain of these antennas quite exactly.
This paper describes a Composite Near-Field Scanning Antenna Range for frequency bands that extend from X- Band in the microwave frequency regime through W- Band in the millimeter-wave regime – i.e. 8.2 through 110 GHz. We show some of the initial checkout data using pyramidal standard gain horns and compare the patterns to theory.
The frequency band 3.1 – 10.6 GHz has been opened for commercial use. Design and measurement of Ultra Wide Band (UWB) antennas in UWB communication systems are growing rapidly due to difficult requirements of UWB antennas such as small size, non-dispersiveness and ultra wide-band characteristics. In this paper, a CPW-fed planar ultra-wideband antenna is presented. Measurement results show that the radiation gain patterns are strongly influenced by the interaction signals between the antenna and the cable, especially at low frequency band. The performance of this antenna is also dependent on the leakage current along the cable. The antenna is mounted on various rectangular metal electronic devices such as DVD players or digital camcorder to investigate the interaction between the antenna and nearby metal objects. The antenna proves to be a good UWB antenna with broad radiation pattern, consistent gain and small group delay variation. The experiment shows that the performance of this antenna depends heavily on the cable interactions and the object that it is mounted on.
It is well known that a microstrip transmission line can radiate if it is excited in its first higher order mode (with the fundamental or dominant mode suppressed). A new microstrip configuration is proposed that supports the first higher order mode while suppressing the fundamental mode. To quantify the leakage constants in the two cases for comparison purposes, several experimental means are considered to determine the source amplitude distribution from which the leakage constants may be deduced. First, an approximation to the source distribution is determined from the far field patterns themselves. Second, the source distribution is determined by carefully probing the near field. This paper uses these techniques to verify the performance of a new leaky wave antenna design.
The Fresnel zone plate lens antenna has seen extensive investigation in the recent past, and has been used at frequencies from the microwave range through the millimeter-wave region to terahertz frequencies. For the usual zone plate antenna employed at these frequencies, path correction (i.e. phase adjustment) is accomplished by cutting different depths (grooves) in a dielectric plate or by using two or more dielectrics having different dielectric constants. Usually the focal length and aperture diameter are comparable, unlike the Fresnel zone plates which have been used at optical wavelengths. The planar configuration offers advantages of low cost, low loss, low weight, and ease of fabrication, while providing better performance, in some cases, than a true hyperboloidal or spherical lens or reflector antenna. Although the gain of the zone plate is normally less than that of a true lens, the reduced attenuation gives a greater overall system gain for the zone plate. Many measurements have been made to determine the antenna patterns (including beamwidth and sidelobe level), gain, efficiency, frequency dependence, focal behavior, aberrations, and bandwidth for both transmission and reflector designs. The major area of current debate is the question of efficiency as understood from analysis compared with actual measurements. This paper summarizes the parameters of zone plate antennas, and defines areas where more measurements are needed to fully describe their characteristics.
Antennas that are used aboard next generation airborne, maritime and ground vehicles are increasingly required to satisfy both conventional radiation pattern and gain requirements as well as new radar cross section (RCS) requirements. In response to these requirements, Nurad and ORBIT/FR recently completed design, installation, and verification of a high performance, multi-purpose antenna and RCS measurement facility at the Nurad site in Baltimore, Maryland. This compact range facility features a 60x36x26 foot shielded anechoic chamber and a precision machined, serrated edge, offset-fed reflector system that produces a 5.3’H x 8’W x 8’L quiet zone over the 2-50 GHz frequency range. The facility includes a unique feed room structure that positions the primary radar components close to the feed mount for RCS measurements, and allows for easy change of compact range feed antennas. A removable pylon assembly is used for test body support during RCS testing, and a unique add on section to the pylon rotator allows for inclusion of a roll axis that enables measurement of small and medium size antenna assemblies without removing the pylon. Measurements performed on low RCS standard targets and antennas made in the chamber demonstrate that the chamber provides a high performance measurement environment while providing ease of use and rapid configuration and target changeover.