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.)
Abstract The undergoing development of GPS system requires the integration of all three GPS bands: L1 (1575MHz), L2 (1227MHz), and L5 (1176MHz) into one miniature antenna. The objective of work is to develop a small GPS antenna (less than 1/10 wavelength) to cover all the three GPS bands with a minimum bandwidth of 24MHz in each band and a minimum gain of 0 dBic (RHCP). Three novel miniature antenna designs: Quad-F antenna (QF), proximity-fed stacked patch (PFSP) antenna and channel fed ring (CFR) antenna were investigated. These antennas utilize high-index inhomogeneous dielectric materials to achieve antenna miniaturization, mode excitation and mode control. The full-wave simulation (HFSS) and measurement results are presented and discussed in this paper.
Abstract— Microwave, total-power radiometers are calibrated by observing sources of known brightness temperature. Free-space calibrations are usually performed assuming far-.eld interactions, although the actual calibration source may be well into the near-.eld region of the radiometer antenna. Here, we simulate the free-space coupling between radiometer and calibration target to explore the potential contribution of proximity effects to measurement uncertainty.
Abstract This paper describes the development of an inexpensive high-precision Compact Antenna Test Range (CATR) located at CSIRO, Australia, for the measurement of electrically large aperture antennas (>250.) at 200GHz. The CSIRO designed CATR is based on a single parabolic offset reflector that has been machined from a single billet of cast aluminum plate to provide a RMS error of better than 16 µm as determined from photogrammetry. The design is unique as it leverages CSIRO’s ability to accurately design and manufacture feed horns with highly optimized radiation patterns; in this case corrugated feed horns with flat amplitude tapers at the beam maximum and fast amplitude roll-off at the edge illumination angle of the reflector. The advantage of using this type of feed horn is that it eliminates the need to specially treat the edges of the CATR reflector and therefore greatly reduces the cost of the system.
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.
Measurements of the insertion loss and impedance in antenna characterization are very important and should be traced back to national attenuation and impedance standards. Vector network analyzers commonly used to measure the impedance are not suitable for millimeter-wave antenna measurements because movement of DUT (Device Under Test) during measurement is required and long cable of high loss for connection between the network analyzer and the DUT mounted high above the floor increases measurement uncertainty. In this paper, a conventional microwave subsystem based on external mixer configuration is modified to measure the impedance of DUT without using the vector network analyzer in millimeter-wave frequency range.
We propose a novel microwave measurement system that consists of transmitting and receiving optical-fiber link systems. The system can measure parameters of S11 and S21 of an antenna under test (AUT) by the procedure of OSLT 1-pass and 2-port calibration, due to the simultaneous measurement of its relevant signals going into, reflected and transmitted from the AUT. It is shown by some experiments that the S11 and S21 of the two log-periodic antennas measured by the optical link system agree very well with those by a conventional system using metal coaxial cables. It is proved that the optical system can be used to evaluate the S11 and S21 of the AUT in broad frequency range without using coaxial cable.
Planar near-field antenna measurement facility at KRISS has been upgraded to V-band (50 GHz – 75 GHz). This paper describes the planar near-field antenna measurement facility that consists of a planar near-field scanner, a microwave subsystem and an extrapolation range, and shows the measurement results of a V-band near-field probe and a Cassegrain antenna.
Polymers are generally characterized in two broad characters: thermoplastic and thermoset. The former, including many of the plastics used in everyday life – such as containers, Frisbees, etc. – have their polymer chains formed prior to use in commercial applications. The latter, and the subject of this paper, have polymer chains that are formed during a curing process. Examples of commonly thermoset polymers are epoxies commonly available in hardware stores. Curing is often accelerated by heating. Curing is also exothermic with a compositional change. It is important to measure the changes in the material properties in order to correctly assess the state of the cure and the resulting material. This final state is critical for antenna applications where the antenna is conformally mounted in a structure, such as fiberglass, that involves a thermoset polymer. In this paper, improvements to Michigan State’s characterization system will be described along with underlying numerical modeling used to investigate thermoset curing.
Electromagnetic material characterization is the process of determining the complex permittivity and permeability of a material sample. One common method uses measured scattering parameters from a sample mounted in a coaxial transmission line to calculate the material’s permittivity and permeability. If the material uniformly fills the cross-sectional area of the transmission line, then the standard Nicolson-Ross-Weir (NRW) algorithm [1][5] can be used since only a single dominant TEM mode will be supported. However, if gaps exist between the material sample and the coaxial conducting boundaries, higher-order modes are excited which introduce error into material characterization measurements since these modes are not accommodated in the NRW algorithm. This paper proposes two techniques for mitigating the air gap error in coaxial test fixtures. The first method utilizes a quasi-TEM approach whereas the second method invokes a more rigorous mode-matching analysis. In either case, expressions for the theoretical scattering parameters are obtained and are subsequently compared to the scattering parameters obtained via measurement. For both methods, the resulting error between the theoretical and measured scattering parameters is iteratively minimized until the material’s properties are calculated within a specified tolerance.
Inversion of the material parameters for a sample usually requires that the sample fill the waveguide cross-section. Alternative methods require that a non-filling sample be aligned along the center-line of the waveguide. However, it is not known how errors in placement impact the accuracy of the inversion. Hence, a numerical simulation to assess these errors is beneficial to the community. The extraction of the S-parameters from a rectangulardielectric-filled waveguide is conducted numerically by means of the Finite Element Method (FEM) and the Thru-Reflect-Line (TRL) calibration technique. Three different ratios of dielectric sample width (d) to waveguide width (a) are primarily studied. The results are then validated with experimental data on the X-band. An assessment of error with respect to position will be presented at the meeting.
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
This paper describes the first experience gained with a new carbon composite compact range reflector (C3R2). The reflector’s backup structure is made entirely of carbon fiber reinforced composite material. An outstanding advantage of this design is its superior mechanical and thermal-environmental stability. This yields improvement in the overall performance. We have revised the process by which compact range reflectors are designed and modeled, making use of professionally authored software. We describe the results of electromagnetic field probe measurements made at the factory. Special attention is given to new results at W-band – in the 75 to 100 GHz regime.
A generally practiced way to improve the sidelobe accuracy in antenna measurements is by repeating and averaging the measurements in different positions in the quiet zone (also referred to as APC or AAPC, depending on the application). An alternative new way for improving the accuracy of compact range measurements is by moving the compact range feed in different locations. This can easily be achieved for both horizontal and vertical directions. Although feed scanning causes a boresight shift, this can be easily compensated if the feed positions are selected intelligently. A significant measurement speed improvement can be realized by using multiple feeds in the relevant locations, instead of moving a single feed sequentially into these locations. Feed scanning APC has been successfully tested in the Ericsson Microwave Systems Compact Range, where it is now practiced in high accuracy radar antenna measurements.
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.
Direction Finding (DF) systems have long been an area of intense research within the Air Force Research Laboratory. There are presently two types of existing DF systems: wideband multi-mode antennas and interferometers. Wideband multi-mode DF systems allow for a large bandwidth but present a low resolution and high variance. Interferometers provide high accuracy and low variance but are narrow band and require a large number of single aperture antenna elements. An effort has commenced to incorporate a broadband DF system with high resolution using two multi-mode spiral antennas. Using an interferometer of multi-mode elements, we can provide high resolution and wideband operation without using numerous antennas. This paper presents the results of extensive wideband measurements carried out on a four-arm spiral antenna and the associated modeformer. These measurements are used to assess and validate the angle estimation capability of the multi-arm spiral antenna.
This paper discusses a miniature low profile UWB spiral antenna design approach. The antenna is miniaturized by using a combination of dielectric loading and inductive loading to slow down the traveling wave on the spiral. In addition, the antenna is backed by a hybrid ferrite/PEC surface which reduces the profile while maintaining the antenna performance at lower frequencies.