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Testing of the MESSENGER Spacecraft Phased Array Antenna
Techniques for measurement of the phased-array antenna system include ambient temperature measurements in a compact antenna range, thermal vacuum testing, and spacecraft level testing. There have been two novel developments in the characterization of the phased-array system. The first is a “gain envelope” response, which is a measurement of the gain of the array at the intended scan angle as the array is electrically scanned in 1° increments. This response was produced through a combination of hardware and test software to synchronize the gain measurement with the mechanical and electrical scanning. The second is a phase steering verification test that utilizes couplers in each steered element in conjunction with previously measured element patterns to confirm that the antenna beam is steered properly. This method allows functional verification of the phased-array system while radiating into an RF absorber-lined hat during spacecraft-level tests.
Antenna Array Measurement Using Multi-port VNA
Measurements of antenna array’s patterns are usually taken with feed networks, but for some digital beam forming arrays, feed networks are not included. To measure such arrays in traditional way, we must design a feed network first, which is too complex and inefficient when steering is required. A VNA can act as a multichannel receiver to form a digital beam forming array for testing. Today’s VNA may have many test ports (for example, 9-ports in Agilent E5091A multiport test set and 11-ports in Advantest R3986 multiport test set.) designed for multiport devices, which is very suitable for measuring small arrays without using feed networks. Another advantage of this method is that it can eliminate errors from imperfect feed networks. Automatic measurement program is required to calculate array patterns from S-parameters, which is easily developed using Labview or Matlab. Test results of a 3-elements adaptive anti-jam array with different jam DOA are demonstrated.
Implementation of Phase Retrieval Techniques for Phased Array Antenna Measurements
For enhancing the performance of existing near field antenna test facilities it is quite reasonable to use both conventional (the amplitude and phase measurements) and the phaseless measurements techniques during electrically scanning phased array antennas (PAA) testing. This simple yet critical approach helps to improve the quality of PAA alignment and testing reducing measurement errors and saving costs. In this way many difficulties related to precise phase measurements are overcome. Both simulation and measurement results will be presented to demonstrate the utility of such approach to PAA alignment and determination of its parameters. Comparison will be made between the PAA patterns for electrically scanned beams calculated using traditional near field - far field (NF/FF) transformations, the phaseless methods and the results obtained applying both measurement techniques.
Varied Windows for Time Domain Antenna Near Field Measurements
This paper presents a novel variable width time gating technique, which is applied to planar and cylindrical near-field data in impulse time-domain antenna near-field measurements. Due to the changing distance between the probe and the antenna under test (AUT) in planar and cylindrical scans, the conventional fixed time gating technique causes problems to remove multiple reflections from the desired AUT response. It further limits the application of time-domain measurement to planar and cylindrical scans. The new variable width time gating technique provides a flexible way to solve these problems. Test results for both planar and cylindrical near-field measurements are presented. The difference of far-field patterns between time-domain and frequency-domain near-field measurements is noticeable. We also show the effects on the far field patterns due to fixed and variable time gating windows. We further conclude that the time-domain technique also works for planar and cylindrical near-field measurements by using variable width time gating technique.
Design and Construction of a Production Antenna Test Cell
In order to accommodate the high volume of RF testing required for a specific large production antenna build, Ball Aerospace designed and built a miniature antenna test cell. The test cell is capable of performing VSWR measurements and antenna patterns, namely principal planes and conics, per the test requirements of the program. A significant effort was made to streamline the manufacturing process of the antennas and minimize the test time in order to reduce costs and meet production goals. The test cell features an integrated laptop PC, barcode scanner, and requires a HP8753E network analyzer. Human factors and process flow were important drivers in the chamber’s design. Specific test parameters for the antennas reside in a database referenced by a unique bar-code serial number attached to the back of each antenna. The operator is not required to have any a priori knowledge of the antenna or its performance parameters. The operation involves scrolling though a set of prompts from the computer. For this chamber, custom mechanical drawings, motor control systems, and software was designed and engineered to provide maximum efficiency on the production floor. The chamber, measuring only 6’ x 6 ‘ x 8 ‘, has provided comparable results to an on-site 75 foot tapered chamber. This approach is expected to be adopted by additional antenna programs internally in order to off-load capacity from large tapered antenna chambers.
General Technique of Antenna Phase Center Determination by NF or FF Measurements
A problem of determination of an antenna phase center (PhC) usually is solved by different ways from a theoretical calculation to the near-field measurements of complex characteristics in the aperture of an antenna or the far-field measurements of the radiation-pattern phase. The present paper is devoted to a general technique of an antenna PhC determination by use of the known (or the measured) distribution of the complex characteristics in the antenna near zone or the phase pattern in the far zone. An algorithm of determination of the phase pattern evolute, based on the lowest moments of distribution, as well as a criterion for PhC existence, which is independent on the observation angle, are offered. A simple expression of PhC for an antenna with a quadratic phase distribution in the aperture is obtained. An error of PhC determination depending on both the error of observation angle and the error of measurement of the phase pattern is considered.
A Laboratory Course on Antenna Measurement
This paper presents background information and experiment procedures for an antenna measurement laboratory course to be held in a new anechoic chamber at California Polytechnic State University. The lab consists of five experiments and one design project intended to give students practical experience with antenna measurement techniques and to creatively apply analytical skills to design, construct, and test antennas that meet given specifications. The experiments reinforce antenna principles including E-field polarization, antenna gain, radiation patterns, image theory, and frequency response. In addition to the experiment procedures, this paper presents the design and characterization of Helical Beam (RHCP and LHCP) and Discone antennas, a Dipole Antenna near Planar and Corner Reflectors, and Dipoles with and without a balun. These antennas demonstrate polarization, antenna gain, broadband matching characteristics, image theory, and feedline radiation due to unbalanced currents. Measured radiation patterns, gain, and axial ratio (helical only) show excellent correlation to theoretical predictions.
Compact Multi-Probe Antenna Test Stations for Rapid Testing of Antennas and Wireless Terminals
Rapid characterization and pre-qualification measurements are becoming more and more important for the ever-growing number of small antennas, mobile phones and other wireless terminals. There is a need driven by the wireless industries for a smart test set-up with reduced dimensions and capable of measuring radiating devices. Satimo has developed a compact, mobile and cost-effective test station called StarLab which is able to perform rapid 3D measurements of the pattern radiated by wireless devices. The StarLab equipment is derived from Satimo’s StarGate systems which are now well established spherical near field test ranges. StarLab uses a circular probe array to allow for real time full elevation cuts and volumetric 3D radiation pattern measurement within a few minutes. It is operating between 400MHz and 6GHz and can be configured for passive measurements and also cable less-active measurements. This paper describes in detail the multi-probe antenna test station and its different configurations for passive and active measurements. The accuracies for gain and power measurements are also presented as well as considerations on the total radiated power measured by the equipment. Additionally, calibration issues are discussed. Finally, measurements performed with the StarLab test station at Satimo are shown and illustrate the capabilities of the system. The measurement results are validated by comparison to the results obtained in other test ranges.
Alenia HIRF - EW Model Study
ORBIT/FR is presently under contract to provide Alenia Aeronautics with the HIRF – EW test facility to perform radiated field immunity testing of aerospace vehicles with high electromagnetic field intensity: radiated emission measurements, which belong to EMC testing; electronic warfare and antenna pattern tests. This unique facility will combine specific EMC, EME, EW measurements as well as specific antenna measurements. An anechoic-shielded chamber therefore, represents the ideal solution to perform these tests, because it provides the electromagnetic shielding and protection against the internal and external electromagnetic environments. While in many cases as little as -10 dB of round trip reflection may be adequate for EMC testing applications, in the EW tests to be performed at frequencies higher than 500 MHz, is required a fairly lower level of reflectivity. The facility will include an anechoic-shielded chamber (ASC) where the System under Test (SUT) is installed and operated in its functional modes to perform susceptibility tests and emission tests. The ASC will be equipped with a turntable having the capability of arranging the System Under Test (SUT) in front of the radiating antennas at different aspect angles. The ASC will provide internal size of 30 x 30 x 20 (H) m. The pyramidal absorber material shall be permanently installed on ASC ceiling, vertical walls and doors. As far as the floor is concerned two configurations are possible: proposed facility. The model will be described and the effort to scale the performance of the full size absorbers. The development and fabrication of scale model antennas. The establishment of measurement techniques, which will allow the correlation of the scale model measurement to the computer model performance predictions and the potential performance of the completed full size chamber.
Near-Field Remote Calibration System with Minimal Sampling For Operationally Large Reflectors
Accurate near-field calibration of a large 60 ft. diameter reflector can be accomplished with a minimal sampling technique. Near-field amplitude and phase is collected as the reflector scans across a receiving calibration tower. The near-field data is then transformed to a far-field pattern using a Fourier transform technique. Information on far-field EIRP, directivity, pointing, axial ratio and tilt, as well as encoder timing is obtained with accuracies comparable to anechoic chamber measurement techniques. The system was analyzed for sampling and multipath effects, as well as the effects of phase and amplitude stability. A spherical wave expansion technique was compared to a straight-forward summation technique for the Fourier transform.
RCS Measurements with a High Resolution Hardgating System
In general, the RF test setups of antenna test facilities are designed and optimized for antenna pattern and gain measurements. However, the operation of test facilities, especially the here considered 'Double Reflector Compact Ranges', can be extended, so that they can also be used for RCS testing. A simple and very practical expansion of the RF antenna test setup - while maintaining the real-time capability - can be achieved with the aid of a hardware gating system. With this type of setup, RCS measurements have successfully been performed in the Compensated Compact Ranges of EADS Astrium. The applied gating system was the high resolution Hard- gating System HG2000 of EADS Astrium, developed together with the Munich Univ. of App. Sciences. Within this paper, the applied facility and the gating system will be described firstly. Subsequently, the modified test setup and the test results obtained by calibration measurements will be shown. They will give an indication of the achievable resolution for the extended test system w.r.t. object size detection and resulting amplitude dynamic range.
A Novel MIMO Antenna for Laptop Type Device
Exploitation of MIMO (Multiple-Input Multiple-Output) system in laptop type device, which size is adequate to integrate several antennas on it, would be the solution to increase attainable capacity e.g. in wireless local area networks (WLAN). Thus, a microstrip prototype antenna with two polarizations is developed for MIMO and also for diversity system purposes. Firstly, two antennas of this type were placed against to each other, which guarantees a good coverage over a whole propagation area. Secondly, two antennas of this type were placed next to each other. The simulated radiation patterns of the prototype antenna are used in the capacity studies of MIMO system using real indoor propagation data. The effect of shadowing by human body as well as different tilting angles of “laptop cover/screen” are considered. Further, different locations of the “device” in azimuth plane were considered identifying the fluctuation of the results due to the environmental and antenna properties. The developed antenna systems perform well as compared to the ideal dipole system.
Study of RCS Measurements from a Large Flat Plate
Abstract. We present new RCS measurements from an 8-foot square flat plate for frequencies from 0.15 to 5.5 GHz. Guided by the theory, we study the peak RCS at normal incidence, the principal plane pattern, and the 3-dB beam-width in detail. The broadside echo from the plate is found to be extremely narrow at higher frequencies. From the errors, we estimate that the wave-field experienced by the plate is reasonably uniform to within +0.3 dB, over a wide dynamic range of 60 dB.
Using a Chirp Z-transform on Planar Near-Field Data to Expand a Portion of the Far-Field with Increased Resolution and No Interpolation
This paper describes the use of a two-dimensional chirp z-transform (2D-CZT) to efficiently concentrate a large number of sample points in a single portion of the far zone without interpolation. This work presents the equivalence of transforms calculated from measured near-field data using both the 2D-CZT and 2D-fast Fourier transform (FFT). The paper also shows that the 2D-CZT is computationally more efficient than a zero-padded FFT when one requires a high resolution over a small area of the pattern.
Development of a Hemispherical Near-Field Range with a Realistic Ground - Part 2
This paper will discuss the development of a VHF/UHF near field test range for the case where there are reflections from a realistic ground surface. We will show the results of a direct computation algorithm where a far field pattern is computed using plane wave synthesis. The performance of a C++ program that implements this algorithm will be discussed.
Comparison of Gains Determined from the Extrapolation and Pattern Integration Methods
Abstract. Scientists at the National Institute of Standards and Technology (NIST) have measured the gain of several antennas using two different methods. The first method is the three-antenna extrapolation method developed at NIST in the early 1970s. The second method is the far-field pattern integration method. We compare gain results and gain uncertainties for several antennas using these two methods.
A Two-Arch Antenna Measurement System
ABSTRACT A design of a spherical two-arch multi-probe antenna measurement system for measuring radiation patterns of mobile phones is presented. The proper functioning of the designed system is shown partly by computer simulations and partly by practical measurements with Rapid Antenna Measurements System (RAMS) at Helsinki University of Technology.
Pattern Measurement Demonstration of an Untouchable Antenna
A method is presented to measure the antenna pattern of an AUT where the antenna port is inaccessible. That means that it is not possible to connect a test cable, nor can the termination be changed physically. In some cases there is no test port at all. The only variation possible is to change the input impedance of the first receiver or LNA by switching it on and off. An RCS-technique can be used to retrieve the radiation pattern. By experimental comparison between the conventional pattern measurement technique and the RCS-technique it is shown that pattern determination via RCS-measurements is feasible. In addition, the measurement method offers the advantage of directly reducing the influence of systematic measurement errors. On the other hand, the penalty is put on power efficiency and a subsequent limited dynamic range.
Wide-Band Dual Polarized Probe for Accurate and Time Efficient Satellite EIRP/IPFD Measurements
Payload testing is the only measurement where the real Significant reductions in the overall test time radiated end-to-end performances of the satellite are requirements for satellite EIRP/IPFD measurements measured and compared with respect to predictions. These are achievable if the traditional single polarization or critical measurements are performed in the ALCATEL narrow band dual polarization illuminators are ALENIA SPACE Compact Antenna Test Range in substituted with efficient wideband probes in dual Cannes as shown in Figure. 1. polarization. For C-band payload testing, the frequency bands of interest cover more than an entire octave: 3.4-4.8GHz (Tx) and 5.6-7.1GHz (Rx). The cross polarization and taper requirements on the field of view are such that a flared aperture horn can satisfy the requirement but the polarization purity places rather stringent requirements on the orthomode transition in terms of on-axis cross polarization levels and port to port coupling. A suitable probe for this application consists of two components: orthomode transition and radiating aperture. A flared aperture horn, including a stepped matching section, has been designed by ALCATEL ALENIA SPACE to satisfy the illumination Fig 1: ALCATEL ALENIA SPACE Compact Antenna specification. A wide-band dual polarized orthomode Test Range in Cannes. transition covering the entire C-band Tx and Rx During payload testing the antenna pattern measurements ranges has been developed by SATIMO to feed the and other systems tests are carried out. Two of the key horn. The effective bandwidth of the orthomode payload tests are the Equivalent Isotropic Radiated Power transition more than exceeds the specification and it is (EIRP) and Input Power Flux Density (IPFD) of the usable even throughout the Ku band. The final spacecraft . illuminator has been manufactured by SATIMO and delivered to ALCATEL ALENIA SPACE for test in The EIRP is an indication of the power level capability of the Compact Antenna Test Range in Cannes. the telecommunication satellite within a given coverage This paper describes the definition of the performance on the earth surface. This performance is directly linked to specifications, the baseline horn and applied OMT the power budget of the satellite and to the requirements technology and final validation measurements. on the end user parabola diameter. The IPFD is a useful parameter to determine the needed power on the earth
Measurements of the CloudSat Collimating Antenna Assembly Experiences at 94 GHz on Two Antenna Ranges
This paper presents measurements of the CloudSat Collimating Antenna (CA) as fabricated for the 94.05 GHz CloudSat radar, which is to be used to measure moisture profiles in the atmosphere. The CloudSat CA is a 3 reflector system consisting of the 3 "final" (relative to the transmitted energy) reflecting surfaces of the CloudSat instrument. This assembly was fed by a horn designed to approximate the illumination from a Quasi-Optical Transmission Line (QOTL). This same horn was employed as a "standard" for measurement of the CA gain via substitution, and its patterns were also measured (this substitution represents a departure from the standard insertion loss technique in the near field range). The CloudSat CA presented a substantial measurement challenge because of the frequency and the electrical size of the aperture is approximately 600 wavelengths in diameter, with a nominal beamwidth of 0.11 degrees. In addition, very high accuracy was needed to characterize the lower sidelobe levels of this antenna. The CA measurements were performed on a 3122-ft outdoor range (this distance was 41% of the far field requirement), which were immediately followed by measurements in an indoor cylindrical Near Field (NF) range. The instrumentation challenges, electrical, mechanical, and environmental are described. Comparison of the outdoor vs. indoor pattern data is presented, as well as the effect of the application of tie-scans to the near field data.
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