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The radiation characteristics for an active phased array receive antenna operating at K Band were measured at the Ipswich Research Facility. On-pole and cross-pole radiation patterns were measured for several scan angles. In this paper we'll discuss the general design of the antenna and the instrumentation ensemble used to perform the far field and near field characterization of this antenna. Measurements taken on a 2600 foot far field range vs. a near field planer scanner are compared.
Norden Inc. has developed and instrumented its JSTARS 1000' Outdoor Antenna Range with a multi-port antenna measurement system designed to acquire antenna data (patterns and other related signals) at the antenna's respective radar system's intermediate frequency (IF). The measurement system utilizes the JSTARS RF microwave receivers attached to the multiple channels of the JSTARS antenna. These receivers obtain the RF signal from these multiple channels and provide the IF signals to the measurement system.
This paper demonstrates a high speed antenna measurement capability recently developed in the MDTI Radar Measurement Center. Originally constructed as a Radar Cross Section facility, the RMC has added the capability to measure antenna patterns on apertures up to 40-feet in length in the far field. Data will be presented to demonstrate system performance through the use of modern output formats, such as global plots and videotape presentations.
Details of a public domain Microsoft Windows-based database program to organize and distribute measured antenna pattern and RCS data are described. Tools for editing, viewing and plotting data are also included.
This paper presents the various aspects involved in the design, development and establishment of Cylindrical Near-Field Measurement(cnfm) facility. A brief description of the hardware and the method of data acquisition are outlined. The capabilities of the CNFM system are brought into focus. The effects of alignment errors are presented. The patterns of various test antennas are presented over different frequency bands.
Accurate multiwavelength radiometric remote sensing of the ocean and the atmosphere from an aircraft requires antennas with the same beamwidth at the various frequencies of operation. Scientists at the National Oceanic and Atmospheric Administration designed an offset antenna with a pressure-compensating corrugated feed horn to meet this criterion. A specially designed fairing was incorporated into the antenna to optimize the aerodynamics and minimize the liquid buildup on the antenna surfaces. The antenna has two positions: the zenith (up) position and the nadir (down) position. The planar near-field facility at the National Institute of Standards and Technology was used to determine the far-field pattern of the antenna. The results show that the antenna beamwidths at 23.87 and 31.65 GHz are nearly the same as expected from the design criterion. This antenna was recently used in an ocean remote-sending experiment and performed according to expectations.
This paper will describe a new type of automotive AM/FM conformal antenna. The slot formed between the body of the automobile and a metal solar heat reduction film imbedded in the front windshield of the automobile is used to form an annular slot. Such partially conducting (4 to 12 ohms per square) metal films represent an opportunity to incorporate an antenna in the overall design at only marginal costs. The characteristic impedance and gain patterns will be described and techniques for improving the impedance match will be shown. A mobile measurement system will be described along with an on-road system to characterize the performance of a number of difference vehicle antenna systems in urban and suburban environments. The application of this system to the measurement of calibrated fain patters will be demonstrated.
The need for practical solutions to radar scattering in high-frequency regime have led to the development of a number of approximation methods. The high-frequency asymptotic methods use approximations based on physical optics (PO), geometrical theory of diffraction (GTD) or physical theory of diffraction (PTD) and their variations. Radar scattering from electrically large conducting surface includes traveling surface wave contributions which are not accounted by the high-frequency asymptotic methods. A hybrid method integrating GTD and traveling wave theory (TW) is used for verification and to illustrate important scattering mechanisms that influence radar cross section (RCS) of a wedge. Analysis of the wedge RCS signature identifies significant contributions of the traveling surface waves to the total RCS. Both measured and predicted RCS of the wedge are considered. Using hybrid GTD-TW method very good agreement between the predicted and measured RCS patterns is observed for all angles.
Accurate, fast, and cost effective antenna test equipment is necessary to meet many programs measurement requirements and schedule and budget constraints. Testing time may be significantly reduced y measuring multiple channels of data simultaneously. Further time savings are realized via the electronic storage of data, which allows easy pattern overlays and changes in the page setup parameters. Electronic storage of data also allows the user to accurately ascertain test parameters. Test data for a dual band, multi-channel antenna measured wit the Scientific Atlanta 1590 Pattern Recorder and multi-channel 1795 Microwave Receiver is presented. This antenna has transmit and receive ports, multiple polarization capability, data and tracking channel outputs and multiple frequency bands. The substantial savings in testing costs are estimated.
The design, alignment and characterization of a compact range facility at the University of California at Los Angeles is summarized. The range is intended to operate from X-Band to 60 GHz, and to accommodate test items up to 3 feet in diameter. The compact range reflector is a circular aperture offset paraboloid which is devoid of edge treatment. Reduction of reflector edge diffraction effects is achieved using an array feed for narrowband test applications, or a horn feed for broadband test requirements. The array feed requires only one relative amplitude excitation coefficient and no phase shifters, so that a simple and cost-effective implementation using a radial transmission line beam-forming network is possible The array pattern displays a deep null at the reflector rim for diffraction reduction, and a flat-topped beam which results in minimum quiet zone field amplitude taper and high reflector aperture efficiently. Structures for support and alignment of the range reflector and feed are discussed, and alignment procedures are summarized. Range performance at X-Band using an array feed is determined using transverse and longitudinal pattern comparison methods.
Test zone field (TZF) compensation increases antenna pattern measurement accuracy by compensating for non-plane wave TZFs. The TZF is measured over a spherical surface encompassing the test zone using a low gain probe. The measured TZF is used in the compensation of subsequent pattern measurements. TZF compensation is demonstrated using measurements taken in an anechoic chamber, far-field range. Extraneous fields produced by reflection and scattering of the range antenna field in the chamber causes the TZF to be non-planar. The effect of these extraneous fields on pattern measurements is shown. Measured TZFs are also shown. TZF compensation results for pattern measurements using a high-gain, X-band slotted waveguide array are presented.
The advantages of mesh antennas include good storability and low mass for large on-board antennas over 10M in diameter. Their weak point is that surface adjustment is necessary to attain high accurate surface. Surface adjustment traditionally involves the repeated measurement of surface node position with a theodolite system and subsequent cable adjustment. These steps take much time. This paper describes a surface adjustment scheme that uses near field measurement for a modular mesh antenna composed of mesh, cable network and supporting structure. The node positions of the antenna are obtained by back projection of the far field pattern generated from the near field pattern. The cable network has low sensitivity to changes in local node position. The results of tests show that the surface accuracy needed to achieve the required RF performance can be obtained quickly without theodolite systems.
A vertical array of antennas is used to beamform the farfield used in the measurement of Radar Cross Section (RCS) on a ground-bounce radar range. By properly weighting (attenuating) and phasing (through line length adjustments) each antenna, a desired far-field pattern can be obtained. This paper discusses some benefits of the technique and outlines a basic mathematical approach. Implementation is considered, and wide band ramifications of a practical design are discussed. At RATSCAT, this basic understanding was used to examine a simple two element array. This paper preceded that study and was originally written just for that purpose.
A technique is presented for obtaining the radiation patterns and the antenna gain of elliptically polarized antennas from two vector measurements of the far-field. The two measurements correspond to different polarizations which can be obtained by rotating one of the antennas around its boresight axis. The discussion emphasizes a particularly interesting case, for which accurate radiation patterns and gain of the antenna under test (AUT) can be obtained without prior knowledge of the polarization of the second antenna. The radiation pattern of a nearly circularly polarized (CP) antenna is conveniently represented by the CP co-polarized and cross-polarized components. The axial ratio and any other quantities commonly used to specify the antenna polarization can also be obtained since the pair of initial vector measurements completely characterize the polarization of the AUT. The technique is illustrated by measurements of a CP patch antenna.
For an anechoic chamber design, one normally spec ifies the field quality throughout the quiet zone in terms of the ripple level requirement. The ripple in the quiet zone field is caused by the interfer ence of various stray signals with the desired plane wave. The stray signals in an anechoic chamber can come from absorber or other parts of cham ber. However, from a range performance point of view, it is more important to know the ef fects of stray signals on the measurement accu racy of an antenna radiation or target scattering pattern. Consequently, it is very critical to eval uate how the chamber stray signals will affect a given measurement. This paper addresses this is sue by simulating pattern measurements of a phase scanned array in a compact range and discuss the effects of various stray signals associated with the scattering from absorber walls and feed spillover.
Present day accuracy requirements on high-performance antenna measurements are difficult to meet on any type of compact range. Numerical correction techniques can offer a good solution. An easy and effective method is the Advanced APC-technique. This method requires patterns to be measured on different locations in the test zone so that disturbances of the plane wave can be distinguished. In case of suitable distances, the "true" pattern can be derived from measured amplitude and phase data. Usually, scanning is performed in longitudinal direction. The advantage is that mutual coupling can be distinguished well, but the field ripple in this direction due to extraneous fields varies much slower than in transversal direction. Consequently, first sidelobes can be corrected more efficiently when transversal scanning is performed. Therefore, in this paper a new and flexible way of positioning is proposed depending on the location of extraneous field sources.
One of the world's most sophisticated antenna test ranges is now fully operational. This was designed by the Deutsche Aerospace (DASA) and is operated by Siemens Plessey Systems (SPS). The presented paper will describe the pioneering design philosophy adopted to ensure the stringent performance features. Although this facility is located outside, it allows extremely high precision probing of cylindrical near field of large and very complex antenna systems, with turning diameters up to 16 meters and up to 20 GHz. Besides the RCS optimized 36 m large scanner tower the significant highlights of this facility consist of a comprehensive air-conditioning system for all accuracy dependent components, a permanent autoalignment system, which ensures high precision cylindrical measurements and an interleaved high speed data collection system, which delivers a maximum of data performance within a minimum time frame. Test results including a pattern comparison of the Ref erence Antenna between measurements in DASA facilities and the SPS Cylindrical Near-Field Test Facility show good range performance. The evaluation of the range performance data demonstrates the measurement integrity of the facility and proves to be qualified to characterize a wide range of antennas.
This paper describes the most recent version of the Model 200 portable RCS diagnostic radar. The Model 200 was designed to provide high-resolution RCS measurements in unprepared rooms indoors as well as on outdoor ranges. The system can provide real aperture measurements, ISAR measurements, or SAR measurements without changing system configuration.
The initial phase of METRATEK's new Model 300 Radar System has been installed at the Navy's Chesapeake Tests Range (CTR) at Patuxent River, MD. This ground-to-air Multimode, Multifrequency Instrumentation Radar System (MMIRS) is a high-throughput frequency-and-polarization agile radar that is designed to drastically reduce the cost of measuring the radar cross section of airborne targets by allowing simultaneous measurements to be made at VHF through Ku Band.
Today's requirements for dynamic Radar Cross Section (RCS) test data set new demands upon instrumentation Radar systems. Transmitters must deliver high power and operate at high data rates. Additionally, noise floor reduction of coherent spurious signals improves raw data and minimizes the need for manipulation of data.