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At the Boeing 9-77 Range, we often encountered the need to support test objects of light to heavy weights with dielectric strings and fishing ropes of varying sizes from small to large. Unlike a metallic material, which reflects the waves from its surface, the dielectric material is a volume scatterer [1]. Usually, the radar echoes from the strings or ropes at broadside to the wave-front are the highest, then they fall off quickly with angles away from normal. In this paper we discuss several interesting cases learned, namely: a). To deduce the dielectric constant of a rope by the ratio of co-pol to x-pol echoes. b). To estimate the effective radius of a rope after being stretched under a heavy load. c). Observation of interference between two or more scatterers in the same scene. d). To process the angular dependent radar data of a tightly stretched rope as a field-probe along that rope. This paper is prepared in memory of and dedicated to a great teacher and friend on RCS [2]. ---------------------------------------------- ** Sam Wei is at: 4123 - 205th Ave. SE, Sammamish, WA 98075-9600. Email: paxwei3@gmail.com, Tel. (425) 392-0175 [1]. E. F. Knott, "Radar Cross Section Measurements," (Van Nostrand Reinhold, New York, 1993), Chapter 3, Target Support Structures, Section 3.2, String Supports, pp. 85-98. [2]. In Memoriam: Eugene Knott, IEEE Antennas and Propagation Magazine, vol. 56, No. 3, June 2014, pp. 132-133.
Dual-calibration was first proposed by Chizever et al. in 1996 [AMTA'1996] and had get wide applications in evaluation of the uncertainty in radar cross section (RCS) measurement and calibration. In 2013, LaHaie proposed a new technique based on jointly minimizing the mean squared error (MMSE) [AMTA'2013] among the calibrated RCS of multiple calibration artifacts, which estimates both the calibration function and the calibration uncertainty for each artifact. MMSE greatly improves the estimation accuracy for the radar calibration function as well as results in lower residual and RCS calibration errors. This paper presents a modified version of LaHaie's MMSE by minimizing the weighted mean squared error (MWMSE) for RCS calibration processing from multiple calibrator measurements, which is related to the following functions and parameters: the calibration function; the theoretical and measured RCS; the number of calibration artifacts the number of frequency samples and the weight for ith calibration artifacts which may be defined in terms of the theoretical RCS of all the calibration artifacts. For example, if the weight is defined as the inverse of the total theoretical RCS of the ith calibration artifacts for all frequency samples, the error then represents the total relative calibration error instead of an absolute error as in MMSE. MWMSE then means that an optimal calibration function is found in terms of minimum total relative calibration error, which is expected for most applications. Numerical simulation results are presented to demonstrate the usefulness of the proposed technique.
In this work, we measure the propagation losses for estimating the performance of a communication link in the frequency band of 300-350 GHz. The losses are measured by having a transmitter and receiver at varying distances upto 8.5 m. Due to limited ability to move the transmitter and receiver, reflection methods are employed. Using this simple method, we show the presence of water absorption lines in the spectra at 380 and 448 GHz. We also study the data-rate enhancement using dielectric lenses. Finally, using the measured data, we estimate that data-rates of 1 Gpbs for 8.5 m and 100 Gbps for 1 m distance are possible via a communication link at 350 GHz.
The design of active electronically steered arrays (AESA) is a challenging, time-consuming and costly endeavor. The design process becomes much more sophisticated in the case of dual-band circularly polarized active phased arrays, in which CP radiating elements at two different frequency bands occupy a common shared aperture. A design process that takes into account various inter-element and intra-element coupling effects at different frequency bands currently relies solely on computer simulations. The conventional near-field scanning systems have serious limitations for quantifying these coupling effects mainly due to the invasive nature of their metallic probes, which indeed act as receiving antennas and have to be placed far enough from the antenna under test (AUT) to avoid perturbing the latter’s near fields. In recent years, a unique, versatile, near-field mapping/scanning technique has been introduced that circumvents most of such measurement limitations thanks to the non-invasive nature of the optical probes. This technique uses the linear Pockels effect in certain electro-optic crystals to modulate the polarization state of a propagating optical beam with the RF electric field penetrating and present inside the crystal. In this paper, we will present near-field and far-field measurement data for a dual-band circularly polarized active phased array that operates at two different S and C bands: 2.1GHz and 4.8GHz. The array uses probe-fed, cross-shaped, patch antenna elements at the S-band and dual-slot-fed rectangular patch elements at the C-band. At each frequency band, the array works both as transmitting and receiving antennas. The antenna elements have been configured as scalable array tiles that are patched together to create larger apertures.
ABSTRACT Spherical near-field error analysis is extremely useful in allowing engineers to attain high confidence in antenna measurement results. NSI has authored numerous papers on automated error analysis and spherical geometry choice related to near field measurement results. Prior work primarily relied on comparison of processed results from two different spherical geometries: Theta-Phi (0 =?= 180, -180 = f = 180) and Azimuth-Phi (-180 =?= 180, 0 = f = 180). Both datasets place the probe at appropriate points about the antenna to measure two different full spheres of data; however probe-to-antenna orientation differs in the two cases. In particular, geometry relative to chamber walls is different and can be used to provide insight into scattering and its reduction. When a single measurement is made which allows both axes to rotate by 360 degrees both spheres are acquired in the same measurement (redundant). They can then be extracted separately in post-processing. In actual fact, once a redundant measurement is made, there are not just two different full spheres that can be extracted, but a continuum of different (though overlapping) spherical datasets that can be derived from the single measurement. For example, if the spherical sample density in Phi is 5 degrees, one can select 72 different full sphere datasets by shifting the start of the dataset in increments of 5 degrees and extracting the corresponding single-sphere subset. These spherical subsets can then be processed and compared to help evaluate system errors by observing the variation in gain, sidelobe, cross pol, etc. with the different subset selections. This paper will show the usefulness of this technique along with a number of real world examples in spherical near field chambers. Inspection of the results can be instructive in some cases to allow selection of the appropriate spherical subset that gives the best antenna pattern accuracy while avoiding the corrupting influence of certain chamber artifacts like lights, doors, positioner supports, etc. Keywords: Spherical Near-Field, Reflection Suppression, Scattering, MARS. REFERENCES Newell, A.C., "The effect of measurement geometry on alignment errors in spherical near-field measurements", AMTA 21st Annual Meeting & Symposium, Monterey, California, Oct. 1999. G. Hindman, A. Newell, “Spherical Near-Field Self-Comparison Measurements”, Proc. Antenna Measurement Techniques Association (AMTA) Annual Symp., 2004. G. Hindman, A. Newell, “Simplified Spherical Near-Field Accuracy Assessment”, Proc. Antenna Measurement Techniques Association (AMTA) Annual Symp., 2006. G. Hindman & A. Newell, “Mathematical Absorber Reflection Suppression (MARS) for Anechoic Chamber Evaluation and Improvement”, Proc. Antenna Measurement Techniques Association (AMTA) Annual Symp., 2008. Pelland, Ethier, Janse van Rensburg, McNamara, Shafai, Mishra, “Towards Routine Automated Error Assessment in Antenna Spherical Near-Field Measurements”, The Fourth European Conference on Antennas and Propagation (EuCAP 2010) Pelland, Hindman, “Advances in Automated Error Assessment of Spherical Near-Field Antenna Measurements”, The 7th European Conference on Antennas and Propagation (EuCAP 2013)
Calibrating a passive, space-fed, phased array antenna is more difficult and time consuming then calibrating corporate-fed arrays because individual elements cannot be activated or deactivated. We will present our method of determining element state-phase curves and insertion phase bias between elements. We will also explain this method’s theoretical basis and validate it by comparing data measured in an anechoic chamber with data measured in a planar near field range. The anechoic chamber data will be compared with the typical, proven, but more time-consuming planar near field calibration method.
Coupling a Chip Antenna to an Antenna Measurement System is typically achieved using a co-planar micro-probe. This micro-probe is attached to a probe positioner that is used to maneuver the micro-probe into position and land it on the chip. Through this process, the chip is held by a chuck. Intentional and unintentional radiation from the Chip Antenna will interact with the micro-probe and chuck. From design conception, the antenna designer must take steps to reduce currents on the chip surface to minimize unintended radiation that will interact with both the measurement setup and the surrounding components of the final design. Even with good design practices, residual currents will still remain and radiate from the chip. Combined with intentional radiation from the chip antenna in the upper hemisphere, these radiated fields will impinge on the micro-probe and the probe positioner. Reflections from both the micro-probe and its positioner will reflect and generate interference patterns with the desired signal in the spherical measurement probe. In this paper, we evaluate, to first order, these effects by experimentation on two types of micro-probes (ACP & Infinity). The residual errors are then evaluated using modal filtering tools that further reduce these effects and the results are presented. Finally the dielectric chuck is modeled in simulation to evaluate the effects of the chuck on antenna patterns at 60 GHz and the results are presented.
The cost of quality is critical to all industrial processes including microwave device production. Microwave device production is often labor intensive and subject to many production defects. Early detection of these defects can markedly improve production quality and reduce cost. A novel approach to industrial defect detection has been demonstrated using a random noise radar (RNR), coupled with Radio Frequency Distinctive Native Attributes (RF-DNA) fingerprinting processing algorithms to non-destructively interrogate microwave devices. The RNR is uniquely suitable since it uses an Ultra Wideband (UWB) noise waveform as an active interrogation method that will not cause damage to sensitive microwave components and multiple RNRs can operate simultaneously in close proximity, allowing for significant parallelization of defect detection systems. The ability to classify defective microwave antennas and phased array elements (prior to RF system assembly) has been successfully demonstrated and presented at the 36th AMTA symposium. This paper expands on the prior research by focusing on the effects of altering interrogation signal characteristics to include operational bandwidth and signal frequency while actively interrogating similar antennas using an UWB noise signal. The focus of the experimental variation was to optimize classifier performance since unique device characteristics will be excited by various interrogation signal traits that can be exploited by the fingerprint generation and classifier algorithms. Experimentation with several typical UWB antennas and a phased array antenna is demonstrated. The effects of signal bandwidth on classifier performance on simulated fault conditions was performed using various antenna terminations and attenuators. Interrogation of the phased array was demonstrated using the array “backend” for signal down-conversion enabling a quick quality check control method with a simple back-end connection. The ability to wirelessly discriminate multiple fault conditions on individual phased array elements and discern phased array operational range of motion, both in pristine and heavy RFI environments is also shown. This method ensures that each produced phased array meets quality and operational requirements.
This paper explores the accuracy capabilities of a two element phase interferometer measurement in a planar near-field scanner. Traditional phase interferometer applications utilize wide field of view antennas such as spirals making the utilization of planar near-field measurements less than ideal. In this application, high directivity antennas were utilized which allowed us to consider a planar near-field measurement solution. Leaving the AUT stationary and the stability of the planar near-field coordinate system were primary considerations in deciding to utilize a planar near-field measurement system. Typical interferometer performance metrics include comparing measured phase differences to ideal element phase differences at the same locations. Often the nominal drawing locations are used to generate the ideal element phase difference curves. The sensitivity of actual element vector displacement values versus ideal displacements can be reduced by deriving the best-fit displacement vector from the measured data and is utilized in the processing and reporting of results. This paper reviews the measurements, analysis techniques and results from this investigation and illustrates the capabilities of a planar near-field scanner to perform these types of measurements with a high degree of measurement fidelity.
The design of modern Compact Antenna Test Ranges (CATRs) is a challenging task, and to achieve strong performance, simulation using computational electromagnetics is a vital part of the design process. However, the large electrical size, geometrical complexity and high accuracy requirements often mean that the available computer resources are not sufficient for running the simulation. In the present paper, we highlight some recent developments that allow for much larger, faster and more accurate simulations than was possible just a few years ago, and apply them to realistic ranges. The conclusion is clear: Modern software tools allow designers of CATRs to achieve better performance in shorter time than was previously possible.
In planar and cylindrical near-field antenna measurements the probe pattern correction is essential, since the used angular sector of the probe pattern extends over large part of the forward hemisphere. But in spherical near-field measurements, the probe is always looking towards an antenna under test (AUT) and the used angular sector of the probe pattern is relatively small: it usually does not exceed some ±30deg, but typically is much smaller, depending on the size of the AUT and the distance to the probe. For this reason, for low-directive probes with little pattern variation in the used angular sector, it is often said that the probe pattern correction can be omitted without introducing significant error in the calculated far-field AUT pattern. However, no specific guidelines on the value of the introduced error have been presented so far in the literature. In this paper, the error in the calculated far-field AUT pattern due to omitted probe pattern correction is investigated by simulations and confirmed by selected measurements. The investigation is carried out for two typical probes, an open-ended waveguide and a small conical horn, and for aperture-type AUTs of different electrical size with different distance to the probe. The obtained results allow making a justified choice on including or omitting the probe pattern correction in practical situations based on the estimated error at different levels of the AUT pattern.
Recent interest in anisotropic metamaterials and devices made from these materials has increased the need for advanced RF material characterization. Moreover, the quest for measurement of inhomogeneous and anisotropic materials at VHF and UHF frequencies has long been one of the primary stretch goals of the RF materials measurement community. To date, the only viable method for these types of materials has been either fully filled or partially filled VHF waveguides, which are large, expensive, and slow. This paper introduces a new fixture design that greatly simplifies the process of obtaining intrinsic properties for inhomogeneous and anisotropic dielectric materials. The fixture combines low frequency capacitance and high frequency coaxial airline concepts to measure cube shaped specimens, and is termed an “RF Capacitor”. Furthermore, a significant limitation of past measurement methods is their reliance on approximate analytical models to invert material properties. These analytical models restrict the available geometries and frequency ranges that a measurement fixture can have. The present method avoids this limitation by implementing a new inversion technique based on a full-wave, finite difference time domain (FDTD) solver to exactly model the measurement geometry. In addition, this FDTD solver is applied in a novel way to enable inversion of frequency-dependent dielectric properties within seconds. This paper presents the fixture design and calibration for this new measurement method, along with example measurements of isotropic and anisotropic dielectric materials. In particular, 3” cube specimens are measured and the bulk dielectric properties in the three principal planes are determined by measuring the same specimen in three different orientations within the measurement fixture. Finally, calculations are presented to show the relative accuracy of this method against a number of probable uncertainty sources, for some characteristic materials.
The radar cross section is the standardized measure for describing scattering of objects. It is however always associated with the idealized propagation model of the Friis transmission equation with several constraints such as plane wave illumination. This contribution discusses the limited applicability of the RCS in some relevant scattering scenarios, e.g. objects like aircraft on ground or induced Doppler shifts from moving objects. In particular, the latter is a current research topic for radar and rotating wind turbines with strong impact on air traffic management. A new and more general description of scattering phenomena is proposed the standard RCS is just a subset of which for static objects under ideal illumination. It actually defines deviations from the ideal plane wave propagation allowing also to include amplitude and frequency modulation of a scattering propagation channel. In analogy to abstract concepts of communication engineering this quantity can be considered and understood as a wave response of a scattering object that can be applied to time-variant propagation channels. A corresponding setup is presented on how to measure this wave response of scattering objects. Measurement examples are shown in a scaled measurement environment for moving, respectively rotating objects, especially for bistatic scattering configurations. Additionally, the illumination issue of objects is discussed reviewing scattering scenarios related to the instrument landing system.
To improve efficiencies and reduce cost in Electromagnetic Compatibility (EMC) testing, a new instrument is developed which merges antennas and amplifiers to overcome difficulties in the traditional EMC Radiated Immunity (RI) setup. A power amplifier is one of the most expensive instruments in an EMC RI test setup. In the conventional setup, according to IEC-6000-4-3, up to 6 dB of the amplifier’s rated power is lost for several reasons, e.g., internal cabling within the amplifier, the amplifier’s output combiner stage, directional couplers, and cables between the coupler and antenna itself. In this paper a novel concept is presented where active antenna arrays, amplifier stages and directional couplers are combined into one unit, termed a Field Generator. In this configuration, the E-field (V/m) requirement is emphasized rather than the rated power (W) of the amplifier. Although this concept is not limited to a certain field strength or frequency range, we will discuss the validation of this concept in the 1-6 GHz frequency range to generate 10V/m E-field at a 3m distance to meet the requirements specified in IEC-61000-4-3. The advantages of this concept and a few design challenges in implementation will be discussed. Simulation and measurement results will be presented.
In the recent years, the microwave and mm wave communities have been experiencing a strong interest in the characterisation of the RF proprieties of materials used in the manufacture of antennas and structures that, in one way or another, interact with propagating electromagnetic fields. Of particular interest are materials used for for space applications, where antennas face a harsh environment at all times making it challenging to keep antenna performances in all orbital conditions, whether in eclipse or under full sunlight exposure. A particular example is the coming Solar Orbiter mission, where the antenna reflector will be exposed to a high intensity of solar energy. This paper describes a measurement system with a custom-built setup that enables the measurement of reflectivity losses of space antenna materials and coatings at very high temperatures - up to 500 degrees Celsius. The design of the high temperature fixture will be presented in detail, together with the development of the necessary measurement and calibration techniques. The paper will conclude with a critical assessment of the obtained results and system performance and achieved accuracies.
Abstract: Essential to the measurement process is the ability to model expected target electromagnetic behavior. As test articles become electrically large, the traditional and preferred full wave prediction tools (where all the interaction physics are included in the formulation) become unwieldy due to limited computer resources of time/memory/costs. The objective of this paper is to introduce to the measurement community a frequency domain Method of Moments EM prediction tool which significantly advances the electrical size capability of such codes. Mercury MOM is a combined surface and volume integral equation monostatic scattering code. Surface boundary condition capabilities include PEC, Dielectric, IBC, RCard, Thin Dielectric, and PMC. Volume complex dielectric properties may inhomogeneous. The full complex polarization scattering matrix is computed for each plane wave incidence angle. Spatial grouping of unknowns leads to low rank interaction matrix blocks between groups. This allows for using the Adaptive Cross Approximation to perform all of the solutions steps: Filling the Z matrix; Performing the block LU decomposition; and Performing the block LU Solve. Memory and operation count requirements are significantly reduced. A very key feature of Mercury MOM is that it solves the system matrix using full LU factorization rather than using an iterative solver. This means that: 1) There are no iterative convergence issues; and 2) There may be any number of RHS illumination angles. The background physics and mathematics of why such capability is possible will be briefly presented followed by a number of scattering examples demonstrating electrical size capability. Included will be results for a PEC corner reflector right angle cone geometry with radius = height = 54.8 lambda resulting in four million unknowns and 7202 right hand sides which was solved on a PC workstation.
There is a lot of interest in measuring the scattered fields from a panel. The panel could be a frequency selective surface (FSS), could consist of lossy dielectric material, resistive material, etc. For these measurements, the panel is mounted in a large ground plane (perfectly conducting) that mimics an infinite ground plane and the back scattered/bistatic scattered fields are measured. These measured fields contain the scattering from the panel under test as well as the diffracted fields from the junction between the panel and the ground plane, and it is quite difficult to discern the two field components. Alternatively, one can measure the scattered fields over a frequency band in the near zone using a fixed transmitting antenna while the receiving antenna is displaced to scan a planar surface or a linear scan. Note that the measurements are similar to one-way probing. The total measured scattered fields can be processed to isolate the scattering from the panel of interest. In this paper, we will present various signal processing techniques that can be applied to the measured scattered field data. These techniques include high resolution down range processing (tie domain), time domain near field focusing, etc. We will also show that it is straight forward to obtain the reflection and transmission coefficient of the panel from the near field measured data.
This paper discusses the application of modern NF measurements and statistical analysis techniques to efficiently characterize the FF radiation pattern statistics of antennas and other EM emitters whose radiated EM fields vary erratically in a seemingly random manner. Such randomly-varying radiation has been encountered, for example, in measurements involving array antenna elements and reflector feed horn(s) containing active or passive devices that affect the relative phases and/or amplitudes of the pertinent RF signals in a non-deterministic manner [1-2]. In-Band (IB) as well as Out-Of-Band (OB) signals may be involved in some cases. Other possible randomly varying EM radiations include leakage from imperfectly-shielded equipment, connectors, cables, and waveguide runs [2- 4] Previous work at GTRI [5-7] has shown that computations of key FF radiation pattern statistics can be made based on NFFF transformations involving a) the sample average value of the complex electric field at each NF measurement point, b) the sample average value (a real number) of the standard deviation of the complex electric field at each NF measurement point, and c) the measured complex cross-covariance functions at all different NF measurement points. The key FF radiation pattern statistics of most interest are typically a) the statistical average FF radiation pattern, b) the standard deviation, c) the probability density function (p.d.f.), and d) the cumulative probability distribution (C.P.D.). Simulated data measurement protocols and the requisite statistical processing of the NF measured data will be presented and discussed in detail at the symposium. The NF cross-covariance functions introduce a new level of complexity in NF measurements and analysis that is absent for “deterministic” EM field measurements because the cross covariance functions must be measured and processed for all different NF measurement points on the NF surface to compute valid Pattern FF statistics. However, pairs of linear or circular probe arrays can be used to great advantage to achieve tolerable NF measurement times for the cross covariance functions and the aforementioned NF statistical quantities, thereby enabling valid computations of the FF pattern statistics. The use of dual probe arrays will be presented and discussed in detail and compared with mechanical scanning of two “single” probes over two NF measurement surfaces. A technique for estimating the cross-covariance functions will be presented and compared with exact values.
MIL STD 461 is the Department of Defense standard that states the requirements for the control of electromagnetic interference (EMI) in subsystems and equipment used by the armed forces. The standard requires users to measure the unintentional radiated emissions from equipment by placing a measuring antenna at one meter distance from the equipment under test (EUT). The performance of the antenna at 1m distance must be known for the antenna to measure objects located at this close proximity. MIL STD 461 requires the antennas to be calibrated at 1 m distance using the Society of Automotive Engineers (SAE) Aerospace Recommended Practice (ARP) 958. This SAE ARP 958 document describes a standard calibration method where two identical antennas are used at 1m distance to obtain the gain at 1m for each antenna. In this paper the authors show using simulations that the SAE ARP 958 approach introduces errors as high at 2 dB to the measured gain and AF. To eliminate this problem the authors introduce a new method for calibrating EMC antennas for MIL STD 461. The Method is based on the well-known extrapolation range technique. The process is to obtain the polynomial curve that is used to get the far field gain in the extrapolation gain procedure, and to perform an interpolation to get the gain at 1 m. The results show that some data in the far field must be collected during the extrapolation scan. When the polynomial is calculated the antenna performance values at shorter distances will be free of near field coupling. Measured results for a typical antenna required for emissions testing per the MIL STD 461 match well with the numerical results for the computed gain at 1 m distance. Future work is required to study the use of this technique for other short test distances used in other electromagnetic compatibility standards, such as the 3 m test distance used by the CISPR 16 standard. Keywords: Antenna Calibrations, EMC Measurements, Extrapolation Range Techniques
Gain over Temperature (G/T) is an antenna parameter of importance in both satellite communications and radio-astronomy. Methods to measure G/T are discussed in the literature [1-3]. These methodologies usually call for measurements outdoors where the antenna under test (AUT) is pointed to the “empty” sky to get a “cold” noise temperature measurement; as required by the Y-factor measurement approach [4]. In reference [5], Kolesnikoff et al. present a method for measuring G/T in an anechoic chamber. In this approach the chamber has to be maintained at 290 kelvin to achieve the “cold” reference temperature. In this paper, a new method is presented intended for the characterization of lower gain antennas, such as active elements of arrays. The new method does not require a cold temperature reference thus alleviating the need for testing outside or maintaining a cold reference temperature in a chamber. The new method uses two separate “hot” sources. The two hot sources are created by using two separate noise diode sources of known excess noise ratios (ENR) or by one source and a known attenuation. The key is that the sources differ by a known amount. In a conventional Y-factor measurement [4], when the noise source is turned off, the noise power is simply the output attenuator acting as a 50 ohm termination for the rest of the receive system. But by using two known noise sources, the lower noise temperature source takes the place of T-cold in the Y-factor equations. The added noise becomes the difference in ENR values. An advantage of this approach is that it allows all the ambient absorber thermal noise temperature change effects to be small factors thus reducing one of the sources of uncertainty in the measurement. This paper provides simulation data to get an approximation of the signal loss from the probe to the antenna under test (AUT). Another critical part of the method is to correctly define the reference plane for the measurement. Preliminary measurements are presented to validate the approach for a known amplifier attached to an open ended waveguide (OEWG) probe which is used as the AUT. [1] Kraus J. Antennas 2nd ed.1988 McGraw-Hill: Boston, Massachusetts. [2] Kraus J. Radio Astronomy Cygnus-Quasar Books 1986. [3] Dybdal R. B. “G/T Comparative Measurements” 30th Annual Antenna Measurement Techniques Association Annual Symposium (AMTA 2008), Boston, Massachusetts, November 2008. [4] “Noise Figure Measurement Accuracy – The Y-Factor Method”, Agilent Technologies, Application Note AN57-2. [5] Kolesnikoff, P. Pauley, R. and Albers, L “G/T Measurements in an Anechoic Chamber” 34th Annual Antenna Measurement Techniques Association Annual Symposium (AMTA 2012), Bellevue, Washington Oct 2012. Keywords: Gain over Temperature (G/T), Satellite Communication, Radio Astronomy, Noise Figure Measurement