Standard Antenna Method Research Articles

Average Rician K-Factor-Based Uncertainty Model of Measured Antenna Efficiency Using the Reference Antenna Method in Reverberation Chambers

Along several decades of development, many methods based on reverberation chambers (RCs) have been proposed for accurate and efficient measurement of antenna efficiency. The standard reference antenna method (RAM) is applicable for almost all frequency bands of interest and all types of antennas, and thus, it may well be the most widely applied method in the industry. In this article, an average Rician <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -factor-based uncertainty model for the standard RAM is proposed. It takes both the number of independent samples and the nonideality of the RC into consideration. Extensive measurements are performed for different RC configurations. It is shown that the newly proposed uncertainty model provides good and stable estimations of the measurement uncertainties for both unloaded and loaded RCs. Moreover, it is experimentally verified that the differences in the radiation characteristics between the reference antenna and the antenna under test (AUT) have little effect on measurement uncertainty regardless of the loading conditions of the RC. The findings of this work allow more flexible and efficient antenna efficiency measurements, including estimation of the associated uncertainty.

Calibration of Biconical Antennas by Vertically Stacking Method

A new way is proposed, and verified by experiment, to measure the free-space antenna factor (F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ) of biconical antennas over 30 to 300 MHz by the standard antenna method. The antennas were horizontally polarized above a metal ground plane. The usual method of calibrating electromagnetic compatibility antennas is to place two antennas at a given separation in a horizontal plane. Biconical antennas have a uniform H-plane pattern, making it possible to stack the antennas in a vertical plane. The (F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ) measured with the new method is in close agreement (difference less than 0.6 dB) to that with the vertically polarized method from the FDIS IEC international standard CISPR 16-1-6. Because the antennas are stacked vertically, a smaller ground plane can be used. Because the antennas are horizontally polarized, the vertically routed cable is orthogonal to the antenna so the interaction of cable and antenna is minimized.

Issue on Calibration of Direct Feed Biconical Antenna in a Semi-Anechoic Chamber Using Standard Antenna Method

Antenna calibration is crucial to ensure the accuracy of Electromagnetic Compatibility (EMC) measurement results. Standard Antenna Method (SAM) is one of the methods widely used in antenna calibration which requires reference antenna with known Antenna Factor (AF) in a free space environment. The work presented in this paper is on the calibration of the AF of a direct-feed biconical antenna in a semi-anechoic chamber (SAC) with considerations given to the effects of ground plane, antenna height, reference antenna type and effects of phase center. The frequency range for the analysis is from 200 MHz to 2 GHz. It is found that antenna located 1.5 m from ground provides the best result compared to modeling. In addition, the phase centers of the reference and test antenna must be at the same positions during the measurements.

시간 영역에서 안테나 이득 측정 연구

There are several antenna calibration methods, so-called 3-Antenna Method, Standard Site Method, and Standard Antenna Method which measure the antenna gains or antenna factors. These methods yield the free space or quasi free space antenna gains in only the frequency domain. In this paper, an antenna calibration method using the time domain in the open area test site is discussed. The reflected waves due to the ground are traced in the time domain. After they are removed by the time gating function of network analyzer, the free space transmission coefficient is extracted. Such a way is applied to the broad band horn antenna ranging 1 GHz to 18 GHz, and the free space gains are obtained by Friis transmission equation. The method is checked by Standard Site Method in open area test site. The results show comparatively good agreement except for 18 GHz.

An Estimation Method for the Free-Space Antenna Factor of VHF EMI Antennas

A novel numerical method is developed for theoretically estimating the free-space antenna factor of an electromagnetic interference (EMI) antenna, especially for the very high frequency (VHF) range where traditional methods are difficult to apply. It requires conventional EMI antenna calibration such as the standard antenna method to obtain the antenna factor of an antenna under calibration as a function of the antenna height. Then, a nonlinear least-squares method is applied to the calibration results to estimate the free-space antenna factor. It is found that the proposed method can yield more accurate estimates of the free-space antenna factor than the averaging method. Attainable accuracy of this method is better than 0.2 dB for tuned dipole antennas and 0.1 dB for biconical antennas and biconi-log antennas. The paper outlines the theoretical background and the validity of this method, with the attainable accuracy demonstrated using method of moments simulations.

Emi antenna calibration on an absorber-lined ground plane to determine free-space antenna factor

Theoretical and experimental investigations are carried out on the establishment of a quasi-free-space environment for electromagnetic interference antenna calibration using ferrite-tile absorbers at the test site. Numerical techniques are developed to evaluate the accuracy of the free-space antenna factor obtained on the absorbers when the ferrite-tile material constants are known. In addition, the antenna impedance measurement on a tuned dipole antenna is proposed for evaluating the calibration error caused by the unwanted ground reflection. Experiments confirm the validity of the numerical techniques and demonstrate that commercially available ferrite tiles can drastically reduce ground reflection even in a lower very-high-frequency (VHF) range. It is concluded that the standard antenna method can yield free-space values of the antenna factor for the entire VHF region with an error of less than 0.3 dB, if ferrite tiles are placed on a metal ground plane greater than 8.7/spl times/8.7 m/sup 2/ and if the antenna under calibration is positioned at a height of about 3 m.

Antenna factors of half‐wavelength dipole antennas with roberts balun

AbstractTo use antenna factors most effectively in either EMI measurement or the reference antenna method, the antenna factor is more accurately derived than the conventionally obtained value when a half‐wave resonant dipole antenna with Roberts balun (ANSI C63.5 Specification) is placed on the ground plane. In the calculation, the antenna is treated as the boundary value problem of Maxwell's equations and is analyzed by the Galerkin moment method. The balun is treated using circuit theory based on power transmission mismatch. To confirm the validity of these theoretical calculations, the computed value of the antenna factor in free space is compared with the measured results by the standard site method and the standard antenna method. It is confirmed that the tendency of the numerical results agrees well with that of the measured values.

VHF Radar Measurements of In-Beam Incidence Angles and Associated Vertical-Beam Radial Velocity Corrections

Abstract Atmospheric backscatter or partial reflections observed with VHF radars are strongly enhanced for angles within a few degrees of the vertical, although the strongest echoes are not necessarily exactly from the vertical direction. Consequently, a nominally vertical beam can actually receive the strongest echoes from a direction slightly off-vertical. The radial velocities measured in the vertical beam, then, are not true vertical velocities but have contributions from both the projection of the vertical and the horizontal velocity along the effective beam direction. We present measurements of the tropospheric and lower stratospheric incidence angles obtained over a period of four days with a spaced antenna radar system and calculate the true vertical velocities by means of a correction derived by combining the incidence-angle measurements, the radial velocities in the vertical beam, and the horizontal winds obtained by the standard spaced antenna method. Typical values for the incidence angles are...

Evalation of dipole antenna Balun loss in the UHF band

Evaluation of the balun loss of a dipole antenna is per- formed at 1.2 and 1.7 GHz based bn the two methods. The balun is constructed by parallel lines which codstitute a choke circuit for un- balanced current. One of the methods is a standard antenna method (11 which substitutes the dipole antenna for a standard gain pyramidal horn antenna inside an anechoic chamber. The other is a direct con- nection method, that is, two identical dipole antennas are connected end-to-end (after their antenna elements are removed) while oriented opposite to each other. The values of balun loss deduced from each method present a close approximation.

A wide-band FET antenna and its calibration

A small and very wideband dipole antenna employing FETs with a bandwidth exceeding 200 Hz to 1000 MHz was developed. The antenna factor in free space was determined by using a TEM cell and the standard antenna method with error within +or-3.2%. The characteristics of the TEM cell calibration system were confirmed, and the antenna factor of the antenna was calibrated at frequencies from 100 Hz to 1300 MHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Standard-Site Method for Determining Antenna Factors

A method for calibrating antennas from site attenuation measurements made on an open-field site is described. The method, termed the standard-site method because the accuracy of the results depends on the quality of the measuring site, requires neitller the use of a standard antenna nor the generation of a standard field. The antenna factors of a number of broad-band antennas calibrated by the standard-site method over the frequency range 30-1000 MHz show good agreement with the antenna factors found by the standard-antenna method.

Field Strength Calibration Techniques at the National Bureau of Standards

The techniques and instrumentation utilized by the National Bureau of Standards to calibrate field strength meters and standards in terms of absolute field strength at frequencies from 10 kHz to 1 GHz are described. Two basic techniques are used: (1) the standard-field method for loop antennas at frequencies from 30 kHz to 30 MHz and (2) the standard-antenna method for horizontally-polarized dipole antennas at frequencies from 30 to 1000 MHz. The accuracy and the limitations of each technique are discussed. Present loop antenna calibration uncertainties vary from 3 to 5 percent depending on the frequency. Dipole antenna uncertainties are presently 12 percent. Various other antenna calibration techniques that have been studied are mentioned, pointing out their limitations. The instrumentation used to calibrate the field strength receiver characteristics is described. These measurements include the calibration of the signal attenuators, calibration of the overall linearity of the receiver, and calibration of the receiver as a two-terminal rf voltmeter. Future plans of the National Bureau of Standards field strength and noise calibration services are discussed. Improved uncertainties and extended services are planned for antennas from 30 Hz to 1000 MHz. New noise calibration services are planned; these include the calibration of random noise generators at selected frequencies from 30 to 1000 MHz, and the calibration of impulse generators in terms of their spectral density.