Normalized Site Attenuation Research Articles

Calculation of Normalized Site Attenuation for Calculable Dipole Antennas

When a pair of calculable dipole antennas (CalDAs) with a 3-dB hybrid balun is used for a validation test of a constructed open area test site (OATS), the theoretical normalized site attenuation (NSA) curves of an ideal OATS for the CalDAs are required. This paper presents a method to calculate this theoretical NSA in the frequency range of 30 MHz to 1 GHz. The theoretical NSA was directly derived using the power mismatch and dissipative loss concepts of an NSA measurement system. Accurate antenna factors (AFs) above the ground plane were also needed and calculated to obtain the theoretical NSA. When free-space AFs are used to determine the measured NSA, AF correction factors known as mutual impedance correction factors are needed. Both free-space AFs and AF correction factors were also considered.

Notice of Retraction: Free-Space Antenna Factor Computation Using Time-Domain Gating and Deconvolution Filter for Site Validation of Fully Anechoic Rooms

An alternative method to compute the free-space antenna factor using time-domain transformation and deconvolution filter for pulse compression is proposed. The deconvolution filter helps in compressing the time-domain pulse to distinguish the direct wave from the reflected wave and help evaluate the free-space antenna factor for site validation of fully anechoic rooms. The antenna pair of ETS-Lindgren Model 3110C and 3180C antennas, simulated with numerical electromagnetics code, is subjected to the proposed method with deconvolution filter and Wiener filter. Based on the simulation results, the proposed method is implemented over the measured results of the antenna pair and used for the site validation of a fully anechoic room. The free-space normalized site attenuation results of the fully anechoic room comply with the ±4 dB specification.

Performance Testing of Anechoic Chamber

Anechoic chambers are widely used in performing EMC measurements according to the established EMC standards. In space area, the elements of EMC measurements such as emission, immunity and susceptibility are critically important to ascertain that all of electrical and electronic components in the satellite body will function correctly without fail, thus ensures the smoothness of satellite operation upon launching into space. Realising this, level of anechoic chamber performance should always be in the optimum state as possible. This paper presents the specific tests that were carried out in the anechoic chamber as to determine the accuracy of its performance. All four types of tests were run in main chamber, control and amplifier room within frequencies range of 10 kHz to 20GHz. The tests will characterize the shielding effectiveness of RF shielded enclosure, the Field Uniformity Area (FUA), Site VSWR and Normalised Site Attenuation (NSA) of anechoic chamber. The basis of the measurement techniques is described and typical test results are discussed. Based on the results, it is concluded that the anechoic chamber is in good condition, ready for testing and capable to produce reliable output.

Proper Antenna Factors for the Normalized Site Attenuation Above a Ground Plane

The antenna factor (AF) above the ground plane changes with respect to the height and obtaining a height pattern of the AF with a sufficient resolution is time consuming. In this paper, a novel method is proposed to obtain an accurate AF at an arbitrary height by a single site insertion loss (SIL) measurement. A ratio of the E-field strength at the location of the antenna under calibration (AUC) to the current amplitude at the transmitting antenna port is introduced. By using this ratio, the AF of the AUC at the height can be obtained by only one SIL measurement. Unlike the conventional method, the multiple SIL measurements are no longer necessary and the proposed method remarkably reduces the measurement time. By using the AFs properly calibrated by the proposed method, the effects of antenna characteristics are significantly reduced in the normalized site attenuation measurement.

The Study On Normalized Site Attenuation With Reflected Rods

Standard sites are important for antenna calibrations. However, many actual sites are not perfect for antenna calibrations due to surrounding reflectors and other measurement uncertainties. Earlier studies were either impractical for actual sites or calculating inaccurately. This paper develops a new method to compute normalized site attenuation (NSA) with reflectors nearby. Based on the conventional NSA, the model with the actual rod-like reflectors is formulated by the wave propagation theory, which is not considered earlier. With this new method, the interferences of rods are considered from the shortest reflected path. The results of the proposed method show good agreement with the numerical simulation results.

Comparison of Normalized Site Attenuation on Finite Ground Plane

The extent of a rectangular conducting plane for measuring electromagnetic interference is discussed. Mutual coupling between the transmit and receive antennas is negligible, the effects of the ground plane on the normalized site attenuation(NSA) are considered by applying GTD(Geometric theory of diffraction). The calculation was done for the case that measuring distance(d) was 3 m for both horizontal and vertical polarizations. As the result, the size of the rectangular ground plane almost never affects upon NSA for horizontal polarization, but for vertical case, when both width and length of the rectangular plane are several times as long as distance, the effects of the edges are reduced under 1 dB.

Open-Area Test Site (OATS) Calibration

Open-area test site (OATS) calibration is discussed in this tutorial. The calibration is performed according to the CISPR and ANSI/IEEE standards. First, theoretical calculations of the normalized-site-attenuation (NSA) procedure are presented. Then, normalized-site-attenuation measurements of a newly established open-area test site are given. Finally, calibration is done through comparisons.

Realization of 3 m Semi Anechoic Chamber by Using Crossed-Wedge Shaped Hybrid EM Wave Absorber Consisting of Thin Corrugated Dielectric Lossy Sheet

This letter proposes a new hybrid EM wave absorber with the crossed-wedge shape, which can be applied to 3m semi anechoic chambers. In this study, we designed a new hybrid EM wave absorber with the crossed-wedge shape, which consisted of the inorganic and organic thin corrugated dielectric lossy sheet containing organic conductive fibers. Then the 3m semi anechoic chamber is constructed in the size of 9.0m × 6.0m × 5.7m (L × W × H) using these absorbers, and also the normalized site attenuation (NSA) is measured according to ANSI C63.4 in the frequency range of 30MHz to 1GHz. As a result, the measured NSA is obtained within ±3dB of the theoretical one.

Antenna Calibration for EMC Tests and Measurements

An antenna is calibrated in an open-field test site (OFTS) and/or an anechoic chamber, which facilities themselves need calibration. The procedures for calibrated test sites (CALTS) are given in the CISPR and ANSI/IEEE standards. The characteristic parameter for calibrated test sites is the normalized site attenuation (NSA). Theoretical calculations and practical measurements of normalized site attenuation are first presented. Antenna-factor (AF) and/or absolute-gain measurement methods are then reviewed. Finally, an alternative antenna calibration approach is given in this tutorial.

A Numerical Investigation of Finite Ground Planes and Reflector Effects on Monopole Antenna Factor using FDTD Technique

An accurate antenna factor (AF) is highly desirable for radiated emission and/or normalized site attenuation measurements. An AF is often measured in the presence of a perfectly conducting ground plane and reflectors. For a receiving antenna; the ground plane or reflectors affects the electromagnetic field by altering the magnitude and distribution of the incident field. It also introduces mutual coupling between the antenna and its image beneath the ground. These effects can cause a different measured AF when the same antenna is polarized horizontally or vertically in respect with ground, or calibrated at a different height. Using a monopole antenna: we conduct a numerical analysis to quantify the influence of the ground and reflector on the AF.

Low-Frequency Model for Rectangular Semi-Anechoic Chambers

An efficient and accurate method to compute the electromagnetic field inside a rectangular semi-anechoic chamber from 30 to 100 MHz is provided. A modal analysis method is used to develop the homogeneous and inhomogeneous solution. They are then combined with a generalized circuital analysis to take into account the effect of the several layers of ferrite and dielectrics on the walls. Several numerical results of the normalized site attenuation (NSA) of a semi-anechoic chamber are provided and compared with measurements, showing a very good agreement

NSA Calculation of Anechoic Chamber Using Method of Moment

NSA characteristics of an anechoic chamber were calculated by using the MoM (Method of Moment), and they were compared with those calculated by the FDTD method as well as the measured results in fully anechoic chamber. Next, we calculated of an anechoic chamber with complicated shapes. We found that first imitating a wave absorber using wire meshes with a limited electric conductivity is effective by controlling the wire interval. The NSA characteristics calculated by the MoM are as well as those calculated by the FDTD method. The NSA characteristics calculated by the MoM also agree with the measured results. And NSA characteristics of an anechoic chamber with complicated shapes were able to be calculated by using the MoM. Based on the results, it is confirmed that the MoM can be used to calculate NSA characteristics for an anechoic chamber. An anechoic chamber is a test room specially designed for completely shielding out external disturbances and for suppressing the echo caused by internal electromagnetic waves. The anechoic chamber for the radiated emission measurement specified by CISPR is usually evaluated by NSA (normalized site attenuation), which is a measure of the transmission characteristics between the standard antennas set inside the anechoic chamber. NSA is usually analyzed by using the ray tracing method (1), but the analytical accuracy of the NSA deteriorates in the low frequency band below several hundreds MHz because the ray tracing method approximates an electromagnetic wave as an optical ray. However, the FDTD (finite difference time domain) method is an analytical method that treats electromagnetic waves purely as waves. Therefore, the FDTD method can analyze NSA characteristics in the low frequency band below several hundreds MHz. The NSA of the anechoic chamber using the FDTD method was obtained by Holloway (2) and Takiguchi (3).

Realization of 3 m Semi Anechoic Chamber by Using Hybrid EM Wave Absorber Consisting of Composite Magnetic Material

This letter proposes the thinnest hybrid EM wave absorber using a composite magnetic material, which can be applied to the 3 m semi anechoic chambers. We experimentally designed a new hybrid EM wave absorber of the wedge shape, which was made from the ferrite powder, the inorganic fiber and binder. As a result, the length of this absorber could be realized only 6 cm, which was ascertained having the non-flammable. The 3 m semi anechoic chamber is constructed in the size of L9 m x W6 m x H5.7 m using this absorber, and then the site attenuation is measured according to ANSI C63.4 in the frequency range of 30MHz-1 GHz. As a result, the measured normalized site attenuation is obtained within ±3 dB to the theoretical normalized site attenuation.

Radiated Electromagnetic Field Immunity Test Method for Wireless LAN Using Opened Parallel Wired Cell

We study radiated RF (radio-frequency) electromagnetic field immunity test system for wireless LAN system by using opened PW (Parallel Wired) cell, in which metal cover is removed. Leakage electric field at distance of 160cm from the opened PW cell decreases until 30 dB, and then does not affect to operation of the AP (Access Point) composed of the wireless LAN system that communicates EUT (Equipment Under Test) installed in the PW cell. NSA (Normalized Site Attenuation) between BUT and AP changes only several dB by inserting the PW cell, and then it can be concluded that the effect of PW cell for radio wave property of wireless communication system is negligible small. In addition, we try to measure dependencies of impressing level of disturbance wave on a throughput of wireless LAN systems IEEE802.11b and IEEE802.11g. As a result, it is confirmed that the radiated RF electromagnetic field immunity test system for wireless LAN system can be composed by using the opened PW cell without affecting from impressing disturbance wave.

MODELING OF ANECHOIC CHAMBER USING A BEAM-TRACING TECHNIQUE

Building an anechoic chamber involves a substantial investment both financially and in physical space. Hence, there is much interest in trying to reduce the required investment while still maintaining adequate performance. The performance of an anechoic chamber depends on the type, size, and array configuration of the absorber elements as well as the geometry of the screened room on which the inner surfaces are covered with RF absorbers. If the room geometry is designed such that an electromagnetic ray from the transmitter will only reach the receiver antenna after a few reflections, the wave energy may be sufficiently damped after a few bounces off the absorbing walls and ceiling. Hence, lower cost RF absorbers can be used to make the anechoic chamber design more economical. In this paper, a variant of beam-tracing technique is used for modeling of anechoic chamber to study the normalized site attenuation (NSA) performance of the anechoic chamber. This allows the chamber performance to be predicted prior to the actual construction. The major advantage of beam-tracing over ray tracing is the path loss information at multiple receiver locations can be determined simultaneously as opposed to running a ray tracing simulation for each receiver location one at a time. As a result, the computing time is greatly reduced. This feature is particularly useful in calculating the field strength at different heights of the receiving antenna in EMC site calibration procedure. The efficient modeling tool has given rise to the successful design and construction of an asymmetrical shape anechoic chamber that supports various measurement needs including EMC tests at the Multimedia University, Malaysia. 24 Chung, Tech, and Chuah

Elimination of the effect of an ambient reflection in the measurement of S parameter between two log‐periodic dipole array antennas

AbstractThe transmission S parameter S21 of transmitting and receiving antennas can be used for site evaluation different from the normalized site attenuation. For instance, the effect of reflection from ambient objects can be removed by the Fourier transform and time domain gating process so that the transmission S parameter without ambient influence can be predicted. In this paper, a log‐periodic dipole antenna is used as a transmission and reception antenna that is a type of broadband antenna. It is shown for this antenna that the time domain gating becomes possible and the effect of reflection can be removed if the complex antenna factor indicating the antenna characteristic is taken into account. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(3): 35–43, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10042

Normalized site attenuation standard correction from numerical computing

In this paper, a numerical model for site attenuation is described. Both horizontal and vertical polarization are presented. Ideal site attenuation values are compared with three-dimensional (3-D) finite-element results in the frequency range required by the standards. The results show significant errors in computing 3-meter (m) site attenuation in the 30-300 MHz frequency range. New values for the normalized site attenuation are then given for 3-m measurements. Such a numerical tool can be used to optimize the performances of indoor test site such as semi-anechoic chamber.

The use of genetic algorithms to maximize the performance of a partially lined screened room

This paper shows that it is possible to use genetic algorithms to optimize the layout of ferrite tile absorber in a partially lined screened enclosure to produce a "best" performance. The enclosure and absorber are modeled using TLM modeling techniques and the performance is determined by comparison with theoretical normalized site attenuation of free space. The results show that it is possible to cover just 80% of the surface of the enclosure with ferrite absorber and obtain a response which is within /spl plusmn/4 dB of the free space response between 40 and 200 MHz.

A mixed model for the determination of normalized site attenuation in OATS

Normalized site attenuation (NSA) has become the standard method for determining the adequacy of open area test sites (OATS) to perform electromagnetic interference (EMI) emission and immunity measurements. Practical experience and measurement data have shown to great extent that in cases where the hypothesis of an infinitely conducting ground plane cannot be fulfilled, the models, up to the present, are not exact. The objective of this paper is to obtain a simple but more accurate model for the measurements of several equipment under test (EUT). The model introduced is based on complex image theory, and also accounts for the near field correction factor and the contribution of Norton surface wave component (vertical electric dipoles cases, only) in a simple algebraic model. Four well-known models are compared to the one presently introduced leading to some useful results, such as the accuracy of the proposed model.

Circularly polarized log-periodic dipole antenna for EMI measurements

Two types of broad-band antennas are widely used for electromagnetic interference (EMI) measurements in the frequency range from 30 to 1000 MHz. Log-periodic dipole antennas (LPDA) are mainly used for the range above 300 MHz and biconical antennas for the range less than 300 MHz. These two antennas have linear polarization. However, EMI measurements can sometimes be more conveniently made with an antenna having circular polarization and so we propose an improved LPDA, which has circular polarization. This LPDA has a second array of dipoles so arranged that each dipole of the second array has a quarter-wavelength phase difference from that of the corresponding dipole of the standard LBDA array for the given radiation field. For this reason, we named it a cross-element LPDA. The cross-element LPDA does not need a broadband 90/spl deg/ hybrid junction to produce circular polarization. We calculated the height pattern and the frequency characteristics of the classical site attenuation (CSA) for the cross-element LPDA when used for both transmitting and receiving, as well as the antenna factor. Moreover, we calculated the normalized site attenuation (NSA) when the cross-element LPDA is used for receiving or for both transmitting and receiving.