Antenna pattern effects in normalized site attenuation

The complex fit normalized site attenuation (CFNSA) method was introduced in 2000 as an enhancement to the normalized site attenuation (NSA) model used in ANSI C63.4 and C63.5. The simple dipole NSA model is insufficient to predict the behavior of complex antennas like log periodic dipole arrays (LPDAs) and horns. Thus, NSA measurements made with these antennas using free-space antenna factors can have significant deviations from that predicted by the model. The CFNSA model is a modification to the simple dipole NSA model to account for the variations in antenna pattern and phase center that are possible in complex antennas. This paper evaluates the effectiveness of the phase center/pattern matching (PCPM) method previously proposed, as well as the use of directly measured pattern and phase center information, for a variety of antenna types.

For decades, site validation measurements below 1 GHz have been framed within the concept of Normalized Site Attenuation (NSA) proposed by Smith et al. in 1982. Conceptually, measured results are compared to a theoretical model, which is derived based on a raytracing model between two antennas over a conducting ground plane. It was quickly realized that the theoretical model cannot fully encompass the complexity of real antennas in geometries needed for site validation, and the individual antenna effects cannot be “normalized” entirely from the site attenuations by a simple subtraction (in dB) of the antenna factors. For dipole antennas, correction factors have been included to amend the errors (derived from numerical simulations). For broadband antennas, there had been no simple solution until Geometry-Specific Correction Factor (GSCF) was introduced in ANSI C63.5 in 2000. It may not have been immediately clear to users of the standards that since the introduction of GSCF, the Smith model NSA has been essentially bypassed. Of the two prescribed methods for site validations, the biconical GSCF provided in the form of correction values is based on a numerical model, while the measurement GSCF is a site-to-site comparison method. ANSI C63 can benefit significantly in clarity by removing the pretence of a simple theoretical dipole NSA model, and rewrite the site validation requirements directly in terms of either the numerical or the site-to-site comparison methods.

A GTD model is proposed to discuss the normalized site attenuation (NSA) associated with an open area test site (OATS) with finite metallic ground plane. In this study, the NSA values for three OATS sites, based on GTD model and measurement, are carefully examined and agreement between calculated and measured results supports the usefulness of the proposed GTD model. The GTD model is then adopted to analyze the deviation in NSA values for several OATS structures. The GTD simulation has revealed that the key factor affecting NSA is the width of rectangle metallic plane which is essential in reducing the NSA deviation under the finite test site condition.

Complex Fit Normalized Site Attenuation (CFNSA) is an improved theoretical model for transmission between broadband antennas over a conducting ground plane. The CFNSA model overcomes the limitations of the original NSA model proposed by Smith, German and Pate, by allowing variable radiation pattern and variable phase center positions as a function frequency. The CFNSA model is well suited for log periodic dipole arrays (LPDAs) from 200 MHz to 1000 MHz because the variable phase centers and antenna pattern deviations relative to dipoles are the dominant source of errors. CFNSA has been shown to be effective to reduce systematic errors in the theoretical NSA model for LPDAs by up to 1 dB per antenna factor (or 2 dB in a site attenuation measurement). Antenna calibration and site validations above 1 GHz are increasingly addressed by using fully anechoic rooms (FAR). This makes earlier efforts to improve the CFNSA model above 1 GHz to be of limited application at present. This paper concentrates on improving the model for below 1 GHz. In this study, the antenna patterns are shown to be better represented by a piecewise function versus radiation angle, as compared to the earlier proposed functions, such as cosn θ, or polynomial functions. Efforts are also made to clarify the mathematical process, so that CFNSA can be adopted by the antenna calibration standards, e.g. ANSI C63.5.

An open test site located at the Telecommunication Lab in Taiwan is characterized by measuring normalized site attenuation (NSA) to determine the suitability of this open test site for antenna measurement. The measured NSA data are compared to the theoretical values. The results show a maximum deviation of less than 3 dB over the frequency range of 30 to 1000 MHz.

This paper describes an analysis methodology that implements the theoretical normalized site attenuation (NSA) model into a standard electronic spreadsheet program, such as Microsoft Excel, that can calculate and plot the exact theoretical NSA value for any given frequency of interest. The theoretical NSA is referenced in ANSIC63.4(1992) and is discussed in numerous papers in the open literature. The mathematical model for the theoretical NSA consists of a set of complex equations for horizontal and vertical polarization and is best suited for calculation via computer automation. The spreadsheet analysis technique addressed in this paper has several advantages: (1) the popularity of spreadsheets today provides an easy to use software platform that can be utilized to fully automate the complex theoretical NSA calculations,( 2) the spreadsheet provides an open framework whereby all areas of the model are open for visual inspection, and (3) the spreadsheet model can be used for "what-if" scenarios whereby the test site input parameters are easily modified and the calculations re-pun for new test site configurations.

For the validation of an open area test site usually the normalized site attenuation (NSA) is considered. However, the model for the calculation of the NSA in the various standards is a point dipole. While this may be a correct assumption for biconical antennas or reference dipoles with a well-defined phase center, it is wrong for the antennas used in an automotive antenna test setup. Measurements of automotive antennas for radio and TV reception generally are done on a dedicated test range consisting of a turntable that can bear the weight of the vehicle and a test antenna that is placed in a considerable distance in order to ensure far field conditions. For broadband measurements often log-periodic antennas are used. In these antennas the phase center is not known exactly for all frequencies. The phase center of the automotive antenna is not known either. This uncertainty in the position of the phase centers in combination with the ground reflection occurring between object under test and test antenna results in a measurement error that cannot be neglected. In this work we show how this error can easily be calculated for all test site geometries and give an exemplary calculation for the test site used at our company.

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.

An efficient method to analyze the electromagnetic field inside rectangular anechoic and semianechoic chambers from 30 to 100 MHz is shown. A modal expansion is employed to develop the homogeneous and the inhomogeneous field. This is combined with circuital techniques to compute the effect of the layers of ferrite and dielectrics in the walls of the chamber. Several numerical results of the Free Space Transmission Loss (FSTL) of an anechoic chamber and the Normalized Site Attenuation (NSA) of a semianechoic chamber are provided.

We compare CDMA and FDMA (or TDMA) schemes in multibeam non-geostationary satellite systems, taking the effects of antenna patterns on inter-cell interference into consideration. The maximum acceptable number of users per cell in the uplink is employed as a measure of the system capacity. We have found that in FDMA (or TDMA) systems the maximum acceptable number of users varies according to the altitude of the satellites. While the performance is insensitive to the altitude in CDMA systems. For this reason, the altitude of the satellites is found to be an important factor for selecting multiple access schemes in non-geostationary satellite systems.

Near‐field patterns of a short electric dipole antenna were measured in the magnetospheric plasma by an instrument aboard the polar orbiting satellite OV1‐20S. The most common antenna pattern observed at the fixed operating frequency, 300 kHz, was a dominantly biconic pattern with major axis parallel to the geomagnetic field. The measured cone angles are in reasonable agreement with those predicted by warm plasma theory.There was no discernible systematic asymmetry in these angles such as could be attributed to field‐aligned currents in the plasma or to the motion of the satellite through it.

Antenna 3D pattern measurement can be a tedious and time consuming task even for antennas with manageable sizes inside anechoic chambers. Performing onsite measurements by scanning the whole 4π [sr] solid angle around the antenna under test (AUT) is more complicated. In this paper, with the aim of minimum duration of flight, a test scenario using unmanned aerial vehicles (UAV) is proposed. A practically optimal scanning strategy is presented. The suggested techniques are beneficial particularly for the case of large directive antennas. The UAV follows a predefined trajectory in the scanning windows around the AUT and reads the field strength. Then, using compressed sensing (CS) method, the antenna pattern is reconstructed. It is shown that applying Bayesian CS algorithm to the samples of field intensity gathered by UAV can efficiently reconstruct the pattern. Discrete cosine Transform (DCT) is utilized for sparsifying the antenna patterns. Performance is evaluated by obtaining the reconstructed patterns for different antenna types. The effects of the antenna type and area of scanning are analyzed. It is shown that satisfying performance can be achieved with measuring about 50 percent of the total pattern samples. The reconstruction error of different CS implementations is computed and superiority of Bayesian CS is illustrated.

With the accelerated deployment of 5G massive multi‐input multi‐output (MIMO)‐structured base stations (BSs), accurate and efficient testing of massive MIMO arrays is essential to ensure that the 5G massive MIMO antenna array can perform as expected. The increasing trend of both antenna element and array physical size makes massive MIMO antenna pattern measurement in the direct‐far‐field OTA environment unrealistic due to the signal attenuation, long measurement time, and ultra‐high test system construction cost. Therefore, the necessity of a compact, efficient, low‐complex, yet accurate OTA test method is evident, especially for 5G massive MIMO BS arrays. This paper proposes a novel multi‐probe‐enabled midfield (MF) OTA test method for 5G massive MIMO devices in compact measurement settings where antenna pattern measurement can be efficiently performed. The detailed theoretical analysis for the 5G massive MIMO array MF antenna pattern reconstruction method is presented, and the simulated validation results based on the typical 5G BS antenna arrays are provided and analysed, which demonstrate the effectiveness of the proposed MF OTA test method and can provide insights into the radio frequency parametric measurement for 5G massive MIMO devices.

This paper reports the influence of antennas on radio signal propagation in tunnels and underground mines. Radio signal propagation measurement results in a concrete tunnel and underground mines using antenna types with various radiation patterns, i.e., omnidirectional, Yagi, patch, and circular, are reported. Extensive measurements were taken in various scenarios which include vertical, horizontal, and circular polarization for line-of-sight (LoS) radio signal propagation at four frequencies (455, 915, 2450, and 5800 MHz) that are common to many voice and data transport radio systems used in underground mines. The results show that antenna pattern has a strong influence on the uniformity of radio signal propagation gain in the near zone and typically does not significantly influence behavior in the far zone, except for a constant gain offset.

Unmanned aerial vehicles (UAVs) are emerging as mobile aerial platforms for radio frequency (RF) spectrum sensing, enabling dynamic monitoring of the spectrum occupancy of cellular systems at different altitudes. The impact of UAV receiver antenna configurations, particularly with respect to altitude, is critical in determining occupancy performance. In this paper, we present a height-dependent analytical framework for UAV-based spectrum occupancy, focusing on how different receiver antenna configurations affect the sensed signal power. We consider two types of 3D antenna patterns: a typical dipole antenna and a downward directional antenna. Using a stochastic geometry-based approach, we derive closed-form expressions for the altitude-dependent sensed power under both antenna configurations. Moreover, we execute ray tracing-based analysis with a real-world 3-D map and realistic antenna patterns. Monte Carlo simulations are conducted to validate the analytical results, revealing that both altitude and antenna directivity critically affect occupancy accuracy and coverage.