Effective Antenna Height Research Articles

A Compact Log Periodic Planar Dipole UHF Array Sensor for Partial Discharge Measurements

A compact log periodic planar dipole UHF array antenna from 500 MHz to 2.2 GHz for partial discharge measurement in power transformers is presented in this paper. The compactness of the designed antenna is achieved by shaping the arms and tuning selected dipole elements of the array to fill the unoccupied areas. Shaped dipole arrangement results in additional capacitance between the antenna elements enhancing the bandwidth. The designed antenna achieves a fractional bandwidth of 126% and the size is ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.495\lambda _{0} \times 0.63\lambda _{0} \times 0.0144\lambda _{0}$ </tex-math></inline-formula> ) at center frequency of 1.35 GHz. The proposed antenna is experimentally validated on FR4 3.2 mm thickness substrate. The measured gain of antenna is 4 ± 0.5 dBi over 800 MHz to 2.2 GHz which provides lower variation in measured partial discharges. The effective antenna height of the proposed antenna is measured to be over 15 mm. The measured return loss is better than 10 dB over the frequency range. Moreover, partial discharge measurements with oil filled test objects demonstrate that the designed antenna can receive partial discharge signals effectively.

Review of Wireless Personal Communications Radio Propagation Models in High Altitude Mountainous Areas at 2.6 GHz

This paper presents five commonly used radio propagation models (RPMs) which are suitable for the prediction of path loss in macrocell environments of LTE wireless communication systems. These RPMs’ application in high altitude mountainous areas networks (HAMANETs) environment requires further validation and studies. Through using the measured path loss in the HAMANETs at 2.6 GHz to calculate the predicted value of the five RPMs and the measured value’s mean error (ME), root mean square error, and error standard deviation (ESTD), we verified the predicted value of the SPM model that is closer to the actual measurement. On this basis, the empirical propagation model in HAMANETs environment is corrected. When correcting, a method to calculate base station’s effective antenna height and propagation distance is provided by using the altitude above sea level data. This method can reduce the error that the mountainous areas are simplified to the flat-terrain in the existed propagation models. A linear least square method is used to calculate the optimal propagation model. Finally, the ME is the smallest, and the ESTD is less than 8 dB, which indicate that the corrected propagation model is more suitable for the actual environmental path loss’s prediction. The results show that the path loss factor of the test area is about 65 dB, including the influence of the high altitude, mountains, vegetation, and air humidity in HAMANETs environment. The study results can provide useful advice to the evaluation and verification of personal wireless communications in the HAMANETs. Furthermore, using the correction method proposed in this paper can correct propagation models suitable for the different propagation environments to improve the accuracy and efficiency of wireless network optimization.

Nano Structured Single Dipole, Broadband Microstip Antennas at GHz Range

Recent trends and technology demands low profile high bandwidth antenna. The requirement of the antenna is fulfil in multi-crystalline thin film development, which reduce the ground radiations impact on radiation as the radiation become constructive. This research is deal with the thin film development of conducting environment with Fe203, aniline and polyanalline transparent thin film placement as new constructive ground plan below the dipole at certain distance as 1.5mm, 2mm, 2.5mm, and 3mm. These practices implement the reduction in reflection losses with increase in the bandwidth with slightly -6db increase or decreased the reflection coefficient at frequency 4.8GHz. The new thin film is place in layer form as multi layer with the physical dimension less than the effective height of antenna under the dipole. These placements of the film, place the strong environmental element plane for boosting the major lobes radiation and absorber interference for other radiation, which causes the losses. This research deals with the reflection coefficient reduction with the thin film place underneath the feed lines and dipole with the variation of resistance in constructive radiation pattern generation with low profiling and dimension

Detection of Soil Moisture Variations Using GPS and GLONASS SNR Data for Elevation Angles Ranging From 2° to 70°

We propose a Global Navigation Satellite System-Reflectometry (GNSS-R) interference pattern technique method to estimate the temporal variations of the soil moisture content of the ground surrounding a single geodetic antenna. Three parameters can be inverted from GNSS signal-to-noise ratio (SNR) acquisitions: amplitude/phase of the multipath contribution to SNR and effective antenna height. Our method is applied to determine the surface moisture of a bare soil at Lamasquere, France, from February 5 to March 15, 2014. First, only data from low satellite elevation angles ( $ ) are taken into consideration and are compared with independent 2-cm depth soil moisture records. The combination of the measurements from all GPS satellites, tested for the first time, improves the quality of the results with a correlation coefficient reaching 0.95, with a 10-min sampling rate. Our study shows that it is also possible to take high satellite elevation angles into account, even if the sign of the correlation appears to be reversed w.r.t. data from low satellite elevation angles. The cutoff angle where the sign of the correlation reverses seems to be around 30°. With regard to the effective antenna height, only a very low correlation is observed for high satellite elevation angles. We propose a new inversion method taking the pseudo-dynamic of the surface into account, which increases the correlation from 0.39 to 0.82. By normalizing and inverting the time series obtained from either low or high satellite elevation angles, it is possible to combine them, which enhances the results (correlation = 0.95).

The Prediction of Propagation Loss of FM Radio Station Using Artificial Neural Network

In order to calculate the propagation loss of electromagnetic waves produced by a transmitter, a variety of models based on empirical and deterministic formulas are used. In this study, one of the artificial neural networks models, Levenberg-Marquardt algorithm, which is quite effective for predicting the propagation is used and the results obtained by this algorithm are compared with the simulation results based on ITU-R 1546 and Epstein-Peterson models. In this paper, the propagation loss of FM radio station using artificial neural networks models is studied depending on the Levenberg-Marquardt algorithm. For training the artificial neural network, as the input data; range (r), effective antenna height (h) and terrain irregularity (△H) parameters are involved and measured values are treated as the output data. The good results obtained in the city area reveal that the artificial neural network is a very efficient method to compute models which integrate theoretical and experimental data. Meanwhile, the results show that an ANN model performs very well compared with theoretical and empiric propagation models with regard to prediction accuracy, complexity, and prediction time. By comparing the results, the RMSE for Neural Network Model using Levenberg-Marquardt is 9.57, and it is lower than that of classical propagation model using Epstein-Peterson for which RMSE is 10.26.

Non-Foster Impedance Wideband Matching Technique for Electrically Small Active Antenna

This paper investigates a non-Foster wideband circuit matching technique for an electrically small antenna (ESA). By introducing a negative impedance convertor into an active network, the active network can obtain an equivalent input gain at input port to improve gain, sensitivity and output ratio of signal to noise. In addition, it also increases the effective height of active antenna. The experimental results have verified the proposed method by using a 100 KHz–30 MHz wideband active receiving monopole antenna.

Study of High Power ICRF Antenna Design in LHD

In large helical device (LHD), antenna loadings are different for minority ion cyclotron heating (MICH with 38.47 MHz) and mode-converted ion Bernstein wave heating (MC-IBW with 28.4 MHz), and it is necessary to improve antenna loading with low heating efficiency to avoid arching on transmission line. To design a new ion cyclotron range of frequencies (ICRF) antenna in LHD, calculation for a simple antenna model is conducted using three-dimensional electrical magnetic code (high frequency structure simulator, HFSS) for an water loading as an imaginary plasma with low heating efficiency. At resonant frequencies, antenna loading is sensitive to strap width, and resonant frequencies are strongly related to strap height. There is no differences of RF current profile on the strap surface between resonant frequency and non-resonant frequency. The strap should be perpendicularly placed against the magnetic field line, since Faraday-shield angle will lead to a decrease in the effective antenna height.

Hex‐band antenna for slim handheld device applications

AbstractIn this article, we present an approach and design of a small antenna for slim handheld device applications. The basic antenna element is the monopole. The small size and the reduced effective antenna height are achieved from two folding approaches of this monopole. The first is in a three‐dimensional manner, which also results in a broad bandwidth at the desired operating frequencies. The second is achieved by wrapping the antenna around the PCB. This wrapping reduces the physical antenna height to the minimum height required to accommodate the main components of the device without compromising the antenna performance. The proposed antenna is prototyped and modeled, where its performance is examined through simulations and measurements. The antenna supports six frequency bands, GSM 800/900/1800/1900 MHz, UMTS 2100 MHz, and Bluetooth 2400 MHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2527–2530, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24670

SBR image approach for radio wave propagation in tunnels with and without traffic

We propose a deterministic approach to model the radio propagation channels in tunnels with and without traffic. This technique applies the modified shooting and bouncing ray (SBR) method to find equivalent sources (images) in each launched ray tube and sums the receiving complex amplitude contributed by all images coherently. In addition, the vector effective antenna height (VEH) is introduced to consider the polarization-coupling effect resulting from the shape of the tunnels. We verify this approach by comparing the numerical results in two canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high-frequency radio propagation inside tunnels where reflection is dominant. We show that the propagation loss in tunnels can vary considerably according to the tunnel shapes and the traffic inside them. From the results we also find a "focusing" effect, which makes the power received in an arched tunnel higher than that in a rectangular tunnel. Besides, the deep fading that appears in a rectangular tunnel is absent in an arched tunnel. The major effect of the traffic is observed to be the fast fading due to the reflection/obstruction of vehicles. Additional considerations, such as time delay, wall roughness, and wedge diffraction of radio wave propagation in tunnels are left for future studies.

A 20-Hz-to-200-kHz magnetic flux probe for EMI surveys

A small magnetic flux probe is described. It exhibits a magnetometer-like response over the frequency range of 20 Hz to 200 kHz with an effective antenna height of 1 m. The E-field equivalent noise floor of this device is approximately 10 mu V/m square root Hz at 10 kHz. A switchable high-pass filter is included to allow the measurement of very low frequency fields in the presence of strong 50-400-Hz power-line fields. The distinguishing features of this probe are its method of winding and shielding. Both the theory of operation and practical construction are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Radio Telegraphic Station at Rome (San Paolo)

The station at San Paolo near Rome is described in detail, including its antenna, down-leads, ground, arcs, controls, and receiving apparatus. The determination of the most desirable antenna construction is considered; and experimental means of measuring effective antenna height are given. The methods of simplex and duplex operation are discussed. The reception from four high power American stations is described, and detailed reception data are given.