Passive Antenna System Research Articles

Electromagnetic–Thermal Analyses of Distributed Antennas Embedded Into a Load-Bearing Wall

The importance of indoor mobile connectivity has increased during the last years, especially during the Covid-19 pandemic. In contrast, new energy-efficient buildings contain structures like low-emissive windows and multi-layered thermal insulations which all block radio signals effectively. To solve this problem with indoor connectivity, we study passive antenna systems embedded in walls of low-energy buildings. We provide analytical models of a load bearing wall along with numerical and empirical evaluations of wideband back-to-back spiral antenna system in terms of electromagnetic- and thermal insulation. The antenna systems are optimized to operate well when embedded into load bearing walls. Unit cell models of the antenna embedded load bearing wall, which are called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">signal-transmissive walls</i> in this paper, are developed to analyze their electromagnetic and thermal insulation properties. We show that our signal-transmissive wall improves the electromagnetic transmission compared to a raw load bearing wall over a wide bandwidth of 2.6-8 GHz, covering most of the cellular new radio frequency range 1, without compromising the thermal insulation capability of the wall demanded by the building regulation. Optimized antenna deployment is shown with 22 dB improvement in electromagnetic transmission through the load bearing wall.

Thermal Impact of 5G Antenna Systems in Sandwich Walls

The 5th generation (5G) cellular networks offer high speeds, low latency, and greater capacity, but they face greater penetration loss through buildings than 4G due to their higher frequency bands. To reduce this loss in energy-efficient buildings, a passive antenna system was developed and integrated into sandwich walls. However, the thermal effects of this system, which includes highly thermally conductive metals, require further study. In this research, three-dimensional heat transfer simulations were performed using COMSOL Multiphysics to determine the thermal transmittances (U-values) of 5G antenna walls. The results revealed that, using stainless steel as the connector material (current design), the U-value rose from 0.1496 (for the wall without antenna) to 0.156 W/m2K, leading to an additional heating loss per year of only 0.545 KWh/m2 in Helsinki. In contrast, with the previous design that used copper as the connector material, the U-value increased dramatically to 0.3 W/m2K, exceeding the National Building Code of Finland’s limit of 0.17 W/m2K and causing 12.8 KWh/m2 additional heat loss (23.5 times more than the current design). The current design significantly reduces thermal bridging effects. Additionally, three analytical methods were used to calculate antenna wall U-values: parallel paths, isothermal planes, and ISO 6946 combined. The isothermal planes method was found to be more accurate and reliable. The study also found that a wall unit cell with a single developed 5G antenna and a wall consisting of nine such cells arranged in a 3 × 3 grid pattern had the same U-values. Furthermore, areas affected by thermal bridging were typically smaller than the dimensions of a wall unit cell (150 mm × 150 mm).

Downlink Vertical Beamforming Designs for Active Antenna Systems

In this paper, we study a vertical beamforming technique for multiple-input multiple-output downlink multi-user systems. In general, the transmit antenna gain is controlled by adjusting the boresight of antennas in directional antennas, and thus the cell average rate varies according to the angle of the boresight. First, we compute the tilting angles for directional antenna systems which maximize the cell average rate. To this end, the probability density function of a three-dimensional user distribution is derived. Based on the result, we analyze the average rate gain of active antenna systems over passive antenna systems for a single user case. Furthermore, for a multi-user active antenna system, beamforming designs to maximize the weighted sum rate are proposed by optimizing the transmit antenna gain and power allocation. Since finding joint optimal parameters requires prohibitively high computational complexity, we separate the optimization problem into two sub-problems of the vertical beamforming and the power allocation. Then a simple vertical beamforming algorithm based on a high signal-to-noise ratio assumption is presented. Also, for a multi-user passive antenna system, we provide a beamforming scheme based on a multi-sector concept. Simulation results show that the proposed beamforming schemes outperform the conventional beamforming schemes.

A passive antenna system for data acquisition in scattering applications

This article describes a passive antenna system based on the modulated scattering technique (MST) implemented in the bistatic configuration. The system uses an array of passive dipoles driven by optical fibers. The array can move and rotate around a square test area and it is possible to measure field-scattered data by cylindrical targets placed inside the test area. Some preliminary experimental results are presented and compared with analytical data. The measurements are in good agreement with theoretical values.

High temperature superconductors and their application in passive antenna systems

The basic physics of superconductivity is reviewed and related to the high-temperature superconductors. The high-frequency characteristics of the new materials are examined, and the two-fluid model is introduced and used to derive an empirical expression for the conductivity of superconductors. The advantages and disadvantages of using these superconductors in the construction of high-frequency transmission lines and passive microwave and millimeter-wave antenna systems are discussed. >

Fast tunable active receiving antennas

With mobile RF communication systems, sensitivity and linearity characterized by the dynamic are the main important qualities of the system on the receiving side. Up to now, especially in the low frequency and the short wave frequency range this problem has not been solved satisfactorily with professional passive antenna systems even though heavy filters are used. Considering nonlinear effects and taking the electromagnetic pulse problem (emp) into account, the short selective active receiving antenna is the optimum solution to this problem. A formula is derived for the field strength sensitivity of the selective active rod antenna. Taking the external noise into account, the minimum height of the antenna is evaluated with respect to optimum sensitivity as well as with respect to minimum nonlinear distortion of the amplifier, which means optimum dynamic range. Antenna heights and dynamic range of the selective active antenna are compared to different systems such as active broadband antennas and standard receiving systems with passtive antennas. For sensitivity reasons, capacitive antenna elements must be tuned by inductive means. In combination with a special switching strategy, premagnetized ferrite inductances are appropriate tuning elements. Nonlinear effects in the ferrites, however, are one of the main problems with electrically tuned antennas, which therefore are taken into account as well.

A Comparative Study of Passive Antenna System as a Conductivity Measuring Device

The data obtained by simultaneous operation of passive antenna system (during charge dissipation period) and Gerdien's conductivity meter at the height of 1m above the ground are analysed for the estimation of atmospheric electric conductivity by each method. The conductivity obtained by using passive antenna, in its transient state, gives consistently higher values than that by Gerdien's conductivity meter. A way to explain this difference lies in the suggestion that the rate at which the transition from one equilibrium state to another takes place, once an electric disturbance is introduced in the atmosphere may be partly governed by the turbulent mixing of atmospheric air layers close to the surface.

The measurements of atmospheric electric held at Gulmarg

Atmospheric electric field was measured continuously in fair weather at Gulmarg by Using passive antenna system with and without snow lying on the ground. The results in general appear to-be consistent with the view that conduction current in the morning is increased as a result of change in the sign of convection current. It is shown that the morning rise in potential gradient at Gl1lmarg is a pronounced effect which gets considerably enhanced under the conditions of snow. The measurements during the period of snow can be explained If excess positive charge is assumed to be predent at the station.

A parametric-excitation-integrated-ferrite antenna

A new type of ferrite antenna with fairly high sensitivity has been studied and experimental results are presented. Although ferrite antennas have long been used as one of the typical antennas of small size, it seems that the remarkable increase of the sensitivity of the ferrite antennas depends upon dimensions and performance of ferrite material, and improvement of those factors is not expected so easily at the present state of the art. One solution for this problem may be the application of the integration technique, that is combining an antenna and active devices in a unified structure with an inseparable form. To form an active device within an antenna, parametric excitation is incorporated into a ferrite antenna structure, and the principle of power transfer between signals, which follows Manley-Rowe's relation, is applied to it for obtaining an active gain within the antenna itself. The permeability variation of the ferrite material is effectively utilized to produce an active function from a passive antenna system. Results show about 5 to 10 dB gain depending upon the pumping power interims of S/N over the conventional passive ferrite antenna having the same size as that of the active antenna.

Signal-to-noise ratio in multielement active and passive antenna systems

Signal-to-noise ratio in multielement active and passive antenna systems