Types Of Antenna Systems Research Articles

Integrated factor of efficiency of antenna system using in the radar

Integrated efficiency factors are used not only at the design stage, but also in the case of choosing a ready-made system. In this case, the purpose of the research is to get an answer to the question of the expediency of its purchase (deployment), or monitoring the effectiveness of the system during its operation and developing proposals for optimizing the ways of its use and modernization. Since any system has limited resources when solving assignment tasks, it is necessary to develop a generalized efficiency factor from the standpoint of analyzing the effective allocation of radar resources when using antenna systems of various types in its composition. The aim of the article is to increase the efficiency of the use of radar resources in the antenna system. Achieving this goal includes solving the following tasks: substantiation of an integrated efficiency factor of the use of the antenna system in the radar, the use of an integrated efficiency factor to compare different types of antenna systems in the radar. А comparison of the efficiency of using a digital antenna array (DAA) with two-dimensional electronic scanning of the radiation pattern and parallel space surveillance, a reflector antenna, a passive phased antenna array with one-dimensional scanning, as well as an active phased antenna array with one-dimensional scanning and parallel space surveillance has been performed. It has been shown that the efficiency of using a DAR with two-dimensional electronic scanning is 2.3...15.6 times higher than the efficiency of other types of antenna systems. The proposed efficiency factor makes it possible to compare the efficiency of the use of radar resources when using different types of antenna systems, taking into account the features of their construction and the requirements for the purpose of the radar.

A Technique for Radar Cross Section Measurements in the Fresnel Region

This letter presents a novel inverse scattering method for estimating the radar cross section of a target placed in the Fresnel region of the radar antennas. By considering a constant current distribution on the transmitting antenna and a uniform illumination of the target and furthermore of the receiving antenna, the electromagnetic field is averaged over the apertures of the antennas. The hypothesis of a constant current distribution stands for ultrawideband antennas, and a quasi-uniform illumination can be assumed for ranges within the Fresnel region and for the particular case where antenna and target sizes are in the same order as the distance to the target. A calibration procedure for the measurement setup is also proposed. A validation of the method through simulations and measurements in an anechoic chamber and in a real, multipath propagation environment is provided by using two different types of antenna systems.

Quasi-fractal axial-symmetric structure feeded by segment of nongrounded coplanar line

Background. Developments in telecommunication technologies and global implementation of wireless systems calls far new types of antenna systems. Microstrip antennas look the most promising in this field since they possess multiband operation capability with small dimensions and low weight, high degree of integration with other microstrip circuits and can be used as elements of phased antenna arrays. Objectives. The goal of this paper was to simulate electrodynamic characteristics of quasi-fractal radiating structure with complex composition based on a microstrip monopole, to optimize parameters of the excitation element in the form of unshielded coplanar waveguide segment. Matherials and methods. Quasi-fractal radiating structure with complex composition based on a microstrip monopole consists of dielectric substrate, microstrip monopole with quasy-fractal aperture, an unshielded coplanar waveguide segment. The analysis was based on the Finite Elements Method with Integral Equation Method used to account for electromagnetic fields at infinity. Results. Within scope of numerical simulation spectral characteristics of the antenna were analyzed. Comparative analysis of spectral characteristics of canonical disk resonator excited with a microstrip line segment and canonical disk resonator excited with a segment of a coplanar line with eigenmode spectrum of a quasi-fractal excited with a segment of a coplanar waveguide was performed. Influence of dielectric substrate permittivity value on frequency and power characteristics of the radiating structure was studied. It was shown that variations in dielectric permittivity value lead to significant changes of frequency response in the higher frequency band only, wherein increase of dielectric permittivity value leads to a shift of frequency response minima towards lower frequencies of the given frequency band. It was determined that radiating structure is dualband and bandwidth of operating bands was different. Lower frequency bandwidth on dB was , and higher frequency bandwidth was . Numerical simulation of power characteristics was performed with the radiation patterns presented as elevation patterns with fixed azimuthal angle at various frequencies. Possible methods of radiating structure parameters correction with the goal of improving power characteristics and external circuits matching were given. Conclusions. Within scope of numerical simulation was determined that the given quasi-fractal radiating structure with complex composition based on a microstrip monopole can provide effective radiation with acceptable parasitic loss rate. The structure can provide acceptable level of external circuits matching in wide enough frequency band. The ability to form radiated fields with given characteristics in two operating bands.

PRACTICAL IMPLEMENTATION OF HARDWARE AND SOFTWARE COMPLEX FOR PLANAR MEASUREMENTS OF ANTENNA CHARACTERISTICS IN THE NEAR ZONE

Directional patterns measurement of antennas is carried out by the methods of far and near zone. Measurements in the far zone are straightforward; however they have a number of disadvantages. Near zone measurement methods are free from measurement shortcomings in the far zone, but it requires complex and expensive equipment for its implementation.Earlier, the authors have developed a concept of hardware and software modular design complex to determine antenna system characteristics as per measurements in the near zone. This concept assumes creation of a universal measuring complex to investigate various types of antenna systems with any type of measurement surface (plane, cylinder, sphere) in order to solve a wide range of applied problems. The purpose of this work lies in practical implementation of a variant of this measuring complex for measurement along the plane and determination of its metrological (hardware and software) capabilities.A working experimental sample of hardware and software complex for measuring the characteristics of antenna systems that realizes a radio-holographic method for measuring along a plane has been developed, created and practically tested. A preliminary estimation of errors in amplitude and phase measurements in the dynamic range of 45 dB and a comparison of the characteristics of several types of antennas measured in far and near zones have been made. Algorithms have been developed, a software for processing, storing and graphical display of measurement results has been created.

DEVELOPMENT OF CONCEPT OF HARDWARE-SOFTWARE COMPLEX OF MODULAR DESIGN FOR DETERMINATION OF ANTENNA SYSTEMS׳ CHARACTERISTICS BASED ON MEASUREMENTS IN THE NEAR FIELD

Measuring the amplitude-phase distribution of the radiation field of complex antenna systems on a certain surface close to the radiating aperture allows solving the problem of reconstructing the free-space diagram in the far field and also helps in determining the influence of various structural elements and defects of radiating surfaces on formation of directional diagram. The purpose of this work was to develop a universal hardware-software complex of a modular design aimed for determining the characteristics of wide range of antenna systems in respect of measurements of the amplitude-phase distribution of the radiation field in the near zone.The equations that connect the structure of radiation fields of the antenna system at various distances from it in planar, cylindrical and spherical coordinate systems as well as structural diagrams of the hardware part of measuring complexes have been analyzed.As a result, the concept of constructing a universal hardware-software complex for measuring the radiation field of various types of antenna systems with any type of measurement surface for solving a wide range of applied problems has been developed. A modular structure of hardware and software has been proposed; it allows reconfiguring the complex rapidly in order to measure the characteristics of any particular antenna system at all stages of product development and testing, and also makes the complex economically accessible even for small enterprises and organizations.

A Novel Method for the Mutual Coupling Calculation Between Antenna Array Radiators: Analysis of the radiation pattern of a single radiator in the antenna array

A novel method for the estimation of the mutual coupling between radiators in antenna arrays is presented in this article. The methodology proposed includes the analysis of the radiation pattern of the single radiator in the antenna array. An algorithm based on the calculation of real and imaginary parts of the antenna mutual impedance using the Kramers-Kronig relations is demonstrated. The validation is performed by comparing the calculated estimations with electromagnetic simulations of the antenna system and wellknown theoretical results evaluated by the method of induced electromagnetic force. The developed procedure is universal and can be applied to different types of antenna systems.

Results of the Monte Carlo simulation of the LORD experiment with allowance made for the antenna system parameters and galactic noise effect

The results of the Monte Carlo simulation of the LORD experiment are presented for two types of antenna systems with various parameters. The effect of possible polarization mismatch and galactic noise “percolation” are taken into consideration.

Satellite-antenna measurement techniques

Initially, the review takes a brief look at the various types of antenna systems that are used on satellites and shows that in terms of the measurement of their radiation characteristics, they can be categorised into two groups, i.e. low-gain (omnidirectional and quasi-omnidirectional) antennas, and medium- and high-gain antennas. With the first group, the main measurement difficulty lies with the suppression of multipath reflections, and the various range configurations that can be used to avoid or overcome this problem are described. Two of these are, for example, the ground reflection mode range and the use of baffles within an anechoic chamber. Following this, direct measurement ranges applicable to medium- and high-gain antennas are reviewed. These far-field approximation test range configurations include the elevated mode range, either in an outdoor environment or within an anechoic chamber, and the semi-open anechoic chamber. Subsequently, the review considers the various near-field and intermediate distance methods. Finally, some special techniques that have been devised to examine some particular satellite-antenna problems, such as the determination of the r.f. transparency of launch vehicle fairings and the effect of conductive thermal-control paint on satellite-reflector antennas, are presented. The review is principally from a European viewpoint.

The antenna system of a distress buoy for use in a maritime satellite communication system (MARSAT)

Two different types of antenna systems for a distress buoy for use in the maritime satellite communication system (MARSAT) are described. The buoy radiates signals alternately on the frequencies 2182 kHz (medium frequency (MF) beacon) and 1.65 GHz ( L band beacon). The L band antennas had to be combined with the MF antenna of a commercial buoy. The antenna systems have been tested with success during the application technology satellite (ATS-6) experiments and during a previous European Space Research Organization (ESRO) balloon communication experiment [1].

Omnidirectional detectors of microwaves

Two isotropic antenna systems for detection of electromagnetic waves have been developed, and graphs of sensitivity versus angle of rotation of antennas about three mutually perpendicular axes have been recorded. The two types of antenna systems had approximately constant sensitivity for incident waves with arbitrary linear polarization. These antenna systems consist of 12 crystal-diode detectors on the surface of a sphere and six crystal-diode detectors on six edges of a tetrahedron. The spherical antenna system is the more omnidirectional of the two when the antenna system is approximately one-third wavelength in diameter or resonant. When the dimensions were reduced to less than one-tenth wavelength, the pyramidal antenna system was most omnidirectional. The immediate concern was to design detectors for the safety of workers near high-power microwave sources and probes for detection of excessive leakage from microwave ovens in the home.

Radio Direction Finding at 1.67-Meter Wavelengths

Different antenna systems such as the Adcock, V-type, double-V-type, parabolic, and the H-type were tested for measuring both the vertical and the azimuthal angles of an incident wave at the wavelength of 1.67 meters. A null method using the Adcock antenna for defining the azimuthal angle and the H antenna for determining the vertical angle was found to be most satisfactory for high angles of incidence. As the frequency used is too high for sky-reflected waves, erroneous directions attributed to the effect of sky waves at longer wavelengths are eliminated. With the antenna system one and one-half wavelengths above ground and with the ground surface dry and homogeneous and no reflecting objects in the immediate vicinity, the direction of the incident wave thus determined agrees within ½ degree with the optical direction in the azimuthal angle and within ±½ degree in the vertical angle. But when the ground is wet, the error in the vertical angle may reach as high as 3¾ degrees. A mathematical analysis of the reception by these two types of antenna systems, taking into consideration the ground-reflected waves, is given. The theoretical response agrees well with the experimental one.

Low-Frequency Transmission over Transatlantic Paths

Continuous records of field intensity taken at several receiving points and on various types of antenna systems are compared. Evidence of incoherent low-frequency fading is found. Several measures of variability are discussed and changes observed are compared with variations in earth potentials. Abnormally low group velocities for low-frequency transmission are discussed.