Pattern In Elevation Plane Research Articles

A NOVEL SINGLE FEED OMNIDIRECTIONAL CIRCULARLY POLARIZED ANTENNA WITH WIDE AR BANDWIDTH

A novel omnidirectional circularly polarized (CP) antenna with single feed is proposed for 2.4GHz WLAN applications. Based on the zeroth-order resonance (ZOR) mode of epsilon negative (ENG) transmission line (TL), the antenna excites uniform vertically polarized E-fleld just as the monopole does. A modifled Alford loop with electromagnetic coupling fed by L-shaped strip consists of four curved branches, which is placed on the top of the antenna and generates an equivalent horizontally polarized magnetic dipole mode. Once the two orthogonally polarized components are equal in amplitude but difierent in phase by 90 - , omnidirectional CP wave can be obtained. The measured results show that the impedance bandwidth (S11 < i10dB) is 6% (2.38{2.53GHz), and the 3-dB axial ratio bandwidth in the azimuth plane is very wide which achieves 54% (1.60{2.80GHz). Additionally, the 3-dB axial ratio beamwidth is over 50 - for radiation pattern in elevation plane. Moreover, the antenna achieves excellent omnidirectional right-hand CP performance with a variation of 0.5dB in the azimuth plane and an average gain over 1.5dB across the operating band, which are well applied to the wireless system.

Dual Strip-Excited Dielectric Resonator Antenna with Parasitic Strips for Radiation Pattern Reconfigurability

A novel pattern reconfigurable antenna concept utilizing rectangular dielectric resonator antenna (DRA) placed over dielectric substrate backed by a ground plane is presented. A dual strip excitation scheme is utilized and both excitation strips are connected together by means of a 50 Ω microstrip feed network placed over the substrate. The four vertical metallic parasitic strips are placed at corner of DRA each having a corresponding ground pad to provide a short/open circuit between the parasitic strip and antenna ground plane, through which a shift of90°in antenna radiation pattern in elevation plane is achieved. A fractional bandwidth of approximately 40% at center frequency of 1.6 GHz is achieved. The DRA peak realized gain in whole frequency band of operation is found to be above 4 dB. The antenna configuration along with simulation and measured results are presented.

Main-Reflector Shaping of Omnidirectional Dual Reflectors Using Local Conic Sections

This work presents an alternative method for GO synthesis of dual-reflector antennas suited for omnidirectional coverage. Both reflectors are bodies-of-revolution where a single conic section generates the sub-reflector while a concatenation of local conic sections represent the main-reflector generatrix, which is shaped to provide an arbitrary radiation pattern in the antenna's elevation plane. To illustrate the method, omnidirectional axis-displaced ellipse (OADE) configurations are synthesized to provide a cosecant squared radiation pattern in the elevation plane. Two different ray structures are considered: with real or virtual main-reflector caustics. The GO shaping results are validated by method-of- moments simulations.

Cosmo SkyMed: antenna elevation pattern data evaluation

In modern SAR instruments the radiometric accuracy represents a fundamental requirement to improve the exploitation of targets reflectivity measurement that depends on the antenna pattern in elevation plane. The large phased array antenna pattern may deviate from the on-ground characterization due to the local different gravitational stresses and temperature gradients on the antenna plane that might deform its structure. A method to evaluate the antenna elevation pattern is represented by the measurement of the distributed targets scattering estimated on focused image. In this paper, the above mentioned procedure for the phased array antenna elevation pattern estimation will be described and some results

Shaped beam printed antenna with waveguide power divider for synthetic aperture radar applications

AbstractThis paper presents design and development of X band 8 × 32 element planar array, with center frequency at 9.65 GHz. Stacked microstrip patch antenna where the lower patch is directly fed by microstrip line has been used as a single radiating element. The complex excitation coefficients have been computed using null perturbation technique, so as to provide shaped beam pattern in elevation plane and pencil beam pattern in the azimuth plane. Eight elements have been used to form shaped pattern. Different sets of coefficients were computed. The set of excitation coefficient that results in minimum current taper ratio has been selected to realize the antenna. H plane septum power divider has been used for high‐power requirement, along with tapered transition from waveguide to microstrip. The simulated and measured data on return loss and radiation patterns have been presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 832–835, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22257

Radiation patterns of a λ/4 monopole mounted on thick finite square and circular ground planes

The present paper is concerned with the study of the elevation plane patterns of a λ/4 monopole mounted on thick finite ground planes. The uniform theory of diffraction (UTD) of Kouyoumjian and Pathak is utilized in this study. Circular and square ground planes are assumed. First and second order diffracted fields are properly added to the geometrical optics solution to get the total field expression. Results of calculations are presented. Experimental models are built, and comparison with measurements is given. Very good agreement between calculations and measurements is shown.

Focal surfaces of offset dual-reflector antennas

An analytical technique is described for finding the best focal surfaces for offset-fed dual-reflector antennas. A ray tracing procedure traces the loci of rays incident on the main reflector onto a plane or ‘screen’ situated perpendicular to a central ray of the antenna system. Given, then, by computer graphics, the best feed locations for azimuth and elevation plane patterns, an aperture diffraction method is used which can compute the sidelobe levels and beamwidths resulting from aperture phase errors on scanned or multi-beam patterns. High-magnification Cassegrain or Gregorian antennas, with tilt angles optimised according to Japanese criteria, produce excellent radiation diagrams many beamwidths from the central, unaberrated pattern direction.

Feed network for dual beam reflector antennas

A primary feed network for doubly curved shaped-beam reflector antennas is described which allows simultaneous signal reception on two distinct elevation plane patterns such that the underside falloff separation between a fixed lower beam and a higher beam can be substantially varied in a lossless manner. A three-element feed array is employed wherein two elements of the array are interconnected by means of a sum-difference hybrid. The sum port generates the fixed low beam while the difference port generates an orthogonal beam pattern suitable for RF combining with an independent high beam generated by the third array element. Adjustment of the combining amplitude and phase relationships permits the variation of the underside falloff separation. The fixed low beam is, of course, also used for transmission at high power. Design parameters for a typical surveillance radar application axe discussed for a linearly polarized case. Calculated antenna patterns and free-space coverage diagrams are presented. The complexities of extending the feed network concept to handle switchable linear/circular polarization cases and an integral directional beacon pattern for L band systems are indicated.

Aircraft antenna system analysis

Diffraction techniques in conjunction with classical geometrical optics methods have been used to analyse the elevation plane patterns of antennas mounted on different locations of an aircraft. The frame of the aircraft has been modelled using wedged and curved surfaces. Computed results have been compared with scaled-model measurements and are in very good agreement. Antenna locations examined are typical for communication and landing systems on an airframe.

A study of KC-135 aircraft antenna patterns

Numerical solutions for the radiation patterns of aircraft antennas provide an excellent means of designing and locating antennas in order to achieve the desired performance. The high frequency solutions presented in this paper are based on fuselage antennas mounted on a general-type aircraft but applied specifically to the KC-135 aircraft. The roll and elevation plane patterns are computed for a monopole, axial slot, and circumferential slot mounted both over and forward of the wings. In each case the calculated patterns compare very favorably with the measured patterns. The precision pattern measurements were taken on a \frac{1}{25} scale model of the KC-135 aircraft at NASA (Hampton, Va.) with special emphasis on reducing the mount and background effects.

Radiation characteristics of current elements near a finite-length cylinder

An analysis using image and geometrical theory of diffraction techniques for calculating the elevation-plane pattern of radial infinitesimal current elements mounted near or on perfectly conducting cylinders of finite length is presented. The radiation problem is resolved into two components, the dipole and the edge contributions. The computed patterns are compared with experimental results since boundary-value solutions are not available. Good agreement between theory and experiment is obtained.