Design and Analyze Cylindrical Reflector

Cylindrical reflector uses a cylindrical shaped surface as a reflector. This reflector coexist with an antenna in various wireless transmission applications such as radar, general satellite communications, and in astronomical applications. The function of the reflector is to focus a beam of signal towards a specific direction for an enhanced antenna gain. The following properties of cylindrical reflector object,reflectorCylindricalare used in this example to define the cylindrical reflector and an exciter system.

GL = 0.3; GW = 0.3; D = 0.075; cref = reflectorCylindrical('GroundPlaneLength',GL,'GroundPlaneWidth',GW,'Depth',D); cref.Tilt = 90; cref.Exciter.TiltAxis = [1 0 0]; cref.Exciter.Tilt = 90; show(cref)

Plot the radiation pattern of the cylindrical reflector at 1 GHz.

pattern(cref,1e9) view(-26,39)

Design and Analyze Spherical Reflector

这种反射器是由一个十字架section from the sphere and suitable for wide-angle scanning. The spherical reflector can provide beam scanning from a fixed reflecting surface without any distortion. This reduces scanning system cost in compared to a conventional reflector antenna systems. The cost reduction comes in eliminating the need to move the primary reflecting surface at all elevation angles. The following properties of the spherical reflector object,reflectorSphericalare used in this example to define spherical reflector and an exciter system.

R = 0.15; D = 0.15; sref = reflectorSpherical('Radius',R,'Depth',D); show(sref)

Plot the radiation pattern of the spherical reflector backed dipole.

pattern(sref,10e9)

Azimuth Plots of Rectangular and Cylindrical Reflectors

Plot the azimuth patterns of rectangular and cylindrical reflectors to compare the radiation characteristics of the two reflectors.

Create the rectangular reflector antenna object.

antR = reflector; antR.Tilt = 90; antR.Exciter.TiltAxis = [1 0 0]; antR.Exciter.Tilt = 90; show(antR)

Plot the azimulth pattern plots for the rectangular and the cylindrical reflectors and compare their results.

pa1 = patternAzimuth(antR,1e9,0,"Azimuth",0:-1:-360); pa2 = patternAzimuth(cref,1e9,0,"Azimuth",0:-1:-360); figure; polarpattern(pa1); holdon; polarpattern(pa2); holdoff; l = legend('Rectangular Reflector','Cylindrical Reflector'); l.Position = [0.6 0.8877 0.2996 0.0869];

Cylindrical reflectors, on account of their curvature, provide higher gain compared to the rectangular reflectors.

Elevation Plots of Spherical and Parabolic Reflectors

Plot the elevation patterns of spherical and parabolic reflectors to compare the radiation characteristics of the two reflectors.

Create a parabolic reflector.

pref = reflectorParabolic; show(pref)

Compare the elevation pattern plots of the parabolic and the spherical reflectors.

pe1 = patternElevation(pref,10e9,0,'Elevation',0:360); pe2 = patternElevation(sref,10e9,0,'Elevation',0:360); figure polarpattern(pe1) holdon; polarpattern(pe2) l = legend('Parabolic Reflector','Spherical Reflector'); l.Position = [0.6 0.8877 0.2996 0.0869];

The elevation pattern plot of the spherical reflector shows more peaks compared to the parabolic reflector. This means that a spherical reflector scans a wider area.

Reference

[1] Balanis, Constantine A.Antenna Theory: Analysis and Design. 3rd ed. Hoboken, NJ: John Wiley, 2005.

[2] Zali H.M., M.T.Ali, I.Pasya, N.A.Halili , H.Ja’afar, M.Hilmi. ''Design of a Cylindrical Parabolic Reflector on Monopole Plasma Antenna''.IEEE International RF and Microwave Conference (RFM), Penang, 2013, pp. 344-348.