K.A. Jose

Bandwidth enhancement by flared microstrip dipole antenna

The authors present the results of a detailed experimental investigation exploring the possibility of improving the impedance bandwidth of a printed dipole antenna. This configuration can give considerable enhancement of impedance bandwidth without adversely affecting the efficiency of the antenna. Specifically, the new microstrip version of the FMDA (flared microstrip dipole antenna) has a bandwidth twice that of a conventional dipole antenna. This enhancement in the bandwidth is not accompanied by any losses. It is noted that this compact broadband microstrip dipole is a substitute for conventional dipoles in phased-array antennas for terrestrial applications.<<ETX>>

Reduction of radar cross section of corner reflectors using strip grating technique

A simple and effective method to reduce the radar cross section (RCS) of a dihedral corner reflector is presented. The RCS of a corner reflector loaded with periodic conducting strips over a dielectric sheet is determined experimentally and is compared with that from the reference target. A typical reduction of 20-30 dB for TE (transverse electric) polarization is shown. The large echo due to the mutual perpendicularity of the two flat surfaces in corner reflector is found to be reduced for TE polarization using the strip grating technique.<<ETX>>

Reduction of radar cross section of metallic cylinders

A method for RCS (radar-cross-section) reduction of metallic cylinders using periodic strip grating techniques is presented. The RCS of a cylinder with a periodic strip-loaded dielectric surface (SLDS) is determined experimentally and is compared with a reference target having the same dimensions. A typical reduction of 30-40 dB is obtained. It is concluded from the experimental results presented that proper implementation of an SLDS over a metallic cylinder would reduce its RCS. Another important advantage of this technique is the possibility of reducing the specularly reflected power for different angles in bistatic RCS measurements.<<ETX>>

Effect of periodic strip structure on reduction of radar cross section of planar surfaces

The authors present the results of the numerical solution to the problem of periodic metallic strips on a dielectric sheet above the ground plane. The present method is an extension of J. H. Richmonds (IEEE Trans. Antennas Propagat., vol.AP-28, p.883-7, 1980) approach. Calculation results agree well with experimental results. The low backscattered surface considered can be used to reduce the radar cross section of metallic objects.<<ETX>>

Moment method solution for the RCS of a strip grating backed with reflector

Periodic strip gratings have widely been used for the reduction of the radar cross sections (RCS) of metallic surfaces and also as frequency selective surfaces. A moment method solution is applied for the determination of the reflectivity from the periodic surfaces and hence the RCS is calculated. The results are verified experimentally. For the strip grating system, the RCS is found to be greatly reduced compared to the plane metallic surface.<<ETX>>

Performance of a YBCO superconducting wire loop antenna

The performance evaluation of a superconducting circular wire loop antenna fabricated using YBCO prepared by a novel microwave method is reported. Compared to the conventional antennas, fabricated using copper, this antenna shows a gain enhancement of about 5 dB. The use of the cold wire extrusion principle eliminates the necessity of the low-loss substrate for the fabrication of YBCO antennas, which are normally brittle and of low strength. This high-gain antenna may find applications in satellite technology.<<ETX>>