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In this paper, a novel planar array antenna for multi-band linear polarization discrimination is proposed. The proposed array antenna consists of 12 patch elements and a double-balanced multiplier. A slot-ring and four diodes used in the multiplier also act as an antenna and amplitude detector, respectively. Furthermore, slot lines which are parts of feeding circuits also act as slot antennas. The Both-sided MIC technology is efiectively employed to realize the feeding circuit which eliminates the extra impedance matching circuit. The array antenna is realized in a very simple and compact structure as all the antenna elements, feeding circuit and the multiplier/amplitude detector are arranged on both sides of a substrate. The proposed array antenna can discriminate §45 - linear polarization in three frequency bands. The ability of the proposed array antenna to discriminate orthogonal linear polarization is successfully conflrmed in C and X band by the experimental investigation.

In this paper, a technical concept and design of circular polarization detection patch array antenna using a double-balanced RF multiplier is proposed. The microwave integration technology is efiectively employed to realize the proposed array antenna. The double-balanced RF multiplier is integrated with an orthogonal planar array antenna. The array antenna which consists of 12 patch elements and the RF multiplier is realized by embedding four zero bias Schottky barrier diodes on a slot-ring. The Both-sided MIC technology is successfully employed to realize the array antenna. The array antenna is realized in a very simple and compact structure as all the antenna elements, feeding circuit and the RF multiplier are integrated on both sides of a dielectric substrate. The ability of the proposed array antenna to detect the orthogonal circular polarization (LHCP and RHCP) is successfully conflrmed by the experimental investigation.

In this paper, a linear polarization switchable planar array antenna with enhanced gain and better crosspolarization is proposed. The proposed array antenna consists of a fed patch and four parasitic patches. Four switching diodes are loaded on the corners of the fed patch. The boundary condition of the fed patch is controlled by using the ON/OFF condition of the diodes, and the polarization angle of the array antenna can be orthogonally switched to §45 - with better than i22dB of crosspolarization. The simulated gain of the array antenna is remarkably increased to 12dBi by using four parasitic patches surrounding the fed patch. For matching the resonance frequency of the parasitic patches with the fed patch, a square slot is formed at the center of each parasitic patch. The characteristics of the proposed array antenna are investigated by the FDTD simulation method. The array antenna is fabricated and the experiment is carried out. Both the simulation and the experimental results of the proposed array antenna demonstrate the polarization switching functionality successfully with the enhanced gain in S-band.