Bandwidth Enhancement Technique Of Low Profile Cavity Backed Antenna

With the rapid development of modern wireless communication, people put forward more and more demandsfor high-speed short-range application. As one solution for high-speed wireless communication link, broadbandtechnology has attracted increasing attention.Millimeter-wave communication will become increasingly important in the future. Compared to lowerfrequency, millimeter-wave has many advantages, such as wider spectral range, larger information capacity, easierto implement narrow beam antenna with high gain, which lead to higher resolution and better anti-interference.However, because millimeter wave suffers serious losses during its propagation, antenna gain becomes veryimportant. For the whole transceiver system, antenna working in millimeter wave frequency is small enough tointegrate with chip. Until now, antenna integrated on chip is suffering from low radiation efficiencies and lowgains, which are unacceptable for millimeter wave transceiver systems. Low profile cavity backed antennas basedon SIW working in 57GHz-64GHz are presented in this paper. For the first one, dual-resonance caused byradiating patch and resonant slot is used. From the Gain-Frequency trace, lower gain in higher frequency band isobserved. When some modifications are made, gain can be higher than 6.9dBi in the whole band. For the secondone, grooves on patch are working as radiators. CPW is used to feed two pair of L-shaped slots, which is locatingin the center of a bowtie shaped window and serving as two magnetic dipole array. With SIW inherent effect tosuppress surface wave, surface wave is suppressed very well, so high gain of 8.2dB and high radiation efficiencyhigher than 95% are achieved.Circularly polarized antennas are widely used to solve the problems of polarization mismatch and multi-pathinterference in radars and communications. Dual circularly polarized antennas are generally utilized to avoidfading loss, realize frequency reuse and enlarge system capability. Low profile SIW cavity back crossed slotantenna with dual circular polarization is proposed, in which a branch line coupler is used as its feeding element.Its axial ratio bandwidth is improved about 4 times compared with that of a single fed circularly polarized antenna.Its gain is more than 5dBi and radiation efficiency is higher than 70%. Performance of this antenna has beenvalidated by measurements.