چكيده به لاتين
Monopulse is one of the most efficient methods for tracking targets in radar and satellite technologies. Using reflector antennas, horn antenna as feed, and waveguide monopulse comparators was common way for designing this radar for years. However, large size and difficulty in instruction led in applying other antennas like microstrip antennas for designing monopulse radar. Low efficiency and radiation of the feed network are the main problems of microstrip monopulse antennas. Several monopulse antennas using substrate integrated waveguide (SIW) technology were reported. Circularly polarized (CP) antennas are widely used in satellites and radar applications. The general requirements for such antennas are light weight, low profile, good return loss, and radiation performance. A good candidate for such an antenna can be based on the SIW technology. Several CP antennas based on the SIW technology have been reported in the literature. Using slots and shortening pin is the most popular approach to obtain a CP wave SIW antenna.
A novel compact monopulse cavity-backed substrate integrated waveguide (SIW) antenna is proposed. The antenna consists of an array of four circularly polarized (CP) cavity-backed SIW antennas, three dual-mode hybrid coupler, and three input ports. TE10 and TE20 modes are excited in the dual-mode hybrid to produce sum and difference patterns, respectively. The antenna is modeled with a fast full-wave hybrid numerical method and also simulated using full-wave Ansoft HFSS. The whole antenna is integrated on a two-layer dielectric with the size of 42 mm × 36 mm. A prototype of the proposed monopulse antenna at the center frequency of 9.9 GHz is manufactured. Measured results show −10dB impedance bandwidth of 2.4%, -3dB axial ratio (AR) bandwidth of 1.75%, 12.3dBi gain, and −28dB null depth. The proposed antenna has good monopulse radiation characteristics, high efficiency, and can be easily integrated with planar circuits.
