A Compact Ka-Band Monopulse Cassegrain Antenna Based on Reflectarray Elements

A compact Ka-band monopulse Cassegrain antenna based on the reflectarray elements is presented in this letter. The proposed antenna consists of a main-reflectarray, a subreflectarray, a substrate integrated waveguide comparator, and a monopulse feed to achieve good sum-difference characteristics. Compared with traditional monopulse Cassegrain antenna, the total length of the proposed antenna is shrunken to 67.85%. The results of measurement agree with that of simulation very well. The measured SUM beam gain of the proposed antenna is 29.4 dBi by eliminating the loss of Ka-band comparator, the 3 dB beamwidth is 3.85°, the first sidelobe level is under -12 dB, the cross-polarization level is better than -20 dB, and the gain ratios between the SUM and DIFF are about 3 and 5 dB in azimuth and elevation plane, respectively. The measured results show that the proposed antenna is a good candidate for the low-cost multimode tracking system with limited space, especially for that working at high frequency.