94 GHz slot-ring antennas for monopulse applications

A four-element array of slot-ring antennas for monopulse applications has been designed, fabricated and tested at 94 GHz. The slot-ring antennas are fed using coplanar waveguide (CPW) transmission lines and are therefore compatible with a uniplanar circuit implementation. Placing the antennas on a dielectric lens eliminates substrate mode problems and results in high gain patterns. Measurements at 94 GHz for the elements of die 2/spl times/2 array exhibit symmetric, off-axis beam patterns with low sidelobes and 3-dB crossover points. The application areas for the slot-ring monopulse array are in millimeter-wave sensors such as active seekers and automobile collision avoidance radars.