Sum and difference beam patterns in resonant slotted-waveguide array

This paper presents an interesting feature of the resonant slotted-waveguide antenna array: the difference pattern at off-center frequencies. Our demonstration uses a 12-element center-fed resonant slot array on rectangular waveguide. The simulation results show that the array produces a sum beam pattern at center frequency, and difference beam patterns at two off-center frequencies (around ±8%). Good return losses at the three frequencies are obtained, and their relative -10 dB impedance bandwidths are around 3.2%, 1.3%, and 1.7%, respectively. This feature has applications for radar, where sum and difference patterns are often used for target tracking, and for frequency diversity, where different patterns are sought.