Compact Dual-Frequency Antenna Array With Large Frequency Ratio

A dual-fed dual-frequency shared-aperture antenna array with a large frequency ratio is investigated. Its unit cell consists of a microwave ground-surrounded patch antenna and a millimeter-wave substrate-integrated 2×2 slot antenna subarray. The former is excited in the fundamental TM
₁₀
mode, whereas the slot elements are excited in their fundamental mode. Based on the dual-frequency antenna unit, a dual-frequency antenna array is designed. To demonstrate the idea, a prototype that consists of a C-band 2×2 patch antenna array and a Ka-band 8×8 slot antenna array was designed, fabricated, and tested. Its matching and radiation characteristics are studied for both bands. Reasonable agreement between the measured and simulated results is observed. Excellent measured intraband isolations of over 32 dB are obtained.