Vertically Integrated Three-Pole Filter/Antennas for Array Applications

Integration of high-quality (Q)-factor cavity filters with high-efficiency slot antennas for array applications is presented in this letter. This proposed integration technique exhibits near-zero transition loss between the filter and antenna, and therefore improves the total efficiency of the filter/antenna system. The filter and antenna are vertically integrated to reduce the footprint that is necessary for array applications. The fabricated filter/antenna unit cell has a center frequency of 10.07 GHz and a bandwidth of 5.5%. Using the proposed integrated filter/antenna structure, a 2 × 2 array is designed, fabricated, and measured. Very close agreement is found in between the measurement and simulation results in terms of reflection coefficient, gain, and radiation patterns. The approach demonstrated in this letter can be applied for filter/antennas with higher orders and at higher frequencies.