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In this letter, a design of broadband microstrip three‐way directional coupler (TWDC) is presented. The broadband performance of the microstrip TWDC is realized by the method of cascading multi‐section. The broadband TWDC is designed to achieve equal power division and −120°, 0°, and +120° phase differences between output signals. To verify the broadband design, a prototype of three‐section microstrip TWDC operating at C‐band is designed, fabricated and measured. The measured results show that the power division error of the designed broadband TWDC is less than ±0.7 dB and phase error is less than ±12° at a relative bandwidth of 16%. To verify its performance in multibeam application, the designed TWDC is used as a beamforming network for multibeam antenna array to generate three orthogonal beams. [ABSTRACT FROM AUTHOR]

A design of millimeter wave (mm‐wave) dual‐polarized multibeam antenna array (MAA) with a boresight beam is presented. In order to generate a boresight beam, a 5 × 6 Butler matrix based on three‐way directional couplers is designed as the beamforming network, which achieves equal power division and −60°, +120°, 0°, −120°, +60° progressive phase differences among the output ports when the five input ports are excited, respectively. By four‐layer design, the two 5 × 6 BMs for horizontal polarization (HP) and vertical polarization (VP) are constructed. The patch is used as radiator element, and the HP and VP wave are excited by aperture coupling and microstrip feed, respectively. A prototype is fabricated and measured to verify the design. The measured results show that the designed mm‐wave dual‐polarized MAA can generate five radiation beams including a boresight beam and the five beams with HP and VP cover the range of ±50° at 28 GHz. In addition, the designed mm‐wave dual‐polarized MAA can be a potential option for mm‐wave multibeam application. [ABSTRACT FROM AUTHOR]