High Directivity Quarter-Wave Microstrip Couplers with Periodic Floating-Conductors on Coupled Edges

This paper presents a new quarter-wavelength microstrip coupler with high directivity, which consists of a periodic sequence of floating metal strips in the slots on the inner edges. After describing the characteristics of the coupled-line, a 15-dB coupler is designed and a high directivity of 30 dB or more in theory is obtained over a considerably wide bandwidth. The validity of the design concept is confirmed by em-simulations and experiments