4-Element Yagi array of microstrip quarter-wave patch antennas

A new kind of Yagi array of microstrip quarter-wave patch antennas is presented. The antenna array has a low profile and provides a high gain and a vertical polarization at endfire. Compared with previous Yagi array of microstrip half-wave patch antennas, the Yagi array of quarter-wave patch antennas has a smaller size and does not suffer the constraint in dielectric constant in the substrate. Besides, the presented Yagi array generates a main beam pointing closer to endfire than the Yagi array of half-wave patch antennas. Measured results show that the presented Yagi array with 4 elements would generate a peak gain of about 9.7 dBi, an endfire gain of about 4.5 dBi, and a bandwidth of 11.3% for a profile of 0.026 wavelengths. The front-to-back ratio of the Yagi array is higher than 10 dB.