PLANE ANTENNA

PROBLEM TO BE SOLVED: To obtain an antenna simple in the configuration of a feeding circuit and having specific polarization characteristics by releasing the degradation of the orthogonal mode of a microstripo antenna being a radiation element to generate a specific polarized wave and desirably using an impedance converter of a specific wavelength between the microstrip antenna and the feeding circuit. SOLUTION: A polarized wave parallel with a line combining the center of the microstrip antenna and a feeding point is excited. The wave polarizing direction of the antenna does not depend on the shape of the microstrip antenna. Though the feeding point must be tilted by 45 deg. with respect to an axis the antenna is arranged at in order to excite the polarized wave of 45 deg., the feeding point does not have to be tilted by 45 deg. when a radiation element itself is an element radiating a polarized wave of 45 deg.. A circuit of symmetrical constitution to be used in the case of ae polarized wave of normal 0 deg. or a polarized wave of 90 deg.. A projecting part 7, a recessed part 8, a slot 9 are provided to release the degradation of the orthogonal mode to excite a polarized wave nearly in the direction of obliquely 45.