Abstract: In an antenna apparatus in which n dielectric layers with .epsilon..sub.r1 -.epsilon..sub.rn in dielectric constants are respectively stacked between a ground plate and a major radiating conductor, the thickness t.sub.1 -t.sub.n of the dielectric layers are determined so as to satisfy substantially the following equations:(t.sub.1 +t.sub.2 + . . . +t.sub.n)/(t.sub.1 /.epsilon..sub.r1 +t.sub.2 /.epsilon..sub.r2 + . . . +t.sub.n /.epsilon..sub.rn)=.epsilon..sub.reff, andt.sub.1 +t.sub.2 + . . . t.sub.n =t.sub.minwith respect to a dielectric constant .epsilon..sub.reff of the antenna defined for a desired beam width, and the minimum value t.sub.min of the dielectric layers capable of ensuring a desired operation band and low reflection losses in this dielectric constant .epsilon..sub.reff. Thus, the thinnest antenna structure which can ensure a desired radiation in directions of low elevation angles, and desired operation bands and low reflection losses can be made.

Abstract: A planar antenna apparatus adapted to excite a small radiating element by electromagnetic coupling is provided. The antenna apparatus has a triplate line including ground conductor plates formed on the upper and lower surfaces of a dielectric substrate and a feed line sandwiched by the ground conductor plates. A coupling hole is formed through one of the ground conductor plates, and a mechanism is provided near the coupling hole for electrically interconnecting the two ground conductor plates. A radiating section coupled to the feed line through the coupling hole has one end grounded to form a short patch antenna. The short patch antenna has a size substantially half the size of a patch antenna. Also, the connecting mechanism prevents unnecessary coupling.

Abstract: An antenna apparatus, a method of manufacturing the same, and a method of designing the same, are provided. A first dielectric layer, first dielectric film, second dielectric layer and second dielectric film are laminated on a flat metal plate in the mentioned order. A radiation element fed through a feeding line is arranged below another radiation element that is not fed through the feeding line. The feeding line forms, along its overall length, a microstrip line having the dielectric layer sandwiched by the feeding line and the flat conductive plate, resulting in no model change from the microstrip line to a triplate line or vice versa, with reduced feeding loss. The thickness of the dielectric layer is so set as to be sufficiently small compared with the used wavelength, to thereby suppress the radiation from discontinuities lying on the microstrip line constituted of the feeding line and flat conductive plate.

Abstract: A circularly polarized microstrip antenna has a ground plane, a disk-shaped driven element, and a disk-shaped parasitic element. The driven element is located between the ground plane and the parasitic element and is parallel to both of them. The driven element and parasitic element both have diametrically opposed notches, or diametrically opposed projections, or diametrically opposed notches and diametrically opposed projections. The driven element is coupled to a conducting strip that parallels the ground plane to form a microstrip transmission line.