This paper presents the basic characteristics of a beam tilting slot antenna element whose forced resonance is realized by reactance loading; its structure complements that of a dipole antenna element. The radiation pattern is tilted using a properly determined driving point position; a single loading reactance is used to obtain the forced resonance without great changes in the tilt angle. Numerical results show that the reactance element needs to be loaded near the driving point in order to obtain the forced resonance of the antenna and the minimum changes in the beam tilt angle at the same time. When the proposed forced resonant beam tilting slot antenna with a 0.8 λ length is driven at -0.2 λ from the center, the main beam tilt angle of 57.7 degrees and the highest power gain of 3.8 dB are obtained. This slot element has a broad bandwidth, unlike the complementary dipole element.

This paper presents the forcible resonant characteristics of a cutoff cavity-backed slot radiator. It has a feed post and a parasitic post inserted parallel to the slot width, done by adding a single external reactance to the top or the bottom side of the parasitic post. The basic radiator characteristics for a perfect matching to a 50-Ω coaxial line due to the connecting position of the external reactance are discussed. Comparisons show that the bandwidth of the top side loading is narrower than the bottom side loading case. The theoretical analysis is verified by the measured return loss.

This paper presents the basic characteristics of a forced resonant type EMI dipole antenna for frequencies below 80 MHz in which two reactance elements are used for the impedance matching at the feed point. The input impedance of the short dipole less than half-wavelength is controlled by the properly determined loading position and the value of loading reactance. The integral equation for unknown current distribution is solved by Galerkin's method of moments with piecewise sinusoidal functions. The numerical results show that the small-sized EMI dipole antenna with lower antenna factors for frequencies below 80 MHz can be realized by the reactance loading. In case the proposed center driven small-sized EMI dipole antenna with 0.3λ length is loaded c=0.133λ from the center, the input impedance is matched at feed line with 50 Ω, and hence the antenna has lower factors in the frequency range of 30 to 80 MHz. Also the normalized site attenuation characteristics are presented for the forced resonant type EMI dipole antenna.

The applications of reactance-loaded beam tilting dipole antennas have been reported by many researchers. The reactance elements loaded on the applications reported up to date have been used only for the purpose of beam tilting. This paper presents the basic characteristics of the beam tilting dipole antenna element in which one reactance element is used for the impedance matching at the feed point. The radiation pattern is tilted by the properly determined driving point position, and the loading reactance is used to obtain forced resonance without great changes in tilt angle. The numerical results demonstrate that the reactance element should be loaded in the region where the driving point is placed to obtain forced resonance of the antenna with little changes in beam tilt angle. In case the proposed forced resonant beam tilting antenna with 0.8λ length is driven at 0.2λ from the center, the main beam tilt angle of 57.7 degrees, the highest power gain of 8.6 dB, and VSWR=2.2 are obtained.