A novel leaky-wave antenna based on an image nonradiative dielectric guide with two dielectric slabs is designed, fabricated and measured. By selecting appropriate values of permittivities and thicknesses for the two slabs, the gain bandwidth can be enhanced to four times wider than the ordinary single-layer nonradiative dielectric antenna. With appropriate thickness of the dielectric slab, the beamwidth can also be adjusted.

This paper introduces a new concept—space equalization into mutual coupling calibration of digital beamforming (DBF) array. Based on the concept, combined optimization method (COM) is developed to minimize element pattern errors in specified narrow angle and keep global errors being suboptimum. By constructing the cost function of COM properly, the complete equations are derived for the calculation of calibration matrix. Experimental results show that COM calibrates element errors efficiently in constrained narrow space and eliminates mutual coupling errors and channel gain and phase errors in a broad angle region.

Radiation region for open guiding structures is known to be further divided into antenna- and reactive-mode regions, and there is no clear cutoff point defined between the two regions. For a leaky-wave antenna, it is crucial that the antenna is designed to operate in the antenna-mode region so as to increase radiation efficiency, whereas in integrated circuits, the leakage should be suppressed to avoid unwanted coupling among circuits. Therefore, a reasonable definition of the two above-mentioned mode regions is necessary. In this paper, we propose a simple, but good alternative to define these two regions by means of a new version of complex effective dielectric constant, where the complex nature is due to leakage rather than dielectric or metal losses, as is customary. With the new approach, the reactive-mode region is found to be consistent with the conventional concept, and our results are similar to those in the literature. The present technique, however, helps in a better understanding of the results in a much easier way. Furthermore, we find for the first time that the attenuation constant in the deep reactive-mode region can be divided into two separate parts, one is due to the cutoff effect, while the other is caused by the leakage effect. Simple closed-form expressions are derived to determine the two kinds of effects. One can, therefore, gain some insight into the leakage effect in the reactive-mode region. A nonradiative-guide leaky-wave antenna is then investigated as a showcase and low radiation efficiency is observed in the reactive-mode region.

Characteristics of a transverse slot in the upper plate of a nonradiative dielectric guide operating in the dominant LSE00 mode have been analyzed. A fundamental radiation phenomenon due to the open property of the guiding structure is observed theoretically. It is found that the propagation direction of the leakage covers the whole angular spectrum in the plane parallel to the metallic plates. Explanation to its physical existence is given. A simple, but efficient method is developed to determine its angular power density. Numerical computation shows that the leakage is substantially high when the slot is near resonance.

A new leaky nonradiative dielectric guide with a double-layer dielectric slab is investigated in this paper by combining a multimode network theory with a mode-matching method. Numerical results show that proper selection of the permittivities can vary the leakage constant over a wide range. A leakage constant larger than 10% of free-space wavenumber can be obtained easily without entering the cutoff region. Leaky-wave antennas with shorter length and medium gain can thus be developed. In addition, the present leaky guide possesses the advantages of simple fabrication and physical stability. Extensive numerical results are provided to guide the antenna designs.