We analyze an infinite planar array of open-ended rectangular waveguides in which the E-plane walls are loaded with dielectric slabs in order to create a hard boundary condition. The analysis is done by using the mode-matching method with Floquet modes in the exterior region. The results show that the hard walls remove the blind spots otherwise present in the element patterns of wide-angle scanning arrays. This occurs both for rectangular and for triangular lattices. In addition, the array becomes better matched to free-space in a rectangular lattice. In limited-scan arrays of large square waveguides, the use of the hard walls increases the array gain by 0.9 dB, it reduces the grating lobe level in the H plane by 11 dB and considerably decreases the difference between the array characteristics in the E and H planes.

Effect of dielectrically loaded hard walls on performance of waveguide antenna arrays

Blindness removal in arrays of rectangular waveguides using dielectrically loaded hard walls

A hard-walled conical horn fed in the TE/sub 11/-mode from a regular circular waveguide is analyzed. The hard wall is formed by a dielectric layer with cylindrical inner surface loaded with longitudinal conducting strips. The analysis is carried out by using a stepwise representation of the horn with subsequent application of the method of generalized scattering matrices in combination with the method of factorization. The approach used refines values of the limiting aperture efficiency by 5 to 15% for diameters up to 3.2 wavelength in comparison with the underrated data based on the Kirchhoff method, and reveals the effect of the sharp worsening of the hard horn performance at some values of the horn length caused by resonances of the strip-line mode excited in the loaded section. Beyond the resonance points, the aperture efficiency remains relatively high (from 80 to 85%), and the crosspolar level is a few decibels lower than that of a standard smooth-walled horn.

Analysis of a hard strip-loaded conical horn by the method of generalized scattering matrices

An infinite planar periodic antenna array of radiating open-ended circular waveguides is considered. The conducting waveguide walls are covered with dielectric layers loaded with longitudinal conducting strips for providing the hard wall boundary condition. Analysis of the array is carried out by the mode-matching method. The waveguide modes involved in the method are calculated by using the asymptotic strip boundary condition. It is shown that they are split into an independent subsystem of TE modes for the whole cross section and two independent subsystems of TM modes: one is for the central region and another is for the layer region. The calculations show that the operation of the hard waveguides in an array with small element spacing is similar to that of the multimode smooth wall waveguides completely filled with dielectric. For large diameters and element spacing, the hard waveguides have significant advantages over the smooth ones. It is shown that unlike an individual hard waveguide, the aperture efficiency of such a waveguide in the array has a nonmonotonic dependence on the waveguide radius. The results characterizing the behavior of the aperture efficiency and cross-polarization level in a frequency band as well as the contribution of certain waveguide modes in the reflected power are presented and discussed. The examples of the element patterns corresponding to minimal cross polarization are also given.

Effect of dielectrically loaded hard walls on performance of waveguide antenna arrays

Citations

Blindness removal in arrays of rectangular waveguides using dielectrically loaded hard walls

Analysis of a hard strip-loaded conical horn by the method of generalized scattering matrices

Performance of an array of circular waveguides with strip-loaded dielectric hard walls

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