Reduction of Internal Reflections in Integrated Lens Antennas for Beam-Steering

Abstract

Abstract-The conventional integrated lens antennas (ILAs) for beam steering suffer from internal reflections that deteriorate the scanning properties. The internal reflections are known to affect side lobes, cross-polarisation level, input impedance of the feed, and mutual coupling. In this paper, ILAs are designed to exhibit very low reflection loss, i.e., to minimize the internal reflections. Wide ranges of realistic relative permittivities of the lens and of the feed element directivities are considered. It is shown that with any permittivity and with any feed directivity it is possible to design the lens shape in such a way that the reflection loss is low, for moderate beam-steering angles, without resorting to a complicated matching layer. The gain, directivity, beam-width, and the resulting distance between the feed elements are compared for all the designed lenses.

Using Optimized Eccentricity Rexolite Lens for Electrical Beam Steering With Integrated Aperture Coupled Patch Array

“…In general, the choice of directivity of the feed element is a compromise. With higher directivity feed elements, the reflection loss would be higher, and with lower directivity feed elements, the total of spillover and reflection losses are higher [7][8][9]. The simulated phase centre is about 0.15 mm below the patch, i.e., below the bottom of the lens.…”

“…In the case of the hemispherical lens, the eccentricity is 0, and the diffraction-limited patterns can be approximated by optimizing the extension length [3][4][5][7][8][9][10][11]. The mechanically simpler extended hemispherical lens is sometimes used to approximate the elliptical lens, e.g., [5,6,10,16].…”

“…The conventional high directivity integrated lens types are the extended hemispherical [3][4][5][6][7][8][9][10][11] and the elliptical lens [6,8,[12][13][14][15][16][17][18]. Diffraction-limited patterns are attained with an elliptical lens that has an eccentricity of e = (ε r ) −1/2 , and its extension length L equals e · a, where ε r is the relative permittivity of the lens material and a is the semimajor axis of the ellipse.…”

“…The beam-steering properties have been widely studied with simulations [3-9, 12, 13], and with measurements without electrical beam steering, i.e., without switches, e.g., in [3,5,9,12]. Moreover, double-shell integrated lenses [19,20], and shaped integrated lens antennas with optimized lens shapes have been studied, e.g., in [13,14].…”

“…The directivity of an extended hemispherical lens can be optimized by selecting the extension length [3][4][5][7][8][9][10][11]. Using a shorter extension leads to lower losses (e.g., [12]), but does not produce the diffraction-limited beam, and thus it is not preferable when narrow beam and high directivity are priority.…”