Non-Uniform Sinusoidally Modulated Half-Mode Leaky-Wave Lines for Near-Field Focusing Pattern Synthesis

Abstract

A novel non-uniform sinusoidally modulated halfmode microstrip structure with application to near-field focused leaky-wave radiation in the backward Fresnel zone is proposed. First, it is presented a dispersion analysis of the constituent backward leaky wave in the sinusoidally modulated unit cell in half-width microstrip technology. This information is then used to design a finite non-uniform line that focuses the radiated fields at the desired point. Finally, eight similar line sources are arranged in a radial array to generate a three-dimensional focused spot located at the desired focal length over the simple central coaxial feeding. Simulated and experimental results are presented to validate the proposed simple approach.Index Terms-Backward radiation, half-mode leaky-wave antennas, near-field focusing, microwave lens, sinusoidal modulation, tapered leaky mode 0018-926X (c) and Head of the Microwaves Group. His research interest includes analytical and numerical methods for planar structures, anisotropic materials, and artificial media modeling. He has coauthored more than 130 book chapters and journal papers on those topics as well as more than 260 conference contributions.He acts as reviewer for more than 40 IEEE, IEE, AIP and IoP journals and he has been member of the TPCs of a number of local and international conferences. He is now Associate Editor of the International Journal of Microwave and Wireless Technologies.

Transmission-Line Model of Nonuniform Leaky-Wave Antennas

“…7 that the accuracy of the analysis decreases with increasing w A and decreasing L p . It is noted that rapidly changing LWAs are often used in periodic structures [34], [35], which is not the general type of problem addressed in this paper. In contrast, for many of applications of continuous-source LWA structures, the method still shows an excellent agreement and high degree of improvement compared to the classical formula as further shown in later sections.…”

A new class of nondiffracting pulses based on focusing leaky waves

“…More generally, the vectorial formulation of Maxwell's equations in a cylindrical reference frame shows that a cylindrical aperture of infinite extent supports the generation of Bessel beams in the nearfield region. Indeed, if we suppose to excite the structure with an azimuthally-symmetric source (e.g., a vertical coaxial feed), the electromagnetic field can completely be described by considering a transverse magnetic (with respect to the vertical z-axis) TM z vector potential A z = H (2) 0 (k r r)e −jk z z [21], which gives rise to the following electric field components [22] E z (r, z) / H (2) 0 (k r r)e −jk z z ,…”

“…where H (2) 0 (•) and H (2) 1 (•) are the outward Hankel functions of order 0 and 1, respectively. We note that the assumption of infinite extent (which also holds for electrically large apertures provided that the field is sufficiently attenuated at the edge truncation, as customarily happens for LWAs [23,24]) allows for retaining only the outward components of a cylindrical wave (generally constituted by a superposition of outward and inward Hankel waves).…”

“…Since an inward cylindrical-wave aperture distribution is needed to focus a Bessel beam [15], and inward and outward Hankel functions are related through [25] H (1) n (k r r) = −H (2) n (−k r r),…”

Design and Measurement of a Novel Seamless Scanning Leaky Wave Antenna in Ridge Gap Waveguide Technology

“…Leaky wave antenna (LWA) has exhibited attractive advantages in wide ranges such as broadband wireless communication, collision-avoidance radar, frequency modulated continuous wave radar, and pattern synthesis [1,2]. Generally, the scanning range is considered specially since it is necessary for practical applications [3].…”