Beam-pattern synthesis using slotted Rotman lenses

Abstract

In this article, the design principle of the Rotman lens is reviewed, and an X-band lens for 10-GHz operating frequency is simulated and analyzed. Rotman lenses with circular and elliptical slots of different orientations are simulated, and their associated radiation patterns are plotted too. The characteristics of the radiation patterns generated by a linear array antenna and the slotted Rotman lenses are functions of the shape, dimensions, location, and orientation of the slots etched on the metallic surface of the lenses that feed the array. The computer simulation results demonstrate that, in addition to the other significant advantages of microwave lenses, there is a strong potential for using slotted Rotman lenses as convenient microwave devices for beam-pattern synthesis.

DESIGN AND PERFORMANCE OF A K_U-BAND ROTMAN LENS BEAMFORMING NETWORK FOR SATELLITE SYSTEMS

“…The satellite Rotman lens has employed the focal arc based on the elliptical curvature on the beam port side with major and minor radiuses r a and r b respectively, the coordinates (X b , Y b ) of any designated beam port on the elliptical arc are determined as (20). The eccentricity parameter e of this focal arc is the crucial parameter affects the minimum phase error along the lens array ports [17], and is given as (21). The satellite lens could employ other focal arc configurations including: parabolic, hyperbolic, straight line, and circular; discussion of the individual design parameters for the mentioned geometries can be found in [18].…”

“…In the satellite lens, the offset RF beam port produces a path length difference and hence a phase gradient along the antenna array in order to perform steerable beamforming. There is also an additional lens parameter that gives the distance R from the lens center point to the focal point F 2 [17], and is given as (22):…”

“…where k 0 = 2π/λ is the wave-number for free space, k = k 0 /(ε r ) 1/2 is the dielectric wave-number, W is the length of the TL (Figure 1) connecting the array port n on the inner contour of the RF lens to the corresponding array element n on the outer contour, and d is the uniform spacing between adjacent microwave antenna array elements. The parameters a n , φ n , and W are functions of the scan angle α i corresponding to the lens focal point F i [17]. The RF lens array ports are connected to the antenna array with constant time-delay, and as the direction of incoming RF signal and corresponding wave-front change, the maximum energy is routed to one of the beam ports.…”