Conference PaperPDF Available

Design Procedure for 2D Slotted Waveguide Antenna with Inclined Coupling Slots for Sidelobe Level Control

Authors:
1
Design Procedure for 2D Slotted Waveguide Antenna with
Inclined Coupling Slots for Sidelobe Level Control
H. M. El Misilmani1,
,M. Al-Husseini2,and K. Y. Kabalan1
1American University of Beirut, Beirut 1107 2020, Lebanon
2Lebanese Center for Studies and Research, Beirut 2030 8303, Lebanon
AbstractSlotted Waveguide Antennas (SWAs) radiate energy through slots cut in a broad
or narrow wall of a rectangular waveguide. They offer clear advantages in terms of their design,
weight, volume, power handling, directivity, and efficiency. SWAs can be resonant (standing
wave) or non-resonant (traveling wave). Resonant SWAs outperform the non-resonant SWAs in
terms of efficiency due to its termination with a short circuit, compared to matching load in the
case of the latter, but with a narrower bandwidth. For broad-wall SWAs, the slot displacements
from the wall centerline determine the antenna’s sidelobe level (SLL). In addition, the rotation
angle of the coupling slot in a 2D system array of SWAs determines the power fed by each slot
into each branchline SWA.
This paper presents an inventive simple procedure for the design of a two-dimensional (2D)
SWA array system with desired sidelobe level (SLL). The system consists of multiple branchline
waveguides with broadwall radiating shunt slots. A main waveguide is used to feed the branch
waveguides through a series of inclined coupling slots with well-defined rotation angles for low
SLLs. For a specified number of identical longitudinal slots, the described procedure finds the
slots length, width, locations along the length of the waveguide, and displacements from the
centerline, for each branch waveguide. Furthermore, for a specified number of branch waveguides,
the method finds the rotation angle of each of the coupling slots.
To explain the controllable-sidelobe 2D SWA design procedure, an SWA with 8×8 elliptical slots,
designed for an SLL lower than 20 dB, is taken as an example. An 8-element 1D SWA with
a desired SLL is designed first. Eight identical such SWAs are then attached side by side. The
proper design of the 1D SWAs ensures having the desired SLL in one principal plane. To enforce
the same SLL over the whole 3D pattern, special care should be given to the design of the feed
SWA, whose slots should power the radiating SWAs according to a correct distribution. For the
taken example, the feed SWA should have 8 slots, separated consecutively by a distance related
to the radiating SWA aperture width and wall thickness. The power fed by each slot in the feeder
and fed to the branchline waveguide is controlled by the inclination angle of the coupling slot.
Figs. 1(b) and 1(c) show a comparison of the gain patterns for the following 2 cases: Case 1
where the radiating slots have a uniform displacement and the coupling slots have a uniform
rotation angle; and Case 2 where the radiating slots have non-uniform displacements and the
coupling slots have non-uniform rotation angles as per the design procedure. As inspected, the
SLL decreased from 12.1 dB in case of uniform displacements and rotation angles to less than
20 dB with the non-uniform displacements and inclinations calculated using the presented
simple design procedure.
(a)
-40
-30
-20
-10
0
10
20
30
0 20 40 60 80 100 120 140 160 180
Gain [dB]
Theta [Degree]
Non-Uniform
Uniform
(b)
-40
-30
-20
-10
0
10
20
30
0 20 40 60 80 100 120 140 160 180
Gain [dB]
Theta [Degree]
Non-Uniform
Uniform
(c)
Figure 1: (a) 2D System, Compared gain pattern results of the uniform and non-uniform displacements and
rotation angles design cases: (b) E-plane, (c) H-plane.
ResearchGate has not been able to resolve any citations for this publication.
ResearchGate has not been able to resolve any references for this publication.