Abstract
In this paper, we describe the design and implementation of a frequency-scanned slotted waveguide antenna with a closed stopband which has a low sensitivity to the fabrication errors. The antenna is implemented as a slotted slow-wave waveguide by loading a standard WR22 waveguide with elliptical posts. A systematic design approach for scanning through broadside and closing the stopband with a reduced sensitivity to fabrication tolerances is discussed in the paper. This approach allows for fabricating the antenna using CNC machining with a tolerance of +/−0.13 mm for the waveguide and a tolerance of +/−0.05 mm for the posts. The antenna beam can be steered from −38° to +27° by changing the frequency from 27 GHz to 34.7 GHz. The effective radiating length of the antenna is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27.6\lambda $ </tex-math></inline-formula> corresponding to a 1.75° half-power beamwidth while its radiation efficiency changes between 54% and 90% throughout the steering range.
Highlights
T HE NEED for low-cost, efficient, and extendable beamsteerable antennas at millimeter frequencies has been rising due to their expanding applications in communication systems, medical imaging, autonomous vehicles radars, and remote sensing [1]- [7]
Due to the considerable drop in the efficiency of tunable electronic components at millimeter-wave frequencies, frequency-scanned antennas can provide better efficiencies at this frequency range, especially if a long electrical length is needed for a small half-power beamwidth (HPBW) and a large gain [8]- [10]
We propose a frequency-scanned slow-wave slotted waveguide antenna at millimeter frequencies using CNC machining
Summary
T HE NEED for low-cost, efficient, and extendable beamsteerable antennas at millimeter frequencies has been rising due to their expanding applications in communication systems, medical imaging, autonomous vehicles radars, and remote sensing [1]- [7]. It is very important to reduce the sensitivity of the closed stopband to the fabrication error when the antenna is implemented using CNC machining This becomes even more important when a high scanning rate is needed. We propose a frequency-scanned slow-wave slotted waveguide antenna at millimeter frequencies using CNC machining. The latter are hybrid modes consisting of both longitudinal electric and magnetic fields resulting in a hybrid propagating mode in the slow-wave waveguide This analysis is done through approximating the posts using strips and diaphragms which simplifies the structure and allows for the derivation of the dispersion relation analytically. Due to the presence of the posts, the proposed slow-wave waveguide should by cut in the H-plane This current confinement reduces the Ohmic loss due to the gap in the middle of the side walls after assembly resulting in an increased radiation efficiency which proves important for series-fed leaky-wave antennas (LWA). As a result, reducing the sensitivity of the stopband to the fabrication errors becomes as important as reducing the stopband itself
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