Polarised Radial Line Slot Array Research Articles

Highly Efficient Circularly Polarized Radial Line Slot Array Antenna Using Non-Uniform Slot Density for 5G Communication System

Highly Efficient Circularly Polarized Radial Line Slot Array Antenna Using Non-Uniform Slot Density for 5G Communication System

Increasing the Gain of Beam-Tilted Circularly Polarized Radial Line Slot Array Antennas

This article presents a new type of beam-tilted circularly polarized (CP) radial line slot array (RLSA) antennas. When the conventional beam tilting method is applied to CP-RLSA antennas, the aperture efficiency of the antenna degrades significantly due to very sparse slots in some parts of the antenna. A new method is presented to prevent this, and hence a much higher gain and aperture efficiency are achieved from the same antenna area. The key to the new method is an aggressively biased truncation of the slot layout that leaves out sparse slots. Consequently, the feed point moves closer to an edge of the TEM waveguide. A reflecting wall is introduced to prevent leakage from this edge. It is shown that the gain of RLSAs with beams tilted to 25° and 45° (measured from normal direction) can be increased by 5.5 dB (from 20.5 to 26 dBic) using the new method as opposed to the conventional method. The new concept and predicted results are validated using a prototype antenna with the beam-tilted to an angle of 25°. The aperture diameter and overall thickness of the prototype are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12\lambda _{0}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.4\lambda _{0}$ </tex-math></inline-formula> , respectively, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the operating frequency of 18 GHz. The measured results confirmed a higher gain of 26.2 dBic, an aperture efficiency of 30%, the overall efficiency of 93.2%, and sidelobe levels (SLLs) less than −25 dB at 18 GHz. The measured 10 dB return loss bandwidth of the antenna is greater than 63.7%, 3 dB axial-ratio bandwidth is 13.3%, and 3 dB gain bandwidth is 6.7%.

270-GHz LTCC-Integrated Strip-Loaded Linearly Polarized Radial Line Slot Array Antenna

A planar linearly polarized radial line slot array (RLSA) antenna is proposed to achieve a high gain with improved impedance matching and suppressed cross-polarization levels at a 270-GHz band. The proposed antenna is integrated in low-temperature cofired ceramic (LTCC). The impedance matching is enhanced by loading each radiating slot individually with a strip pair and employing an integrated feeding transition to an external standard waveguide in measurement. The cross-polarized radiation level is suppressed at all directions by aligning the orientations of the radiating slots. The antenna prototype exhibits the measured $\vert S_{11}\vert$ less than $-$ 10 dB over the frequency band of 261.3–282.2 GHz, a maximum boresight gain of 27.6 dBi at 275.2 GHz, and a 3-dB gain bandwidth of 9.8 GHz (271.2–281 GHz).

A Novel Technique in Simplifying the Fabrication Process and Improving the Reflection Coefficient of the Linear Polarized Radial Line Slot Array (LP-RLSA) Antennas

A novel technique in simplifying the fabrication process of LP-RLSA antenna as well as improving the reflection coefficient of LP-RLSA antenna is proposed in this paper. This technique utilizes a FR4 board added on the top of the normal LP-RLSA antenna. Theoretically, FR4 dielectric material is able to reduce antenna reflection coefficient since it produces the signal that has a different phase with the propagating signal within the antenna cavity. Moreover, by utilizing the copper part of the FR4 board as the radiating element, the fabrication process can be simplified since the antenna slots can be cut utilizing the simple low cost etching process. In this paper, the theory about how the utilization of the FR4 board can improve the reflection coefficient response is explained. The parameters that influence the capability of FR4 board in improving the reflection coefficient response are also discussed. A LP-RLSA antenna with FR4 board and a LP-RLSA antenna without FR4 board are designed and simulated at frequency of 5.8 GHz. The simulation result shows that the thickness and permittivity values of FR4 board influence the reflection coefficient response and the antenna gain. The best values of the permittivity and thickness of the FR4 board are 4.3 and 1.6, respectively. The simulation result shows that these values can improve antenna gain up to 2.45 dB. They can also improve reflection coefficient response significantly from –3 dB to –25 dB. It is discovered that the LP-RLSA with FR4 board also produces the beamsquint effect from –10° up to 10° from the boresight direction. The prototype of the designed antennas is fabricated and measured. The measurement and simulation results show that the LP-RLSA with FR4 board has a better gain and better reflection coefficient than the LP-RLSA without FR4 board, thus prove the concept of the novel technique.

Optimization Technique for Linearly Polarized Radial-Line Slot-Array Antennas Using the Multiple Sweep Method of Moments

This paper presents an effective full-wave procedure to optimize linearly polarized radial-line slot-array antennas. The procedure is based on a recursive method for solving large matrix equations known as the multiple sweep method of moments. As a result of this paper, new design suggestions have been introduced which greatly contribute to the performance improvement of this type of antennas. These elements are the arrangement of the slots in concentric ellipses instead of circles and a slight but crucial modification on the usual collocation of the reflection-canceling slots.