Dual-band Circularly Polarized Slot Antenna Research Articles

Design Approach for a Dual-Band Circularly Polarized Slot Antenna With Flexible Frequency Ratio and Similar In-Band Gain

This letter presents an effective approach to design a dual-band circularly polarized (CP) slot antenna with flexible frequency ratio (FFR) and similar in-band gain under the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</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">$\it\lambda$</tex-math></inline-formula> -mode radiation. Initially, a CP slot antenna is realized in virtue of two orthogonal slot radiators. Then, by folding both slot radiators at a 1/4 length position from the short-circuited terminal, a CP slot antenna operating at two distinct bands is successfully realized based on the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</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">$\it\lambda$</tex-math></inline-formula> -mode, where stable gain with similar level for the dual working bands is achieved. After that, two pairs of slot stubs are properly introduced to effectively reallocate the higher band based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode, thus acquiring for a wide frequency ratio ranging from 1.85 to 1.26. Finally, for experimental validation purposes, two specific CP slot antennas with distinctive frequency ratios of 1.85 and 1.26 are implemented and tested. A similar-level gain within their dual operating bands can be achieved as another merit in addition to the FFR.

Dual-Band Dual-Sense Polarization Reconfigurable Circularly Polarized Antenna

This letter presents a novel dual-band circularly polarized slot antenna. The far-field polarization of the antenna can be switched electronically between left-hand circular polarization and right-hand circular polarization. A 50 Ω microstrip feed line is divided into four arms those excite a ground plane slot. The p-i-n diodes are introduced in the arms for polarization switching. A prototype dual-band dual-sense antenna with f 01 = 2.4 GHz and f 02 = 5.2 GHz is fabricated using a 1.6 mm thick FR4 substrate. The measured 3 dB axial ratio bandwidths are more than 16.6% and 5.7% at the lower and upper bands, respectively. The measured return loss is more than 10 dB over the wireless local area network (LAN) bands.

The U-Shaped Structure in Dual-Band Circularly Polarized Slot Antenna Design

The U-shaped structure is presented for designing a dual-band circularly polarized (CP) slot antenna that has a single metallic layer and is fed by a coplanar waveguide (CPW). To evaluate the performance of the versatile structure, a U-slot and a U-strip slot antenna have been designed for 2.6/3.6 and 2.5/3.5 GHz bands application. By employing a Differential Evolution (DE) algorithm to optimize some primary parameters of the proposed antennas, the optimum impedance and axial-ratio bandwidths at the given operating frequency can be achieved without using the trial-and-error method. Prototypes of the two proposed designs were constructed and studied experimentally. The measured results show that the frequency ratio of the upper band to the lower band is 1.4 (3.6/2.6 GHz, 3.5/2.5 GHz) or less. Other characteristics such as impedance bandwidths, axial-ratio bandwidths, radiation patterns, and peak gains will also be presented for design validation.