Archimedean Spiral Antenna With Two Opposite Uni-Directional Circularly Polarized Radiation Bands Designed by Resonance Based Reflectors

Abstract

Abstract-Two opposite uni-directional radiation bands with good circular polarization (CP) characteristics are achieved in an Archimedean Spiral Antenna (ASA). A sandwich configuration is formed by utilizing two resonance based reflectors (RBRs) at the bottom and top sides of the ASA. Owing to the resonance characteristic, the RBRs do not act as reflectors at the other operational band, then, opposite uni-directional radiations are obtained, and the two uni-directional bands can be tuned independently. The proposed ASA with two uni-directional bands (ASA-TUB) has a wide impedance bandwidth about 4.4 : 1 (1.8-8 GHz), while its front-fire band (FFB) ranges from 1.8 GHz to 2.2 GHz (20.0%), and its back-fire band (BFB) is 4.4-7.1 GHz (46.9%) for front-to-back ratio (FBR) larger than 5 dB. The maximal FBRs for the FFB and BFB are 11.3 dB and 20 dB, respectively. Moreover, good CP performances are also obtained for the FFB and BFB. Besides, the whole profile of the proposed antenna is only 0.16λ at the lowest operational frequency. The proposed antenna has the properties of dual opposite uni-directional radiation bands, low profile, good FBR and CP.

A Low-Profile and Wideband Unidirectional Antenna Using Bandwidth Enhanced Resonance-Based Reflector for Fifth Generation (5G) Systems Applications

“…Besides, the FBR characteristics are not discussed in [8], [10], and [13]. The FBR bandwidths of the antennas in [15]- [17] and [25] are narrower than this design, even they are based on a lower FBR standard. For example, the antennas in [15] obtains an FBR bandwidth of 37.29%, even in a low FBR standard of 5 dB (FBR > 5 dB).…”

“…The performances comparisons between the proposed RBR antenna and other designs in [8], [10], [13], [15]- [17], and [25] are given in Table 2. The antennas in [8] and [13] occupy large areas, and the antenna in [10] has a high profile.…”

“…For example, the antennas in [15] obtains an FBR bandwidth of 37.29%, even in a low FBR standard of 5 dB (FBR > 5 dB). In [16], though additional director is used to enhance the FBR bandwidth (which complicates the structure and results in higher profile), its FBR [8], [10], [13], [15]- [17], and [25] (λ L is calculated at the lowest operating frequency of antennas). bandwidth is only 17.26% with FBR > 10 dB.…”

“…In [17], though the antenna presents uni-directional radiation in a very wide band, its FBR bandwidth is not mentioned, and its max FBR value is only 9 dB. In [25], the antenna utilizes two RBR and achieves two opposite uni-directional circular polarized radiation bands. One is the front-fire band (FFB) and the other is the back-fire band (BFB).…”

“…In this design, the FBR bandwidth is up to 55% with a high FBR standard of 10 dB (FBR > 10 dB). Besides, the antennas in [15], [16], and [25] are fed by gradual baluns that is perpendicular to the antennas, which would be negative effect for the profiles of the antennas. In this design, the antenna is fed by co-planar balun, which would be beneficial for some applications.…”