Circularly polarized loop‐line antennas

Electron. Comm. Jpn. Pt. I

2005

Self Cite

SUMMARYTwo types of microstrip line antennas made of loop elements are treated and a basic study of dual circular polarizations is performed. The analytical values obtained by the method of moments are used for the study. Dual polarizations are attempted with an antenna combining two conventional series loop-line antennas. Unwanted radiation near an elevation angle of 0° in the radiation pattern is recognized. The radiated field is separated into emissions from various parts of the antenna. The study results indicate that the radiation from the loop elements is weak. Next, based on the study results, a parallel loop-line antenna is proposed. After a design method for the antenna is presented, the dual polarization characteristics are demonstrated. In comparison with the case of a series loop-line antenna, the unwanted radiation at an elevation angle of 0°i s decreased from -9 dB to -18 dB. Finally, the frequency characteristics of the parallel loop-line antenna are studied. It is shown that a circular polarization with an axial ratio of less than 3 dB can be obtained over a bandwidth of 1%.

“…1(b) [15]. In this mechanism, the important matter is what determines the direction of the circular polarization.…”

Section: Methods Of Analysis and Seriesmentioning

confidence: 97%

Section: Methods Of Analysis and Seriesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Circularly polarized loop‐line antennas: Fundamental study on dual polarization

Hirose

Kanazawa

Electron. Comm. Jpn. Pt. I

2005

Self Cite

Circularly polarized grid array antenna composed of open-loop elements for beam scanning

Iitsuka

Yamauchi

2010 IEEE Antennas and Propagation Society International Symposium

2010

IntroductionAn edge-fed Kraus-type grid array antenna (GAA) radiates a linearly polarized (LP) beam, whose direction varies with frequency [1]. The long and short side lines of each grid cell for this GAA act as the transmission-line and radiation elements, respectively.To radiate a circularly polarized (CP) beam, the short side lines of each grid cell for this GAA have been replaced with spiral elements in [2]. This spiral GAA has a 16% frequency bandwidth for a 3-dB axial ratio criterion. Within this frequency range, the beam direction varies from the zenith toward the horizontal direction with an increase in frequency.The spiral GAA in [2] shows that, as the frequency is increased, the half power beam width becomes wider, resulting in a decrease in the gain. In addition, fabricating the spiral GAA is found to be difficult due to the three-layer structure.This paper proposes a novel GAA that radiates a CP beam whose direction varies with frequency. The proposed GAA is composed of open-loop elements [3], instead of spiral elements; the proposed GAA has a two-layer structure leading to easy fabrication, unlike the spiral GAA [2]. The radiation characteristics, including the beam direction, axial ratio, and radiation pattern, are analyzed and discussed. Fig. 1 shows a proposed CP GAA, which is a modification of a spiral GAA. The spiral elements are replaced with open-loop elements, which are located at height H GP above the ground plane. Point F is the feed point and point T is the terminal port loaded with a resistor R (= 50 Ω). The number of open-loop elements is n (= 27). The grid cell is defined by L x × L y (= 0.5λ 12 × 1λ 12 , where λ 12 is the wavelength at a test frequency 12 GHz). Two wire radii are used: ρ 1 (= 0.002λ 12 ) and ρ 2 (= 0.01λ 12 ). The circumference of the open-loop is approximately 1.2λ 12 . This CP GAA is designed to radiate a right-handed CP wave. The ground plane is assumed to be of infinite extent in the following analysis. Configuration978-1-4244-4968-2/10/$25.00 ©2010 IEEE DiscussionAnalysis is performed using the method of moments [4]. A frequency range of 10 to 15 GHz is used. Fig. 2 shows the frequency response of the axial ratio in the direction of the main beam. There are two distinct frequency regions, where the axial ratio is less than 3 dB: one ranging from 10.7 to 12.0 GHz (a bandwidth of approximately 11%) and the other ranging from 12.4 to 14.0 GHz (a bandwidth of approximately 12%). The beam direction within the former (lower) frequency region varies from θ = −29 o to 1 o and the beam direction within latter (higher) frequency region varies from θ = 4 o to 33 o in the x-z plane, as shown in Fig. 3, where 0-degree beam direction (broadside direction) is obtained at a frequency near 12 GHz. Detailed investigation reveals that the proposed CP GAA has a wider beam scanning range than the conventional CP GAA with spiral elements. Fig. 4 shows the representative radiation patterns in the x-z plane. The proposed CP GAA radiates a backward beam at low frequency 11.5 GHz and a for...

Coplanar spiral antenna

2011 IEEE International Symposium on Antennas and Propagation (APSURSI)

Arao

Ōyanagi

et al. 2011

A coplanar spiral antenna (CSAT) in free space is analyzed using the finite-difference time-domain method. It is found that the CSAT radiates a circularly polarized wave over a relatively wide frequency range (13%). The gain is found to be an approximately 4.8 dBi. Subsequently, a CSAT with a glass plate is investigated. It is found that impedance matching is achieved by partially removing the conducting areas between the antenna filaments.