A Loop-Line Antenna with Enhanced Bandwidth of Circular Polarization

Abstract

We investigate a circularly polarized (CP) transmission-line antenna composed of loop radiation elements, called a loop-line antenna. To enhance the CP wave bandwidth, an isolated loop radiation element is first analyzed using the method of moments. It is found that a CP wave bandwidth for a 3 dB axial-ratio criterion has a maximum value of 8%. On the basis of the analysis results, we design the loop-line antenna. It is found that the antenna shows a CP wave bandwidth of 6%, which is twice as wide as that of a conventional loop-line antenna. The analysis results are verified with experimental ones. In addition, a condition for wideband CP radiation is discussed and found to be a composite radiation element consisting of two CP loops.

A loop antenna with quasi‐two sources for circular polarisation

“…The comparisons are summarised in Table 1. It is seen that the present antenna has radiation characteristics comparable to those of loops with perturbation [3] and parallel wires [4]; the antennas have an axial ratio bandwidth and gain of approximately 10% and 7 dBi, respectively.…”

“…It should be noted that the bandwidth of 10% is easily obtained for the present antenna, while it has been attained for loop antennas [3, 4], where each loop height above the ground plane is selected. Furthermore, the present antenna has an advantage over shape‐deformation loop antennas [5–7] in that it has a wider CP wave bandwidth.…”

Bent and Branched Microstrip-Line Antennas for Circular Polarization

“…Note that a finding of (1) has never been presented in the authors' publications [3,4,7], including a preliminary conference paper [9]. Moreover, note that in [9], there has been no experimental result to validate a finding of (2).…”

“…Figure 2. Antenna configurations in [3,7]: (a) bent line antenna [3]; (b) branched line antenna [7].…”

“…There have been many studies on microstrip transmission-line antennas (line antennas) radiating a circularly polarized (CP) wave [1,2]. The line antenna is created by using the feedline itself that is periodically bent [3][4][5] or branched [6][7][8] above the ground plane. It has the advantage of a simple feed system for a series-fed linear array.…”