This article suggests a dipole electrically steerable parasitic array radiator (ESPAR) antenna that uses a crossed coplanar waveguide (CPW) transmission line that can be applied to beamspace multi‐input‐multioutput communication. The dipole antenna, which uses a vertically standing cylindrical structure, requires a feeding method that uses coaxial cable as the cable is connected inside the cylinder. As a result, it has the shortcoming of having to use cable with a limited diameter due to the cylindrical diameter as well as weak structure because of the flexible characteristic of coaxial cable. The antenna suggested in this article is rigid because it has a crossed PCB structure and it also has easier impedance matching than the cable feeding method because has a CPW transmission line. Moreover, the crossed CPW dipole ESPAR antenna turned out to have a radiation pattern similar to a dipole ESPAR antenna composed of a cylindrical structure. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2238–2242, 2015

In this article, a broadband omnidirectional horizontally polarized dipole antenna with branch lines is proposed. The proposed antenna consists of a dipole element with T‐shaped branch lines arranged in a circle in four directions on one microstrip substrate; power is supplied through an integrated balun. To check the broadband characteristics of this antenna, its radiation characteristics were examined while changing the width of the feed line, the distance between the dipole antenna and the branch line, the length of the branch line, and the distance between branch lines. As a result, the return loss in a structure with no branch line was −10 dB or less in the 16% band of 1.7–2 GHz, but in the structure with branch lines, it was −15 dB or less in the 38% band of the PCS/IMT/WLAN (1.7–2.5 GHz), which is broader by about 500 MHz than in a conventional antenna. The gain of the proposed antenna was atleast 1 dBi in the band used. The proposed antenna has a thin profile, as it consists of a single substrate. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2901–2905, 2015

In this article, an electrically steerable passive array radiator antenna was designed, consisting of a cylindrical dipole active element and four flat dipole parasitic elements. Using a varactor diode, which is a variable capacitor, reactance was applied to the parasitic elements and beam steering to a preferred direction can be achieved through the reactance change. A common ground was used for negative voltage applied lines, which were DC bias lines to control varactor diode voltage, with the active element ground. Using this structure, the number of DC bias lines could be reduced, resulting in the advantage of constructing a simple control circuit. In addition, using a quarter-wave meander strip line in the negative voltage applied lines, a voltage standing wave ratio characteristic was improved and an antenna gain was increased.

frequency 3.35 GHz) and 16.52% (at center frequency 3.57 GHz) in the broadside direction (h 5 08, U 5 08) shown in Figure 7. It is observed that in the Figure 8 the RHCP is stronger than the left hand circular polarization (LHCP) in broadside direction so, the proposed antenna is called RHCP. The simulated and measured RHCP and LHCP radiation patterns in xz-and yz-plane at 3.35, 3.55, and 3.75 GHz are shown in Figure 8. It has been found that in broadside direction the RHCP leads the LHCP by 226.63 dB, 219.28 dB, and 226.05 dB at 3.35 GHz, 3.55 GHz, and 3.75 GHz, respectively. The electric field distribution observed inside the DRA at different phase, that is, 08, 908, 1808, and 2708 confirms the proposed design is CP and it also confirms that the mode of DRA is TE 12d mode shown in Figure 9. The average gain and radiation efficiency is 4.69 dB and 74.84% in the working band shown in Figure 10. Table 1 show the comparison of earlier published work. It has been observed that proposed work shows improvement in AR bandwidth within working band over earlier reported design. CONCLUSIONIn this article, a new modified microstrip-line-fed rectangular dielectric resonator antenna coupled with slotted ground plane for circular polarization has been proposed. The measured impedance bandwidth is 17.87% (at center frequency 3.58 GHz) and measured AR bandwidth of proposed antenna is 16.52% (at center frequency 3.57 GHz) in the broadside direction (h 5 08, U 5 08), respectively. The proposed dielectric resonator antenna offer simple construction with sufficient bandwidth and excellent far-field properties. TE 12d mode has been excited in this proposed antenna. It has been observed that the proposed antenna shows RHCP in broadside direction (h 5 08, U 5 08). This antenna can be suitable for Wi-MAX (3.3-3.6 GHz) applications.

This article suggests a new 5‐element electrically steerable passive array radiators (ESPAR) antenna using a Koch fractal structure for the purpose of adding wideband characteristics to the conventional ESPAR antenna, and its characteristics were confirmed through design and fabrication. The Koch fractal ESPAR antenna with a monopole structure where two crossed boards stand vertically on a circular ground has four parasitic elements arranged around a single active element with a fixed radius and reactance is loaded on each parasitic element. It satisfied the return loss less than −15 dB from 1.7 to 2.4 GHz on the 700 MHz band and showed directivity and gain that have similar radiation patterns according to frequency. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2108–2112, 2015