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A monopole antenna with dual (linear/circular) polarization reconfigurability for X-band applications is presented in this paper. The antenna consists of a bent arm cross-shaped (BACS) slot created on the inverted triangular staircase fractal (ITSF) shaped patch. Two PIN diodes are embedded on the opposite side of the horizontal arm of the BACS slot for electronic switching between two different polarization states. By varying the biasing conditions of PIN diodes, the measured antenna’s 3 dB axial ratio (AR) operational band for left-hand circular polarization (LHCP) is observed from 9.88 GHz to 11.06 GHz, whereas linear polarization (LP) is achieved from 7.95 GHz to 12.64 GHz. The measured peak gain of the antenna is 5.71 dBi, whereas the average peak gain is obtained as 4.97 dBi. The size of the antenna is $1.57\mathrm {\lambda }_{\mathrm {g}}\times 1.25\mathrm {\lambda }_{\mathrm {g}}$ where, $\mathrm {\lambda }_{\mathrm {g}}$ is guided wavelength at the lowest cutoff frequency, 7.95 GHz. The proposed monopole antenna’s progressive design steps, an equivalent lumped circuit model analysis, and a comparative study between electromagnetic (EM) simulation and measured results are carried out to validate the antenna’s performance.

A circularly-polarized-reconfigurable patch antenna based on fluidic control method is proposed in this paper. A liquid dielectric, ethyl acetate, is introduced to change the substrate of a patch antenna from homogeneous to inhomogeneous. Two orthogonal fundamental transverse magnetic (TM) modes are excited with a 90° phase difference in order to produce circularly polarized (CP) radiation. Then, the polarization of the proposed patch antenna is switchable between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) through the injection of the liquid dielectric to different channels in the substrate. For demonstration, the proposed antenna is designed at 2.4 GHz for radio frequency identification (RFID) application. According to the measured result, the proposed circular-polarization-reconfigurable patch antenna has a stable circularly polarized (CP) gain of 8 dBic and an efficiency of 90 % across the effective frequency band. Additionally, the measured overlapped impedance bandwidth of two polarization state is from 2.24 to 2.52 GHz which can fully cover the measured overlapped 3-dB axial ratio (AR) bandwidth from 2.38 to 2.43 GHz.

This paper presents a novel polarization-reconfigurable antenna based on the combination of circularly polarized (CP) modes, which is capable of changing its polarization states among arbitrary linear polarizations (LPs), left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP). A truncated square patch with two isolated aperture-coupling feeds is used as radiation element operating at 2.45 GHz, which can operate in two orthogonal CP modes with low crosstalk. By exciting one of the two feeding microstrip lines, LHCP or RHCP mode can be independently generated. Meanwhile, by simultaneously exciting the two feeding microstrip lines with identical amplitudes but with different initial phases, LP mode with polarization plane oriented in any desired azimuth direction can be obtained. The simulated and measured peak gain of the proposed antenna remains at about 6.8 dBi at 2.45 GHz and the impedance matching bandwidth ranging from 2.25 to 2.60 GHz is fully overlapped for all the polarization states. Experimental results show a good performance of the proposed antenna.

A combined frequency and polarization reconfigurable textile based wearable disc monopole antenna is proposed in this paper. The antenna consists of a disc monopole as the radiator and four PIN diodes for realizing the agility property. By varying the different switching combination of the PIN diodes, frequency reconfigurability is achieved between the GSM and ISM band. Two circular polarization states, right hand circular polarization (RHCP) and left hand circular polarization (LHCP) are also realized in each operating frequency band. The upper band polarization state is controlled by a L shaped stub introduced in the ground plane whereas the lower band polarization agility depends on the length of the parasitic arc placed around the main radiator. The antenna is fabricated and its performance is measured to validate the proposed design.

In this paper, a penta-polarization reconfigurable antenna with mushroom-type metamaterial loading is proposed, which can operate in x-direction linear polarization (x-LP), y-LP, 45°-LP, left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). In order to realize polarization reconfigurability, a dual-port dual LP mushroom antenna excited by crossed H-shape slot is designed by characteristic mode analysis (CMA). Through shifting the states of PIN diodes on the reconfigurable feeding network, the amplitude and phase distributions of two ports of the dual LP antenna can be dynamically controlled and the five polarization modes can be achieved. A prototype with a profile of 0.06λ0 at 5.2 GHz (λ0 is the operated wavelength in free space) is simulated and measured. The measurement results exhibit a wide impedance bandwidth over 33.2% for LPs and over 38.7% for CPs. In addition, the measured axial ratio bandwidths are 28.0% for LHCP and 30.3% for RHCP, and the maximum measured boresight gains of all modes are higher than 8.2 dBi. The simulated and measured results verify that the proposed antenna can achieve a balance between low-profile and broadband on the basis of penta-polarization reconfigurability. The proposed antenna can be applied to polarization diversity and C band satellite communication.

In this paper, an electronically polarization reconfigurable circular patch antenna with fixed resonant frequency operating at Wireless Local Area Network (WLAN) frequency band (2.4-2.48 GHz) is presented. The structure of the proposed design consists of a circular patch as a radiating element fed by coaxial probe, cooperated with four equal-length slits etched on the edge along x-axis and y-axis. A total of four switches was used and embedded across the slits at specific locations, thus controlled the length of the slits. By activating and deactivating the switches (ON and OFF) across the slits, the current on the patch is changed, thus modifying the electric field and polarization of the antenna. Consequently, the polarization excited by the proposed antenna can be switched into three types, either linear polarization, left-hand circular polarization or right-hand circular polarization. This paper proposes a simple approach that able to switch the polarizations and excited at the same operating frequency. Simulated and measured results of ideal case (using copper strip switches) and real case (using PIN diode switches) are compared and presented to demonstrate the performance of the antenna.