Wideband polarization reconfigurable circularly polarized antenna with omnidirectional radiation pattern

This paper presents a wideband reconfigurable circularly polarized (CP) antenna with omnidirectional radiation pattern. The antenna is based on a shorted monopolar patch surrounded by multiple curved branches and it is proximity‐fed by a disk‐loaded coaxial cable. The polarization reconfigurability is realized by introducing PIN diodes on junctions between the patch and the branches to alter the current direction flowing on the branches. By properly controlling the ON/OFF states of the diodes, the antenna's polarization can be switched between right‐hand circular polarization (RHCP) and left‐hand circular polarization (LHCP). A reconfigurable prototype has been fabricated and measured. The experiments show that the prototype has wide overlapped bandwidth from 2.3 to 3.1 GHz, in which the reflection coefficient and the axial ratio (AR) are less than ?10 dB and 3 dB for both polarization states. Besides, the antenna radiates dipole‐like patterns with the realized gain of around 0.6 dBic across this operating band.     

Novel planar reconfigurable circularly polarized complementary antenna for unidirectional end‐fire radiation

In this article, a novel planar reconfigurable circular polarization (CP) complementary antenna for unidirectional end‐fire radiation is proposed. Its radiator is the combination of a shorted quarter wavelength patch and an electric dipole, which provide the vertical and horizontal polarizations, respectively. By adding a 90° phase delay line, the proposed antenna radiates CP electromagnetic waves in the unidirectional end‐fire direction. Four p‐i‐n diodes are also inserted at joints of the electric dipole and the phase delay lines, and two orthogonal CP states, left‐hand (LH) and right‐hand (RH) CPs, can be switched. In order to reduce the number of DC bias lines, electric dipole arms on both sides of the substrate are connected by metal via‐holes, which simplifies the DC bias lines. The proposed antenna at 2.45 GHz is designed and fabricated. Its measured impedance bandwidth with |S₁₁| < ?10 dB and 3‐dB axial ratio bandwidth are 2.1% and 10.7%, respectively. Additionally, its maximum half power beamwidth in xoz plane is 196°. Reasonable agreement between the measured and simulated results validates the polarization reconfigurability of the proposed antenna.     

Low‐profile omnidirectional circularly polarized antenna based on substrate integrated waveguide technology

A substrate integrated waveguide (SIW) circularly polarized (CP) antenna with omnidirectional radiation in the azimuthal plane is proposed. The antenna consists of five identical end‐fire CP antenna elements in a pentagonal array configuration, which is loaded on a circular substrate. Each element contains an H‐plane horn antenna in SIW structure and a printed dipole antenna. Five parasitic curve elements are introduced to improve the omnidirectional property of the antenna. Combined with complementary dipoles theory and SIW technology, prototype antenna is designed, fabricated and measured. With a low profile of 0.024λ₀, the antenna has a 10‐dB return‐loss impedance bandwidth of 4.08% (2.4～2.5 GHz) and a 3‐dB axial‐ratio (AR) bandwidth of 5.76% (2.36～2.50 GHz). The antenna works well in the 2.45 GHz ISM band, with good cross‐polarization and excellent omnidirectional property.     

A novel circularly polarized cavity backed SIW antenna with capability to change polarization diversity by a reconfigurable polarizer structure

This article examines a substrate integrated waveguide (SIW) cavity‐backed circularly polarized diversity antenna. In the proposed novel antenna, parasitic patch and reconfigurable diodes are used to change polarization diversity from left hand to right hand and vice versa, respectively. In addition to, what makes distinctive proposed antenna in compared with similar works, is ability to change linear polarization from a SIW slot to circularly polarization by a parasitic patch. Chopping off two diagonally opposite corners makes the resonance frequency of the mode along this diagonal to be higher than that for the mode along the unchopped diagonal. By exciting parasitic patch with a slot along axes of it the orthogonal modes are generated which causes to CP. The comparison between simulation and measurement results validate antenna design. The measured impedance BW (VSWR < 2) for state 1 and 2 are 22.18% (11.86‐14.82 GHz) and 21.68% (11.88‐14.77 GHz), and The measured 3‐dB AR BW for states 1 and 2 are about 11.46% (11.43‐12.82 GHz) and 11.23% (11.43‐12.79 GHz), respectively. Finally, the measured maximum gain is 9.81 dBic.     

Multi‐petal antenna with omnidirectional circular polarized radiation

This article presented an omnidirectional circularly polarized antenna with simple and low‐cost configuration designed by combination of tilted loops for unmanned aerial vehicles such as drones and quadcopters. Length of each loop was 1 wavelength and was repeated around antenna axis with a specific angle. The 90° phase difference between 2 equally orthogonal polarized components was inherently provided by the loops without the need for exciting the loops 90° out of the phase. Symmetric configuration antenna yields circular polarization in both the azimuthal and elevation planes. The measured results showed that the 10‐dB impedance bandwidth was 390 MHz (ranging from 2.1 to 2.5 GHz) at the frequency of 2.45 GHz and the axial ratio bandwidth for < 3 dB was 400 MHz (ranging from 2.1 to 2.5 GHz). Moreover, this antenna had the right hand circular polarization with the difference between the measured left hand and right hand circular polarization gains being about 20 dB; the right hand circular polarized gain was about 1.4 dB.     

Broadband circularly polarized Z‐shaped dipole antenna with parasitic strips

A Z‐shaped dipole antenna with parasitic strips is proposed for wideband and unidirectional circular polarization operation in this article. The dipole arms are bent into L‐shape for circular polarization, and printed balun is used to achieve good impedance matching. To further extend the axial ratio bandwidth, two parasitic strips are employed to introduce an additional band of circularly polarized operation at the high frequency. Measured results demonstrate that the proposed antenna has a 10‐dB impedance bandwidth of 63.3% (1.64‐3.16 GHz) and a 3‐dB axial ratio bandwidth of 51.1% (1.72‐2.9 GHz). Stable radiation patterns with gain around 9 dBic along +z‐axis are also observed.     

Novel wide‐beam cross‐dipole CP antenna for GNSS applications

A wide‐beam circularly polarized (CP) cross‐dipole antenna for GNSS applications is proposed in this article. This cross‐dipole antenna is fed by a coaxial cable, on which the slots is added to optimize the impedance matching. These two pairs of dipole arms are designed with different lengths to obtain the circularly polarized radiation. Enhanced wide‐beam CP radiation characteristics can be achieved by curving the dipole arms and adjusting the distance between the arms and the metallic ground plane. The study of proposed antenna performance with different geometric parameters has been conducted. The final antenna exhibits a good impedance bandwidth (IBW) of ～13.1% (1.50‐1.71 GHz), and the 3‐dB axial‐ratio bandwidth is over 7% (1.52‐1.64 GHz). Broad pattern coverage of more than 140°, pure CP radiation at all designed bands and a wide 3 dB axial‐ratio beamwidth (ARBW) of nearly 150° makes this antenna an excellent candidate for satellite communications and navigation systems.     

A polarization‐reconfigurable array design based on mode combination technique

This article reports a novel polarization‐reconfigurable antenna array using the technique of mode combination (MC). It can electronically alter its polarization states between left‐hand circular polarization mode, right‐hand circular polarization mode, and linear polarization (LP) mode. The antenna array consists of 2 × 2 microstrip antenna elements with one L‐slot on each square patch and two PIN diodes located in the slot region. Instead of degenerating circular polarization (CP) and LP modes by exciting different radiation parts of the antenna element, the LP one is combined by orthogonal CP modes generated by adjacent elements of the proposed antenna array. To verify the concept, a prototype is manufactured and tested. Experimental results show that the proposed antenna has an overlapped ?10 dB impedance bandwidth of around 11.2% for both CP modes and the LP one. The realized maximum gains are around 7.5 dB for the CP modes and 5.6 dB for the LP mode, which are satisfactory for wireless local area network in wireless communication systems.     

A dual‐band and wideband omnidirectional circularly polarized antenna based on VO2

In this article, a dual‐band and wideband omnidirectional circularly polarized (CP) antenna based on the vanadium dioxide (VO₂) is investigated. The operating bandwidth of such an antenna can be regulated by altering the outside temperature (T), which is attained by the insulator‐metal transition of VO₂. The omnidirectional CP antenna is based on a loop antenna‐dipole model, which is composed of four tilted metal and VO₂ resonant units that are loaded around a cuboid and a feeding network for broadening bandwidth. The simulated results show that when T = 50°C (State I), the 10‐dB impedance bandwidth is 45.7% (1.67‐2.66 GHz), and the 3‐dB axial ratio (AR) bandwidth is 40% (1.9‐2.85 GHz). When T = 80°C (State II), the 10‐dB impedance bandwidth is 13.8% (1.62‐1.86 GHz), and the 3‐dB AR bandwidth is 21.8% (1.68‐2.09 GHz). In order to further characterize the concept of the proposed antenna, the related parameters of such an antenna are studied using simulation software HFSS.     

A polarization reconfigurable omnidirectional antenna realized by the gravity field tailored

In this article, a polarization reconfigurable omnidirectional antenna realized by the gravity field tailored is proposed, which is composed of the liquid metal Hg. The antenna is composed of four horizontal glass containers for omnidirectional horizontally polarized (HP) operating state (State I) and four tilted glass containers for omnidirectional circularly polarized (CP) working state (State II). By rotating the antenna, the position of Hg can be changed due to the effect of the gravity field, and different resonant structures can be formed to realize the regulation of polarization states between HP and CP working states. A reflector based on electromagnetic band gap (EBG) structure also is introduced, which can increase the gain and widen axial ratio (AR) bandwidth. The simulated results show that when the antenna is not rotated (State I), the 10‐dB impedance bandwidth is 21.2% (2.83~3.5 GHz). When the antenna is rotated (State II), the 10‐dB impedance bandwidth is 37.7% (2.35~3.44 GHz), and the 3‐dB AR bandwidth is 28.5% (2.35~3.13 GHz). After introducing the reflector, the max gain is increased to 2.1 dBic in State I and 2.2 dBic in State II, respectively. To further characterize the concept of the proposed antenna, a parametric study is carried out using HFSS.     

A wideband polarization reconfigurable isosceles trapezoidal monopole antenna

In this article, a polarization reconfigurable isosceles trapezoidal monopole antenna for the circular polarization (CP) is presented. A trapezoidal monopole and the ground plane are on the same side of the dielectric substrate. The monopole is excited by a reconfigurable T‐shaped 50 Ω microstrip feed line and reconfigurable vertical slots are incorporated in the ground plane to realize switchable wideband CP. For the different switching states of the p‐i‐n diodes, linear polarization, left‐handed and right handed CP can be achieved in the boresight direction (+z direction). The antenna prototype is fabricated and tested. The measured reflection coefficient bandwidth (|S11| < ?10 dB) is 31.2% (2.13 ‐ 2.91 GHz) and axial ratio bandwidth (axial ratio < 3 dB) is 22% (2.18 ‐ 2.72 GHz) for the CP. The measured reflection coefficient bandwidth is 18.56% (2.15 ‐ 2.59 GHz) for linear polarization.     

Single layer CPSSA array with change polarization diversity in broadband application

The present study proposes a novel broadband circularly polarized (CP) multiple‐input multiple‐output antenna array designed for C‐band applications. The first step was the introduction of a reconfigurable circularly polarized square slot antenna (CPSSA) capable of changing polarization diversity, which could cover impedance bandwidth (BW) from 4.48 to 8.21 GHz with 1.9 GHz of ?3 dB axial ratio (AR) BW. Then, a feed network composed of 90° and 180° couplers, a crossover, and delay lines was presented. The CPSSA with two metalized via‐holes adopted with two ports polarization diversity fed the networks. A number of reconfigurable CP array antennas using the polarization diversity technique have been presented so far. However, given that the proposed layout designed in a single layer had advantages of reduced antenna size and increased antenna gain and ARBW, this approach has received due attention over recent years. Another promising feature of this approach is its capability to change the polarization diversity by rotation of phases in the array feed network using PIN diodes.     

A wideband circularly polarized antenna array with sequential rotation feed

A novel wideband circularly polarized (CP) antenna array is designed, which consists of a horizontally placed wideband phase shifting feed network and four vertically placed linearly polarized dipole antenna elements, and the circular polarization is realized based on sequential rotation feeding technology. By placing two parasitic strips and two grounding strips on the top and side of each T‐shaped dipole antenna element, the impedance bandwidth and circular polarization performance of the antenna can be further improved. The simulation results show that the 10‐dB impedance bandwidth of the antenna is 93% (1.56‐4.27 GHz) and the 3‐dB AR bandwidth is 80.7% (1.7‐4.0 GHz). The measured results are in good agreement with the simulation results. Due to the use of orthogonally placed wideband feed network and wideband array elements, the proposed antenna array has a wider circular polarization bandwidth than the similar antenna arrays reported.     

Double triangular monopole‐like antenna with reconfigurable single/dual‐wideband circular polarization

A polarization and frequency reconfigurable circularly polarized (CP) antenna is proposed based on a novel bilateral switching mechanism. Two triangular monopole antennas are connected to each other in an L‐shaped form by a narrow link to produce a CP operation. In the proposed technique, 4 PIN‐diode‐based switches are designed with desired insertion loss and isolation, and only 2 DC‐voltage controllers. These switches are located on the links and the feed lines to realize a polarization reconfigurable feature including both right‐hand CP (RHCP) and left‐hand CP (LHCP) modes. Moreover, 2 CP states, a single wideband operation and a dual‐band operation, can be supported by this mechanism. In a special performance of the switches, CP reconfigurability can be obtained in a narrow‐band mode around 2.45 GHz. Two general simulations are performed based on the simple microstrip links and a diode‐circuit model. The measured results exhibit a wide overlapped bandwidth (AR < 3 dB and VSWR < 2) of 44.4% (1.63–2.56 GHz) with a peak gain of 2.88 dBi in the first state and 5.5% (1.22～1.29GHz) and 20.6% (2.12–2.61 GHz) with the peak gains of 0.52 and 3.0 dBi in the second state, respectively. A wide beamwidth is obtained more than 75°. This work is appropriate for L‐ and S‐band CP diversity applications.     

Water dense dielectric patch antenna with wide-band and circular polarization reconfigurability

A wide-band circularly polarized reconfigurable antenna based on a pure water dielectric patch antenna is proposed. By changing the shape of pure water in the plexiglass container symmetrically, the circularly polarized states of the antenna can be switched. And the available bandwidth of right-hand circular polarization and left-hand circular polarization remain unchanged. The interface between pure water and air with a great difference in relative dielectric constant is equivalent to an electrical wall. When feed with an L-shaped metallic probe, the axial ratio of a wide band can be formed, and the impedance bandwidth of antenna can be fully utilized. Under the two circularly polarized states of the antenna, the measured results show that the 3-dB axial ratio bandwidth is above 24.4% for |S₁₁| < ? 10 dB, the radiation efficiency is concentrated at 58%–71%, and the maximum gain reaches 3.5 dBi.     

Reconfigurable polarization rotation surfaces applied to the wideband antenna radar cross section reduction

A reconfigurable polarization rotation surface (PRS) using chessboard‐like geometry is introduced for the radar cross section (RCS) reduction of a Yagi‐Uda antenna in this article. The reconfigurable PRS reflector can be switched between low‐RCS PRS reflector and metal reflector. When the reconfigurable PRS reflector with ON‐state diodes is used in the Yagi‐Uda antenna, the antenna has a similar radiation characteristic compared with Yagi‐Uda using metal reflector. The PRS reflector can be used to achieve a low‐RCS characteristic reflector by chessboard configuration with OFF‐state diodes. Finally, the status of RCS can be switched according to the working state of diodes. The results show that the radiation performance of the Yagi‐Uda is preserved. The monostatic RCS of the Yagi‐Uda using PRS reflector with OFF‐state diodes can be reduced more than 25 dB.     

Semicircular shape hybrid reconfigurable antenna on Jute textile for ISM,Wi‐Fi,Wi‐MAX,and W‐LAN applications

This article presents the development of a conformal reconfigurable frequency circularly polarized jute textile antenna, working at 2.4, 3.5, 5.8, and 5.9 GHz in Wi‐Fi, Wi‐MAX, Industrial, Scientific and Medical radio bands and W‐LAN. The antenna topology is based on a semicircular structure as the main radiating component. The conductivity is realized by using copper paint, which was brush‐painted. The patch structure is rehashed in another side of the substrate against the ground with a rotation turn 180°. Two BAR64‐03 W PIN diodes switches are placed in between a semi‐elliptical structure and a rectangular structure on the bottom side of the ground plane. By governing the state of the switches, this antenna can operate at different operating frequencies. Furthermore, the antenna has an accomplished axial ratio (AR) of less than 3 dB for resonating frequencies at all four switching states. Other electromagnetic properties of the proposed jute textile antenna accomplished in simulations were confirmed through the measurement of the antenna in an anechoic chamber. The reconfigurable circularly‐polarized jute textile antenna shows a peak gain of 4.93, 5.67, 8.86, and10.07 dBi at 2.4, 3.5, 5.8, and 5.9 GHz (Wi‐Fi, Wi‐MAX, ISM, W‐LAN).     

Dual‐band reconfigurable circularly polarized monopole antenna

A microstrip antenna with dual‐band reconfigurable circular polarization (CP) characteristics in Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) bands is presented in this article. The proposed antenna has a symmetrical U‐shaped slot with PIN diodes on the ground plane. The slotted ground generates a resonant mode for broad impedance‐band width, and excites contrary CP state at 2.45 GHz for WLAN and 3.4 GHz for WiMAX, respectively. Because switching the states of PIN diodes on the slot can redirect the current path, the CP state of the proposed antenna can be simply switched between the right‐handed CP and left‐handed CP. The proposed antenna has a low profile and a simple structure. Measured results of the fabricated antenna prototype are carried out to verify the simulation analysis. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:109–114, 2015.     

Epsilon‐shaped circularly polarized strip and slot‐loaded ultra‐wideband antenna for Ku‐band and K‐band

A compact epsilon‐shaped (ε) ultra‐wideband (UWB) antenna for dual‐wideband circularly polarized (CP) applications has been investigated in this article. It consists of a stepped stub loaded modified annular ring‐shaped radiator and modified CPW ground plane. The ground plane is loaded with two semicircular notches and a spiral‐shaped slot. The impedance bandwidth (IBW) is 97.02% (10.4‐30 GHz) along with an overall footprint of 20 × 20 mm². The fractional axial ratio bandwidth (3‐dB ARBW) for two wide bands is 38.50% (13.30‐19.64 GHz) and 6.45% (26.25‐28.00 GHz), respectively. The proposed antenna is left‐hand circularly polarized with a peak gain of about 5.09 and 5.14 dB in both 3‐dB ARBW bands. The proposed antenna is dominating other reported CP antenna structures in terms of number of CP bands, 3‐dB ARBW, IBW, peak gain, and dimensions.     

Dual‐band circular‐polarization reconfigurable liquid dielectric resonator antenna

A novel single‐fed dual‐band circular‐polarization (CP) reconfigurable liquid dielectric resonator antenna (LDRA) using 3D printing technology is proposed in this article. With the quasi‐TE₁₁₁ and ‐TE₁₁₃ modes of the rectangular LDRA excited, a dual‐band design is achieved. To realize the CP reconfigurability, a combined container, holding the fluidic dielectric (Ethyl acetate, ε _r = 6.6), is fabricated by 3D printing technology. Therefore, the CP can be switched between two different states: (1) left hand CP (LHCP), when the right oblique container is full of the liquid solution; (2) right hand CP (RHCP), when the liquid solution is transferred into the left oblique one. Measured results demonstrate that the proposed antenna can achieve the CP reconfigurability in dual band, with the wide bandwidths (|S₁₁| < ?10 dB and AR < 3 dB) of 10.4% (1.55‐1.72 GHz) and 9.7% (2.29‐2.52 GHz), which cover GPS and WLAN bands.