Perturbed hexagonal microstrip antenna for circular polarization

This paper presents a single-feed circularly polarized (CP) microstrip antenna achieved by defected ground structure. With the proposed DGS, a new resonant mode is added, which is orthogonal to the original resonant mode. These two modes will have the same magnitude and the 90° time-phase difference by adjusting the DGS dimensions, which contributes to achieve the CP radiation. Both the simulated and measured 10-dB impedance bandwidth of the CP microstrip antenna are 30 MHz, while the 3-dB axial-ratio bandwidth is 6 MHz. The CP gain across the 3-dB AR band ranges from 4.6 to 5.0 dBic.

In this paper, a framework of a novel communication system based on circular polarization modulation called Offset Circular Polarization Modulation (OCPM) is proposed which not only increases the channel capacity but also provides data security against eavesdropping. In conventional circular polarization modulation (CPM), only one bit of data (1 or 0) can be transmitted at one time by using either left hand circular polarization (LHCP) or right hand circular polarization (RHCP), limiting it to only 2-states polarization modulation scheme. However, the proposed OCPM scheme provides eight-fold increase in the polarization states. In OCPM, typical CPM constellations (LHCP or RHCP) can be shifted to different quadrants using an offset vector in order to increase the number of polarization states. In addition to switching the swing of circular polarization (CP) in OCPM, quasi-dc offset vectors are added to the horizontal and/or vertical components of the CP wave with different combinations. The reason why quasi-dc offset vectors have been used is because pure dc offsets cannot be wirelessly transmitted. The quadrant of the modulation is determined by the offset vectors. For instance, in order to shift a CP constellation (LHCP or RHCP) in the first quadrant, two positive offset vectors are required: one along horizontal-axis and the other along vertical-axis of the EM wave. Thus, OCPM is a dual dimension CPM scheme with polarization state as well as offset state. The eavesdropper would require both dimensions (i.e. Polarization state and offset state) to correctly determine the overall state of the OCPM scheme.

This study presents a lightweight planar patch-array reflectarray at Ku-band for satellite communications. The reflectarray is composed of two separate planar structures: the radiating interface formed by a planar multi-layered broadband patch array, and a phase shifting device formed by 3 dB/90° couplers. The radiating element is a multi-layered patch structure, designed to provide circular polarisation (CP). Each array cell phase is controlled by open-ended shifting lines of variable length connected to the 3 dB/90° couplers. The use of this kind of couplers maintains the same CP received/transmitted: the design imposes that if a right-hand CP (RHCP) [or left-hand CP (LHCP)] is received coming from the feeder, the same RHCP (or LHCP) configuration is re-radiated by the reflectarray. Additionally, the feeding horn can be moved in the x or y axes, so that the feeder angular position let re-define the radiation pattern and its pointing direction. Finally, measurements of a lightweight portable planar reflectarray prototype are provided and very good agreement is observed when compared with theoretical results.

The frequency‐dependent circular dichroism is proposed to extend the wave manipulating capability of coding metasurfaces. As a proof of concept, the bispectral circular dichroic coding metasurfaces (CDCMs) are realized using circular dichroism resonators (CDRs) implemented via introducing loss resistors into the circular polarization conversion resonators. The CDRs are distinguished into left‐handed CDRs and right‐handed CDRs. Left‐handed CDRs absorb left‐handed circularly polarized (LCP) wave and convert right‐handed circularly polarized (RCP) wave into LCP wave. Conversely, they are defined as right‐handed CDRs. Two bispectral CDRs are designed with the left‐handed (right‐handed) and right‐handed (left‐handed) working bands in 7–8.5 and 22.2–22.5 GHz, respectively. And then, 1 bit bispectral CDCM with 0101…/1010… coding sequence is designed. Simulated results indicate that the designed CDCM strongly absorb the incident LCP (RCP) waves in the frequency region 7–8.5 GHz (22.2–22.5 GHz), but the incident RCP (LCP) waves are anomalously reflected into four beams of the LCP (RCP) waves with high efficiency. The measured results agree well with the simulations. The results in this work may provide an effective solution for the inverse and helicity‐dependent manipulation of the electromagnetic waves in two distinct frequency regions.

본 논문은 UHF RFID 시스템을 위해 편파를 선택할 수 있는 리더 안테나를 설계 및 구현하였다. 제안된 리더 안테나는 두 개의 급전부를 가지는 마이크로 스트립 패치 안테나와 두 개의 SPDT 스위치와 하나의 SP4T 스위치와 3dB hybrid coupler로 구성되어 있다. 각각의 스위치 전압을 조절하여 수직 방향의 선형 편파와 수평 방향의 선형 편파, 좌수 원형 편파와 우수 원형 편파를 선택할 수 있다. 제안된 안테나는 902MHz~928MHz 대역에서 VSWR 2:1 기준으로 UHF RFID 주파수 대역인 902MHz~928MHz를 만족한다. 안테나의 최고이득은 X-Y Plane을 기준으로 선형 편파가 선택되어질 때 7.71dBi, 7.55dBi 로 측정되었고 원형 편파가 선택되어질 때 7.31dBic, 7.81dBic 로 측정되었다. 또한 원형 편파(LHCP, RHCP)가 선택 되어질 때 축비는 각각 2.01~2.83dB, 2.02~2.60dB로 측정되었고 이는 3dB 이하의 축비를 만족한다. TIn this paper, it is designed the polarization selective antenna for UHF RFID system. The proposed antenna is consist of microstrip patch antenna with dual feeding and two SPDT switches and a SP4T switch and 3dB hybrid coupler. Through control of voltage of switches, the proposed reader antenna can select horizontally linear polarization, vertically linear polarization, left-hand circular polarization (LHCP) and right hand circular polarization (RHCP). The proposed reader antenna satisfied 2:1 VSWR at 902MHz~928MHz. and it has under 3dB AR(axial ratio). Peak gain of antenna is 7.71dBi, 7.55dBi with linear polarization and 7.31dBic, 7.81dBic with circular polarization at x-y plane. Also Axial ratio of antenna is 2.01~2.83dB and 2.02~2.60dB respectively. It is satisfied 3dB axial ratio.

This article presents the circularly polarized antenna operating over 28 GHz mm-wave applications. The suggested antenna has compact size, simple geometry, wideband, high gain, and offers circular polarization. Afterward, two-port MIMO antenna are designed to get Left Hand Circular Polarization (LHCP) and Right-Hand Circular Polarization (RHCP). Four different cases are adopted to construct two-port MIMO antenna of suggested antenna. In case 1, both of the elements are placed parallel to each other; in the second case, the element is parallel but the radiating patch of second antenna element are rotated by 180°. In the third case, the second antenna element is placed orthogonally to the first antenna element. In the final case, the antenna is parallel but placed in the opposite end of substrate material. The S-parameters, axial ratio bandwidth (ARBW) gain, and radiation efficiency are studied and compared in all these cases. The two MIMO systems of all cases are designed by using Roger RT/Duroid 6002 with thickness of 0.79 mm. The overall size of two-port MIMO antennas is 20.5 mm × 12 mm × 0.79 mm. The MIMO configuration of the suggested CP antenna offers wideband, low mutual coupling, wide ARBW, high gain, and high radiation efficiency. The hardware prototype of all cases is fabricated to verify the predicated results. Moreover, the comparison of suggested two-port MIMO antenna is also performed with already published work, which show the quality of suggested work in terms of various performance parameters over them.

This article proposes a design method for a circularly-polarized (CP) antenna, which is realized by using coupling effects. Initially, the desired electric(magnetic) coupling between two identical <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda$ </tex-math></inline-formula>/4 short-circuited microstrip line (MS-L) resonators can be generated when the short-circuited (opencircuited) ends of the resonators are in close proximity to each other. Besides, an orthogonal arrangement in space for these two resonators has been adopted to yield two orthogonal linearly-polarized (LP) waves. Therefore, a desired CP rotation can be achieved by choosing corresponding coupling types. Meanwhile, two equivalent circuit models are established and analyzed to deduce the formulas of the mutual inductance and mutual capacitance for the desired CP radiation. Afterwards, a binary array consisting of a magnetically coupled (MC) pair of resonators and an electrically coupled (EC) pair of resonators is proposed for expanding the axial ratio bandwidth (ARBW) and enhancing peak gain. Finally, a right-handed circularlypolarized (RHCP) antenna with magnetic coupling, a left-handed circularly-polarized (LHCP) antenna with electric coupling and a binary array are fabricated and tested. And an excellent agreement is validated between the experiment and simulation results. The measured results show that the binary array achieves a maximum gain of 5 dBic within its measured ARBW range of 3.535 – 3.615 GHz. In contrast, the single pairs (EC or MC pair) exhibit a gain of 3 dBic. Additionally, the array demonstrates a fivefold expansion in ARBW compared to the single pair.

In this paper, a circular polarized corrugated horn fed nonuniform reflectarray antenna of dual sense i.e left hand circular polarization (LHCP) and right hand circular polarization (RHCP) is presented for X band applications. The antenna consists of only a grounded dielectric layer 2.4 permittivity with variable thickness h from 0.5 to 10 mm. Design is completed within the 3D CST environment. The feeding unit having the circularly polarized characteristic is achieved by exciting two modes in a circular waveguide simultaneously and feeding the X-band Corrugated Horn Antenna (CHA). It can be concluded that all the simulated 3D CST radiation characteristics have shown that based on the feed port excitated the antenna can radiate LHCP or RHCP fields in a good performance.

A wideband circularly polarized reconfigurable microstrip patch antenna fed by L- shaped probes is proposed. The L-shaped probes are connected to a matching network underneath the ground plane, which two polarizations, right hand circular polarization (RHCP) or left hand circular polarization (LHCP), could be excited. With the use of PIN diodes and some biasing/RF components, an electrical switch has been designed. The antenna is capable to radiate either RHCP or LHCP by a single feeding port, with suitable biasing voltage on the switches. Preliminary study found that the antenna attains a bandwidth of about 20% with VSWR<2 and axial ratio<3 dB.

In this article, a wideband circularly polarized rectangular dielectric resonator antenna (RDRA) coupled through orthogonal slots and excited with a new microstrip circular ring has been investigated. Circular polarization has been achieved by using plus shaped (+) slot on the ground plane and excited through a new microstrip circular ring feed. TE11δ mode has been excited in the RDRA which has been confirmed through the distribution of E-field and dielectric waveguide model (DWM) method of RDRA. Circularly polarized (CP) RDRA offering measured −10 dB input impedance bandwidth of 20.79% (centered at 3.27 GHz) and 3 dB axial ratio bandwidth in broadside direction of 12.09% (centered at 3.39 GHz), respectively. From the CP radiation pattern, proposed design confirms that right-handed CP (RHCP) in broadside direction. The difference between RHCP field and left-handed CP (LHCP) field are above −26 dB in operational band. In addition, the proposed CP antenna offers stable gain and radiation efficiency in working bands and it is suitable for IEEE 802.16e/d Wi-MAX (3.3-3.7 GHz) band.

In this paper, a miniaturized circularly polarized (CP) continuous wave Doppler radar system operating at 2.4 GHz is presented. The radar front end consists of one left-handed CP (LHCP) antenna and one right-handed CP (RHCP) antenna, which share a single patch antenna aperture. Orthogonal polarization is achieved through a modified ring-shaped quadrature hybrid coupler (QHC), and the resulting isolation between the two CP antennas is better than 30 dB. With 0 dBm input power to the transmitting antenna, the proposed radar system can accurately detect heartbeat and respiration movements of human test subjects under 1 m and over a wide angular range. The single dual CP antenna achieves 280% size reduction compared to a traditional two linear polarization patch antenna array with the same isolation level.

A spiral antenna is a broadband element exhibiting circular polarization: right-hand circularly polarized (RHCP) or left hand circularly polarized (LHCP) depending on its winding. An array of spirals with dual polarization must therefore have spirals winding both right and left. A simple configuration alternates every other RHCP element with a LHCP element. In that case, the spacing is such that the frequency at which the grating lobes appear (so the maximum frequency of the array) is lower than the minimum frequency of the spiral (and, so, of the array, with a return loss less than −10dB).

In this paper, a switchable linear-to-circular polarizer based on varactor-loaded metasurface is proposed. With an incident 45° linear polarization (LP) plane wave, the polarization of the transmission wave through this polarizer can be switched between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) by controlling the bias voltage of the varactors. Simulation results show that the designed polarizer exhibits transmission losses better than -1 dB, and 3 dB axial ratio bandwidth of LHCP and RHCP is 1.7GHz (or 5.7%) and 1.5GHz (or 5%), respectively.

In this paper, the reconfigurable annular ring slot antenna with circular polarization diversity is proposed for SDMB(satellite digital multimedia broadcasting) system. The proposed antenna consists of a ring slot with tuning stubs. Four PIN diodes are attached to achieve circular polarization diversity. By switching the diodes on or off, the proposed antenna can be operated either RHCP(right hand circular polarization) mode or LHCP(left hand circular polarization) mode. The experimental result shows that the proposed antenna has an impedance bandwidth( VSWR les 2 ) of 2.47~3.04 GHz(570 MHz) at LHCP mode, an impedance bandwidth( VSWR les 2 ) of 2.45~3.01GHz(560 MHz) at RHCP mode, a maximum gain of 3.1dBi at RHCP mode, 4.76dBi at LHCP mode. The 3dB CP bandwidth of about 100 MHz at both RHCP and LHCP mode is achieved at the center frequency 2.63 GHz. The proposed antenna is suitable for application such as mobile satellite communications, WLAN(wireless local area networks), and broadband wireless communication systems.

This communication proposes a dual-band circularly polarized (CP) reflectarray design scheme based on precoding technology. Compared with traditional co - aperture arrays, this design allocates two circularly polarized elements to different frequency channels at 23 GHz and 26 GHz, respectively. This enables independent manipulation of dual-band beams, with the higher and lower bands boasting a mere frequency ratio of 1.13. By introducing the element sequential rotation technology and 1-bit active coding, the axial ratio (AR) bandwidth of the array is effectively improved, and the beam scanning ability is realized. To validate its performance, a 10 × 10 reflectarray prototype was simulated and fabricated. Experimental results demonstrate that the array achieves a beam scanning range of ±30° in the two-dimensional (2D) plane. At the 0° direction, the peak gains for the 23 GHz right-hand circularly polarized (RHCP) and 26 GHz left-hand circularly polarized (LHCP) beams are 18.12 dBic and 18.35 dBic, respectively. The 3-dB gain bandwidths are 7.8% (22.3 to 24.1 GHz) and 7% (25.0 to 26.8 GHz), while the 3-dB axial ratio bandwidths are 7.05% (22.15 to 23.77 GHz) and 5.85% (25.04 to 26.55 GHz). The aperture efficiencies are 13% @ 23 GHz and 10.85% @ 26 GHz, respectively.