A 3-D Pattern-Reconfigurable Antenna Array With Multipolarization

In this article, a circular microstrip tunable wideband frequency and polarisation reconfigurable antenna are investigated. The wideband tunability is achieved by placing the four varactor diodes between circular microstrip patch and circular ring. The impedance bandwidth of 2.09–2.96 GHz (34.52%) is realised by tuning the capacitance value from 4.15 pF (0 V) to 0.94 pF (6 V). Both frequency tunability and polarisation reconfigurability are controlled in the antenna using the proposed cascaded branch line coupler feed network. The four single pole double throw and two dual in‐line package switches are used in the feed network to control the tunable impedance bandwidth of the antenna over a wideband from 1.25 to 2.95 GHz. The vertical linear polarisation and horizontal linear polarisation (H‐LP) are achieved by any one of the feed port excited in the antenna. Similarly, the right‐hand circular polarisation and left‐hand circular polarisation are realised by exciting both the feed ports in the antenna with±90° phase difference. The impedance bandwidth of proposed feed network is well matching with the tunable bandwidth of the patch antenna. Simulated and experimental verification results show good agreement.

This article presents a reconfigurable antenna feeding network for circular and linear polarization diversity. The proposed cir- cuit consists of two hybrid couplers and two single pole four throw switches for four configuration modes: left-hand circular polarization, right-hand circular polarization, vertical linear polarization, and hori- zontal linear polarization. For verification, a reconfigurable antenna with the proposed feeding network is designed at 917 MHz and meas- ured for switchable circular and linear polarizations. V C 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:893-896, 2014; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.28243

The conventional approaches to estimate the angle of arrival (AOA) have the limitations of hardware complexity, and where algorithms are used to optimize the estimation, there is the associated computational cost. This work presents a simplified approach in which the sum and difference of the received signals using a hybrid rat race (HRR) coupler forms the basis for the estimation of AOA. A 2 × 1 array designed to operate at 10 GHz is fed with quarter wave transformer impedance matching technique and is integrated with HRR coupler. The integrated array is evaluated for AOA estimate in both the azimuth and elevation planes. The transmit antenna foot print of 0° to ± 90° is considered. Result of the study indicates that the designed HRR coupler works optimally, exhibiting minimal reflection loss at each port, reasonable isolation between ports and acceptable phase difference at the sum (Σ) and difference (Δ) ports. The array exhibits a resolution capacity of ± 55° in the azimuth plane and ± 48° in the elevation plane, with an RMS error of less than 5° in both the planes. Beyond the estimated AOA, the array exhibits very high values of RMS error. Typically, in the transmit antenna footprint of ± 80°, the RMS error is as high as 42.5°. An important observation from the study is that the RMS error is independent of the position of the radiators in space, geometry of the array elements, and mis-orientation in the planes of the array. For a specific transmit antenna footprint of + 15° in the azimuth plane, the gain is optimal compared to that in the elevation plane. The proposed design is easy to implement, without the complexity of scanning or phased array. In addition, the absence of algorithm of any type eliminates the computation cost issue that is common in estimators based on adaptive beam forming and smart antenna.

A novel omnidirectional circularly polarized (CP) antenna with single feed is proposed for 2.4GHz WLAN applications. Based on the zeroth-order resonance (ZOR) mode of epsilon negative (ENG) transmission line (TL), the antenna excites uniform vertically polarized E-fleld just as the monopole does. A modifled Alford loop with electromagnetic coupling fed by L-shaped strip consists of four curved branches, which is placed on the top of the antenna and generates an equivalent horizontally polarized magnetic dipole mode. Once the two orthogonally polarized components are equal in amplitude but difierent in phase by 90 - , omnidirectional CP wave can be obtained. The measured results show that the impedance bandwidth (S11 < i10dB) is 6% (2.38{2.53GHz), and the 3-dB axial ratio bandwidth in the azimuth plane is very wide which achieves 54% (1.60{2.80GHz). Additionally, the 3-dB axial ratio beamwidth is over 50 - for radiation pattern in elevation plane. Moreover, the antenna achieves excellent omnidirectional right-hand CP performance with a variation of 0.5dB in the azimuth plane and an average gain over 1.5dB across the operating band, which are well applied to the wireless system.

A new broadside and conical beam reconfigurable dielectric resonator antenna (DRA) with three orthogonal linear polarizations (LPs) and two orthogonal circular polarizations (CPs) agility is presented. It consists of a quad-strip-fed DRA element and a reconfigurable feeding network. First, the DRA element is designed to make unidirectional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{HEM}}_{11 \delta }$ </tex-math></inline-formula> mode and omnidirectional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{TM}}_{01 \delta }$ </tex-math></inline-formula> mode operate in the same wide band by tactfully removing a concentric annular column from its interior. Furthermore, a center-loaded metal post helps to improve the impedance matching of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{TM}}_{01 \delta }$ </tex-math></inline-formula> resonance significantly. Afterward, the switchable feed network is designed to implement diverse phase distributions of four output ports, i.e., providing the quad-port in-phase excitation, dual-port differential excitations, and quad-port sequentially rotated phase excitation strategies for a vertical LP, ±45° slant horizontal LPs, and two CPs, respectively. Finally, a fully functional prototype is designed, fabricated, and measured to validate the design. The measured results show that the overlapping impedance bandwidth of 36.8% for all the states and the axial-ratio bandwidth of 33.8% for the CPs are obtained.

The modified positive position feedback (MPPF) controller, an active vibration control method that uses collocated piezoelectric actuator actuators and sensors, is developed using an adaptive controller. The adaptive mechanism consists of two main parts: (1) frequency adaptation and (2) adaptive controller. Frequency adaptation only tracks the frequency of vibrations using fast Fourier transforms. The obtained frequency is then fed to MPPF compensators and the adaptive controller. This provides a unique feature for MPPF by extending its domain of capabilities from controlling tonal vibrations to broadband disturbances. The adaptive controller mechanism consists of a reference model that is of the same order as the MPPF system and its compensators. The adaptive law provides the additional control force that is needed for controlling frequency changes caused by broadband vibrations. The experimental results show that the frequency adaptation method that is derived has worked quite well. The results also indicate that the MPPF can provide significant vibration reduction on a cantilever beam that is used throughout the experiments.

Linear polarization (LP) has been the traditional transmission strategy employed in current mobile wireless communication systems. Recently, circular polarization (CP) has regained much interest as CP proves to be a potential candidate to maximize the polarization efficiency component of the link budget. In this paper, the essential concepts of CP are first reinforced by a tutorial description in terms of mathematical insight, propagation characteristics, as well as related applications. Most reported works on CP chiefly focus on the theoretical description of its propagation benefits, such as significant amplitude fade and delay spread (DS) reduction, without simultaneously providing convincing proofs. In other words, CP propagation has not been investigated in sufficient depth. Therefore, we then propose a method for synthesizing CP that is implementation friendly to practical antennas. The engineering validity is subsequently verified by a series of chamber measurements. Intuitively, the polarization trajectory of a synthetical circularly polarized electromagnetic wave is illustrated to further prove the point. Finally, by conducting channel measurement campaigns in a typical urban macrocell scenario, radio propagation characteristics with a dipole as the receive apparatus are analytically extracted for both LP and CP. To facilitate fair competition, the radiation field patterns of two relevant transmitting antennas are intentionally designed to be identical. Numerical results quantitatively demonstrate that, compared with LP, CP can significantly alleviate branch power imbalance between vertical and horizontal polarizations and decrease DS. These advantages are in line with theoretical anticipation and can be fully exploited to upgrade the performance limits of current mobile wireless communication systems.

This paper presents an ultrawideband (UWB), wide-scanning, vertically polarized endfire phased linear array with a customized feeding network, specifically designed for the large-curvature wing-borne conformal (LC-WBC) skin across the P-L band. First, the mechanism for achieving a high-gain endfire beam is analyzed under the stringent spatial constraints of the skin. To maximize space utilization and form an endfire beam, ultralow-profile ferrite-loaded tightly coupled dipoles are strategically integrated on both the upper and lower sides of the wing-borne skin. Then, a novel wingtip-connected dipole element arrangement is proposed to obtain enhanced vertically polarized radiation by ensuring continuous current distributions on the array aperture. Additionally, this arrangement effectively resolves the intersecting beam problems caused by the skin’s large curvature (159 m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>) while simplifying the ground plane to a triangular-shape configuration. Finally, a compact three-dimensional (3D) multifunctional feeding network is developed and fully integrated with the array to achieve a customized phase excitation, thereby generating the desired high-gain endfire beam in the azimuth planes. To validate this design, a 1×8 prototype is fabricated and measured. Experimental results show that the proposed array is capable of scanning within a ±60° azimuth range from 0.28 to 1.96 GHz, and the average aperture efficiency is approximately 72.5% at broadside and 88.5% at 60° scan angle, confirming its superior performance and potential for applications in aircraft platforms.

A fiber laser is easily applied for micro welding owing to the excellent beam quality. Furthermore, a fiber laser is expected to be a promising heat source for adaptive control since the peak power is variable within sub-micro-second period. The objective of the research was to develop a new laser system with inprocess monitoring and adaptive control for the stable production of sound welds in thin sheets. The bead-on–plate welding of 0.1 mm-thick stainless steels was performed with a 75 W fiber laser beam of 1,090 nm wavelength. The stability of bead widths of laser welds made with or without monitoring and adaptive control was investigated in welding the sheet on the plate with a hole which should affect heat conduction and transfer. It was revealed that the heat radiation signal was sensitive to the increase in the bead width according to the change from heat transfer process to heat-insulated process. Moreover, the peak power was adaptively controlled in the minimum 50 ms-short period in order to produce stable weld bead width regardless of the existence or absence of the heat transfer plate. Consequently, it was confirmed that the fiber laser was an excellent oscillator for laser micro welding as well as for adaptive control.

This paper presents a design of mm Wave antenna array unit for imaging radar to determine the position of an object in the three-dimensional space. Proposed design gives the following advantages in comparison with existing solutions: high field-of-view to resolution ratio for the radar at minimum transceiver numbers, smallest possible sensor size in both elevation and azimuth plane, multi-functional support for both objects tracking and objects imaging. Antenna array unit provides supports 4 transmitting and 4 receiving channels (forming 16 virtual channels). Field of view is 21° and resolution is 10.5° in elevation plane. Field of view is 80° and resolution is 10.8° in azimuth plane. (Abstract)

A broadband low profile magneto-electric dipole (ME-dipole) antenna is proposed which can control the steering of the antenna beam in the elevation plane and azimuth plane. A reflective phase gradient metasurface (RPGMS) is designed to act as the partially reflecting surface of the antenna and provides two different phase shifts for it. By rotating and translating RPGMS around the center of the antenna can reshape the wavefront shape, realize beam steering with directions (, )= (±40°, 0°), (±30°, 0°), (±20°, 0°), (±20°, 90°). The results of full wave simulation are in good agreement with the measured results, the beam tilted range of ± 40° in E-plane and ± 20° in H-plane are obtained at 8 GHz. The bandwidth is between 42.5% and 48.4%, with a maximum gain of 6.29dBi.

Pattern reconfigurable technology can change the shape or beam direction of the antenna radiation pattern. The application of pattern reconfigurable antenna based on reconfigurable network is proposed in this paper, which designs a two-element and a four-element reconfigurable antenna array. The element of the array is composed of a cross-placed dipole, which the S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> is below −15 dB at 1.67 GHz–2.7 GHz with the bandwidth of 45%, and the isolation $S_{12}\lt -21 \mathrm{dB}$ in that bandwidth. In the array, the element is integrated with reconfigurable network by controlling the on/off states of the PIN diodes. There are three states for the two-element array and eight states for the four-element array. The S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> of the antenna is less than -10 dB between 1.7 GHz–2.7 GHz. The pattern reconfigurable antenna array is used as the feed of the plane luneberg lens in this paper, which realizes beam scanning. The two-element reconfigurable feed can realize 3 beam scanning with coverage of ±10°, and the four-element reconfigurable feed can realize 7 beam scanning, from large to small scanning angles are 32°, 19°, 10°, 0°, −10°, −19° and −32°, can achieve beam coverage from −32° to +32°. The two groups of reconfigurable antenna arrays designed in this paper are applied to a plane luneberg lens as the feed, with the location of elements changed, the beam direction changes. The reconfigurable antenna array is used as the lens feed, which simplifies the design of the feed and has high application value.

A wideband antenna with quad-polarization reconfigurable operation is proposed. It consists of a crossed tri-port feed linearly polarized (LP) radiation structure and a switchable feed network. A dual-port LP element with wideband characteristic and good port isolation is first introduced. The inherent 180° phase difference (PD) between two feed ports vastly simplifies the complexity of the design and improves the efficiency of the feed network. By assembling two grooved LP elements, the crossed tri-port feed radiation structure is formed. Meanwhile, a wideband 90° phase shifter and an unequal Wilkinson power divider are applied in designing the switchable feed network. Through controlling the PIN diodes implanted in the feed line, four working modes with equal amplitude and reconfigurable PD (0° or 90°) are achieved. Based on this, the desired quad-polarization reconfiguration, including two orthogonal linear polarization (LP) states and two orthogonal circular polarization (CP) states, is realized. Measured results show that the proposed antenna has a wide overlapped operation impedance bandwidth of 84.5%, ranging from 1.36 ~ 3.35 GHz, for all polarization states within a compact volume. The measured 3-dB AR bandwidth is 100%, covering the operation impedance frequency range. Radiation patterns exhibit unidirectional and stable quality from the point view of beam slant and split. Besides, a peak efficiency of 75% and a peak gain of 7.8 dBi are achieved.

view Abstract Citations (21) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar Circular Polarization and the Dielectric Nature of Dust Grains Chlewicki, Grzegorz ; Greenberg, J. Mayo Abstract The relationship between interstellar linear and circular polarization is reexamined. The derivation of optical constants for relevant materials is described, emphasizing general constraints on the electromagnetic response of an optical medium (Kramers-Kronig relations) which also provide the basis for the subsequent analysis of interstellar polarization. The formulas that relate the observed polarization to the properties of individual grains are summarized. It is shown that the apparent upper limit on the visual absorptivity of grains derived from earlier Mie theory calculations results from a violation of the Kramers-Kronig relations in the assumed optical constants of the particles. The analysis of circular and linear polarization in the interstellar medium is presented, and the implications of this analysis for grain models are addressed. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169474 Bibcode: 1990ApJ...365..230C Keywords: Circular Polarization; Dielectrics; Interstellar Extinction; Interstellar Matter; Optical Properties; Interstellar Gas; Linear Polarization; Mie Scattering; Astrophysics; INTERSTELLAR: GRAINS; POLARIZATION full text sources ADS |

Cross-polarization discrimination of MIMO antenna configuration at a mobile station in indoor propagation environment