High Cross-polarization Isolation Research Articles

Metasurface with high cross-polarization isolation using rectangular split rings for simultaneous amplitude and phase controls

Metasurfaces have demonstrated significant potential for versatile modulation of electromagnetic waves. To enhance the control of electromagnetic waves, simultaneous control of amplitudes and phases is often essential in certain applications. The C-shaped split ring (SR) with polarization conversion and its deformed structures can fulfill this requirement; however, such structures encounter the challenge of low polarization isolation, which is mainly reflected in its inherent characteristics of low polarization isolation and the deterioration of polarization isolation in amplitude control. In this paper, a reflective metasurface with improved polarization isolation is proposed. The designed metasurface consists of rectangular split ring (R-SR) elements, which can realize both amplitude and phase controls simultaneously and independently while exhibiting higher polarization isolation than the conventional SR element. Furthermore, an alternating mirror rotation method (AMRM) for the arrangement of amplitude-control elements is proposed to suppress the degradation of polarization isolation caused by amplitude control. Several metasurfaces are designed to verify the characteristics of the proposed R-SR structure and the effectiveness of the AMRM. Finally, two reflective metasurfaces composed of R-SR elements and SR elements with identical configurations are designed and manufactured. Both the simulation and measured results demonstrate the versatility of the proposed design and its advantages in terms of polarization isolation and transfer efficiency.

An approach to improve the polarization measurement accuracy of fully polarimetric phased array radar

High cross-polarization isolation (CPI) is crucial to the accurate polarization measurement for the fully polarimetric phased array radar (PPAR). In this paper, we propose a polarization state configuration (PSC) method to improve the cross-polarization isolation based on the triple feed microstrip patch element. Compared with the conventional fixed polarization state of radiated wave whether it has linear, circular or elliptical polarization state, our PSC approach configures the polarization state on the basis of beam steering. The CPI improvement is formulated as an optimization problem, thereby achieving the optimum configuration of magnitude and phase for the fully polarimetric antenna. To facilitate the uniform representation for the polarization measurement application of PPAR, the universal expressions of intrinsic and measured backscatter matrices are derived for arbitrary polarization states. The dual-polarization dipole array is used to evaluate the priority of the proposed method. Simulation results reveal that our approach could obtain higher cross-polarization isolation while being available in a larger scanning range. The configured CPI could improve the polarization measurement accuracy for the fully PPAR.

An Adaptive Direction-Dependent Polarization State Configuration Method for High Isolation in Polarimetric Phased Array Radar

High cross-polarization isolation (CPI) is crucial to the accurate polarization measurement using polarimetric phased array radar (PPAR). In this article, we propose an adaptive direction-dependent polarization state configuration ( AD <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PSC) method to improve the polarization isolation. Compared with the conventional fixed polarization state of radiated wave whether it is linear, circular, or elliptical polarization state, our AD <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PSC approach configures the polarization state on basis of beam steering. To achieve the adaptive configuration of magnitude and phase of the dual-polarization antenna, an improved steepest descent algorithm is put forward. To facilitate the uniform representation for the polarization measurement application of PPAR, the universal expressions of intrinsic and measured backscatter matrices are derived for arbitrary polarization state. The dual-polarization dipole array is used to assess the priority of our proposed method. Compared with the conventional approaches, our approach could obtain higher CPI while being available for a larger scanning range. The configured CPI meets the specific polarization requirement for PPAR.

Cross-finned UWB monopole for wireless applications: Design insight and characterization

A simple yet novel cross-finned geometry of a monopole has been explored to realize a strong contender in the family of ultra-wideband antennas. This promises a consistent monopole like radiation over an ultra-wide impedance bandwidth (127%) with improved radiation characteristics. An extensive study supported by experiments has resulted in a reliable design guideline with a strong physical insight. A cross-finned top loaded structure having individual fin length (L) 11 mm and width (W) 5 mm and fin thickness (t) 0.7 mm, fed by probe pin of height h = 2 mm, is fitted to a circular ground plane of radius (Ga) 15 mm. It has been experimentally demonstrated to operate from 5 to 22.5 GHz with as much as 1–7 dBi peak gain and over the band high co-to cross polarization isolation (26–31 dB). The design is found to exhibit desired transmission and reception characteristics in time domain and is extendable up to 32 GHz to the upper side and 1.5 GHz to the lower side of the microwave band. This commercially viable design should find potential applications in compact and miniaturized wireless transceiver systems.

A 42.2-Gb/s 4.3-pJ/b 60-GHz Digital Transmitter With 12-b/Symbol Polarization MIMO

The unlicensed 57–71-GHz wireless spectrum offers high throughput and scalable personal area connectivity. To implement high-speed energy-efficient signaling, we present a power back-off-efficient digital polar transmitter (TX) supporting multi-gigasymbol per second switching rates and higher order modulations up to orthogonal frequency-division multiplexing (OFDM) 64-QAM. Pulse shaping of the direct digitally modulated waveform outputs for spectral filtering is achieved in low power with a low oversampling ratio and analog filtering. Channel bonding and selection is supported with a frequency configurable local oscillator (LO) chain. Multiple-input multiple-output (MIMO) is implemented with low area overhead using a differential dual-polarization (DP) printed circuit board (PCB) antenna supporting simultaneous vertical/horizontal (V/H)-polarization data streams and high cross-polarization (X-pol) isolation. The 0.9-V 28-nm CMOS TX prototype with polarization MIMO achieves up to 42-Gb/s throughput at 4.3-pJ/b efficiency and 12 b/symbol of OFDM/single-carrier (SC) signaling.

A metamaterial-enabled design enhancing decades-old short backfire antenna technology for space applications

Nearly two decades of intense study have passed since the term metamaterials was first introduced in 1999. In spite of their great promise, however, metamaterials have been slow to find their way into practical devices, and examples of real-world applications remain rare. In this paper, an Advanced Short Backfire Antenna (A-SBFA), augmented with anisotropic metamaterial surfaces (metasurfaces), has been designed to achieve a very high aperture efficiency across two frequency bands. This performance is unprecedented for an antenna that has seen widespread use, but few design changes over its more than 50 year existence. The reduced weight, compact design, hexagonal aperture, high dual-band efficiency, high cross-polarization isolation, as well as low multipaction and passive intermodulation (PIM) risk make the A-SBFA ideal for spaceborne applications. This transformative design demonstrates how practical metamaterials, when applied to conventional antenna technology, can provide significant performance enhancements.

Theoretical and Experimental Comparison Results of Dual-Channel 3D Quasi-Optical Network System between Frequency Selective Surface and Wire Grid Polarizer

A dual-channel 3D quasi-optical network (QON) system is analyzed and compared by theoretical and experimental results. It is divided into dual-channel signals by frequency selective surface (FSS) or wire grid polarizer (WGP) for transmitting the 324 GHz signal on the top layer while diverting the 183 GHz signal to the bottom layer. The system structure based on the beam radius is traced by the complex beam parameter and system transfer matrix for deciding the positions of cascade mirrors. The design principles and test results of FSS with perforated hexagonal array and WGP printed on the dielectric substrate are discussed together. In order to evaluate channel performance, the output planar near-fields of QON system are simulated and tested by the four reflections and three transmission results, respectively, where both scalar and vector conversion efficiencies are used to evaluate the quality of output beams. For the distortion phenomenon and energy loss in planar field, the aperture modes of corrugated horn feeds are analyzed by spherical wave expansion (SWE) to explain the asymmetrical pattern characteristic. The cut section of the far-field pattern is also directly measured in the compact antenna test range (CATR), comparing with the far-field patterns that are indirectly obtained based on the principle of near-to-far-field transformation and ideal aperture field integral of quiet zone (QZ). The differences between the near- and far-field test in QON have been compared, and discussion that the corresponding experimental results verify the WGP has better work performance in the good pattern symmetry, high cross-polarization isolation, low energy loss, and side-lobe level.

Optimizing Radiation Patterns of a Cylindrical Polarimetric Phased-Array Radar for Multimissions

Accurate radar remote sensing requires a radar system with high cross-polarization isolation, highly matched dual-polarization patterns, and low sidelobes. A cylindrical polarimetric phased-array radar (CPPAR), which has polarization purity and scan-invariant beam properties, has recently been introduced to the weather and air surveillance communities. To achieve low sidelobes and matched beams, pattern synthesis using an optimization method is presented. Results reported herein support the idea that CPPARs can be designed and implemented for accurate weather measurements. Furthermore, some uncertainty analysis is performed to show the effects of the amplitude and phase errors on the radiation patterns of the PAR.

The ACTS multibeam antenna

The Advanced Communication Technology Satellite (ACTS), to be launched in 1993, is introduced briefly, and then the Ka-band multibeam antenna, consisting of electrically similar 30 GHz receive and 20 GHz transmit offset Cassegrain systems utilizing orthogonal linear polarizations, is described. Dual polarization is achieved by using one feed assembly for each polarization in conjunction with nested front and back subreflectors, the gridded front subreflector acting as a window for one polarization and a reflector for the other. The antennas produce spot beams with approximately 0.3 degrees beam width and gains of approximately 50 dBi. High surface accuracy and high edge taper produce low sidelobe levels and high cross-polarization isolation. A brief description is given of several Ka-band components fabricated for ACTS. These include multiflare antenna feedhorns, beamforming networks utilizing latching ferrite waveguide switches, a 30 GHz HEMT low-noise amplifier, and a 20 GHz TWT power amplifier.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>