Jianxing Li

Dual-band polarization angle independent 90° polarization rotator using twisted electric-field-coupled resonators

A bilayered chiral metamaterial is proposed to realize a dual band polarization angle insensitive 90° polarization rotator. The unit cell of the chiral metamaterial is composed by twisted electric field coupled resonators in four-fold rotation symmetry. The simulation and measured results show that this device can work in dual band with an extremely low loss and polarization conversion ratio of more than 99%. The study of the current and electric fields distribution indicates that the cross-polarization transmission is due to both the electric coupling and the magnetic coupling.

Gradient Metasurface With Both Polarization-Controlled Directional Surface Wave Coupling and Anomalous Reflection

A gradient metasurface is proposed to obtain both surface wave coupling and anomalous reflection. The unit cell of the gradient metasurface is composed by six electric field coupled resonators in different rotation angle, which provides a phase gradient. The simulation and measured results show that this gradient metasurface can work at 7.8 GHz as a surface wave coupler and at 10.288 GHz providing a phenomenon of anomalous reflection. At the two frequencies, the direction of the reflection is polarization-controlled, and the efficiencies are polarization-invariant. At left-handed polarization incidence, the direction of the coupled surface wave and the anomalous reflection are opposite to the situation at right-handed polarization incidence.

Broadband cross polarization converter using plasmon hybridizations in a ring/disk cavity

In this paper, we report on the design, fabrication and subsequent investigation of a broad band cross polarization converter based on a C2-symmetric ring/disk cavity. Different plasmon hybridization modes are excited in the ring/disk cavity and enable the polarization manipulations. The designed cross polarization converter can convert the x or y polarized incident wave to its cross polarized wave in the frequency range from 9.65 to 14.16 GHz with a bandwidth of ~38% of the central wavelength and an efficiency higher than 80%. At 9.25 GHz and 14.35 GHz, the x (y) polarized incident wave is converted to a left (right) handed and right (left) handed circularly polarized wave, respectively.

Quad-Band Probe-Fed Stacked Annular Patch Antenna for GNSS Applications

A novel probe-fed stacked annular patch antenna is proposed for Global Navigation Satellite System (GNSS) applications. The antenna has been designed to operate at the satellite navigation frequency bands including GPS, GLONASS, BDS-1, and BDS-2. In the design, four annular patches are stacked to achieve multiband operation and compactness. Quadrature phase feed network comprising four 90° stripline baluns is employed to ensure circularly polarized (CP) radiation. Another key feature of our design is the stepped-radius shorting pillar to reduce the well-known inductance due to longer feeding probes. The final antenna exhibits good impedance matching, broad pattern coverage, and pure CP performance at all designed bands. Details of design considerations and experimental results are presented and discussed.

Fast and Accurate Rank Selection Methods for Multistage Wiener Filter

Reduced-rank adaptive processing (RRAP) has received considerable attention in recent years. One of the key problems with this technique is how to determine an appropriate dimension for the reduced-rank subspace. In this paper we study in detail four types of rank selection methods for the widely used RRAP approach-multistage Wiener filter (MWF). All of these methods have a computational complexity of order O(1), compared with other existing methods with an order of O(i) or even O(i2) at the ith stage of the MWF. The main idea underlying these methods is to find a recursive algorithm to calculate the stopping criterion. The first two algorithms, based on the generalized discrepancy principle (GDP) and error estimation (EE) respectively, are fast versions of existing approaches. The last two algorithms, based on fast Ritz values estimation (RVE) and new information (NI) respectively, are new and proposed in this paper. In addition to requiring less computation, simulation results show that the proposed algorithms have a higher accuracy in adaptive beamforming applications for both narrowband and broadband signals.

Designing Graphene-Based Absorber by Using HIE-FDTD Method

A hybrid implicit explicit-finite-difference time-domain (HIE-FDTD) method is used to simulate a graphene-based absorber. Both the interband conductivity and intraband conductivity of the graphene are incorporated into the HIE-FDTD method directly through an auxiliary difference equation. Because the time step size in the proposed method is not confined by the fine spatial cells in the graphene layer, the simulation time of the proposed method is greatly reduced compared with that of the conventional FDTD method. By using the proposed HIE-FDTD method, a graphene-based absorber is simulated and analyzed. The numerical result shows that the operating frequency of the absorber is tunable through controlling graphene’s chemical potential. It also shows that the interband conductivity has an important effect on the performance of the graphene device, especially at the frequency band larger than 10 THz.

Dual-band capacitively loaded annular-ring slot antenna for dual-sense circular polarization

Abstract This paper investigates a simplified and new capacitively loaded annular-ring slot antenna (ARSA) for dual-band and dual-sense circular polarization. The antenna is comprised of two concentric annular-ring slots coupled to a microstrip feed line to achieve dual-band operation. With introducing proper distributed capacitances fulfilled by two closely spaced T-shaped arc strips across the outer and inner annular-ring slots at opposite positions with respect to the microstrip feed line, the dual-sense circular polarization can hence be obtained. The antenna features that the impedance and circular polarization characteristic for the upper band can be independently adjusted. Numerical analysis and experimental validation have been carried out. The measured 10-dB return loss impedance bandwidths for both bands are greater than 22.0%. The measured 3-dB axial ratio (AR) bandwidths are 3.6 and 5.6%, respectively, for the lower and upper bands.

Design of a 4-element Antenna Array for BDS Anti-jamming Applications

Abstract In this paper, a compact 4-element antenna array with the dimension of 150 mm × 150 mm is proposed for BeiDou navigation satellite system (BDS) anti-jamming applications. The proposed antenna array comprises of four identical microstrip right-handed circularly polarized (RHCP) antenna elements. The four microstrip antenna elements are placed in the same polarity with a distance of 80 mm between adjacent elements. The antenna element which employs dual probe-fed structure has a relatively small volume of 45 mm × 45 mm × 5 mm. The antenna array has been fabricated and measured. The experimental results show that the proposed antenna array is quite suitable for BDS anti-jamming application.

Microstrip-line-fed reactively loaded circularly polarized annular-ring slot antenna

Abstract A simple and novel reactively loaded annular-ring slot antenna (ARSA) fed by a microstrip line is proposed and investigated for circularly polarized (CP) radiation. An appropriate reactive component, i.e. lumped capacitor/inductor, is introduced across the annular-ring slot at a proper position to achieve CP radiation. To validate the design concept, a capacitively loaded ARSA (CL-ARSA) and an inductively loaded ARSA (IL-ARSA) were implemented and measured, showing that good CP characteristics have been attained. The measured 3-dB axial ratio (AR) bandwidths for the CL-ARSA and IL-ARSA are 5.5 and 6.7%, respectively.

Miniaturized Single-Feed Cross-Aperture Coupled Circularly Polarized Microstrip Patch Antenna

A novel miniaturized single-feed cross-aperture coupled circularly polarized (CP) microstrip patch antenna loaded by four identical shorting strips is proposed and discussed. Each shorting strip underneath the edges of the radiating patch is connected to the ground plane via an array of three identical and equidistant shorting pins. With the assistance of the capacitance offered by the radiating patch and the shorting strips, and the inductance induced by the shorting pins, the patch size and overall size of the proposed antenna have been significantly reduced by 75% and 69%, respectively, compared with the conventional antenna. An antenna prototype with an overall size of 50 mm× 50 mm× 7.548 mm (0.317λ0 × 0.317λ0 × 0.048λ0) and a patch size of 29.43 mm × 27.85 mm (0.186λ0 × 0.176λ0) has been fabricated and measured, which shows a measured 10-dB return loss bandwidth of 92 MHz (4.76%) from 1.886 to 1.978 GHz with a maximum right-handed CP (RHCP) gain of 4.9 dBic. The measured 3-dB axial ratio (AR) bandwidth is 28 MHz (1.46%) from 1.899 to 1.927 GHz with a 3-dB AR beamwidth of more than 140 ◦ across the operating bandwidth.