In this article, a wideband high-selectivity filtering linear polarization converter is proposed and applied for ultra-narrow isolation-band bifunctional metasurface. As the contribution of this ...work, the developed polarization converter based on slot-line loaded triangular resonator unit not only achieves the in-band multi-mode resonant characteristic, but also introduces two additional controllable zeros out-of-band, so as to enable simultaneous implementation of the wideband and high selectivity features. With the detailed analysis of the modes, field, and surface current distributions, the mechanisms of wideband, high selectivity, and polarization conversion are revealed. Finally, the linear polarization converter as well as the bifunctional metasurface are fabricated for demonstration. The linear polarization converter can attain a conversion bandwidth of 45% under a polarization conversion ratio of >90%. Due to the excellent filtering characteristic of the proposed linear polarization converter, the constructed bifunctional metasurface can reduce its isolation band to only 2.7%. As expected, the proposed converter has the attractive advantages of wideband operation and high selectivity, which are of great significance for reducing the isolation-band and improving the spectral utilization in various application of multifunctional metasurfaces.
This brief proposes a broadband linear polarization converter with pre-determined notched band. By loading a H-shaped slot line on the basis of the rectangular resonator, a pair of resonator modes as ...well as pre-determined polarization conversion zeros can be additionally allocated inside the band, thereby realizing broadband and band-notch characteristics, simultaneously. The multi-mode resonant mechanism to realize broadband and the conversion zero control principle for notched band are analyzed in detail. Finally, a notch-band broadband linear polarization converter is designed and fabricated, and the simulated and measured results are agreed well with each other. As the main advantage, the proposed multi-mode resonant structure realizing the notched band can achieve flexible isolation band design while hardly affecting the broadband filtering characteristics, and is especially suitable for pre-determined spectrum windows of broadband electromagnetic control devices.
In this letter, a pin‐loaded triple‐mode square patch resonator is proposed for bandpass filter (BPF) design. By loading short‐circuited pins underneath the patch, the patch resonator not only ...enables DC‐blocking, but also brings out one additional resonant mode, thus a triple‐mode patch resonator can be formed up under operation with a pair of degenerate modes. According to the field distributions, these three resonant modes can be tuned by virtue of loaded slots and pins, while these two degenerate modes can be properly split by offset‐positioning the two sets of pins. In final, a pin‐loaded triple‐mode patch BPF is designed, fabricated and measured to validate the predicted results.
The previous work on reflective linear polarization converters has mostly focused on wideband characteristics, while the out-of-band selectivity has received rare attention. To achieve wideband and ...high selectivity simultaneously, a wideband reflective linear polarization converter with quasi-elliptic filtering characteristic is proposed based on multi-mode resonant metamaterial. Through the loading of the cross-shaped slotlines and inter-unit connecting lines, the inherent degenerate modes of a square patch can be excited and separated, and two additional resonant modes and two independently controllable conversion zeros are introduced to achieve excellent wideband and quasi-elliptic filtering characteristics. After the principles of generating in-band resonant modes and out-of-band conversion zeros are revealed, the mechanism of polarization conversion is analyzed in detail from the perspective of the amplitude-phase imbalance between its polarization components. Finally, a polarization converter is designed, fabricated, and measured. The main-polarization reflection coefficient is less than − 10 dB in fractional bandwidth of 50%, wherein the polarization conversion rate is 90%, and the polarization conversion rate squareness is about 0.9. The proposed converter with excellent frequency selectivity provides great potential for applications in multi-band and multi-functionality systems for reduced isolation band.
A metamaterial‐based frequency reconfigurable microstrip antenna is proposed with wideband tuning range and enhanced gain. By co‐designing the main reconfigurable microstrip patch unit and the ...upper‐layer located reconfigurable negative‐permeability‐metamaterial resonant loop, the gain of the resultant proposed antenna is readily improved. The wideband reconfigurability of the microstrip antenna and the metamaterial unit is realized by tuning the capacitance values of the varactor diodes through altering their bias voltages. Furthermore, the effect of different number of reconfigurable metamaterial units on the gain of the proposed antenna is extensively explored, which shows the radiation pattern is largely improved since the electromagnetic energy is more concentrated and directed. Finally, the proposed antenna is fabricated and measured. The experimental results demonstrate that the operating range of the proposed antenna is within 8.6–10.3 GHz, and the reflection coefficient is less than −10 dB, and the gain is above 6 dBi. The radiation efficiency of the antenna is above 85%. The electrical size of the antenna is 0.58λ0 × 0.58λ0. As expected, the proposed antenna has the main advantage of enhanced gain performance, while performing comparable frequency tuning range.
Composite structures may be subjected to internal damages caused by impact events, which can seriously degrade the property of the structures. Hence, impact monitoring is of great importance to ...ensure the applications of composite, especially in aerospace engineering. This paper puts forward, for the first time, a new multi-response-based wireless sensor network (WSN) to realize the large-scale impact monitoring with the weight and complexity of the monitoring system reduced greatly. A novel multi-response-based global impact localization method that can unite multiple leaf nodes to solve the problems of localization confliction and mid-region localization is proposed for the WSN. Evaluations performed on large-scale complex composite structures have shown the advantages of the presented new methods.
This letter proposes a miniaturized wideband Butler matrix (BM) based on dual-layer half-mode substrate integrated waveguide (HMSIW) structure. By virtue of the excellent features of shorter guided ...wavelength, flatter in-band phase slope, and more compact size of HMSIW, simple and compact couplers and phase shifter are newly designed for BM. Finally, a BM prototype is designed, fabricated, and measured. Benefiting from the proposed structure, size miniaturization over 90% is achieved in comparison with the traditional single-layer substrate integrated waveguide (SIW) type.
In this communication, a wideband rectifying metasurface for RF energy harvesting is proposed. By virtue of the two resonant modes of the paralleling metasurface resonator, it is not only the ...wideband feature can be obtained but also enables direct impedance matching between the high impedance diode and high impedance metasurface, eliminating impedance matching. A DC feed structure is proposed where each unit of the metasurface is connected by the chip inductors, and DC energy can be combined and exported directly, eliminating power combining networks. Then, A 6 × 6 array was designed and fabricated. Experimental results show that the proposed rectifying metasurface system operates at 5.32-6.66 GHz with a fractional bandwidth of 22.4%, and the peak efficiency is 74.5%. As a contribution to this work, RF energy on a broader frequency range can be captured by the proposed system with higher system efficiency, while maintaining a simple structure. This shows its great potential in wireless power transfer and indoor RF energy harvesting.
Modified coupled feed-lines (MCFLs) and coupled-line stubs (CLSs)/coupled-line stub-loaded resonators are proposed and applied to design wideband balanced filters to obtain high selectivity and ...common-mode suppression. MCFLs are implemented by loading short- and open-circuited stubs at the end of the traditional parallel-coupled feed-lines to perform bandpass and bandstop response, respectively. Impedance matching and additional transmission poles guarantee that the filters have wideband differential-mode (DM) passband. Transmission zeros can be allocated to suppress the common mode through different electrical length of stubs. Moreover, the CLSs and its stub-loaded resonators have the property of dual transmission zeros outside the passband, which improves the selectivity of the DM passband. Specifically, two prototypes based on CLSs with second harmonic suppression and CLS-loaded resonators with sharp rejection (Δf3dB / Δf20dB=0.97) are designed and fabricated for demonstration. The simulation and measurement results are in good agreement.
Summary
A tunable circularly polarized square patch antenna with parasitic elements is designed for a wide frequency tuning range and high gain characteristics. The proposed antenna is constructed by ...one main patch and four semi‐elliptic parasitic units. By loading four varactor diodes and adjusting their capacitance values, the tunable feature is performed to reallocate the corresponding working frequency. Moreover, the diagonal corners of the antenna are cut and loaded with varactor diodes, which provide the appropriate perturbation between the two orthogonality modes of the antenna, so as to ensure the circular polarization characteristic in the entire operating tuning band. The experimental results demonstrate that the reflection coefficient and axial ratio are less than −13 dB and 3 dB, respectively. The proposed antenna features a relatively wide continuously tuning range of 24% within 1.9‐2.3 GHz and a stable gain of over 7 dBi with a radiation efficiency of above 85%.
A tunable circularly polarized square patch antenna with parasitic elements is proposed, by utilizing the method of varactor‐diode‐loaded patches and varactor‐diode‐loaded perturbation, a wide frequency tuning range and high gain characteristic are readily achieved simultaneously.
