A closely located dual-band meander-line antenna array with isolation enhancement by inserting novel split electromagnetic bandgap (EBG) uniplanar structure is proposed. The meander-line antenna is ...coupled to a parasitic rectangular patch to achieve the dual-band operation. Splits are applied on the surface of an EBG structure to cause decoupling at the first resonant mode and utilizing an EBG structure to decouple at the second resonant mode. The prototype of the proposed structure achieves a dual band of 180 MHz (3.42-3.6 GHz) and 400 MHz (4.7-5.1 GHz). The mutual coupling is significantly reduced by 26 and 44 dB at 3.48 and 4.88 GHz, respectively, compared to the reference antenna. In addition, the structure has high front-to-back ratio radiation characteristics.
A new synthesis method for the design of broadband impedance matching network has been introduced to match the transistor input. The proposed matching network would be a realistic alternative to ...those that are frequently designed in low-pass structure. Easy-to-use design equations are given for this filter-based matching network. The required impedance of the stubs and the connecting lines can be directly calculated from the equations. This synthesis method simplifies the implementation of the network in the distributed form as compared with the LC low-pass matching network where equivalences are necessarily required in the rough conversion from lumped-to-distributed elements. The high-efficiency mode of operation is guaranteed by the constructed output low-pass matching network, since the LC low-pass network can provide the prescribed load terminations at fundamental frequencies and at harmonics. A commercially available 10-W GaN HEMT device (CGH40010) was used in this investigation. The proposed broadband power amplifier exhibits band-pass Chebyshev response in S-parameter measurements, and yields good gain flatness (±0.5 dB) and input return loss (>13 dB). Power-added efficiency of 58%-72% has been measured in large-signal measurements. After digital predistortion, the measured adjacent channel leakage power ratio is below -50 dBc at ±5- and ±10-MHz offset, when driven by 5- and 10-MHz WCDMA signals at 7-dB power back off.
This paper presents an unequal Wilkinson power divider operating at arbitrary dual band without reactive components (such as inductors and capacitors). To satisfy the unequal characteristic, a novel ...structure is proposed with two groups of transmission lines and two parallel stubs. Closed-form equations containing all parameters of this structure are derived based on circuit theory and transmission line theory. For verification, two groups of experimental results including open and short stubs are presented. It can be found that all the analytical features of this unequal power divider can be fulfilled at arbitrary dual band simultaneously.
A novel generalized coupled-line circuit structure for a dual-band Wilkinson power divider is proposed. The proposed power divider is composed of two coupled lines with different even- and odd-mode ...characteristic impedances and two lumped resistors. Using rigorous even- and odd-mode analysis, the analytical design equations for this proposed power divider are obtained and the ideal closed-form scattering parameters are constructed. Since the traditional transmission line is a special case of coupled line (coupled coefficient is zero), it is found that traditional noncoupled-line dual-band (including single band) Wilkinson power dividers and previous dual-band coupled-line power dividers are special cases of this generalized power divider. As a typical example, which could only be designed by using this given design equations, a compact microstrip 3-dB power divider operating at both 1.1 and 2.2 GHz is designed, fabricated, and measured. There is good agreement between calculated and measured results.
In this paper, a novel terminated coupled line structure (TCLS) is introduced, which is constructed by a coupled line section and four terminations loaded on it. Introducing different kinds of ...terminations, three types of bandpass filters (BPFs) based on TCLSs are proposed, theoretically analyzed, and fabricated, including two single-ended wideband BPFs with fractional bandwidths (FBWs) of 67% and 40% respectively, and a wideband differential BPF with 74% differential-mode FBW. These BPFs can achieve wide passband bandwidth, low in-band insertion loss, high passband selectivity, as well as deep stopband rejection performance simultaneously, benefited from the multiple transmission zeros and transmission poles obtained by the TCLSs. The practical design procedures of these BPFs are presented and explained. The agreement among theoretical predictions, EM-simulated, and measured results validates our proposed filter structures. Finally, the generalized multistage filter topology based on TCLSs is proposed to design high-order filters with better filtering performances.
Reconfigurable intelligent surface (RIS), equipped with a large number of small, low‐cost, and re‐configurable elements, is envisioned as a potential enabler for the upcoming 5G‐Advanced and 6G ...networks. Here, based on a flexibly tunable and readily programmable RIS, the capability of beamforming toward arbitrary desired directions and coverage enhancement are investigated and experimentally demonstrated. The theory of RIS‐based beamforming is introduced, the simulated beamforming radiation patterns are provided, and an over‐the‐air radiated testing platform is designed for characterizing RIS beamforming performance. The RIS beam steering radiation performance tests are conducted, and the radiation patterns for different directions are extracted and analyzed. In addition, the indoor field trials on the RIS performance evaluation of enhancing coverage are reported. The field trials for multiple RIS‐deployed scenarios, including RIS mirror placement, RIS non‐mirror placement, and non‐RIS assisted scenarios, are conducted, and the channel characteristics for those scenarios are extracted and modelled. Significant improvements in overcoming path loss and shadow fading in typical coverage holes can be observed. The proposed testing method and measurement results may provide some insights into the design and optimization of RIS‐aided wireless communications.
Here, based on a flexibly tunable and readily programmable reconfigurable intelligent surface (RIS), the capability of beamforming toward arbitrary desired directions and coverage enhancement are investigated and experimentally demonstrated. The theory of RIS‐based beamforming is introduced, the simulated beamforming radiation patterns are provided, and an over‐the‐air radiated testing platform is designed for characterizing RIS beamforming performance. The RIS beam steering radiation performance tests are conducted, and the radiation patterns for different directions are extracted and analyzed. In addition, the indoor field trials on the RIS performance evaluation of enhancing coverage are reported.
In this paper, a novel design method of generalized dual-band unequal filtering power divider (DUFPD) is proposed. Using this method, the power divider (PD) could be designed to realize the dual-band ...filtering response with arbitrary power division, arbitrary frequency ratio, arbitrary real terminated impedances, independently controllable bandwidth, and excellent isolation. To satisfy these characteristics, a proper dual-band filtering structure is selected to replace the conventional quarter-wave length transmission line in the PD. In addition, a single resistor structure is utilized to obtain effective isolation between the output ports. Furthermore, the complete design procedures and analytical equations of the proposed generalized DUFPD are presented based on the circuit and transmission line theories. To demonstrate the validity of the proposed design method, a DUFPD with different real terminated impedances is designed, fabricated, and measured. We show that there is a good agreement between the simulated and measured results.
In this article, a flexible high-selectivity single-layer coplanar waveguide (CPW) bandpass filter using interdigital spoof surface plasmon polaritons (SSPP) of bow-tie cells is proposed, simulated, ...and fabricated. The low and high cut-off frequency can be adjusted independently, which is one of the characteristics of the presented bandpass filter. The SSPP of bow-tie cells is used to adjust the high cut-off frequency, while the interdigital coupling structure of the SSPP is designed to adjust the lower one. The proposed filter also has advantages of single-layer structure and high selectivity. Simulated results of the proposed filter show a theoretical 3-dB bandwidth from 2.28 to 5.12 GHz (about 76.8%) with high selectivity (<inline-formula> <tex-math notation="LaTeX">\vert S_{11}\vert < -15 </tex-math></inline-formula> dB and −0.4 dB <inline-formula> <tex-math notation="LaTeX">> \vert S_{21}\vert > -1.1 </tex-math></inline-formula> dB in the passband), and measured results agree well with simulated ones. Since the filter in this article is designed based on the flexible printed circuit (FPC) board, the circuit can be tested in bent, folded, and even twisted states, and these measured results are all basically consistent with the test result of the flat state circuit. This characteristic can greatly reduce the size of the filter and increase the flexibility of the circuit application.
In this paper, the bilayer polymer-dispersed liquid crystals possessing a PDLC-PVA-PDLC structure were prepared by integrating two monolayer PDLCs. The effect of the polymer mesh size on the ...electro-optical properties of a bilayer PDLC was investigated by comparing the micro-morphology and electro-optical curves under different polymerization conditions. In addition, the impact of doping MoO
nanoparticles with surface modification on the comprehensive performance of the bilayer PDLC was further researched. The contrast ratio of the bilayer PDLC prepared under the optimal conditions was improved by more than 90% and still maintained excellent progressive driving performance. Therefore, the development of a bilayer PDLC with optimal electro-optical properties will significantly enhance the technological prospects for the application of PDLC-based devices in smart windows, displays, and flexible devices.
In this letter, we propose a practical three-section dual-band transformer, which can terminate frequency-dependent complex load impedance at two arbitrary bands simultaneously. Analytical equations ...are derived to achieve the exact closed-form solutions. Numerical examples are examined to verify the validity. This three-section transformer can be utilized to match the complex load impedance with unequal values at two different frequencies, such as microwave amplifiers based on transistors, mixers, various kinds of antennas, and so forth.
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