Oscillator noise reduction in cavity-backed active microstrip patchantenna

A rectangular cavity-backed active microstrip patch antenna has been investigated Experimental results show that 25 dB oscillator noise reduction can be achieved for the active patch antenna at a carrier frequency of 4.1 GHz and an offset frequency of 8 kHz by using a rectangular cavity     

Optimised design of corner microstrip fed nearly square patchantenna for circular polarisation

A procedure is described by which the design of a corner fed nearly square microstrip patch antenna is optimised with respect to the perturbation element in order to produce circular polarisation. New fast form expressions are used to determine the individual orthogonal mode impedances based on the Green's function approach     

Novel low-cost beam-steering techniques using microstrip patchantenna arrays fed by dielectric image lines

This paper presents novel low-cost beam-steering techniques using microstrip patch antenna arrays fed by dielectric image lines (DILs). Two approaches are designed and used. The first, DILs without reflector plate, are used for feeding microstrip patch antenna arrays. Antenna array radiation beams are scanned when the operating frequency sweeps. The second, a dielectric image line with a movable reflector plate (DILWRP), is developed. The beam direction of the antenna array is controlled and steered by changing the perturbation distance between DIL and movable reflector plate at a given operating frequency. Both types of patch antenna array structures are simple, low cost, easily fabricated, stable, and reliable. Eight-element patch antenna arrays fed by DIL and DILWRP have been designed, fabricated, and tested. Experiments show good performance and results. Measurement results of scanning angles agree well with theoretical predictions     

Miniaturized biocompatible microstrip antenna using genetic algorithm

Biocompatible antennas are an area of recent research that can facilitate remote communication with medical implants. This paper shows several possible designs of a "waffle-type" antenna created using genetic algorithms (GAs) that are of a size potentially suitable for cardiac pacemakers in the 402-405 MHz MICS band. In addition, methods to constrain the simulation and speed up the convergence of the GA for this type of antenna are explored. Even simple constraints such as fixing the feed and ground locations and encouraging the antenna to grow preferentially in the horizontal direction to take advantage of the longer physical dimensions of a pacemaker in that direction can appreciably improve convergence speed. One exception to this was constraining the patches to be connected together rather than distributed randomly, which caused the system to converge slower rather than faster. Also notable was that when a larger physical size was allowed, the system also converged more quickly despite a sizeable increase in the number of unknowns (subpatches) in the model. Thus, this paper provides a smaller, better matched microstrip antenna for biotelemetry and a choice of GA constraints for designing it.     

Wideband high-temperature superconducting microstrip antenna

A novel high temperature superconductor microstrip antenna with the distributed Josephson inductance approach having been used is presented. The antenna shows a wide bandwidth property which is obtained by varying the DC current flowing through the patch.     

基于CRLH的小型化三频LTE微带天线设计

研究了一种基于复合左右手传输线理论(CRLH)的小型化三频长期演进(LTE)微带天线,利用CRLH的零阶谐振特性,实现微带天线的小型化,仿真结果显示微带天线的3个工作频段分别为1 840~1 860 MHz,2 130~2 160 MHz,2 620~2 660 MHz。准确覆盖频分双工(FDD) LTE规划的Band3,Band4和Band7,整个天线的电尺寸仅为0.17λ。最后通过对微带天线进行加工实测,验证了仿真的准确性和有效性。多频小型化天线不仅可以大幅节约基站的天馈资源,而且可以有效降低基站建设的成本,该方案具有很强的工程实用价值。     

基于新型互补开口谐振环的小型多频微带天线

基于提出的一种新型的具有超材料性质的互补开口谐振环,设计了一款小型多频带微带天线。首先设计了一个工作于6 GHz频段的微带天线,然后在此天线的金属接地板上刻蚀新型的互补开口谐振环。利用三维电磁仿真软件HFSS分别对新型的互补开口谐振环和加载互补开口谐振环的天线进行仿真分析,并最终设计了一款小型化的天线。仿真分析结果表明,在相同的谐振频率下,加载了新型互补开口谐振环的小型化天线的尺寸与普通天线相比,尺寸减小了25.85%,并且在6 GHz,7.07 GHz,7.73 GHz三个频率处产生了谐振,实现了天线的小型化和多频化。     

Superstrate loading effects on the circular polarization andcrosspolarization characteristics of a rectangular microstrip patchantenna

The authors present the superstrate loading effect on a circularly polarized rectangular microstrip antenna. The design parameters of the superstrate-loading microstrip antenna for achieving circular polarization at the main-beam direction are discussed. The circular polarization property in the entire main-beam region is also analyzed. Next, the crosspolarization characteristics of a rectangular patch antenna due to the superstrate loading are studied. A great dependence of the copolarized and crosspolarized radiations on the superstrate permittivity and thickness is observed     

Miniaturized microstrip branch-line coupler with good harmonic suppression performance

This paper presents a miniaturized microstrip branch-line coupler with good harmonic suppression performance. The proposed coupler consists of four branch-line sections, each of which is loaded by open-circuit stubs both at the center and the two ends. This type of loading can realize size reduction and harmonic suppression. As an example, a proposed branch-line coupler operating at 1.0 GHz is designed, fabricated and measured. The results show that the proposed branch-line coupler occupies 67% size of a conventional one and has better than 20 dB suppression from 1.9 to 5.8 GHz. Furthermore, the high slop of the transition band ensures good selectivity of the coupler.     

高温超导微带天线的谐振特性研究

传输线模型是分析微带天线的一种最简单的方法,但其未将导体的特性参数考虑到天线的分析中去,针对这一缺点,为研究超导体的表面阻抗对高温超导微带天线输入阻抗和谐振频率的影响,把导体特性对天线的影响看作一种微扰来处理,对传统的传输线模型进行了修正,并通过与谱域矩量法相比较,验证了修正后方法的有效性.进而利用修正后的方法计算分析了高温超导矩形微带贴片天线的输入阻抗和谐振频率,给出了关于高温超导微带天线输入阻抗和谐振频率的若干结论.     

Miniaturized microstrip bandpass filter designed using rectangular dual spiral resonator

A miniaturized microstrip bandpass filter based on a rectangular dual spiral resonator (DSR) is proposed in this paper. The rectangular DSR bandpass filter is centered at 3.65 GHz to suit for Wireless LAN (IEEE802.11y) application. The proposed filter offers transmission zero at the high side of out-of-band response. Across the bandwidth, the measured minimum insertion loss is about 1.7 dB, while the measured return loss is better than 19 dB. Measurement results are good agreement and closed to the simulated ones. The total circuit size of the miniaturized bandpass filter is about 0.145λ_g by 0.135λ_g, where λ_g is the guided wavelength at 3.65 GHz.     

Miniaturized microstrip lowpass filter using cylindrical-shaped resonators for integrated applications

A novel compact microstrip lowpass filter is presented in this paper. The structure uses stepped impedance and radial patches and it has the ??3 dB cut-off frequency at 4.39 GHz. The proposed lowpass filter has a wide rejection band from 6 to 30 GHz with rejection level more than ??20 dB. It has also other advantages such as: low insertion-loss <?0.1 dB and high return-loss more than 22 dB in 80% of the passband. The circuit size of the presented filter is about 90 mm². Such important advantages make the proposed lowpass filter applicable to be integrated in many high frequency circuits such as power amplifiers, oscillators, couplers and power dividers. It also can block the unwanted video transmitter interference nearby 4 GHz such as implementing between transmitter and antenna. The lowpass filter has simulated and fabricated and a good agreement was seen between the simulation and fabrication results.     

Modeling and analysis of high-temperature superconductor terahertz photomixers

Photomixing phenomenon in superconductors is studied. For a photo-excited superconductor film the fundamental equations for the carriers motion inside the superconductor material have been used in connection with the two-temperature model to find an analytic expression for the generated terahertz (THz) photocurrent inside the film. The dependency of the resulting photocurrent on the material and laser parameters, temperature, and photomixer configuration for a photomixer made of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// high-temperature superconductor is studied.     

Magnet cable technology development for high-temperature superconductor composite wire

Magnet cabling technology has been developed for Bi-based HTS composite wire. Concentric round cabling as well as Rutherford cabling has been proven in > 100 m lengths. For Bi-2223 precursor composite wire, post-cabling deformation is required to achieve high transport engineering current density (J_e), and early results have reached 5500 A/cm² at 77 K and self-field. Cable-and-deform conductor has similar magnetic field retention and anisotropy as conventional, nontransposed multifilament Bi-2223 composites with comparable J_e. HTS magnet cabled composites have great potential for providing high I_c, J_e, and reducing fabrication cost.     

Thermal and electrical stabilization of high-temperature superconductor powder-in-tube conductor

High-temperature superconductor (HTS) powder-in-tube conductors often require thermal and/or electrical stabilization to ensure their long-term integrity. An example of such a stabilization need is the safety bypass lead of an HTS current lead intended for application to superconducting magnetic energy, storage (SMES) devices. The bypass lead functions include current sharing during upset conditions and conductor element temperature control. This paper presents a bypass lead design for an HTS current lead in an 0.5 MW h SMES system. Included are predictions of thermal and electrical stabilization and current lead heat leaks. The results of a supporting development program are presented, as are details of a method to connect conductor element/bypass leads, an assembly procedure, a cleaning method, and thermal-stress tolerance measurements.     

Analysis of a high-temperature superconductor quantum fluxparametron operating at 77 K

A Quantum Flux Parametron (QFP) circuit designed for implementation with high-temperature superconductors is analyzed with thermal noise at 77 K. Experimental considerations are discussed and design parameters given for fabrication of the device using a YBa₂ Cu₃O₇ thin film on a SrTiO₃ bicrystal substrate. An application of the high T_c QFP for the detection of single flux quantum pulses is also described     

Miniaturized microstrip lowpass filter with wide stopband using double equilateral U-shaped defected ground structure

A compact double equilateral U-shaped defected ground structure (DGS) unit is proposed. In contrast to a single finite attenuation pole characteristic offered by the conventional dumbbell DGS, the proposed DGS unit provides dual finite attenuation poles that can be independently controlled by the DGS lengths. A 2.4-GHz microstrip lowpass filter using five cascaded double U-shaped DGS units is designed and compared with conventional DGS lowpass filters. This low pass filter achieves a wide stopband with overall 30-dB attenuation up-to10 GHz and more than 42% size diminution.     

Third-order intermodulation measurements of microstrip bandpass filters based on high-temperature superconductors

The insufficient power-handling capability of high-temperature superconducting microwave filters has been a serious barrier to their application. To clarify the key parameters for improving the power-handling capability of RF filters based on high-temperature superconductors (HTSs) with microstrip structures, we synthesized bandpass filters with different layouts using several kinds of HTS thin films and performed third-order intermodulation measurements on them. The experimental results indicate that increasing the film thickness and utilizing molecular-beam-epitaxy-grown films of NdBa/sub 2/Cu/sub 3/O/sub 7/ (NBCO) are effective in obtaining microstrip filters with high power-handling capability. For NBCO filters, we also investigated the effects of oxygen annealing, passband width, and the frequencies of the input signals on the power-handling capability.     

Capacitor-loaded frequency control scheme for circular patchantenna

A frequency-varying patch antenna design with a loaded capacitor is presented. Unlike traditional patch size reduction schemes, this capacitor-loaded scheme does not significantly affect the radiated power efficiency of the antenna. In some cases, the maximum radiated power can even be improved     

Miniaturized quad-channel microstrip diplexer with low insertion loss and wide stopband for multi-service wireless communication systems

Wireless Networks - In this paper, a compact four-channel diplexer is designed using a microstrip structure to separate input signals at 2.07/3.94&nbsp;GHz and 2.37/4.49&nbsp;GHz and load...