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11.
Design techniques for dual-passband filters   总被引:1,自引:0,他引:1  
This paper introduces two possible approaches to the design of microwave filters presenting two passbands separated by one rejection band, which is created by suitably placing transmission zeros in the stopband. In the first method, the two passbands have almost equal extension and the transmission zeros are symmetrically placed in the stopband; the second method instead allows the synthesis of filters with different passbands width and all the transmission zeros in the stopband placed at the same frequency. Both design methods are based on suitably defined frequency transformations and employ well-established prototype synthesis techniques; the practical implementation is performed through the classical multiple-coupled cavity topology. Two test filters operating in the global system for mobile communication 800-MHz band, designed with the described procedures and actually fabricated, have validated the novel design methods.  相似文献   
12.
The application of a new boundary-integral technique to the study of planar circulators in stripline/microstrip technology is described. The technique employs Green's second identity with plane waves as weighting functions, and leads to a very efficient algorithm for the analysis of planar devices in anisotropic media. Extensive comparison is made with results from the standard contour-integral formulations with very good agreement between the two techniques. The new technique is more stable in the critical region (μeff close to 0) and is somewhat faster  相似文献   
13.
An approach to the design of multistage microwave amplifiers in a prescribed frequency band with requirements about the transducer gain flatness and the maximum magnitude of the reflection coefficient at input and output is presented. The interstage equalizers are designed by imposing a suitable constraint on the maximum transducer gain, obtainable directly from the specifications; the input and output equalizer are obtained by imposing only the matching requirement. The method proposed allows a separate design of each network, which can be performed either through direct optimization or by means of a numerical synthesis  相似文献   
14.
Broad-band stripline circulators are studied by means of a mixed numerical technique which employs both boundary integral and segmentation methods; this technique allows the analysis of planar circuits where the substrate is constituted by several regions with arbitrary shapes and different electrical properties. It is known that tracking circulators require matching structures because they present a low-gyrator impedance (real and almost constant in an octave frequency band). The matching structures (generally tapers or multisection's transmission line transformers) must be realized on a reciprocal substrate. The overall device (circular disk on ferrite substrate and matching structure on dielectric substrate) constitutes a planar circuit with an inhomogeneous medium. The method of study presented here allows the determination of the overall impedance matrix of the planar circuit constituted by the nonreciprocal disk with sections of striplines connected to each port; in this way, the discontinuities between reciprocal and nonreciprocal medium are included in characterization of the overall device. Moreover the accuracy of the representation is increased, In fact, the coupling ports of the overall device may be located at a suitable distance from the disk boundary where higher-order modes excited by the discontinuities have been sufficiently attenuated and only the TEM mode is present on the striplines (which is the only one considered in the design of the matching structures)  相似文献   
15.
In this article, a process that might be described as "synthesis and approximation" was outlined. Starting from an exact prototype, the desired physical configuration using equivalent circuits and corrections to the resonators due to the influence of the coupling networks was approximated. A process that might be described as "approximation and optimization" was also outlined. Starting from an approximate filter network, optimization can be used to find an exact equal ripple solution. The starting point can be generated using synthesis or narrow-band approximations when appropriate. Applying optimization in an intelligent way allows the designer to circumvent some of the limitations of the classic ladder synthesis method. This article explores some ways to mix approximate filter dimensioning (based on network synthesis) and optimization (based on EM modeling), allowing a fast and accurate design of microwave filters  相似文献   
16.
Aerobic and Cometabolic MTBE Biodegradation at Novato and Port Hueneme   总被引:1,自引:0,他引:1  
Methyl tert-butyl ether (MTBE), a gasoline oxygenate additive, is present in groundwater aquifers at the Department of Defense Housing Facility, Novato, Calif. (Novato), and the Naval Base Ventura County, Port Hueneme, Calif. (Port Hueneme). A microcosm study was conducted to examine and compare the potential for and performance of aerobic, anaerobic, and aerobic cometabolic MTBE biodegradation processes using soils and groundwater collected from the Novato and Port Hueneme sites. Propane and butane were tested as the cometabolic growth substrates. Nitrogen requirements were tested by preparing microcosms with and without nitrate as a nitrogen source. The results of this study demonstrated the potential for aerobic MTBE biodegradation and mineralization at both sites. In the commingled, or upgradient, portion of the Novato plume, nitrate enhanced aerobic MTBE biodegradation; in the absence of nitrate or under anaerobic conditions, MTBE degradation was insignificant. Downgradient, where the groundwater was impacted only by MTBE, the MTBE was readily degraded with and without nitrate addition and without other external nutrient amendments. Mineralization studies showed that MTBE was mineralized at both sites, with maximum recoveries approaching 80% of the radiolabeled carbon added to the microcosms. In the downgradient, MTBE-only portions of both sites, the addition of propane and butane to stimulate cometabolic MTBE degradation provided negligible improvement over direct oxidation under aerobic conditions. Furthermore, when nitrate was not present, propane and butane were not degraded and the residual propane and butane in the bottles appeared to inhibit the MTBE degradation; this inhibition was most pronounced in the Port Hueneme microcosms where MTBE degradation all but ceased in the presence of residual propane and butane. In the upgradient, commingled Novato plume, propane plus nitrate-fed microcosms outperformed the aerobic, nitrate-fed microcosms; this was the only condition where cometabolism enhanced MTBE degradation over direct aerobic oxidation.  相似文献   
17.
An efficient algorithm to compute the static capacitance of periodic SAW (surface acoustic wave) interdigital transducers is proposed. The method is based on a new formulation of the well-known relationship giving the capacitance as a linear combination of the charges induced on an infinite transducer for one-electrode excitation. Besides computational efficiency, an interesting physical interpretation of static capacitance results. The algorithm itself is also tailored to split-finger transducers.  相似文献   
18.
This article presents a microstrip implementation of a manifold multiplexer. The design procedure is based on evaluation, through an efficient synthesis algorithm recently proposed, of the characteristic polynomials of the triplexer, including the channel filters. Both the manifold and channel filters parameters are also available at the end of the synthesis. This approach, based on polynomial modeling of the triplexer, has been experimentally validated for the first time through a practical implementation in planar technology. The fabricated prototype consists of three channel filters of third order centered at 1.84, 1.95, and 2.14 GHz, with bandwidth of 75, 60, and 60 MHz respectively. This work illustrates in detail the design and implementation of the practical triplexer, starting from the initial specifications and obtaining the final physical dimensions of the structure. Following the technique here shown, each filter is synthesized taking into account for the loading effects of the whole manifold; the filters dimensioning can be carried out with the filters separated from the multiplexer. In this way the optimization tasks are greatly simplified as compared with previous techniques for multiplexer design. The measured results of a manufactured prototype show return losses under 17 dB and minimum isolation between channels equal to 25 dB. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23:690–698, 2013.  相似文献   
19.
In this paper, a general simple technique for reducing any canonical n+2 coupling matrix to the more useful modular (i.e., cascaded N-tuplets) form is presented. This is accomplished by performing a suitable sequence of matrix rotations whose angles are not derived through optimization, but are analytically computed from the starting coupling matrix elements and the transmission zeros frequencies. The proposed technique allows the association of a transmission zero to a specific block (i.e., a triplet or a quadruplet) increasing the degree of freedom in the filter design process.  相似文献   
20.
Describes a method for synthesizing an inline prototype filter with a triplet section starting from source and/or from load. This topology allows placing one or two transmission zeros without using cross-couplings inside the filter (it is only required to couple the source (or the load) to the first (or the last) two resonators). The proposed method employs the coupling matrix of a generic prototype, obtained through well-established procedures; then, the coupling matrix of the desired inline topology is determined with a procedure based on multiple matrix rotations (similarity transforms) and numerical optimization  相似文献   
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