Microstrip Lowpass Filter Research Articles

Analysis of passive microwave devices by using three‐dimensional tangential vector finite elements

AbstractThere are two major difficulties in applying the finite element method to the analysis of microwave devices in three dimensions. One is to obtain a stable vector finite element which does not generate spurious modes, or non‐physical solutions, in the numerical analysis. The other is to model efficiently the coupling of port regions and the discontinuity region. In this paper, we describe the application of two new finite element techniques, the tangential vector finite element method and the transfinite element method, for modelling three‐dimensional microwave devices. The tangential vector finite element method, unlike the conventional nodal finite element methods, imposes only the tangential continuity of the vector unknown across elements' boundaries. As a result, there would be no spurious modes, and reliable solutions are obtained. The transfinite element method, which combines the modal basis functions and the finite element basis functions through the variational technique, provides an efficient way to model the open boundary nature of the device. To validate the current analysis, a low VSWR waveguide connector and two microstrip low‐pass filters are analysed. Numerical results agree very well with the measurements or those obtained by other methods.

Computer-aided design of microstrip filters by iterated analysis

An iterative method for the design of microstrip low-pass elliptic function filters is described. The method, which is a direct extension of the work of H.J. Orchard (IEEE Trans. Circuit Syst., vol.CAS-32, no.11, p.1089-96, 1985), determines the microstrip line parameters that produce the same locations of the frequencies of transmission zeros and reflection zeros of an equivalent lumped-element prototype. Effects of the discontinuities at the junction are easily accounted for in the iteration. A design example is included, and an experimental seventh-order filter designed and constructed using the procedure gives measured results that agree closely with theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Image Parameter Design of Noncommensurate Distributed Structures: An Application to Microstrip Low-Pass Filters

The direct application of the image parameter method (IPM) to distributed structures is suggested in order to overcome some limitations of classical design methods for microwave filters. Several advantages are pointed out: 1) Wider degrees of freedom are obtained using noncommensurate structures. 2) The IPM can be applied directly to a microwave structure without any use of lumped prototypes. 3) Possible technological constraints can be easily incorporated in the design procedure. 4) Filters designed according to the IPM can be cascaded together in order to improve their characteristics. An application to the design of a class of microstrip low-pass filters, which have been previously designed on a low-frequency approximation basis, is illustrated in detail. The IPM is shown to provide an effective control of both the passband and stopband, leading to filters with improved characteristics, as demonstrated by the experimental results.

Low-Loss Microstrip Filters Developed by Frequency Scaling

Low-pass and band-pass microstrip filters up to 30 GHz have been built on silica substrates by photolithographic reduction of optimized low-frequency models. Scaling accuracies of 1.8 percent or better have been achieved. An insertion loss of 0.28 dB has been measured for a five-section low-pass filter with a cutoff frequency of 5.7 GHz. The insertion loss of a 12-percent band-pass filter at 8.18 GHz is 0.16 dB. Good agreement between measured and calculated losses has been obtained. Circuit dimensions are given to facilitate scaling of the low-pass and band-pass microstrip filters to other frequencies.

Computer Aided Design and Analysis of a 2-4 GHz Broadband Balanced Microstrip Amplifier

In this paper, a computer-aided design and analysis of a 2-4 GHz broadband balanced microstrip amplifier using a full computer simulation program developed by the author and others is presented. A short and efficient CAD procedure for broadband amplifier design is introduced. The first step is to design an initial narrow-band high gain microstrip amplifier at 3-GHz central frequency. The second step is to optimize the initial lengths and widths of the input and output microstrip-matching circuits to get the broadband amplifier over the range 2-4 GHz. The analysis of both narrow and broadband amplifiers is investigated. In addition, with the design and analysis of a low-pass microstrip filter, the paper introduces the design and analysis of a Lange coupler. The final AC schematic diagram of the designed amplifier with the lengths and widths of microstrip lines is presented.Key Words: Computer-Aided Design and Analysis, Microstrip Amplifier, Microwave Amplifier.