Petrie Meyer

Creating accurate multivariate rational interpolation models of microwave circuits by using efficient adaptive sampling to minimize the number of computational electromagnetic analyses

A fast and efficient adaptive sampling algorithm for multivariate rational interpolation models based on convergents of Thiele-type branched continued fractions (BCFs) is presented in this paper. We propose a variation of the standard BCF that uses approximation to establish a nonrectangular grid of support points. Starting with a low-order interpolant, the technique systematically increases the order by optimally choosing new support points in the areas of highest error until the required accuracy is achieved. In this way, accurate surrogate models are established by a small number of support points without any a priori knowledge of the data. The technique is evaluated on several passive microwave structures.

Design of a Ten-Way Conical Transmission Line Power Combiner

Axially symmetric power combiners, such as radial line and conical line combiners, are very effective in combining the output signals from a large number of power amplifiers over a wide band with low losses. The main problem with radial lines is the behavior of the characteristic impedance against radial distance, which makes design of radial combiners difficult and normally optimization based. In this paper, a step-by-step design procedure is presented for the design of a conical line combiner. The design strategy relies on the transverse electromagnetic properties of the conical line to eliminate the need for complex full-wave optimization in the design process. Circuit models are instead employed and optimized to achieve a wide matched bandwidth. A ten-way prototype was developed at X-band, which displayed more than an octave matched bandwidth with low insertion loss

A robust integrated multibias parameter-extraction method for MESFET and HEMT models

An integrated multibias extraction technique for MESFET and high electron-mobility transistor (HEMT) models is presented in this paper. The technique uses S-parameters measured at various bias points in the active region to construct one optimization problem, of which the vector of unknowns contains a set of bias-dependent elements for each bias point and one set of bias-independent elements. This problem is solved by an extremely robust decomposition-based optimizer, which splits the problem into n subproblems, n being the number of unknowns. The optimizer consistently converges to the same solution from a wide range of randomly chosen starting values. No assumptions are made concerning the layout of the device or the bias dependencies of the intrinsic model elements. It is shown that there is a convergence in the values of the model elements and a decrease in the extraction uncertainty as the number of bias points in the extraction is increased. Robustness tests using 100 extractions, each using a different set of random starting values, are performed on measured S-parameters of a MESFET and pseudomorphic HEMT device. Results indicate that the extracted parameters typically vary by less than 1%. Extractions with up to 48 bias points were performed successfully, leading to the simultaneous determination of 342 model elements.

Filter Parameter Extraction for Triple-Band Composite Split-Ring Resonators and Filters

A configuration of composite resonators consisting of three split-ring resonators is proposed to obtain a triple-band response with two transmission zeros between the passbands. Two new topologies are presented to design triple-band filters with controllable responses. A systematic filter design approach is presented based on a filter coupling model. The model is established to enable triple-band filter design with controlled passbands. Two methods are proposed and compared for the extraction of filter parameters. Coupling between nonadjacent elements is considered in the model and shown to have a significant effect. By changing the orientation of the coupled composite resonators, it is possible to introduce additional transmission zeros. Two sixth-order filter examples illustrate the use of the coupling model with the filter design approach to design filters with specified responses. The limitations of this filter topology are discussed.

A shorted waveguide-stub coupling mechanism for narrow-band multimode coupled resonator filters

A shorted waveguide-stub coupling mechanism is presented for implementing narrow-band multimode coupled cavity filters without coupling screws. The coupling element is a shorted rectangular waveguide stub placed in the end walls of cylindrical filter cavities, using perturbation of the magnetic fields to obtain coupling between degenerate modes. This structure is well suited to analysis and design with the efficient and accurate mode-matching method. Coupling coefficients and resonator frequencies can be controlled by varying cavity dimensions and the length, width, and depth of the rectangular coupling element. The accuracy with which the coupling can be realized and the elimination of coupling screws reduce the amount of tuning substantially. A third-order Chebyshev filter, realized in a triple-mode cavity with no coupling screws and only two tuning screws, is presented to verify the use of the coupling structure.

Performance and limitations of decomposition-based parameter extraction procedures for FET small-signal models

A recently proposed optimizer-based parameter-extraction technique using adaptive decomposition is subjected to a systematic and rigorous evaluation. The technique is shown to be robust and accurate under varying starting conditions. A study of convergence performance based on decomposition theory and test results is presented. Robustness tests are used to show that commonly used statistical descriptions such as mean and standard deviation are inadequate for presenting these types of test data.

The Design of Miniature Multilayer Bandpass Filters With Mixed Couplings

This paper introduces a new design process for miniature coupled resonator filters with mixed couplings, which can better preserve wideband response matching with coupling matrix prototype. A special type of matrix transformation is introduced in this paper to transform the coupling matrix into a configuration that consists of an equal number of capacitive and inductive main couplings. Based on this, lumped-element circuit models can be produced. Then, by using π to T transformations for some parts of the circuit, all the elements have realizable values. A miniature bandpass filter with a fractional bandwidth of 20% of this type based on N×N coupling matrix is demonstrated with both simulated and measured response. The filter is implemented using multilayer liquid crystal polymer circuit technology and has a compact size of 0.0294λg × 0.0303λg ×0.00052λg, where λg is the guided wavelength at the center frequency of 250 MHz.

On the design of waveguide devices using multiple propagating modes

This paper presents a number of strategies which can be used when designing waveguide devices with multiple propagating modes. Three types of devices are discussed by way of example, namely bandstop filters for microwave heating applications, narrow band coupled resonator filters, and rectangular monopulse feeds.

Designing high-performance finline tapers with vector-based optimization

A novel two-step optimization algorithm is presented for the design of high performance finline transitions. The method exploits the vector representation of the integral form of the reflection coefficient of smoothly varying tapers. Measured results of a very short taper, exhibiting less than 30 dB of reflection across the whole of the X-band, are presented as an example.

Wideband crossed-guide waveguide directional couplers

Crossed-guide X-band waveguide couplers with bandwidths of up to 40% and coupling factors of better than 5 dB are presented. The tight coupling and wide bandwidth are achieved by using reduced height waveguide. Design graphs and measured data are presented.