Milka M. Potrebic

Compact Dual-Band Bandpass Waveguide Filter with H-Plane Inserts

A novel compact dual-band bandpass waveguide filter is presented in this paper. H-plane metal inserts with complementary split-ring resonators are implemented as resonating elements in the standard (WR-90) rectangular waveguide. Design starts from the models of the waveguide resonators with two resonant frequencies (9GHz and 11GHz) using a single flat or folded metal insert. Further, folded inserts are used for the second-order dual-band filter design. The equivalent circuits are proposed for the considered waveguide resonators and filter. A good agreement of the amplitude responses obtained for three-dimensional electromagnetic models and microwave circuits is achieved. Finally, compact dual-band bandpass waveguide filter is proposed as a novel solution using miniaturized inverters for both central frequencies. Compact filter model is further modified in order to obtain solution customized for easier fabrication. For the compact filter model, amplitude response is experimentally verified. The required filter response is preserved, as verified by a good agreement of the results obtained for the original dual-band filter and for the compact filter solutions.

Design and analysis of bandpass waveguide filters using novel complementary split ring resonators

This paper presents models of the bandpass waveguide filters using novel complementary split ring resonators. These resonators are employed as single-mode and dual-mode. Dual-mode resonators are developed from the single-mode ones. The filter response is analyzed in terms of various parameters of the resonators. The possibility to independently tune single-mode resonators, contained in the dual-mode resonator, is also investigated, in order to evaluate this solution for modeling of the resonators with multiple resonant frequencies.

Design of open-loop dual-mode microstrip filters

This paper presents the design of compact second-order bandpass ¯lters based on dual-mode open-loop resonator. A ¯lter design procedure is provided to facilitate the design process. The paper also describes the nature of the inherent transmission zero associated with the structure and presents a method of generating two additional zeros for improving stop-band performance. Finally, a ¯lter design example is presented to validate the argument.

WIPL-D modeling and results for waveguide filters with printed-circuit inserts

This paper presents a three dimensional electromagnetic (3D EM) modeling of waveguide filters and the corresponding results of the full-wave simulation with WIPL-D EM Solver. The filters are designed as rectangular waveguide structures with planar resonators implemented as printed-circuit inserts. WIPL-D models of building blocks for bandpass and bandstop filters are realized.

Modeling and simulation of large memristive networks.

Summary The paper deals with the modeling of memristors operating in extremely large memristive networks such as crossbar structures for memory and computational circuits, memristor-based neural networks or circuits for massively parallel analog computations. Because the non-convergence and other numerical problems increase with increasing complexity of the simulated circuit, suitable models of the individual memristors need to be choicely developed and optimized. Three different models are considered, each representing a specific trade-off between speed and accuracy. Benchmark circuits for testing the applications of various complexities are used for the transient analysis in HSPICE. It is shown how the models can be modified to minimize the simulation time and improve the convergence. Copyright

RF/Microwave Applications of Memristors

Memristor-based technology could be utilized, potentially, to enhance performance of many RF/microwave subsystems. Application of memristors in RF/microwave circuits, and in a broader context in electromagnetic systems, is another challenging field for researchers and engineers. In this application frontier, the research efforts might be divided, for example, into the following important classes of applications: (1) frequency selective surface, reconfigurable planar absorber, (2) reconfigurable antenna, direct antenna modulation, (3) RF/microwave filter, split-ring resonator filter, hairpin-line filter, capacitively coupled resonator filter, quasi-Gaussian lossy filter, (4) Wilkinson power divider. Memristors could be exploited as linear resistors with programmable resistance, which can be accurately adjusted to a desired or specified value. Precise controllability of the memristance value might be important for tuning microwave circuits and optimizing their performance. In several applications, such as filters, the high-frequency range of the operation enforces the memristor into the role of a linear resistor whose resistance can be adjusted electronically. On the other hand, some applications, such as reconfigurable electromagnetic absorbers, benefit from memristors as electromagnetic switches. Due to the unavailability of commercial memristors, it is necessary to use accurate circuit-level simulations for experimenting with the memristor-based RF/microwave circuits and for studying their performance. RF/microwave circuit simulators, which use the HSPICE engine for the time-domain transient simulation, such as NI AWR Microwave Office, can be used to verify the expected functionality of the considered memristor-based circuits.

A Novel Compact Dual-Band Bandpass Waveguide Filter

A novel design of second-order dual-band H-plane band pass wave guide filter is presented in this paper. Filter design is relatively simple and is based on the use of complementary split ring resonators, implemented as metal septa, with properly shaped slots, in the transverse planes of the standard (WR-90) rectangular wave guide. The positions of the resonators on the same septum are chosen in such a manner that there is no mutual coupling between them. This approach is used for the design of the wave guide resonator with two resonant frequencies (9 GHz and 11 GHz). Further, the second-order dual-band band pass wave guide filter, with symmetrically positioned folded septa, is presented. The equivalent circuits of the considered resonators and filters are developed. The proposed dual-band band pass filter design is verified by a good agreement of the filter responses obtained for three-dimensional electromagnetic models and equivalent microwave circuits. Finally, the method for filter miniaturization is introduced and applied to the second-order dual-band filter. The required filter response is preserved.

Bandstop waveguide filters with two or three rejection bands

This paper presents a novel design of bandstop waveguide filters with two or three rejection bands, using quarter-wave resonators. Bandstop waveguide filters are designed using printed-circuit inserts realized with single-mode and multi-mode resonators. The filter response is analyzed depending on the parameters of the resonators and their positions on the printed-circuit insert. Various models of dual-band and triple-band filters are developed by employing different combinations of the resonators, as examples of the proposed multi-band filter design.

Structure for precise positioning of inserts in waveguide filters

This paper presents a structure for precise positioning of inserts in waveguide filters. Here, the model of the dual-mode bandstop waveguide filter of the third order, using split ring resonators, is considered. Split ring resonators are implemented as printed-circuit inserts in a form of reduced dielectric plates, supported by thin dielectric strips. The challenge of such design is to develop the model with stable printed-circuit inserts, which actually emulates the filter implementation, without degradation of the filter performance.

Understanding Computation of Impulse Response in Microwave Software Tools

In modern microwave engineering curricula, the introduction of the many new topics in microwave industrial development, or of software tools for design and simulation, sometimes results in students having an inadequate understanding of the fundamental theory. The terminology for and the explanation of algorithms for calculating impulse response in microwave software tools are not always beginner-oriented and might be over-sophisticated for undergraduate students. This paper presents a comprehensive analysis of the impulse response computation from the viewpoint of microwave engineering education. A new method of teaching the impulse response computation is presented. The new method should help students to gain a thorough understanding of how to compute the impulse response either in the time domain or from frequency response samples.