Michel Aubourg

Direct electromagnetic optimization of microwave filters

This article explores an optimization procedure for microwave filters and multiplexers. The procedure is initialized by a classical filter synthesis based on a segmented electromagnetic synthesis that provides the basic dimensions of the structure. The optimization loop, which combines a global electromagnetic analysis and a coupling identification, improves the structure response compared to an empirical optimization.

Bulk acoustic wave filters synthesis and optimization for multi-standard communication terminals

This article presents a design methodology for bulk acoustic wave (BAW) filters. First, an overview of BAW physical principles, BAW filter synthesis, and the modified Butterworth-van Dyke model are addressed. Next, design and optimization methodology is presented and applied to a mixed ladder-lattice BAW bandpass filter for the Universal Mobile Telecommunications System (UMTS) TX-band at 1.95 GHz and to ladder and lattice BAW bandpass filters for the DCS1800 TX-band at 1.75 GHz. In each case, BAW filters are based on AlN resonators. UMTS filter is designed with conventional molybdenum electrodes whereas DCS filters electrodes are made with innovative iridium.

Hollow-core resonator based on out-of-plane two-dimensional photonic band-gap crystal cladding at microwave frequencies

We report on the demonstration of a resonator based on electromagnetic field confinement in a hollow-core by implementing an out-of-plane two-dimensional ﲤ2Dﲥ photonic band-gap ﲤPBGﲥ crystal cladding. In contrast with in-plane 2D PBG crystal devices, the PBG crystal studied here is perpendicular to the propagation axis. A resonator was constructed with silica rods to prove the concept at frequencies around 30 GHz. We show that the technique has the potential to reach quality factors ﲤQﲥ of 5 ﲡ 105.

New classes of microstrip resonators for HTS microwave filters applications

The rapid growth of mobile communication means creates a great interest for the use of the superconducting technology, especially for base station and satellite communication systems. Planar devices with HTS films allow one to conceive narrowband filters with very low loss and small dimensions. A novel class of cross shaped planar resonators is proposed for superconducting applications. This includes dual-mode and single-mode resonators. A four pole elliptic function filter at 4 GHz is realized and measured at room temperature. Theoretical and experimental results are presented.

Invited Article: Dielectric material characterization techniques and designs of high-Q resonators for applications from micro to millimeter-waves frequencies applicable at room and cryogenic temperatures

Dielectric resonators are key elements in many applications in micro to millimeter wave circuits, including ultra-narrow band filters and frequency-determining components for precision frequency synthesis. Distributed-layered and bulk low-loss crystalline and polycrystalline dielectric structures have become very important for building these devices. Proper design requires careful electromagnetic characterization of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique for microwave applications, which has now become the standard for characterizing low-loss structures. This paper will give some of the most common characterization techniques used in the micro to millimeter wave regime at room and cryogenic temperatures for designing high-Q dielectric loaded cavities.

Design Considerations for the Implanted Antennas

Different aspects of the design of implanted devices is discussed by numerical analysis of a conceptual model. Different antenna topologies are compared for their efficiency and sensitivity to variations in thickness and dielectric constant of a lossy superstrate (which models the skin). It was shown that microstrip patch and loop antennas are the most viable candidates among basic antenna topologies. A modified objective function is proposed which can take into account the strong detuning due to lossy superstrate. Finally the effect of a protective lossless superstrate is investigated intensive numerically. The trade-offs involved in the size of the protective superstrate are addressed by finding the trends in which the antenna performance varies with the dimensions of the protective layer.

Design of Microwave Components using Topology Gradient Optimization

In this paper, we used a topology gradient method coupled with a finite element method in order to optimize the shape of a microstrip component. We appended a 2D distribution of metal on the substrate and tried to optimize its form by taking benefits of the topology gradient method. The concept of topology gradient using a numerical method is given in this article, and finally, the results of using this approach in the context of microwave component optimization is shown

Planar Ka-band high temperature superconducting filters for space applications

The impressive explosion of the satellite communication systems during the last few years has led to new constraints in regards to filtering requirements. The development of multimedia satellites and the saturation of the operational frequency bands, necessitates an increase in frequency coverage. This paper presents the design of High Temperature Superconducting (HTS) preselect receive fitters for communication satellites. Attention has been focused on obtaining low insertion loss and small dimensions, at frequencies of 4 GHz and 30 GHz.

Microwave breakdown in output multiplexer filters

A theoretical investigation is made of microwave breakdown in output multiplexer filters. The effects of the electrical breakdown cause irreversible damage to the device and so the power level, which generates such a phenomenon, must be predicted. This study needs a pluridisciplinary approach with a combination of three fields of the science: the electromagnetism, the thermic and the plasma physics.

A nonlinear distributed FET-model, for millimeter-wave circuit design by harmonic balance techniques

A systematic procedure is proposed for deriving a nonlinear, distributed FET model that can be implemented in harmonic balance simulators for nonlinear design at millimeter waves. The model is derived from the knowledge of the conventional lumped nonlinear equivalent circuit and the geometrical dimensions of the FET. A FET-finger is modeled by N sliced sections. Each section includes a nonlinear two-port, inserted between two linear four-ports. Element values of the nonlinear two-port are derived from the lumped model by appropriate scaling rules. Element values of the linear four-port are derived from an electromagnetic analysis of the transverse structure of the FET, taking into account coupling and distributed effects along the electrodes. The model is applied to the nonlinear analysis of a millimeter-wave FET.<<ETX>>