Designing H-shaped micromechanical filters

Abstract

Abstract. This paper investigates the design constraints and possibilities given when designing a micromechanical band pass filter for intermediate frequencies (e.g. 10 MHz). The class of filters are based on coupled clamped-clamped beams constituting an H-shaped structure. A primary beam can electrostatically be activated in one of its different harmonic modes, setting the filter center frequency. The motion is transferred to an accompanying beam of equal dimensions by a mechanical coupling beam. The placement or coupling points of the quarterwavelength coupling beam which connects the vertically resonating beams is critical with respect to the bandwidth of the filters. Of special concern has been to investigate realistic dimensions allowing the filters to be processed by an actual foundry process and to find out how the choice of materials and actual dimensions would affect the performance. IntroductionVarious MEMS (Micro Electro Mechanical System) technologies have shown their possibilities to bring forth components of quite different kinds, e.g. pressure sensors, gyroscopes or micro mirrors for projectors. A class of MEMS components can preferably be used in RF (Radio Frequency) systems, RF MEMS, enabling compact implementations and high performance [1]. Micromechanical parts can replace their electronic counterparts in effective ways. Most mature in the RF MEMS area are mechanical switches which have demonstrated very low insertion loss and high isolation [2]. Of special interest to our work is mechanically resonating (or vibrating) structures which can be used to implement oscillators, mixers or filters. By taking advantage of the mechanical properties high performance and miniaturization can be obtained by cost effective batch processing. Such MEMS resonators can replace off-chip crystals or can be used in implementing filter banks with unique selection properties [1].In this paper H-shaped filter structures based on coupled clamped-clamped (c-c) beams are studied. Figure 1 shows the 3-D model of our filter where one of the beams is electrostatically activated and output is taken from a second beam. The performance depends on various parameters related to the actual MEMS process, geometrical dimensions, material selection for the structural layer, offset voltage and placement of the coupling beam. A systematic way of choosing an appropriate set within the design constraints is vital. A commercial foundry process, [3], has been chosen to give a realistic parameter choice. In section 2 the design method is described, and results from a concrete design are shown and discussed in section 3, preceding the conclusion.

Bound States and Many-Body Effects in H-Shaped Quantum Wires

“…Henkiewicz et al have studied the manifestation of the spin Hall effect in a two-dimensional electronic system with Rashba spin-orbit coupling via dc-transport measurements in a realistic H-shaped structure [31]. Designing of H-shaped micromechanical structure has been studied by Arhaug and Soeraasen [32]. Our investigation shows that there is no other concrete study of these structure in existing literature.…”

Many-Body Effects and Bandgap Renormalization in H-Shaped Quantum Wires

“…Hankiewicz et al have studied the manifestation of the spin Hall effect in a two-dimensional electronic system with the Rashba spin-orbit coupling via dc-transport measurements in a realistic H-shaped structure [31]. Designing of H-shaped micromechanical structure has been studied by Arhaug and Soeraasen [32].…”

Effects of electric and magnetic fields on the bandgap renormalization of H-shaped quantum wires

“…Henkiewicz et al have studied the manifestation of the spin Hall effect in a two-dimensional electronic system with Rashba spin-orbit coupling via dc-transport measurements in a realistic H-shaped structure [28]. Designing an H-shaped micromechanical structure has been studied by Arhaug and Soeraasen [29]. H-shaped QWs have been considered by Zibold et al in their study of semiconductor QW-based singleand two-qubit gates [30].…”