Abstract: A ladder filter comprising a plurality of bulk acoustic wave resonators, the resonators comprising a plurality of series resonators series resonators in series between an input terminal and an output terminal of the filter, and one or more shunt resonators each connected between a junction between two series resonators and a common terminal, the series resonators comprising an input series resonator connected to the input terminal and an output series resonator connected to the output terminal, and wherein the shunt resonators are designed to satisfy: a unity aspect ratio and wherein the series resonators are designed to satisfy an aspect ratio different from unity. The aspect ratio is defined as the ratio of length to width of the resonator.

Abstract: An electro-acoustic resonator (1, 8, 17) of the membrane or FBAR type (1) or the solidly-mounted or SBAR type (8), with electrodes comprising a single conducting layer or multiple conducting layers, i.e. sandwich construction (17) with an optimum coupling factor kr and thus an improved filter bandwidth. The optimum coupling factor kr is achieved by the arrangement that the top electrode (6, 15, 25) is thinner than the bottom electrode (4, 13, 23). The coupling factor is independent of the resonator's layout defined by the mask.

Abstract: A bulk acoustic wave resonator comprising a substrate (5), a Bragg reflector (4), a top (1) and a bottom (3) electrode and a piezoelectric layer (2) with means for suppression of the pass-band ripples in a bulk acoustic wave filter. The means for absorbing or scattering the spurious modes are a roughened rear side of the substrate (6), an absorbing layer (5) disposed on the rear side of the substrate (6) and/or an absorbing layer (5) disposed on the front side of the substrate.

Abstract: A multi-mode radio module (22) comprises a terminal (11) for connection to an antenna (10). A transmitting branch (DCS/PCS) and a branching circuit are coupled to the terminal (11). The branching circuit comprises at least a first and a second branch for receiving signals in first and second frequency bands (DCS, PCS), respectively. Each of the first and second branches comprise, respectively, a phase shifting circuit (PS1, PS2), a BAW or SAW band pass filter (RXF2, RXF3) coupled to the phase shifting circuit, the bandwidth of the filter being selected to pass a wanted signal in one of the first and second frequency bands but reject an unwanted signal in the other of the second and first frequency bands, and a low noise amplifier (LNA2, LNA3) coupled to an output of the band pass filter. The response of each of the band pass filters (RXF2, RXF3) is phase shifted to present an open circuit at the wanted frequency in the other branch.

Abstract: A filter structure, comprising a first signal line, a second signal line, a third signal line and a fourth signal line, said first and third signal lines defining an input port and said second and fourth signal lines defining an output port of a section of said filter structure, said section being defined by a first bulk acoustic wave resonator (A) which is connected between said first signal line and said second signal line, a second bulk acoustic wave resonator (G) which is connected between said third signal line and said fourth signal line, a third bulk acoustic wave resonator (C) which is connected between said first signal line and said fourth signal line, and a fourth bulk acoustic wave resonator (E) which is connected between said second signal line and said third signal line; is characterized in that a frequency pulling factor defined d of at least one of said acoustic wave resonators is non-zero, said frequency pulling factor d being defined by for first and second bulk acoustic wave resonators havi

Abstract: A bulk wave resonator comprising: a substrate (1); a layer (3) of piezoelectric material deposited on the substrate; a first electrode (2) and a second electrode (4) which are arranged on opposite surfaces of the layer (3) of piezoelectric material, the overlapping area of the first electrode (2) and second electrode (4) defining the resonance range of the bulk wave resonator, characterized in that the overlapping area in an intersecting plane parallel to at least one of the electrodes (2, 4) has an aspect ratio in the range from 1 (b/a) 100, where a is the length and b the width of the bulk wave resonator. The invention also relates to a bulk wave filter comprising such bulk wave resonators.

Abstract: The invention relates to a filter device equipped with at least one bulk acoustic wave resonator, which comprises a resonator unit and a reflection element (2) comprising several layers (6, 7, 8). The layers (6, 7, 8) each comprise a mixture of at least two materials. Within each layer (6, 7, 8), the composition of the mixture varies continuously and periodically relative to the layer thickness.