Abstract: A wafer bonded CMUT array comprising a plurality of CMUT elements distributed across a substrates, each element comprising a cavity and a signal electrode formed in the substrate, and a conductive membrane closing the cavity and forming a ground electrode, wherein the membranes of the individual elements form an unbroken ground plane across the surface of the array and wherein electrical connection to the signal electrodes is provided by means of a conductive vias depending therefrom through the substrate from the signal electrode to the rear of the substrate.

Abstract: The invention relates to an identification chip for insertion in an object located in a liquid. The identification chip comprises an acoustic resonator (100), which exhibits a number of distinct resonant frequencies, where the combination of resonant frequencies is unique to the identification chip. This enables the identification chip to be identified by exposing it to an acoustic polling signal, measuring an acoustic response signal and analysing the frequency of the response signal. The resonator (100) comprises a cavity-forming part (110, 120) and a membrane (130). The acoustic resonant frequencies are determined by at least one cavity (140), which is enclosed by the cavity-forming part (110, 120) and the membrane (140). The identification chip can be implanted in a fish, with the object of identifying the fish when it is located in water.

Abstract: A transducer element for ultrasound reception comprises a first active transducer layer connected to a first receiver, and a second active transducer layer laminated to the first active transducer layer and connected to a second receiver. A transducer element for ultrasound transmission comprises a first active transducer layer connected to a first transmitter, and a second active transducer layer laminated to the first transducer layer and connected to a second transmitter. Further aspects of the present invention include a transducer element for ultrasound transmission and reception, a transducer array for ultrasound transmission and reception, and methods for transmitting and receiving ultrasound signals.

Abstract: A transducer element for ultrasound reception comprises a first active transducer layer connected to a first receiver, and a second active transducer layer laminated to the first active transducer layer and connected to a second receiver. A transducer element for ultrasound transmission comprises a first active transducer layer connected to a first transmitter, and a second active transducer layer laminated to the first transducer layer and connected to a second transmitter. Further aspects of the present invention include a transducer element for ultrasound transmission and reception, a transducer array for ultrasound transmission and reception, and methods for transmitting and receiving ultrasound signals.

Abstract: A procedure to correct the amplitude of the frequency or the impulse response for signal processing filter based entirely or partly on acoustic surface waves has been described. The method may be applied where the acoustic wave follows different paths inside the component depending on the signal frequency or on the signal time delay in the filter. The method is based on changing the signal phase in an essentially periodic way for instance by etching metal films placed on the surface of the component in order to make correction possible. Laser induced etching can be an efficient way to carry out amplitude correction according to the invention due to the good geometric resolution of this method and because correction of the phase pan of the response can be earned out with the same equipement in accordance with established techniques.

Abstract: A method and apparatus for converting electronic signals from frequency-division multiplex format into time-division multiplex format while retaining substantially all phase and amplitude information of a band-limited continuous signal. A continuous frequency-division multiplex format signal is multiplied with a first chirp signal having a periodic sequence with period T, a constant amplitude and a phase variation having a non-zero constant amplitude second derivative of said phase variation with respect to time .mu.. A convolution is then performed of said multiplied signal with a convolution filter having an impulse response defined byh.sub.0 (t).times.e .sup.j(.omega..sbsp.0.sup.t-.mu.t.spsp.2.sup./2)wherein h.sub.0 (t) is a function having finite delay greater than T, and .omega..sub.0 is a constant.