Advanced Saw Products Sa

Nokia Mobile Phones Limited

Thales

Victor P Plessky

Serguei Kondratiev

Clinton S Hartmann

David P Morgan

Laurent Kopp

Thor Thorvaldsson

Dongpei Chen

Sergei N Kondratyev

Mohammed A Sharif

The invention relates to a surface acoustic wave filter (or SAW filter) comprising a symmetrical network with differential inputs/outputs, in particular for mobile telecommunication systems. A network of the ladder or balanced bridge type comprises at least one structure of the surface acoustic wave resonator type, that comprises at least two transducers in the same acoustic channel, two of said transducers being substantially identical, connected to two symmetrical branches of the network and arranged in such a way that the acoustic waves generated by the two transducers are in phase. Advantageously, arrays of reflectors are placed on either side of the structure. Apart from saving space, this structure makes it possible in particular to simplify the production of the filter and to achieve better control in balancing the branches.

Surface acoustic wave filter

A surface acoustic wave filter provided on a substrate, in which input 'hot' and ground busbars and output 'hot' and ground busbars are disposed substantially symmetrically with respect to an axis lying between the input and the output of the filter.

Acoustic wave filter

A surface acoustic wave filter provided on a substrate, comprising a transducer and a first reflector for surface acoustic waves at one end of the transducer, the first reflector being integral with conductive material that defines a busbar of the filter.

Acoustic wave impedance element ladder filter having a reflector

A SAW filter having an even number of tracks, each track comprising reflective input and output IDTs having a partially reflecting grating disposed between them. One of the IDTs of each pair of tracks has its electrodes connected in opposite polarity to those of the other IDTs of the pair of tracks and the separation of the input and output IDTs of respective tracks of each pair of tracks is substantially the same. The relative dispositions of the partially reflecting gratings are such that waves launched into respective tracks of a pair of tracks undergo at least one reflection from the partially reflecting grating prior to being coherently incident on the output IDTs. By virtue of the oppositely connected electrodes of one of the IDTs, direct coupling through the tracks is inhibited at substantially all frequencies.

Saw filter including electrodes of opposing polarity

This invention relates to an electronic device having a frequency dependent signal transfer characteristic which is electrically coupled to at least one SAW transducer. The SAW transducer acts as a SAW impedance element since it exhibits frequency dependent electrical characteristics. Such characteristics are utilised so that the transmission loss of the SAW impedance element is high in a relatively low signal transfer region of the signal transfer characteristic of the electronic device, and low in a relatively high signal transfer region of the signal transfer characteristic of the electronic device. This has the advantage that signals outside of the passband of the electronic device can be attenuated without increasing the transmission loss of the electronic device in its passband.

Saw filter with a coupled saw impedance element

The invention relates to a SAW filter comprising a first and second pair of substantially equivalent SAW transducers electrically coupled to form a bridge circuit. Each of the transducers of the first pair of transducers have a center frequency which is slightly different to the center frequency of each of the transducers of the second pair of transducers. The product of the static capacitance of the first pair is the same as the product of the static capacitance of the second pair. In use, signals input to the filter and having a frequency within the passband of the filter are coupled to the output of the bridge circuit via one or other or both arms of the bridge, as in normal bridge circuit operation. However, out of band signals are blocked since all the transducers are equivalent capacitors having the same capacitance (i.e., static capacitance). Thus, transmission of out of band signals through the filter is inhibited by the balanced nature of the bridge.

Growing community of inventors

Geneveys Sur Coffrane, Switzerland

Victor P Plessky