Nokia Mobile Phones Limited

Advanced Saw Products Sa

Temex

Serguei Kondratiev

Victor P Plessky

Clinton S Hartmann

Dongpei Chen

Mohammed A Sharif

The invention relates to a method for realizing surface acoustic wave filter arrangements of the kind comprising a piezo-electric substrate and on said substrate metallic strip elements constituting impedance filter elements arranged in a network scheme. In such an arrangement by electrostatic interaction between the network elements is produced a parasitic resonance at a frequency different from the operational resonance frequency. The method is characterized in that means are provided in the filter arrangement which produce a shifting of the parasitic resonance frequency to a frequency substantially equal to said operational resonance frequency. The invention can be used for filter arrangements.

Method for realizing surface acoustic wave filter arrangements and filter arrangement obtained in accordance to this method

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

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.

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Neuchatel, Switzerland

Serguei Kondratiev