Oscillator having reduced sensitivity to acceleration

Abstract

An oscillator includes resonator portions each mounted to a substrate via one or more mountings at one end and having an active resonance region defined between a set of electrodes. Each resonator portion has a longitudinal axis directed along the resonator portion from the mounted end to a free end. The resonator portions are mounted such that their longitudinal axes are directed in different directions, e.g. an anti-parallel arrangement, so that acceleration sensitivity vector components aligned with the longitudinal axis cancel each other out.

1 . An oscillator comprising:
 a plurality of resonator portions, each said resonator portion having an active resonance region defined between a set of electrodes capable of receiving signals caused by oscillator resonance in said active resonance region during operation of said oscillator,   each of said resonator portions being mounted in said oscillator using one or more mountings, each resonator portion comprising first and second ends, the first end of each resonator portion being mounted to a substrate via at least one of said one or more mountings, the second end of each resonator portion being free, and the resonator portions each having a respective longitudinal axis which is directed along the resonator portion from the first end to the second end of the resonator portion,   wherein said resonator portions are mounted in said oscillator such that the longitudinal axes of the resonator portions are directed in different directions so as to reduce the sensitivity of the oscillator to acceleration.   
     
     
         2 . An oscillator according to  claim 1 , wherein said oscillator comprises two or more individual resonator portions separately mounted therein. 
     
     
         3 . An oscillator according to  claim 2 , wherein two or more of said individual resonator portions are mounted within separate housings. 
     
     
         4 . An oscillator according to  claim 2 , wherein two or more of said individual resonator portions are mounted within the same housing. 
     
     
         5 . An oscillator according to  claim 1 , wherein said oscillator comprises two integrally formed resonator portions. 
     
     
         6 . An oscillator according to  claim 5 , wherein said resonator portions are connected via a central portion and said mountings for each resonator portion are located in said central portion. 
     
     
         7 . An oscillator according to  claim 1 , wherein said one or more mountings comprise a cantilever mounting arrangement. 
     
     
         8 . An oscillator according to  claim 7 , wherein said cantilever mounting arrangement comprises a pair of mountings adjacent the first end of each resonator portion, the connections providing both mechanical coupling to the substrate and electrical coupling to said set of electrodes. 
     
     
         9 . An oscillator according to  claim 1 , wherein each active resonance region is located towards the second end of its respective resonator portion. 
     
     
         10 . An oscillator according to  claim 1 , wherein each said resonator portion comprises an elongate member having sides of a relatively large dimension and top and bottom ends having a relatively small dimension and a longitudinal axis extending between said top and bottom ends. 
     
     
         11 . An oscillator according to  claim 10 , wherein said mounted and free ends of each elongate resonator portion correspond to the top and bottom ends of each elongate resonator portion. 
     
     
         12 . An oscillator according to  claim 10 , wherein each said active region has a relatively large acceleration sensitivity along a dominant axis, and a relatively small acceleration sensitivity along axes orthogonal to said dominant axis, and wherein said dominant axes are substantially aligned with the longitudinal axes of said elongate resonator portions. 
     
     
         13 . An oscillator according to  claim 1 , wherein the acceleration sensitivities of the respective active resonance regions are directed in substantially opposite directions. 
     
     
         14 . An oscillator according to  claim 1 , wherein said resonator portions comprise a piezoelectric crystal. 
     
     
         15 . An oscillator according to  claim 14 , wherein one or more of said resonator portions comprises a Bulk Acoustic Wave (BAW) device. 
     
     
         16 . An oscillator according to  claim 14 , wherein one or more of said resonator portions comprises a Surface Acoustic Wave (SAW) device. 
     
     
         17 . An oscillator according to  claim 14 , wherein one or more resonator portion comprises one or more of:
 quartz (SiO2),   lithium tantalate (LiTaO3),   lithium niobate (LiNbO3).   
     
     
         18 . An oscillator according to  claim 1 , wherein said resonator portion comprises one or more Micro Electrical Mechanical System (MEMS) devices. 
     
     
         19 . An oscillator according to  claim 1 , wherein said plurality of resonator portions are electrically coupled in series. 
     
     
         20 . An oscillator according to  claim 1 , wherein said plurality of resonator portions are electrically coupled in parallel. 
     
     
         21 . An oscillator circuit comprising an oscillator according to  claim 1  and further comprising an integrated circuit electrically coupled to each of the resonator portions for providing a frequency output that exhibits substantially reduced sensitivity to acceleration. 
     
     
         22 . A mobile telephone comprising an oscillator according to  claim 1 . 
     
     
         23 . A mobile global positioning system (GPS) device comprising an oscillator according to  claim 1 . 
     
     
         24 . A method of manufacturing an oscillator with reduced sensitivity to acceleration, the method comprising the steps of:
 providing a plurality of resonator portions;   for each said resonator portion, defining an active resonance region between a set of electrodes so as to be capable of receiving signals at said electrodes caused by oscillator resonance in said active resonance region during operation of said oscillator;   mounting each of said resonator portions in said oscillator using one or more mountings, each resonator portion comprising first and second ends, the first end of each resonator portion being mounted to a substrate via at least one of said one or more mountings, the second end of each resonator portion being free, the resonator portions each having a respective longitudinal axis which is directed along the resonator portion from the first end to the second end of the resonator portion; and   mounting said resonator portions in said oscillator such that the longitudinal axes of the resonator portions are directed in different directions so as to reduce the sensitivity of the oscillator to acceleration.