SURFACE ACOUSTIC WAVE DRIVING CIRCUIT AND OSCILLATOR THEREFOR

• US 20100134194A1
• Filed: 07/18/2008
• Published: 06/03/2010
• Est. Priority Date: 08/06/2007
• Status: Active Grant

• Current Assignee: Ste Industries S.r.l.
• Original Assignee: Ste S.A.S. Di G. Moiraghi & C.
• Inventors: Moiraghi, Paolo, Moiraghi, Guido, Moiraghi, Luca
• Granted Patent: US 8,134,416 B2
• Time in Patent Office: Days
• US Class Current: 331/116.M
• CPC Class Codes: H03B 5/06 Modifications of generator to ensure starting of oscillations
• CPC Class Codes: H03B 5/326 the resonator being an acoustic wave device, e.g. SAW or BAW device

Abstract

A driving circuit of a surface wave resonator (X1) is described; the resonator comprises a static capacitor (Co) and the driving circuit is adapted to supply a voltage (Vx) to the resonator. The driving circuit comprises reactive means (L3) adapted to resonate in combination with said static capacitor (Co) of the resonator at a predetermined frequency (Fo) in the initial driving period of the resonator at said voltage; the driving circuit comprises passive means (R3) adapted to determine oscillations at said predetermined frequency (Fo).

Claims

1. A surface wave resonator driving circuit, said resonator comprising a static capacitor and said driving circuit being adapted to supply a voltage to said resonator, wherein it comprises reactive means adapted to resonate in combination with said static capacitor of the resonator at a predetermined frequency of the initial driving period of the resonator at said voltage, said driving circuit comprising passive means adapted to determine oscillations at said predetermined frequency.

2. The circuit according to claim 1, wherein said reactive means have a value so as to be essentially negligible with respect to the total reactance of the surface wave resonator after a predetermined initial period of time from the application of said voltage to said surface wave resonator.

3. The circuit according to claim 2, wherein said passive means are adapted to force the surface wave resonator to essentially oscillate at said predetermined frequency after said predetermined initial period of time.

4. The circuit according to claim 1, wherein said reactive means are an inductor.

5. The circuit according to claim 1, wherein said passive means are a resistor.

6. The circuit according to claims 4, wherein said inductor and said resistor are arranged reciprocally in parallel and in series to said surface wave resonator.

7. The circuit according to claim 6, wherein it comprises a bipolar transistor having the collector terminal coupled to a supply power by means of another inductor, the base terminal coupled at a polarization voltage by means of another resistor, the emitter terminal coupled to ground by means of the parallel of a further resistor and another capacitor, said circuit comprising a further capacitor arranged between the collector terminal and the emitter terminal.

8. The circuit according to claim 7, wherein it comprises a further inductor connected between said other capacitor and ground.

9. The circuit according to claim 3, wherein said initial period of time is essentially 50 nanoseconds.

10. The oscillator comprising a surface wave resonator and a driving circuit as defined in claim 1.