System and method for tuning an oscillator

• US 20040183610A1
• Filed: 03/21/2003
• Published: 09/23/2004
• Est. Priority Date: 03/21/2003
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Parssinen, Aarno, Hallivuori, Juha, Seppinen, Pauli
• Granted Patent: US 6,833,769 B2
• Time in Patent Office: Days
• US Class Current: 331/177V
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: C23F 4/00 Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• CPC Class Codes: H03B 5/1253 the transistors being field-effect transistors
• CPC Class Codes: H03B 5/1265 switched capacitors
• CPC Class Codes: H03B 5/1293 having means for achieving a desired tuning characteristic, e.g. linearising the frequency characteristic across the tuning voltage range
• CPC Class Codes: H03J 2200/36 Circuit arrangements for, e.g. increasing the tuning range, linearizing the voltage-capacitance relationship, lowering noise, constant slope in different bands

Abstract

A voltage-controlled oscillator includes a resonator circuit and a voltage source. The resonator circuit includes a capacitive circuit that has a plurality of analog voltage controlled capacitive elements coupled to one another. The voltage source is coupled to the resonator circuit and provides a voltage to the plurality of analog voltage controlled capacitive elements. Each of the plurality of analog voltage controlled capacitive elements is activated as a function of the voltage thereby increasing linearity of a frequency tuning voltage parameter of the resonator.

Claims

1. A voltage-controlled oscillator comprising:

a resonator circuit that includes a capacitive circuit, the capacitive circuit including a plurality of analog voltage controlled capacitive elements coupled to one another; and

a voltage source, coupled to the resonator circuit, the voltage source adapted to provide a voltage to the plurality of analog voltage controlled capacitive elements,

where individual ones of the plurality of analog voltage controlled capacitive elements are activated as a function of the magnitude of the voltage thereby increasing linearity of a frequency tuning voltage parameter of the resonator.

2. The oscillator apparatus of claim 1, where the analog voltage controlled capacitive elements comprise a diode varactor and at least one MOS transistor.

3. The oscillator apparatus of claim 1, where the analog voltage controlled capacitive elements include a plurality of MOS transistors.

4. The oscillator apparatus of claim 1, where the analog voltage controlled capacitive elements function as a PN varactor.

5. The oscillator apparatus of claim 1, where the analog voltage controlled capacitive elements function as a MOS varactor.

6. The oscillator apparatus of claim 1, where the analog voltage controlled capacitive elements are activated in a predetermined sequence established by a DC biasing network that is coupled to said plurality of capacitive elements.

7. The oscillator apparatus of claim 1, where the capacitance of the capacitive circuit is a function of the capacitance of each of the analog voltage controlled capacitive elements.

8. The oscillator apparatus of claim 1, further comprising a bias voltage source coupled to the plurality of analog voltage controlled capacitive elements, the bias voltage source adapted to provide, in combination with a resistive network, a distinct bias voltage to each of the analog voltage controlled capacitive elements.

9. The oscillator apparatus of claim 1, where the plurality of analog voltage controlled capacitive elements are coupled to one another in parallel.

10. The oscillator apparatus of claim 1, further comprising at least one inductor coupled to block direct current components of an electric current.

11. A variable capacitor comprising:

a pair of nodes comprising an input node and an output node for coupling to a resonator;

a plurality of analog voltage controlled capacitive elements that are electronically coupled to one another and to said pair of nodes; and

a control voltage input for coupling to a control voltage source and coupled in common to each of the plurality of analog voltage controlled capacitive elements, the control voltage input adapted to provide a control voltage to each of the analog voltage controlled capacitive elements,

where individual ones of the plurality of analog voltage controlled capacitive elements are activated as a function of the control voltage, in concert with a biasing network, to provide a substantially linear change in resonator resonant frequency over a range of control voltages between the input node and the output node.

12. The variable capacitor of claim 11, further comprising at least one inductor coupled to block direct current components of an electric current.

13. The variable capacitor of claim 11, where the analog voltage controlled capacitive elements include a diode varactor and at least one MOS transistor.

14. The variable capacitor of claim 11, where the analog voltage controlled capacitive elements include at least one MOS transistor.

15. The variable capacitor of claim 11, where the analog voltage controlled capacitive elements function as a PN varactor.

16. The variable capacitor of claim 11, where the analog voltage controlled capacitive elements function as a MOS varactor.

17. The variable capacitor of claim 11, where the analog voltage controlled capacitive elements are activated in a predetermined sequence.

18. The variable capacitor of claim 11, where the capacitance of the varactor is a function of the capacitance of each of the analog voltage controlled capacitive elements.

19. The variable capacitor of claim 11, further comprising a bias voltage input, coupled to a bias voltage source and coupled in common to each of the plurality of analog voltage controlled capacitive elements via said biasing network, the bias voltage input adapted to provide, in combination with said biasing network, a different bias voltage to each of the analog voltage controlled capacitive elements.

20. The variable capacitor of claim 11, where the plurality of analog voltage controlled capacitive elements are coupled to one another in parallel.

21. A variable capacitor device comprising:

a first capacitive circuit;

a diode circuit, coupled to the first capacitive circuit; and

a voltage source to provide a control voltage to the first capacitive circuit and the diode circuit,

where the first capacitive circuit and the diode circuit are activated in a sequence that is a function of the control voltage, and the first capacitive circuit is further activated as a function of a bias voltage.

22. The variable capacitor device of claim 21, where the diode circuit comprises a plurality of capacitive diode elements.

23. The variable capacitor device of claim 21, where the first capacitive circuit comprises at least one MOS transistor.

24. The variable capacitor device of claim 21, where the diode circuit comprises at least one PN junction device.

25. The variable capacitor device of claim 21, further comprising:

a bias voltage input coupled to the first capacitive circuit, the bias voltage input adapted to provide a bias voltage to the first capacitive circuit for setting at least an activation point of said first capacitive circuit.

26. The variable capacitor device of claim 25, where the bias voltage activates the first capacitive circuit such that the first capacitive circuit affects a resonator tuning curve of the diode circuit for a case where the derivative of the capacitance is not constant.

27. A method of operating a voltage controlled oscillator, comprising:

generating a control voltage;

providing a capacitive circuit that includes a plurality of analog voltage controlled capacitive elements coupled to one another in parallel; and

sequentially activating individual ones of the plurality of analog voltage controlled capacitive elements as a function of the control voltage to increase the linearity of a frequency tuning voltage parameter.

28. The method of claim 27, further comprising blocking a direct current component of an electric current.

29. The method of claim 27, further comprising applying a biasing voltage to bias each of the plurality of analog voltage controlled capacitive elements.

30. The method of claim 27, further comprising at least one fixed capacitive element that is switchably coupled with at least one analog voltage controlled capacitive element to provide a plurality of discrete resonator tuning ranges.

31. A mobile station comprising a frequency synthesizer comprised of a phase lock loop (PLL) that includes a voltage controlled oscillator (VCO), a frequency output of said VCO being tuned with a resonator that comprises a variable capacitance, said variable capacitance comprising a plurality of voltage controlled capacitive elements coupled in parallel, further comprising activating means for sequentially activating individual ones of the plurality of voltage controlled capacitive elements as a function of an input analog control voltage and a bias network for increasing linearity of a frequency tuning curve of said VCO.

32. A mobile station as in claim 31, where said analog control voltage is sourced by a PLL phase detector.

33. A mobile station as in claim 31, where said bias network comprises a resistive network coupled to said voltage controlled capacitive elements, said resistive network being coupled to a fixed bias voltage.

34. A mobile station as in claim 31, where said bias network comprises a resistive network coupled to said voltage controlled capacitive elements, said resistive network being coupled to a variable bias voltage.

35. A mobile station as in claim 31, where said bias network comprises a resistive network coupled to said voltage controlled capacitive elements, said resistive network being coupled to a bias voltage established by one of an operational mode or a frequency selection logic of said mobile station.

36. The mobile station as in claim 31, further comprising at least one fixed capacitive element that is switchably coupled with at least one voltage controlled capacitive element to provide a plurality of discrete frequency tuning ranges.