Voltage controlled oscillator

• US 8,957,738 B1
• Filed: 10/18/2012
• Issued: 02/17/2015
• Est. Priority Date: 10/18/2012
• Status: Active Grant

• Current Assignee: Hittite Microwave, LLC (Analog Devices, Inc.)
• Original Assignee: Hittite Microwave Corporation (Analog Devices, Inc.)
• Inventors: Koechlin, Michael, Oran, Ekrem, Zhang, Cemin, Chiesa, John, O'Neill, Christopher, Poelker, John
• Primary Examiner(s): Johnson, Ryan
• Application Number:
  US13/654,846
• Time in Patent Office: 852 Days
• Field of Search: 331/117.R, 331/117.FE, 331/167, 331/177.V, 331/36.C
• US Class Current: 331/117.R
• CPC Class Codes: H03B 2200/0008 Colpitts oscillator
• CPC Class Codes: H03B 2200/009 Reduction of phase noise
• CPC Class Codes: H03B 2200/0094 Measures to ensure starting of oscillations
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1218 the generator being of the balanced type
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• 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

Abstract

A voltage controlled oscillator including an RF output terminal and a DC control terminal, an active circuit, and a resonant circuit interconnected with the active circuit and including a plurality of series resonators each having an electrically variable capacitance and fixed inductor; the active circuit includes at least one transistor having an operating current density which is approximately 35% or less of the peak f_T operating current density and/or the active circuit includes a multi-transistor bank disposed in at least two separate sections, each pair of sections spaced apart to provide improved thermal uniformity among the transistors without substantially increasing parasitic impedance among them for providing an improved lower phase noise output at said RF output terminal.

Claims

1. A voltage controlled oscillator comprising:

an RF output terminal and a DC control terminal;

an active circuit; and

a resonant circuit interconnected with said active circuit and including at least three series resonators each having an electrically variable capacitance and a fixed inductor;

said active circuit including at least one transistor having an operating current density which is approximately 35% or less of a peak transition frequency (f_T) operating current density for providing an improved lower phase noise output at said RF output terminal.

2. The voltage controlled oscillator of claim 1 in which there are four series resonators each having a variable capacitance and a fixed inductor.

3. The voltage controlled oscillator of claim 1 in which there are five series resonators each having a variable capacitance and a fixed inductor.

4. The voltage controlled oscillator of claim 1 further including an inductance coupled in series between the DC control terminal and each of the electrically variable capacitances to adjust the frequency of the oscillator.

5. The voltage controlled oscillator of claim 1 further including an inductance and a resistance coupled in series between the DC control terminal and each of the electrically variable capacitances to adjust the frequency of the oscillator.

6. The voltage controlled oscillator of claim 4 in which said inductance is coupled to said electrically variable capacitances at a point of RF voltage minimum.

7. The voltage controlled oscillator of claim 1 in which each of said electrically variable capacitances includes a varactor.

8. The voltage controlled oscillator of claim 7 in which each of the varactors includes two diodes coupled together.

9. The voltage controlled oscillator of claim 7 in which each of said varactors includes only one diode.

10. The voltage controlled oscillator of claim 1 which is implemented on a planar monolithic substrate.

11. The voltage controlled oscillator of claim 10 in which said monolithic substrate is selected from the group of a GaAs substrate and a Si substrate.

12. The voltage controlled oscillator of claim 7 in which each of said varactors includes a p-n junction.

13. The voltage controlled oscillator of claim 7 in which each of said varactors includes a field effect transistor (FET) and includes a capacitance between the gate and a source of the FET.

14. The voltage controlled oscillator of claim 1 in which each of said electrically variable capacitances includes a ferroelectric based capacitance.

15. The voltage controlled oscillator of claim 7 in which each of said varactors includes a MEMs based capacitance.

16. The voltage controlled oscillator of claim 7 in which each of said varactors includes a switchable capacitor.

17. The voltage controlled oscillator of claim 1 in which said resonant circuit and said active circuit are configured as single ended oscillator.

18. The voltage controlled oscillator of claim 10 in which the monolithic substrate is disposed in a surface mount package.

19. The voltage controlled oscillator of claim 1 in which said resonant circuit and said active circuit are configured as a push-push oscillator.

20. The voltage controlled oscillator of claim 1 in which said resonant circuit and said active circuit are configured as a Colpitts oscillator.

21. The voltage controlled oscillator of claim 1 in which said active circuit includes a bipolar transistor.

22. The voltage Controlled oscillator of claim 1 in which said active circuit includes a field effect transistor.

23. A voltage controlled oscillator comprising:

a RF output terminal and a DC control terminal;

an active circuit; and

a resonant circuit interconnected with said active circuit and including a plurality of series resonators each having an electrically variable capacitance and fixed inductor;

said active circuit including a multi-transistor bank disposed in at least two separate sections, each pair of sections spaced apart to provide improved thermal uniformity among transistors of the multi-transistor bank without substantially increasing parasitic impedance among them for providing an improved lower phase noise output at said RF output terminal.

24. The voltage controlled oscillator of claim 23 in which there are three series resonators each having a variable capacitance and a fixed inductor.

25. The voltage controlled oscillator of claim 23 in which there are four series resonators each having a variable capacitance and a fixed inductor.

26. The voltage controlled oscillator of claim 23 in which there are five series resonators each having a variable capacitance and a fixed inductor.

27. The voltage controlled oscillator of claim 23 said sections are spaced apart approximately 200-500μ

from section center to center.

28. The voltage controlled oscillator of claim 23 in which said sections include bipolar transistors and are connected in common emitter configuration.

29. The voltage controlled oscillator of claim 27 in which said sections include bipolar transistors and are spaced 215μ

from section center to center with said transistor bank made with a GaAs HBT process.

30. The voltage controlled oscillator of claim 23 further including an inductance coupled in series between the DC control terminal and each of the electrically variable capacitances to adjust the frequency of the oscillator.

31. The voltage controlled oscillator of claim 23 further including an inductance and a resistance coupled in series between the DC control terminal and each of the electrically variable capacitances to adjust the frequency of the oscillator.

32. The voltage controlled oscillator of claim 30 in which said inductance is coupled to said electrically variable capacitances at a point of RF voltage minimum.

33. The voltage controlled oscillator of claim 23 in which each of said electrically variable capacitances includes a varactor.

34. The voltage controlled oscillator of claim 33 in which each of the varactors includes two diodes coupled together.

35. The voltage controlled oscillator of claim 33 in which each of said varactors includes only one diode.

36. The voltage controlled oscillator of claim 23 which is implemented on a planar monolithic substrate.

37. The voltage controlled oscillator of claim 36 in which the monolithic substrate is selected from the group of a GaAs substrate and a Si substrate.

38. The voltage controlled oscillator of claim 33 in which each of said varactors includes a p-n junction.

39. The voltage controlled oscillator of claim 33 in which each of said varactors includes a field effect transistor (FET) and includes a capacitance between the gate and a source of the FET.

40. The voltage controlled oscillator of claim 23 in which each of said electrically variable capacitances includes a ferroelectric based capacitance.

41. The voltage controlled oscillator of claim 33 in which each of said varactors includes a MEMs based capacitance.

42. The voltage controlled oscillator of claim 33 in which each of said varactors includes a switchable capacitor.

43. The voltage controlled oscillator of claim 23 in which said resonant circuit and said active circuit are configured as single ended oscillator.

44. The voltage controlled oscillator of claim 36 in which the monolithic substrate is disposed in a surface mount package.

45. The voltage controlled oscillator of claim 23 in which said resonant circuit and said active circuit are configured as a push-push oscillator.

46. The voltage controlled oscillator of claim 23 in which said resonant circuit and said active circuit are configured as a Colpitts oscillator.

47. The voltage controlled oscillator of claim 23 in which said active circuit includes a bipolar transistor.

48. The voltage controlled oscillator of claim 23 in which said active circuit includes a field effect transistor.

49. A voltage controlled oscillator comprising:

an RF output terminal and a DC control terminal;

an active circuit; and

a resonant circuit interconnected with said active circuit and including a plurality of series resonators each having an electrically variable capacitance and fixed inductor;

said active circuit including at least one transistor having an operating current density which is approximately 35% or less of a peak transition frequency (f_T) operating current density;

said active circuit further including a multi-transistor bank disposed in at least two separate sections, each pair of sections spaced apart to provide improved thermal uniformity among transistors of the multi-transistor bank without substantially increasing parasitic impedance among them for providing an improved lower phase noise output at said RF output terminal.