Method to Increase the Tuneability of Varactors

• US 20080197947A1
• Filed: 09/06/2005
• Published: 08/21/2008
• Est. Priority Date: 06/09/2005
• Status: Active Grant

• Current Assignee: Optis Cellular Technology LLC (Brevet Capital)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Gevorgyan, Spartak, Jacobsson, Harald, Deleniv, Anatoli
• Granted Patent: US 7,936,235 B2
• Time in Patent Office: Days
• US Class Current: 334/15
• 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
• CPC Class Codes: H03J 3/185 with varactors, i.e. voltage variable reactive diodes
• CPC Class Codes: H03J 3/20 of single resonant circuit by varying inductance only or capacitance only
• CPC Class Codes: H03J 7/10 Modification of automatic frequency control sensitivity or linearising automatic frequency control operation

Abstract

The present invention relates to a tunable circuit, or admittance, arrangement comprising at least one capacitive branch with at least a tunable first capacitor, and tuning application means. It further comprises at least one resonant branch comprising at least a second capacitor and an inductor, said second capacitor and said inductor being connected in series. Said at least one capacitive branch and said at least one resonant branch are connected in parallel, and said tuning application means are adapted for application of a DC tuning voltage. The capacitance of said first and/or second capacitor and/or the inductance of said inductor are selected such that the frequency dependency of the tunability of a varactor arrangement forming the equivalent varactor arrangement of the admittance arrangement can be controlled at least in a selected frequency range.

Claims

1-24. -24. (canceled)

25. A tunable circuit comprising:

at least one capacitive branch with at least a tunable first capacitor and tuning application means;

at least one resonant branch comprising at least a second capacitor and an inductor, said second capacitor and said inductor being connected in series,

wherein said at least one capacitive branch and said at least one resonant branch are connected in parallel, said tuning application means being adapted for application of a DC tuning voltage; and

wherein the capacitance of said first and/or second capacitor and/or the inductance of said inductor are selected such that the frequency dependency of the tunability of a varactor arrangement forming the equivalent varactor arrangement can be controlled at least in a selected frequency range.

26. The tunable circuit according to claim 25, wherein the capacitance of the second capacitor is selected to give a given frequency dependence or a frequency dependence with a given maximum deviation or tolerance in said frequency range.

27. The tunable circuit according to claim 25, wherein the capacitance of the second capacitor is of substantially the same order of magnitude as the capacitance of the first capacitor.

28. The tunable circuit according to claim 25, wherein the capacitance of first and the second capacitors are variable.

29. The tunable circuit according to claim 25, wherein the capacitance of at least one of said first and second capacitors is variable.

30. The tunable circuit according to claim 25, wherein the first and/or second capacitor and/or the inductor are so selected that tunability of the tunable circuit in a given or selected frequency range is substantially frequency independent, or frequency independent with a given allowed deviation of frequency dependent within specified limits.

31. The tunable circuit according to claim 25, wherein the capacitance of the second capacitor is so selected that the equivalent capacitance or the tunability of the tunable circuit in a given or selected frequency range is substantially frequency independent, or frequency independent with a given allowed deviation or frequency dependent within specified limits.

32. The tunable circuit according to claim 25, wherein the first capacitor or the capacitive branch is tunable.

33. The tunable circuit according to claim 32, wherein the second capacitor, or the resonating branch, is tunable to one of (i) a limited extent, (ii) considerably less than the first capacitor, or (iii) not tunable.

34. The tunable circuit according to claim 25, wherein the equivalent capacitance is given by the frequency ranges where the frequency ω

is higher than the parallel resonant frequency ω

_2p.

35. The tunable circuit according to claim 25, wherein the capacitive branch comprises a first variable capacitance arrangement with the first capacitor connected in series with a secondary first capacitor connected in series with a secondary inductor, and further wherein the resonating branch comprises the second capacitor connected in series with the first inductor having five active elements.

36. The tunable circuit according to claim 25, wherein the resonant elements thereof are made of a ferroelectric material, including BaSrTiU3, BSTO, with a tunable dielectric constant.

37. The tunable circuit according to claim 25, wherein the resonant elements thereof are made of a polymer material or a liquid crystal material.

38. The tunable circuit according to claim 25, wherein the resonant elements thereof are made of a superconducting material, a high or a low temperature superconducting material, e.g. YBCO.

39. The tunable circuit according to claim 25, having a size of approximately 5-20×

30-70 μ

m, preferably 10×

50 μ

m.

40. The tunable circuit according to claim 25, arranged to operate a controllably high tunability of about 1 GHz-10 GHz in the region of 100 GHz to 900 GHz when the active elements, at least the first and second capacitors and the inductor are appropriately selected.

41. The tunable circuit according to claim 25, arranged to operate to in a frequency region which is lower than 1 GHz, when the active elements, at least the first and second capacitors and the inductor, are appropriately selected.

42. The tunable circuit according to claim 25, adapted to be used in a phase shifter, in a tunable filter or in a tunable matching circuit.

43. The tunable circuit according to claim 25, wherein the first and/or second capacitors is/are implemented as planar or parallel plate or multilayer varactors in a circular, elliptical, rectangular, square shaped, interdigital or other appropriate shape.

44. A method of providing a tunable circuit or admittance arrangement comprising the steps of:

providing a capacitive branch with at least one tunable first capacitor, providing a resonant branch with at least a tunable second resonator and an inductor in series;

connecting said capacitive and resonant branches in parallel;

establishing a frequency range, while giving the maximum allowable tolerance or frequency dependent deviation of a varactor forming the equivalent varactor of the tunable circuit or admittance arrangement; and

selecting the capacitance of the first and second capacitors and the inductance of the inductor so in dependence of one another that the frequency dependency of tunability of the equivalent varactor arrangement can be controlled.

45. The method according to claim 44, further comprising the steps of:

selecting said first or second capacitor as a reference parameter capacitor;

fixing the capacitance of said reference parameter capacitor;

calculating the capacitance of said other capacitor not used as a reference parameter capacitor and the inductance of said inductor using the fixed capacitance value, the upper and lower frequency values defining the frequency range, and the maximum allowable tolerance/deviation.

46. The method according to claim 44, further comprising the step of applying a DC biasing voltage.

47. The method according to claim 44, further comprising the step of establishing a maximum allowable deviation in percentage.

48. The method according to claim 44, wherein the varactors comprising a dielectric substrate with a tunable dielectric constant of BSTO, or of a superconducting material.