Analog phase shifter using cascaded voltage tunable capacitor
View Patent ↗A circuit topology is configured to flatten out a phase- and amplitude-response over a specified range of frequencies. The circuit topology also provides a large cumulative phase-shift. In one embodiment, the circuit topology cascades a plurality of all-pass sections, with the center-frequencies of each all-pass section staggered to create a substantially flat phase-response over a frequency range. Further, in one embodiment the plurality of all-pass sections has at least one all-pass section that is different from another all-pass section. Each all-pass section includes a tunable capacitor and has a center-frequency that can be varied by electronically tuning the capacitor. Each center frequency is selected to obtain substantially constant amplitude and phase response over a desired frequency range and capacitance tuning range.
1. A phase shifter comprising:
a plurality of all-pass sections, each all-pass section including a first tunable capacitor and having a center-frequency different from another all-pass section, each center frequency selected to provide a composite response corresponding to a substantially constant phase response over a predetermined frequency range, wherein the first tunable capacitor of an all pass section of the plurality of all-pass sections comprises a semiconductor diode varactor and the semiconductor diode varactor comprises a material from a group consisting of silicon, gallium arsenide, and silicon germanium.
2. A phase shifter comprising:
a plurality of all-pass sections, each all-pass section including a first tunable capacitor and having a center-frequency different from another all-pass section, each center frequency selected to provide a composite response corresponding to a substantially constant phase response over a predetermined frequency range, wherein the first tunable capacitor of an all pass section of the plurality of all-pass sections comprises a micro-electro-mechanical (MEMS) device.
3. A phase shifter comprising:
a plurality of all-pass sections cascaded in series, each all-pass section including a first tunable capacitor and having a center-frequency different from another all-pass section, each center frequency selected to provide a composite response corresponding to a substantially constant phase response over a predetermined frequency range, wherein each all-pass section further comprises:
an input and an output, the first tunable capacitor connected between the input and the output;
a plurality of series-connected inductors connected between the input and output; and
a second tunable capacitor connected between a junction of the plurality of series-connected inductors and a ground.
4. The phase shifter of claim 3 , wherein each of the first tunable capacitor and the second tunable capacitor of an all-pass section comprises a dielectric varactor disposed upon a substrate.
5. The phase shifter of claim 4 , where each of the dielectric varactors comprises a dielectric selected from a group consisting of strontium titanate (STO), barium titanate (BTO), and barium strontium titanate (BST).
6. The phase shifter of claim 5 , wherein the predetermined frequency range is an RF frequency range.
7. The phase shifter of claim 5 , wherein a center frequency for at least one of the all-pass sections falls outside the predetermined frequency range.
8. The phase shifter of claim 5 , wherein at least two of the all-pass sections have a same center frequency and said at least two all-pass sections are separated from each other by other all-pass section(s) with different center frequencies.
9. The phase shifter of claim 5 , wherein the plurality of series-connected inductors is also disposed upon the substrate.
10. The phase shifter of claim 5 , wherein the phase shifter is capable of phase shifts of 360 degrees or more.
11. The phase shifter of claim 10 , wherein the phase shifter is capable of a phase shift of 360 degrees at a bias voltage for the tunable capacitors of 20 volts or less.
12. The phase shifter of claim 4 , wherein the phase shifter is capable of phase shifts of 360 degrees or more.
13. The phase-shifter of claim 3 , wherein the ground comprises a plurality of ground conductors.
14. The phase-shifter of claim 13 , wherein the plurality of ground conductors is configured for electrical coupling during packaging of the phase shifter.
15. The phase-shifter of claim 3 , farther comprising direct current (DC) blocking capacitors at the input and output of the phase-shifter.
16. The phase-shifter of claim 15 , further comprising a bias voltage source configured to apply a bias voltage to all of the first and second tunable capacitors in the circuit.
17. The phase-shifter of claim 15 , farther comprising a resistor coupled with a DC control voltage to one of the input, the output, and a signal path between the input and the output of at least one all-pass section.
18. The phase-shifter of claim 3 , where an inductor is included in series with the second tunable capacitor.
19. The phase-shifter of claim 3 , wherein the series inductors comprise a spiral inductor disposed upon a chip.
20. The phase-shifter of claim 3 , wherein the series inductors comprise a distributed element.
21. The phase-shifter of claim 20 , wherein the distributed element comprises a transmission-line segment.
22. The phase-shifter of claim 3 , wherein the ground comprises a common ground conductor.
23. The phase-shifter of claim 3 , wherein the first tunable capacitor between the input and output of each all-pass section comprises:
a plurality of series-connected tunable capacitors; and
a biasing resistor connected between a junction of the series-connected tunable capacitors and the ground.
24. A phase shifter comprising:
a low-pass bridged section, including a tunable capacitor and having a first center-frequency;
a high-pass bridged section, including a tunable capacitor and having a second center frequency, the high-pass bridged section coupled with the low-pass bridged section, the first and the second center frequencies selected to provide composite response corresponding to a substantially constant phase response over a predetermined frequency range.
25. The phase shifter of claim 24 , wherein the tunable capacitor in the low-pass bridged section and the tunable capacitor in the high-pass bridged section each comprises a dielectric varactor disposed upon a substrate.
26. The phase shifter of claim 25 , where each of the dielectric varactors comprises a dielectric selected from a group consisting of strontium titanate (STO), barium titanate (BTO), and barium strontium titanate (BST).
27. The phase shifter of claim 26 , wherein at least two of the all-pass sections have a same center frequency and said at least two all-pass sections are separated from each other by other all-pass section(s) with different center frequencies.
28. The phase shifter of claim 26 , wherein a center frequency for at least one of the all-pass sections falls outside the predetermined frequency range.
29. The phase shifter of claim 26 , wherein the predetermined frequency range is an RF frequency range.
30. The phase shifter of claim 26 , wherein the phase shifter is capable of phase shifts of 360 degrees or more.
31. The phase shifter of claim 30 , wherein the phase shifter is capable of a phase shift of 360 degrees at a bias voltage for the tunable capacitors of 20 volts or less.
32. The phase shifter of claim 25 , wherein the phase shifter is capable of phase shifts of 360 degrees or more.
33. The phase shifter of claim 24 , wherein the tunable capacitor of the bridged low-pass section and the tunable capacitor of the bridged high-pass section each comprises a micro-electro-mechanical (MEMS) device.
34. The phase shifter of claim 24 , wherein the tunable capacitor of the bridged low-pass section and the tunable capacitor of the bridged high-pass section each comprises a semiconductor diode varactor.
35. The phase shifter of claim 34 , wherein each semiconductor diode varactor comprises a material from a group consisting of silicon, gallium arsenide, and silicon germanium.
36. The phase shifter of claim 24 , wherein the tunable capacitor of the bridged low-pass section and the tunable capacitor of the bridged high-pass section each comprises a tunable dielectric.
37. The phase shifter of claim 36 , wherein each of the tunable dielectric comprises one from a group consisting of strontium titanate (STO), barium titanate (BTO), barium strontium titanate (BST), and bismuth zinc niobate (BZN).
38. The phase shifter of claim 24 , wherein the high-pass bridged section couples with a second low-pass bridged section including a tunable capacitor and having a third center frequency, the third center frequency selected to provide a composite response corresponding to a substantially constant phase response over a predetermined frequency range.
39. The phase shifter of claim 38 , wherein the second low-pass bridged section couples with a second high-pass bridged section including a tunable capacitor and having a fourth center frequency, the fourth center frequency selected to provide a composite response corresponding to a substantially constant phase response over a predetermined frequency range.
40. A phase shifter comprising:
a plurality of all-pass sections cascaded in series, each all-pass section including a first tunable capacitor and having a center-frequency different from another all-pass section, each center frequency selected to provide a composite response corresponding to a substantially constant phase response over a predetermined frequency range, wherein each all-pass section further comprises:
an input and an output, the first tunable capacitor comprising a plurality of tunable capacitors connected in series between the input and output;
a first inductor connected between the input and the output; and
a second inductor connected between a ground and a junction of two tunable capacitors of the plurality of tunable capacitors connected in series.
41. The phase-shifter of claim 40 , wherein the series inductors comprise a distributed element.
42. The phase-shifter of claim 41 , wherein the distributed element comprises a transmission-line segment.
43. The phase-shifter of claim 40 , wherein the ground comprises a common ground conductor.
44. The phase-shifter of claim 40 , wherein the ground comprises a plurality of ground conductors.
45. The phase-shifter of claim 44 , wherein the plurality of ground conductors is configured for electrical coupling during packaging of the phase shifter.
46. The phase-shifter of claim 40 , wherein the series inductors cokprise a spiral inductor disposed upon a chip.
47. The phase shifter of claim 40 , wherein each of the plurality of tunable capacitors of an all-pass section comprises a dielectric varactor disposed upon a substrate.
48. The phase-shifter of claim 47 , wherein the phase shifter is capable of phase shifts of 360 degrees or more.
49. The phase shifter of claim 47 , where each of the dielectric varactors comprises a dielectric selected from a group consisting of strontium titanate (STO), barium titanate (BTO), and barium strontium titanate (BST).
50. The phase shifter of claim 49 , wherein the phase shifter is capable of phase shifts of 360 degrees or more.
51. The phase shifter of claim 50 , wherein the phase shifter is capable of a phase shift of 360 degrees at a bias voltage for the tunable capacitors of 20 volts or less.
52. The phase shifter of claim 49 , wherein the predetermined frequency range is an RF frequency range.
53. The phase shifter of claim 49 , wherein a center frequency for at least one of the all-pass sections falls outside the predetermined frequency range.
54. The phase shifter of claim 49 , wherein at least two of the all-pass sections have a same center frequency and said at least two all-pass sections are separated from each other by other all-pass section(s) with different center frequencies.
55. The phase shifter of claim 49 , wherein the first inductor and the second inductor are also disposed upon the substrate.
56. the phase-shifter of claim 40 , further comprising direct current (DC) blocking capacitors at the input and output of the phase-shifter.
57. The phase-shifter of claim 56 , further comprising a resistor coupled with a DC control voltage to one of the input, the output, and a signal path between the input and the output of at least one all-pass section.
58. The phase-shifter of claim 40 , further comprising a third inductor connected in series with the first inductor between the input and the output of each all-pass section.