Coupled coils inter-stage matching network
An amplifier circuit having an improved inter-stage matching network and improved performance. In one embodiment, an RF signal source having an output impedance Z SOURCE is approximately impedance matched through an inductive tuning circuit to a power amplifier having an input impedance Z PA . The inductive tuning circuit includes a tunable capacitor element C 1 and inductive elements L 1 , L 2 , which may be fabricated as stacked conductor coils. Since the capacitance of C 1 is tunable, impedance matching is available over a broad range of RF frequencies. Also provided are DC isolation between the RF signal source and the power amplifier, coupling of a voltage source to the output of the RF signal source through L 1 , and coupling of a bias voltage to the input of the power amplifier through L 2.
1. A radio frequency (RF) amplifier circuit, including:
(a) a power amplifier having an input with impedance Z PA ;
(b) an inductively coupled tuning circuit including first and second inductive elements having a mutual inductance and each having a first terminal and a second terminal, and a tunable capacitor element coupled to the first terminal of the first inductive element and configured to be coupled to circuit ground, wherein:
(1) a node between the first terminal of the first inductive element and the tunable capacitor element is configured to be coupled to an RF signal source having an output with impedance Z SOURCE ;
(2) the second terminal of the first inductive element is configured to be coupled to a first DC voltage source;
(3) the first terminal of the second inductive element is coupled to the input of the power amplifier; and
(4) the second terminal of the second inductive element is configured to be coupled to a second DC voltage source;
wherein the output of the RF signal source is inductively coupled to the input of the power amplifier and the inductive tuning circuit is tunable to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
2. A radio frequency (RF) amplifier circuit, including:
(a) an inductively coupled tuning circuit including first and second inductive elements having a mutual inductance and each having a first terminal and a second terminal, and a tunable capacitor element coupled to the first terminal of the first inductive element and configured to be coupled to circuit ground;
(b) an RF signal source having an output with impedance Z SOURCE , the output being coupled between the first terminal of the first inductive element and the tunable capacitor element;
(c) a power amplifier having an input with impedance Z PA , the input being coupled to the first terminal of the second inductive element;
(d) a first DC voltage source coupled to the second terminal of the first inductive element; and
(e) a second DC voltage source coupled to the second terminal of the second inductive element;
wherein the output of the RF signal source is inductively coupled to the input of the power amplifier and the inductive tuning circuit is configured to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
3. A radio frequency (RF) amplifier circuit, including:
(a) an inductively coupled tuning circuit including first and second stacked inductive coils having mutual inductance and each having a first terminal and a second terminal, and a digitally tunable capacitor element coupled to the first terminal of the first inductive element and configured to be coupled to circuit ground;
(b) a driver circuit having an output with impedance Z SOURCE , the output being coupled between the first terminal of the first inductive element and the tunable capacitor element;
(c) a power amplifier having an input with impedance Z PA , the input being coupled to the first terminal of the second inductive element;
(d) a first DC voltage source coupled to the second terminal of the first inductive element; and
(e) a second DC voltage source coupled to the second terminal of the second inductive element;
wherein the output of the driver circuit is inductively coupled to the input of the power amplifier and the inductively coupled tuning circuit is configured to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
4. The invention of claim 1 or 2 , wherein the first and second inductive elements are fabricated on an integrated circuit as stacked inductive coils.
5. The invention of claim 1 or 2 , wherein the RF signal source is a driver circuit.
6. The invention of claim 1 or 2 , wherein the tunable capacitor element is a digitally tunable capacitor.
7. The invention of claim 1 , 2 , or 3 , further including a first bypass capacitor coupled to the second terminal of the first inductive element.
8. The invention of claim 1 , 2 , or 3 , further including a second bypass capacitor coupled to the second terminal of the second inductive element.
9. The invention of claim 1 , 2 , or 3 , wherein the RF amplifier circuit is fabricated as an integrated circuit.
10. The invention of claim 9 , wherein the integrated circuit is fabricated on a high Q substrate.
11. The invention of claim 9 , wherein the integrated circuit is fabricated on a silicon-insulator (SOI) substrate using complementary metal oxide semiconductor (CMOS) technology.
12. A method of impedance matching a radio frequency (RF) source signal having an output with impedance Z SOURCE to a power amplifier input having an input with impedance Z PA , including:
(a) inductively coupling the output of the RF source signal to the input of the power amplifier through an inductive tuning circuit including first and second inductive elements having a mutual inductance, and a tunable capacitor element coupled to the first inductive element and configured to be coupled to circuit ground;
(b) providing a first DC voltage to the output of the RF source signal through the first inductive element;
(c) providing a second DC voltage to the input of the power amplifier through the second inductive element; and
(d) tuning the inductive tuning circuit to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
13. A method of impedance matching a radio frequency (RF) source signal to a power amplifier input in an amplifier circuit, including:
(a) providing a power amplifier having an input with impedance Z PA ;
(b) providing an inductively coupled tuning circuit including first and second inductive elements having a mutual inductance and each having a first terminal and a second terminal, and a tunable capacitor element coupled to the first terminal of the first inductive element and configured to be coupled to circuit ground, wherein:
(1) a node between the first terminal of the first inductive element and the tunable capacitor element is configured to be coupled to an RF signal source having an output with impedance Z SOURCE ;
(2) the second terminal of the first inductive element is configured to be coupled to a first DC voltage source;
(3) the first terminal of the second inductive element is coupled to the input of the power amplifier; and
(4) the second terminal of the second inductive element is configured to be coupled to a second DC voltage source;
(c) inductively coupling the output of the RF signal source to the input of the power amplifier; and
(d) tuning the inductive tuning circuit to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
14. A method of impedance matching a radio frequency (RF) source signal to a power amplifier input in an amplifier circuit, including:
(a) providing an inductive tuning circuit including first and second inductive elements having a mutual inductance and each having a first terminal and a second terminal, and a tunable capacitor element coupled to the first terminal of the first inductive element and configured to be coupled to circuit ground;
(b) providing an RF signal source having an output with impedance Z SOURCE , the output being coupled between the first terminal of the first inductive element and the tunable capacitor element;
(c) providing a power amplifier having an input with impedance Z PA , the input being coupled to the first terminal of the second inductive element;
(d) providing a first DC voltage source coupled to the second terminal of the first inductive element;
(e) providing a second DC voltage source coupled to the second terminal of the second inductive element;
(f) inductively coupling the output of the RF signal source to the input of the power amplifier; and
(g) tuning the inductive tuning circuit to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
15. A method of impedance matching a radio frequency (RF) source signal to a power amplifier input in an amplifier circuit, including:
(a) providing an inductively coupled tuning circuit including first and second inductive stacked inductive coils having a mutual inductance and each having a first terminal and a second terminal, and a digitally tunable capacitor element coupled to the first terminal of the first inductive element and configured to be coupled to circuit ground;
(b) providing a driver circuit having an output with impedance Z SOURCE , the output being coupled between the first terminal of the first inductive element and the tunable capacitor element;
(c) providing a power amplifier having an input with impedance Z PA , the input being coupled to the first terminal of the second inductive element;
(d) providing a first DC voltage source coupled to the second terminal of the first inductive element;
(e) providing a second DC voltage source coupled to the second terminal of the second inductive element;
(f) inductively coupling the output of the driver circuit to the input of the power amplifier; and
(g) tuning the inductive tuning circuit to approximately impedance match Z SOURCE to Z PA over a selected range of RF frequencies.
16. The method of claim 13 or 14 , further including fabricating the first and second inductive elements on an integrated circuit as stacked inductive coils.
17. The method of claim 13 or 14 , wherein the RF signal source is a driver circuit.
18. The method of claim 13 or 14 , wherein the tunable capacitor element is a digitally tunable capacitor.
19. The method of claim 13 , 14 , or 15 , further including providing a first bypass capacitor coupled to the second terminal of the first inductively coupled element.
20. The method of claim 13 , 14 , or 15 , further including providing a second bypass capacitor coupled to the second terminal of the second inductive element.
21. The method of claim 13 , 14 , or 15 , further including fabricating the RF amplifier circuit as an integrated circuit.
22. The method of claim 21 , further including fabricating the integrated circuit on a high Q substrate.
23. The method of claim 21 , further including fabricating the integrated circuit on a silicon-on-insulator (SOI) substrate using complementary metal oxide semiconductor (CMOS) technology.