Power amplifier employing thin film ferroelectric phase shift element

• US 20060139091A1
• Filed: 12/29/2004
• Published: 06/29/2006
• Est. Priority Date: 12/29/2004
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Fratti, Roger A.
• Granted Patent: US 7,248,108 B2
• Time in Patent Office: Days
• US Class Current: 330/124.R
• CPC Class Codes: H03F 1/0288 using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers
• CPC Class Codes: H03F 2200/423 Amplifier output adaptation especially for transmission line coupling purposes, e.g. impedance adaptation
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/602 Combinations of several amplifiers

Abstract

An amplifier includes a signal splitter operable to receive an input signal and generate at least first and second split signals, a first amplifier adapted to receive the first split signal and to generate a first amplified signal, and a second amplifier adapted to receive the second split signal and to generate a second amplified signal. A combining circuit is adapted to generate an output signal which is a sum of the first amplified signal and the second amplified signal. The amplifier further includes a phase control circuit arranged in a signal path of one of the first and second amplifiers, the phase control circuit comprising at least one thin film ferroelectric element. The amount of phase shift provided by the phase control circuit is selectively variable as a function of a control signal applied thereto.

Claims

1. An amplifier, comprising:

a signal splitter operable to receive an input signal and generate at least first and second split signals;

a first amplifier adapted to receive the first split signal and to generate a first amplified signal;

a second amplifier adapted to receive the second split signal and to generate a second amplified signal;

a combining circuit adapted to generate an output signal which is a sum of the first amplified signal and the second amplified signal; and

a phase control circuit arranged in a signal path of one of the first and second amplifiers, the amount of phase shift provided by the phase control circuit being selectively variable as a function of a control signal applied thereto, the phase control circuit comprising at least one thin film ferroelectric element.

2. The amplifier of claim 1, wherein the phase control circuit follows the first amplifier.

3. The amplifier of claim 1, wherein the phase control circuit precedes the first amplifier.

4. The amplifier of claim 1, wherein the phase control circuit is arranged in the signal path of the first amplifier, and wherein the amplifier further comprises a second phase control circuit arranged in the signal path of the second amplifier, the amount of phase shift provided by the second phase control circuit being selectively variable as a function of a second control signal applied thereto, the second phase control circuit comprising at least one thin film ferroelectric element.

5. The amplifier of claim 4, wherein the amount of phase shift provided by the phase control circuits is substantially the same relative to one another.

6. The amplifier of claim 4, wherein the amount of phase shift provided by the phase control circuits is different relative to one another.

7. The amplifier of claim 1, wherein the control signal is a function of a frequency of the input signal.

8. The amplifier of claim 1, further comprising a frequency detector circuit adapted to receive at least a portion of the input signal and to generate a detector signal that is representative of a frequency of the input signal, the control signal being a function of the detector signal.

9. The amplifier of claim 1, wherein the first amplifier is configured in a class A mode of operation.

10. The amplifier of claim 1, wherein the second amplifier is configured in a class C mode of operation.

11. The amplifier of claim 1, wherein the first and second amplifiers are configured in a class A mode of operation.

12. The amplifier of claim 1, wherein the power amplifier is configured as a Doherty amplifier.

13. The amplifier of claim 1, wherein the power amplifier is configured as a balanced amplifier.

14. The amplifier of claim 1, wherein the thin film ferroelectric element comprises at least one barium strontium titanate capacitor.

15. The amplifier of claim 1, further comprising a second phase control circuit adapted to receive the output signal and to generate a phase-shifted output signal that is shifted in phase by a desired amount compared to the output signal.

16. The amplifier of claim 1, further comprising a second phase control circuit adapted to receive the output signal and to generate a phase-shifted output signal that is shifted in phase by a desired amount compared to the output signal, the amount of phase shift of the output signal being selectively variable as a function of a second control signal applied thereto, the second phase control circuit comprising at least one thin film ferroelectric element.

17. The amplifier of claim 1, wherein the signal splitter comprises an in-phase signal splitter operative to split the input signal into at least first and second split signals of substantially equal power.

18. The amplifier of claim 1, wherein the combining circuit comprises an in-phase combining circuit.

19. The amplifier of claim 1, wherein the at least one phase control circuit comprises:

a first inductor connected in series between an input node and a first node of the phase control circuit;

a first capacitor connected between the first node and a common node;

a first variable capacitor connected in parallel with the first capacitor;

a second inductor connected between the first node and a second node;

a second variable capacitor connected between the second node and the common node;

a second capacitor connected in parallel with the second variable capacitor; and

a third inductor connected between the second node and an output node.

20. The amplifier of claim 1, wherein the control signal is a substantially linear function of a frequency of the input signal.

21. The amplifier of claim 1, wherein the signal splitter comprises a first interconnection element connected between an input of the power amplifier and a first node the input signal being applied to the input of the power amplifier, a second interconnection element connected between the first node and a second node, the first split signal being generated at the second node, and a third interconnection element connected between the first node and a third node, the second split signal being generated at the third node.

22. An integrated circuit including at least one amplifier, the at least one amplifier comprising:

a signal splitter operable to receive an input signal and generate at least first and second split signals;

a first amplifier adapted to receive the first split signal and to generate a first amplified signal;

a second amplifier adapted to receive the second split signal and to generate a second amplified signal;

a combining circuit adapted to generate an output signal which is a sum of the first amplified signal and the second amplified signal; and

a phase control circuit arranged in a signal path of one of the first and second amplifiers, the amount of phase shift provided by the phase control circuit being selectively variable as a function of a control signal applied thereto, the phase control circuit comprising at least one thin film ferroelectric element.