Wideband AFT Power Amplifier Systems With Frequency-Based Output Transformer Impedance Balancing

• US 20140028398A1
• Filed: 03/15/2013
• Published: 01/30/2014
• Est. Priority Date: 07/27/2012
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: OWEN, Christopher Michael
• Granted Patent: US 9,214,901 B2
• Time in Patent Office: Days
• US Class Current: 330/276
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/391 the output circuit of an amplifying stage comprising an LC-network
• CPC Class Codes: H03F 2200/537 A transformer being used as coupling element between two amplifying stages
• CPC Class Codes: H03F 2200/541 Transformer coupled at the output of an amplifier
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/2176 Class E amplifiers
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03F 3/265 with field-effect transistors only
• CPC Class Codes: H03F 3/602 Combinations of several amplifiers
• CPC Class Codes: H03F 3/604 using FET's

Abstract

A radio frequency system includes a first power splitter, a first push-pull power amplifier and a second push-pull power amplifier. The first power splitter is configured to receive a first radio frequency signal and generate a first output signal and a second output signal. The first push-pull power amplifier is configured to amplify the first output signal. The first push-pull power amplifier comprises a first set of transistors including at least two radio frequency power transistors and a first output transformer. The second push-pull power amplifier is configured to amplify the second output signal. The second push-pull power amplifier includes a second set of transistors including at least two radio frequency power transistors and a second output transformer. An output of the first transformer is galvanically and directly connected to an output of the second output transformer.

Claims

1. A radio frequency system comprising:

a first power splitter configured to receive a first radio frequency signal and generate a first output signal and a second output signal;

a first push-pull power amplifier configured to amplify the first output signal, wherein the first push-pull power amplifier comprises (i) a first set of transistors including at least two radio frequency power transistors, and (ii) a first output transformer; and

a second push-pull power amplifier configured to amplify the second output signal, wherein the second push-pull power amplifier comprises (i) a second set of transistors including at least two radio frequency power transistors, and (ii) a second output transformer,

wherein an output of the first output transformer is galvanically and directly connected to an output of the second output transformer at an output terminal.

2. The radio frequency system of claim 1, further comprising:

a second power splitter configured to receive a second radio frequency signal and generate a third output signal; and

a third push-pull power amplifier configured to amplify the third output signal, wherein the third push-pull power amplifier comprises a third set of transistors including at least two radio frequency power transistors,

wherein an output of the third push-pull power amplifier is galvanically and directly connected to the output terminal.

3. The radio frequency system of claim 2, further comprising a fourth push-pull power amplifier configured to amplify a fourth output signal, wherein the fourth push-pull power amplifier comprises a fourth set of transistors including at least two radio frequency power transistors,

wherein the second power splitter is configured to generate a fourth output signal, and

wherein an output of the fourth push-pull power amplifier is galvanically and directly connected to the output terminal.

4. The radio frequency system of claim 1, further comprising a first shunt capacitance connecting the output terminal to a ground reference.

5. The radio frequency system of claim 1, further comprising a variable class module comprising:

an inductor connected between the output terminal and a load of the radio frequency system; and

a second shunt capacitance connecting an output of the inductor to a ground reference.

6. The radio frequency system of claim 5, wherein:

the radio frequency system is configured to operate in a selected mode characteristic of one of a plurality of power amplifier classes based on a configuration of the variable class module; and

the configuration of the variable class module is modifiable to operate in the selected mode.

7. The radio frequency system of claim 1, wherein:

the first push-pull power amplifier comprises a first input transformer configured to receive the first output signal and includes a first output and a second output,

wherein the first output of the first input transformer is connected to (i) a first transistor of the first set of transistors via a first capacitance, and (ii) a ground reference via a first resistance, and

wherein the second output of the first input transformer is connected to (i) a second transistor of the first set of transistors via a second capacitance, and (ii) the ground reference via a second resistance; and

the second push-pull power amplifier comprises a second input transformer configured to receive the second output signal and includes a first output and a second output,

wherein the first output of the second input transformer is connected to (i) a first transistor of the second set of transistors via a third capacitance, and (ii) the ground reference via a third resistance, and

wherein the second output of the second input transformer is connected to (i) a second transistor of the second set of transistors via a fourth capacitance, and (ii) the ground reference via a fourth resistance.

8. The radio frequency system of claim 1, further comprising:

a first inductor connected between the output terminal and a load of the radio frequency system; and

a first shunt capacitance connecting an output of the inductor to a ground reference.

9. The radio frequency system of claim 8, wherein the first push-pull power amplifier comprises:

a first transistor;

a second transistor;

a second capacitance connected to the first transistor;

a first resistance connecting the second capacitance to the ground reference;

a third capacitance connecting the second capacitance to the ground reference;

a fourth capacitance connected to the second transistor;

a second resistance connecting the fourth capacitance to the ground reference; and

a fifth capacitance connecting the fourth capacitance to the ground reference.

10. The radio frequency system of claim 8, further comprising:

a second shunt capacitance connecting an output of the first push-pull power amplifier to the ground reference; and

a third shut capacitance connecting an output of the second push-pull power amplifier to the ground reference.

11. The radio frequency system of claim 10, further comprising a variable class module comprising:

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

a fourth shunt resistance connecting an output of the second inductor to the ground reference.

12. The radio frequency system of claim 11, wherein:

the radio frequency system is configured to operate in a selected mode characteristic of one of a plurality of power amplifier classes based on a configuration of the variable class module; and

the configuration of the variable class module is modifiable to operate in the selected mode.

13. A radio frequency amplifier system comprising:

an input module configured to receive and amplify an input signal to generate an amplified output signal, wherein a frequency of the input signal varies within a predetermined frequency range; and

a first set of power amplifiers, wherein each of the first set of power amplifiers comprises an output and is configured to receive the amplified output signal, and wherein the outputs of the first set of power amplifiers are galvanically and directly connected to each other at a first output terminal,

wherein power from the first set of power amplifiers is supplied to a load via the first output terminal.

14. The radio frequency amplifier system of claim 13, wherein the frequency of the input signal varies ±

5-10% from a center frequency.

15. The radio frequency amplifier system of claim 13, wherein:

the first set of power amplifiers comprises an output module; and

the output module comprises a plurality of capacitances connected between the outputs of the first set of power amplifiers and a ground reference.

16. The radio frequency amplifier system of claim 15, wherein the output module is void of an inductance and includes only one capacitance per power amplifier in the first set of power amplifiers.

17. The radio frequency amplifier system of claim 15, further comprising a variable class module connected to the first output terminal, wherein the radio frequency amplifier system is configured to operate in a selected mode characteristic of one of a plurality of power amplifier classes based on a configuration of the variable class module, and wherein the configuration of the variable class module is modifiable to operate in the selected mode.

18. The radio frequency amplifier system of claim 17, wherein the variable class module comprises:

an inductance having a first end and a second end, wherein the first end is connected to the first output terminal; and

a second capacitance connected between the second end and the ground reference,

wherein the power from the first set of power amplifiers is supplied to the load via the second end of the inductance.

19. The radio frequency amplifier system of claim 15, the output module comprises:

a first inductance having a first end and a second end, wherein the first end is connected to the first output terminal; and

a second capacitance connected between the second end and the ground reference,

wherein the power from the first set of power amplifiers is supplied to the load via the second end of the first inductance.

20. The radio frequency amplifier system of claim 19, further comprising a variable class module connected to the output module, wherein the radio frequency amplifier system is configured to operate in a selected mode characteristic of one of a plurality of power amplifier classes based on a configuration of the variable class module, and wherein the configuration of the variable class module is modifiable to operate in the selected mode.

21. The radio frequency amplifier system of claim 20, wherein the variable class module comprises:

a second inductance having a first end and a second end, wherein the first end of the second inductance is connected to the second end of the first inductance; and

a third capacitance connected between the second end of the second inductance and the ground reference,

wherein the power from the first set of power amplifiers is supplied to the load via the second end of the second inductance.

22. The radio frequency amplifier system of claim 13, wherein:

the first set of power amplifiers comprises three power amplifiers;

a center frequency of the input signal is greater than 40 MHz;

a turns ratio of each transformer in each of the first set of power amplifiers is 3;

1; and

an output impedance of each of the first set of power amplifiers at the first output terminal is 145-155Ω

.

23. The radio frequency amplifier system of claim 13, wherein:

the first set of power amplifiers comprises four power amplifiers;

a center frequency of the input signal is greater than 40 MHz, a turns ratio of each transformer in each of the first set of power amplifiers is one of 3;

1 and 4;

1; and

an output impedance of each of the first set of power amplifiers at the first output terminal is 195-205Ω

.

24. The radio frequency amplifier system of claim 13, wherein:

the first set of power amplifiers comprises four power amplifiers;

a center frequency of the input signal is less than 60 MHz and greater than 40 MHz;

a turns ratio of each transformer in each of the first set of power amplifiers is 4;

1; and

an output impedance of each of the first set of power amplifiers at the first output terminal is 195-205Ω

.

25. The radio frequency amplifier system of claim 13, further comprises:

an output module connected to the first output terminal and converting a first impedance at the first output terminal to a second impedance; and

a variable class module connected to the output module and configured to set an operating class of the radio frequency amplifier system,

wherein a center frequency of the input signal is less than 60 MHz.

26. The radio frequency amplifier system of claim 13, further comprising a power combiner receiving an output of the first set of power amplifiers and an output of a second set of power amplifiers,

wherein a circuit between (i) the first set of power amplifiers and the second set of power amplifiers and (ii) the power combiner, is void of an inductance, and

wherein a center frequency of the input signal is greater than or equal to 40 MHz.

27. The radio frequency amplifier system of claim 13, further comprising:

a variable class module connected to the first output terminal and configured to set an operating class of the radio frequency amplifier system; and

a power combiner receiving an output of the first set of power amplifiers and an output of a second set of power amplifiers,

wherein a circuit between (i) the first set of power amplifiers and the second set of power amplifiers, and (ii) the power combiner is void of an inductance other than an inductance in the variable class module, and

wherein a center frequency of the input signal is greater than or equal to 40 MHz.

28. The radio frequency amplifier system of claim 13, further comprising:

a second set of power amplifiers, wherein each of the second set of power amplifiers comprises an output and is configured to receive the amplified output signal, and wherein each of the outputs of the second set of power amplifiers are galvanically and directly connected to each other at a second output terminal; and

a non-isolated combiner configured to combine signals received from the first output terminal and the second output terminal.

29. The radio frequency amplifier system of claim 13, further comprising a circuit connected to the output terminal and configured to maintain an output power of the radio frequency amplifier system at a predetermined output power level ±

0.5% of the predetermined output power level while frequency of the input signal varies.

30. The radio frequency amplifier system of claim 13, further comprising a circuit connected to the output terminal and configured to maintain a current level out of the radio frequency amplifier system at a predetermined current level ±

0.5% of the predetermined current level while frequency of the input signal varies.

31. The radio frequency amplifier system of claim 13, further comprising a plurality of transmission traces, wherein each of the plurality of transmission traces connects one of the outputs of one of the first set of power amplifiers to the output terminal, and wherein paths along the plurality of transmission traces are void of a capacitance-inductance-capacitance network.

32. The radio frequency amplifier system of claim 13, wherein each of the first set of power amplifiers comprises:

a first transistor comprising a first control terminal;

a second transistor comprising a second control terminal;

a first capacitance connected between the first control terminal and a ground reference; and

a second capacitance connected between the second control terminal and the ground reference.

33. The radio frequency amplifier system of claim 32, wherein each of the first set of power amplifiers further comprises:

an input transformer having a first output and a second output, wherein the first capacitance is connected to the first output of the input transformer, and the second capacitance is connected to the second output of the input transformer; and

an output transformer having a first input and a second input, wherein the first input of the output transformer is connected to a drain of the first transistor, and the second input of the output transformer is connected to a drain of the second transistor.

34. The radio frequency amplifier system of claim 33, further comprising:

a first resistance connected to the first output of the input transformer and to the ground reference; and

a second resistance connected to the second output of the input transformer and to the ground reference.

35. The radio frequency amplifier system of claim 34, further comprising:

a third capacitance connected to the first output of the input transformer and to the ground reference; and

a fourth capacitance connected to the second output of the input transformer and to the ground reference,

wherein the third capacitance and the first resistance are connected in parallel between the first output of the input transformer and the ground reference, and

wherein the fourth capacitance and the second resistance are connected in parallel between the second output of the input transformer and the ground reference.