EP4244983A1

EP4244983A1 - Reconfigurable power amplifier

Info

Publication number: EP4244983A1
Application number: EP21893063.4A
Authority: EP
Inventors: Brian Carl HICKS; Blerta Bajramaj MARKOWSKI; David BONANNO; Freddie Santiago
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 2020-11-10
Filing date: 2021-11-10
Publication date: 2023-09-20
Also published as: WO2022104333A1; EP4244983A4

Abstract

A power amplifier is described herein. The power amplifier may include a driver amplifier, a primary amplifier, and a modular output filter. The modular output filter is configured to be replaceable and enables configuration of the power amplifier for operation across a wide bandwidth. The output filter may be formed as a module separate from the other components of the power amplifier.

Description

RECONFIGURABLE POWER AMPLIFIER

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Non-Provisional Patent Application No. 17/094,721 filed November 10, 2020, the entirety of which is incorporated herein by reference.

FEDERALLY-SPONSOR RESEARCH AND DEVELOPMENT

The United States Government has ownership rights in this invention. Licensing inquiries may be directed to Office of Technology Transfer, US Naval Research Laboratory, Code 1004, Washington, DC 20375, USA; +1.202.767.7230; referencing 109418-USL

BACKGROUND

An amplifier is a circuit that produces an output that is an increased version of its input signal. There are many forms of amplifiers, for example, operational amplifiers, small signal amplifiers or large signal or power amplifiers.

In certain applications where high switching currents are needed, such as radio frequency (RF) communications, power amplifiers are widely used. Conventional power amplifier designs may suffer from disadvantages, such as inadequate power over the entirety of the operating frequency band or having an inflexible design that is not sustainable in the long term. That is, the existing designs may provide greater power at a few channels of the operating frequency band and diminished power over the remainder of the band. Moreover, the existing designs are application-specific, and are thus inflexible and cannot be easily re-targeted to new applications. These designs are also not extensible so as to provide enduring value over time.

A power amplifier may be modified for a new application by changing the operating frequency range, but this may require an entirely new design, including different circuit components, extensive simulation, and a new circuit board layout, all of which require considerable resources and time.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

A power amplifier is described herein. The power amplifier includes a driver amplifier, a primary amplifier coupled to the driver amplifier; and a modular output filter coupled to the primary amplifier. The output filter enables configuration of the power amplifier for operation across a wide bandwidth.

A method of fabricating a power amplifier is also described herein. The method includes fabricating a first circuit board that comprises a driver amplifier and a primary amplifier. The method further includes fabricating a second circuit board that comprises an output filter that enables configuration of the power amplifier for operation across a wide bandwidth, the second circuit board being coupled to the first circuit board.

Another power amplifier is described herein. The power amplifier includes a circuit board that includes a driver amplifier and a primary amplifier. The power amplifier further includes a module coupled to the circuit board, the module including an output filter that enables configuration of the power amplifier for operation across a wide bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a reconfigurable power amplifier.

FIG. 2 is a flowchart of a method of fabricating a reconfigurable power amplifier.

FIG. 3 depicts a printed circuit board of a reconfigurable power amplifier.

FIG. 4 is a plot of power of a reconfigurable power amplifier across an operational frequency band.

The features and advantages of embodiments will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.

DETAILED DESCRIPTION

Introduction

References in the specification to “one embodiment,” an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It is noted that any section/subsection headings provided herein are not intended to be limiting. Embodiments are described throughout this document, and any type of embodiment may be included under any section/subsection. Furthermore, embodiments disclosed in any section/subsection may be combined with any other embodiments described in the same section/subsection and/or a different section/subsection in any manner.

Terminology

The terminology used in the specification is for the purpose of describing particular embodiments, and is not intended to be limiting. In the description of the embodiments and the claims, the following terminology will be used in accordance with the definition set out below.

As used herein, the singular forms “a,” “an,” and “the” do not preclude plural referents, unless the content clearly dictates otherwise.

As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

As used herein, the term “about” when used in conjunction with a stated numerical value or range denotes somewhat more or somewhat less than the stated value or range, to within ± 10% of that stated value or range. Terminology used herein should not be construed as being “means-plus- function” language unless the term “means” is expressly used in association therewith.

Overview

The conventional power amplifier is narrowband, has low power efficiency, has an intrinsically lower bandwidth gain element, and an inflexible harmonic output filter. Such power amplifier has no upgrade path to more modem components with increased bandwidth. Thus, the conventional power amplifier may require extensive redesign to change the harmonic output filter to enable operation in another frequency band. Moreover, the conventional power amplifier may be much less efficient (e.g., up to 15%) than the reconfigurable power amplifier described herein.

The reconfigurable power amplifier described herein is optimized for battery operated radio frequency communications, although it is not so limited. Compared to conventional devices, this power amplifier provides higher output power, which translates to better data transmission over longer distances, improved resource usage, and more reliable communications. The reconfigurable power amplifier provides solid output across a wide band that is limited only by the design of the output filter and the bandwidth of the primary amplifier device selected. Moreover, this reconfigurable power amplifier has a relatively flat power output across significantly large frequency bands, with high efficiency that is greater than 60 percent. The high-efficiency factor renders the reconfigurable power amplifier suitable for battery-powered applications. In addition, the design of the reconfigurable power amplifier enables easy reconfiguration for different applications by replacement of the modular output filter. Accordingly, it is straightforward to adapt this design to existing and emerging communication platforms.

Example Embodiments

RF signals are typically difficult to manage in circuit design as they are inherently high-frequency signals that may be at low voltage levels and may accumulate added noise from multiple sources. Thus, it is beneficial and oftentimes necessarily to use an RF amplifier to modify and boost the RF signal. An RF amplifier may be used for basic signal amplification, matching signal to converter span, acting as a buffer for RF signals, and/or providing the signal power needed to drive low-impedance or non- resistive loads at high speed with a low level of distortion. In wireless transmissions, RF signals may be sent over long distances over a wireless medium (e.g., air). The RF signals may be transmitted using antennas and the range of transmission is dependent on the magnitude of power of the RF signals fed to the antennas. Thus, an RF power amplifier, such as the reconfigurable power amplifier described herein, may be used to drive an antenna of a transmitter by converting a low- power RF signal into a higher power RF signal. The transmitter may be used in conjunction with receiver(s) for wireless communications.

FIG. 1 is a block diagram of a reconfigurable power amplifier 100. Power amplifier 100 is an electronic device configured to increase the magnitude of the voltage, current or power of an input signal. Thus, power amplifier 100 may receive a weak input signal and may generate a stronger output signal by utilizing an external power source. Power amplifier 100 may include a chain of components, including a driver amplifier 102, a primary amplifier 104, and an output filter 108 connected to an antenna 110. Power amplifier 100 may further include a power supply 108. Power amplifier 100 may include fewer or more components and in different configurations than shown in FIG. 1. Each of the components of power amplifier 100 may be a commercial-off-the-shelf (COTS) product or a custom-designed element. Furthermore, these components may have industry standard footprints to add flexibility and extensibility to the design of power amplifier 100.

Driver amplifier 102 may be a general purpose linear amplifier. Driver amplifier 102 may receive an RF signal as its input and is configured to output a modified/amplified version of that RF signal. In an embodiment, driver amplifier 102 has a low noise figure (e.g., 1.2 dB) to enable amplification of the RF signal without adding too much noise. In another embodiment, driver amplifier 102 may be a high- linearity RF amplifier integrated circuit that is suitable for use as a linear/low noise amplifier. In such embodiment, driver amplifier 102 may be a device manufactured on a gallium arsenide (GaAs) or similar process and may include parameters, such as a 5- 1500 megahertz (MHz) operating frequency, 20 decibels (dB) of small signal gain, 25 decibel-milliwatts (dBm) output power, a 5-9 volts (V) positive power supply.

Primary amplifier 104 may be an amplifier that is configured to receive the amplified RF signal from driver amplifier 102 and to amplify that signal to produce an output signal. In an embodiment, primary amplifier 104 is a wideband and high efficiency amplifier that has a frequency range of 30-1215 MHz. For example, the power added efficiency (the output power of the amplifier minus the input power divided by the DC supply current to the amplifier) of primary amplifier 104 may be in excess of 60 percent across the entire frequency band. The efficiency may vary as it is influenced by the power supply selected. In another embodiment, primary amplifier 102 has an integrated wideband matching network that enables wideband gain and power performance, while the output may be matched on board to optimize power and efficiency for any region within the band. The wideband matching networks enables flexibility and extensibility to the overall design of power amplifier 100. In this embodiment, primary amplifier 104 may be built with gallium nitride (GaN) or similar technology, and may include parameters such as: 24W of output power at 1 GHz, typical linear gain of 19dB at 1 GHz, typical power added efficiency of about 78 percent at 1 GHz, and an operating voltage of 28V.

Power supply 106 may be an electronic circuit that provides the appropriate power level to driver amplifier 102 and primary amplifier 104. Power supply 106 may include a switching regulator to efficiently convert electrical power from an alternating current (AC) or direct current (DC) source to a DC load. For example, power supply 106 may be configured to convert a battery voltage (e.g., 12-28 V DC) to a higher constant voltage (e.g., 28V). In this example, power supply 106 may be a wide compliance switching power supply because it enables power amplifier 100 to operate over a very wide supply voltage input range (12-28 V). Power supply 106 may be any type of power supply, such as an unregulated power supply, a linear regulated power supply, or a switch-mode power supply. In an embodiment, power supply 106 may be a high efficiency (e.g., approximately 90% efficient) switchmode power supply circuit that includes one or more transistors (e.g., metal oxide silicon field effect transistor (MOSFET)), regulators, converters, resistors, capacitors, diodes, inductors, etc. In an embodiment, power supply 106 is integral to power amplifier 100, although it may be external in some embodiments.

Output filter 108 may be a filter configured to extract the input RF signal and to remove unwanted harmonic components from the output signal to generate a final output signal, which may be a scaled replica of the input RF signal. Thus, it may be referred to as a harmonic output filter. Output filter 108 may be electronically coupled to primary amplifier 104. In an embodiment, output filter 108 may be a modular L-C low-pass filter that includes one or more inductors and capacitors. The layout, types and values of these components may be determined based on the desired application of power amplifier 100. In an embodiment, output filter 108 may be formed as separate module (e.g., as a separate circuit board or integrated circuit) that is separately populated and/or designed. For example, the components of power amplifier 100 (e.g., driver amplifier 102, primary amplifier 104, power supply 108) may be placed on a first circuit board and output filter 108 may be placed on a second circuit board with castellated holes to enable the second circuit board to be soldered to the first circuit board in a stack. This enables the first circuit board to be produced at scale to utilize resources more efficiently and save on costs and time. The second circuit board may be designed for a frequency band specific to an intended application and then combined with the first circuit board. The topology of the modular output filter enables extensibility to power amplifier 100. Therefore, emerging devices may be accommodated without requiring substantial redesign of the entire power amplifier. Output filter 108 may be removed and/or added on as needed post fabrication/assembly. In embodiments, power amplifier 100 may be reconfigured to operate in alternative frequency allocations across a wide bandwidth (e.g., 30 MHz to over 1 GHz) by replacement of output filter 108.

Antenna 110 may wirelessly transmit the final output signal over any transmission medium.

The reconfigurable power amplifiers described herein may be made using various processes. For example, FIG. 2 is a flowchart 200 of a method of fabricating a reconfigurable power amplifier, such as power amplifier 100. The steps of flowchart 200 may be performed in an order different than shown in FIG. 2 in some embodiments. Furthermore, not all steps of flowchart 200 need to be performed in all embodiments.

Flowchart 200 begins with step 202. In step 202, a first circuit board that comprises a driver amplifier and a primary amplifier is fabricated. For instance, in an embodiment, a first circuit board may be fabricated that includes at least a driver amplifier, such as driver amplifier 102 of FIG. 1, and a primary amplifier, such as primary amplifier 104. In such embodiment, further components may be included, for example, switchmode power supply 106.

In step 204, a second circuit board that comprises an output filter that enables configuration of the power amplifier for operation across a wide bandwidth is fabricated, the second circuit board being coupled to the first circuit board. For example, in an embodiment, a second circuit board that includes an output filter, such as output filter 108 of FIG. 1, may be fabricated separate from the first circuit board. The second circuit board may be specifically designed for a particular application or a set of requirements. The first circuit board and the second circuit board may be electrically and physically combined in any manner. In an embodiment, the second circuit board may be coupled, via soldering, to the first circuit board. The second circuit board may include castellated holes to enable the second circuit board to be coupled to the first circuit board in a stack. In a printed circuit board, a via may include two pads in corresponding positions on two different layers of the board. The two pads are electrically connected by a hole through the board. When a via is placed at the edge of the board so that it is cut in half when the board is separated, a castellated hole is formed. This is useful for combining two circuit boards together or a module to a primary circuit board.

Further Embodiments

In an embodiment, power amplifier 100 is a modular power amplifier optimized for battery operated communications, for example, in field radios, unmanned vehicles, and sonobuoys that operate in maritime environments. A field radio may be utilized in any telecommunication system designed to transmit and receive radio signals. An unmanned vehicle may be a vehicle with no pilot on board, and is thus remotely or autonomously controlled. A sonobuoy is an expendable acoustic sensor that is typically air-deployed and may be used to detect submarine or for underwater acoustic research. Such sonobuoy has a floating component that includes a radio transmitter for communication and an underwater component that may include sensors and other equipment. Accordingly, the reconfigurable power amplifier described herein may be utilized in the radio transmitter of these types of devices/systems for wireless communication, among other applications.

FIG. 3 depicts a printed circuit board 300 of a reconfigurable power amplifier, which may be an implementation of power amplifier 100 shown in FIG. 1. Circuit board 300 includes a second circuit board 304 that is formed as a separate module from the second circuit board 302. In an embodiment, second circuit board 304 may include a modular harmonic output filter (e.g., output filter 108 of FIG. 1), second circuit board 304 may be coupled with first circuit board 302 using any suitable means. In such embodiment, first circuit board 302 may include components of power amplifier 100 other than the output filter. This reconfigurable power amplifier is configured to provide exceptional link quality for all sonobuoy channels in the sonobuoy band (e.g., 136-173 MHz) at distances up to 125 nautical miles (NM). In contrast, existing solutions enable operation for only several channels at distances up to 81 NM.

FIG. 4 is a plot 400 of power of an example reconfigurable power amplifier, such as power amplifier 100, across an operational frequency band. In plot 400, the output power is shown on the vertical axis and the frequency band is shown on the horizontal axis. An ideal power amplifier would provide an efficiency rating of 100 percent where the output power would be equal to the input power. However, in operation, some power is dissipated in the form of heat and the power amplifier itself consumes power during the amplification process. The efficiency of a power amplifier is the ratio of the output power and the input power. In FIG. 4, the entire frequency sweep of the output power of the reconfigurable power amplifier is shown as a relatively straight line 402. For comparison purposes, the output power values of two conventional power amplifiers are also plotted as data point 404 and data point 406. As shown in FIG. 4, the conventional power amplifiers have much lower output power for the same input power and are thus less efficient than the reconfigurable power amplifier. For example, the reconfigurable power amplifier may deliver nearly 12W of power across the entire sonobuoy frequency range, whereas the conventional amplifiers deliver less than half of this power and only for a few select channels located within this band.

Conclusion

While various embodiments of the disclosed subject matter have been described above, it should be understood that they have been presented by way of example only, and not limitation. Various modifications and variations are possible without departing from the spirit and scope of the embodiments as defined in the appended claims. Accordingly, the breadth and scope of the disclosed subject matter should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS What is claimed is:

1. A power amplifier, comprising: a driver amplifier; a primary amplifier coupled to the driver amplifier; and a modular output filter coupled to the primary amplifier, the output filter enabling configuration of the power amplifier for operation across a wide bandwidth.

2. The power amplifier of claim 1, wherein the wide bandwidth comprises a range of at least 30 megahertz to 1 gigahertz.

3. The power amplifier of claim 1, wherein the primary amplifier is a wideband and a high power efficiency amplifier.

4. The power amplifier of claim 1, further comprising: a switchmode power supply coupled to the driver amplifier and the primary amplifier.

5. The power amplifier of claim 4, wherein the switchmode power supply is approximately 90 percent efficient.

6. The power amplifier of claim 1, wherein the driver amplifier and the wideband primary amplifier are on a first circuit board, and wherein the output filter is on a second circuit board separate from the first circuit board.

7. The power amplifier of claim 6, wherein the second circuit board comprises castellated holes that enable the second circuit board to be coupled to the first circuit board.

8. The power amplifier of claim 1, wherein the output filter is configured to be replaceable.

9. A method of fabricating a power amplifier, comprising: fabricating a first circuit board that comprises a driver amplifier and a primary amplifier; and fabricating a second circuit board that comprises an output filter that enables configuration of the power amplifier for operation across a wide bandwidth, the second circuit board being coupled to the first circuit board.

10. The method of claim 9, further comprising: coupling the second circuit board to the first circuit board, the second circuit board comprising castellated holes to enable the second circuit board to be coupled to the first circuit board in a stack.

11. A power amplifier, comprising: a circuit board that includes a driver amplifier and a primary amplifier; a module coupled to the circuit board, the module comprising an output filter that enables configuration of the power amplifier for operation across a wide bandwidth.

12. The power amplifier of claim 11, wherein the wide bandwidth comprises a range of at least 30 megahertz to 1 gigahertz.

13. The power amplifier of claim 11, wherein the primary amplifier is a wideband and a high power efficiency amplifier.

14. The power amplifier of claim 11, further comprising: a switchmode power supply coupled to the driver amplifier and the primary amplifier.

15. The power amplifier of claim 14, wherein the switchmode power supply is approximately 90 percent efficient.

16. The power amplifier of claim 11, wherein the output filter is configured to be replaceable.