# Patent

## Title
Remotely reconfigurable power amplifier system and method

## Abstract

A system and method for remotely monitoring, communicating with, and reconfiguring power amplifier systems. A communications link is provided in field-deployed PA systems, for enabling remote communication with appropriate digital components such as microprocessors or other communications-capable portions of the power amplifier systems. The communications link permits operating parameters of the PA to be monitored and sent back to a remote terminal such as a web server or other computer mainframes via any suitable wired or wireless connection including internet, Ethernet, wireless, WiFi, WiMAX, cellular, local area networks (LAN), wide area networks (WAN), Bluetooth, and so forth. The communication is bi-directional, so that the remote host can download to the PA updates, cMobile operators and/or other service providers can reduce significant operating and capital expenses related to their radio networks maintenance and PA replacement by practicing this invention.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part and claims the benefit of U.S. patent application Ser. No. 12/108,502, entitled “Digital Hybrid Mode Power Amplifier System,” filed Apr. 23, 2008, and through it U.S. Pat. Appn. Ser. No. U.S. 60/925,603, filed on Apr. 23, 2007, and further claims the benefit of U.S. Provisional Application Ser. No. 61/172,642 filed Apr. 24, 2009, both of which are hereby incorporated by reference in their entirety for all purposes.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to wireless communication systems using complex modulation techniques. More specially, the present invention relates to single and multi-carrier power amplifier systems that contain a microprocessor or other similar digital components, such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC).
2. The Prior Art
A wideband mobile communication system using complex modulation techniques such as wideband code division access (WCDMA) and orthogonal frequency division multiplexing (OFDM) has a large peak-to-average power ratio (PAPR) and requires a high linearity of the base-station's power amplifiers (PA). The conventional feedforward linear power amplifier (FFLPA) has been widely utilized due to its excellent linearity performance in spite of poor power efficiency. In order to overcome this poor efficiency, digital baseband predistortion (PD) has been demonstrated due to the recent advances in digital signal processors. A Doherty power amplifier (DPA) has also been applied to these linearization systems to maximize the power efficiency. The variation of the linearity performance of the amplifier due to the environment changing such as temperature and the asymmetric distortion of the output signal of the amplifier resulting from memory effects also needs to be compensated.
Conventional high power amplifiers (HPA), FFLPA, and DPA are known to fail frequently with mean time between failures (MTBF) from a few months to a few years. Low power efficiency means most of the energy is dissipated in the form of heat. Since most electronic components are known to be vulnerable to thermal damage, this significant thermal heat generated by the conventional PA systems is generally perceived to be one of the main cause of PA failures.
A failed PA would ordinarily cause the related base-station, repeater, or other transmission systems to stop functioning. Since a typical mobile operator or service provider depends on its voice and/or data traffic for revenues, a failed PA could be costly to its mobile operator in terms of loss revenue and questionable radio network reliability. Currently, conventional PA systems have local alarm features such as lights, audio indicators, displays, and etc. that signal a system failure. Mobile operators often have to react to such failures by sending technicians to replace the failed PAs after the failures were discovered in their radio networks. In some cases, mobile operators would measure a radio network technician's career performance in terms of “seconds” of a base-station or network downtime. In such cases, those network technicians are typically incentivized with cash bonus compensation to replace failed PA systems as soon as the latter are discovered. In other cases, some mobile operators implement a pre-emptive policy of replacing all PA systems after well less than the expected product lifetime, even though the PA systems were functioning perfectly well. This policy, of course, can be wasteful and inefficient.
Aside from PA failures, rapid advancements in mobile communications have also induced rapid changes in mobile communication systems such as modulation scheme evolutions, communication equipment firmware updates, radio frequency front-end systems enhancements, and etc. Conventional digital baseband PD systems are usually tailored to a specific wireless modulation scheme, such as CDMA, CDMA2000 EVDO, UMB, OFDM, WCDMA, TDS-CDMA, GSM, EDGE, etc., with a specific set of specifications such as PAPR, error vector magnitude (EVM), adjacent channel power ratio (ACPR), operating radio frequency, bandwidth, and etc. Usually, any updates or changes in specifications require an update of digital baseband PD systems, or in some cases, a wholesale replacement of the entire PA system. The high cost and labor intensity of making such updates and changes have driven up significantly the cost of capital equipment upgrades, and in turn, reduced the mobile operators' desire to deploy most state-of-art wireless technology in their radio networks for the end users among the general public.
Hence, a need remains for remotely monitoring the power amplifier performance and providing an advance indication or prediction when a power amplifier will fail. A need also remains for enabling a power amplifier already deployed in radio networks to be upgraded or enhanced via software upgrades, especially those managed remotely. Such features would save mobile operators significant operating and capital expenses relating to radio networks maintenance and PA replacement. If such an arrangement existed, mobile operators could also deploy the latest wireless technology for the general end users while preserving their existing capital investments.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an efficient and effective method of remotely communicating with, monitoring and upgrading power amplifier systems. To achieve the above objectives, according to the present invention, remote connectivity such as internet, Ethernet, wireless, WiFi, WiMAX, cellular, local area networks (LAN), wide area networks (WAN), Bluetooth, and etc. (collectively, the “Remote Media”), is added to the power amplifier systems.
The present invention is applicable to any power amplifier systems that have software defined radio (SDR) capability, such as digital signal processing, digital PD, and etc. In an embodiment, a communication link is established between a microprocessor (or other digital components) of a PA system and a remote computer terminal or command centre through the Remote Media. Depending upon the embodiment, the microprocessor (or other digital components such as digital sensors) inside the PA systems is configured to measure the operating conditions of functioning PA systems such as temperature, gain, current, voltage, time, time-delay, in-phase and/or quadrature baseband signal (I and Q Signals), coefficients of the PA amplitude-amplitude (AM-AM) and/or amplitude-phase (AM-PM) curves, coefficients of the PD look-up table and/or algorithms, frequency, bandwidth, transistor junction temperatures, non-linearities, and other tangible physical characteristics. In an embodiment, the values measured by microprocessor are recorded, processed, and/or transmitted real-time or non-real-time, and can be stored in the microprocessor's onboard or external memory. Any suitable networking protocol, such as TCP/IP, and standard microprocessor interfacing features are implemented to transmit or receive information to-and-from the microprocessor (or other digital components) and the remote system. The PA's microprocessor then communicates the monitored data to a remote host such as a web server or computing mainframe to synthesize, digest, monitor, display, evaluate, calculate, compute, update, compare, send, direct, redirect, download, upload, etc. the data collected from the microprocessor(s) in the PA system(s).
More specifically, failing PA systems are known to exhibit abnormal electrical current characteristics. A Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC) that incorporates a processor, such as a Power PC or Microblaze, controls the data flow to and from the Remote Media. In terms of standard networking protocol, an Ethernet MAC can be used to send and receive packets using TCP/IP networking. A computer network server, or host, such as a web server can be used to establish the remote communication to the power amplifier, while allowing the end user or an automated management program to monitor the PA status. In the case of remote upgrading the software of the PA system, the remote server can upload a software patch or a complete new operating system or kernel via the Remote Media to the microprocessor and perform a remote restart or reboot of the PA system, thereby remotely upgrading the system.



BRIEF DESCRIPTION OF DRAWINGS
Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a block diagram showing a remotely monitorable and reconfigurable power amplifier system for base-station and repeater applications.
FIG. 2 is a flow chart of a method for communicating with the power amplifier of the present invention.
FIG. 3 is a block diagram showing a remotely reconfigurable digital hybrid mode power amplifier system for base station and repeater applications according to another embodiment of the present invention.
FIG. 4 is a block diagram showing another embodiment of a remotely reconfigurable digital hybrid mode power amplifier system.



DETAILED DESCRIPTION OF THE INVENTION
The present invention applies standard networking protocol and interface procedures to power amplifier systems that have digital operations capability through microprocessors in the PA systems. In particular, the invention provides system operators the ability to remotely reconfigure PA's within their network to accommodate improvements in the performance of the PA. The remote connection enables upgrades, adjustments, and/or changes as requested by the mobile operators and/or service providers. The remote connection also enables remote monitoring of the performance of the power amplifier. The method provided by the present invention is referred as the remotely reconfigurable power amplifier (RRPA) system hereafter.
Preferred embodiments of the RRPA system according to the present invention will now be described in detail with reference to the accompanying drawings.
Referring first to FIG. 1, there is shown therein in block diagram form an embodiment of an RRPA system in accordance with the invention. The RRPA system for base-station applications receives a multi-carrier digital signal 300 at the input and generates an RF signal 350 at the output, respectively. In an embodiment, the RRPA system comprises an FPGA-based digital subsystem 310, an up-converter subsystem 320 and a power amplifier subsystem 330. It will be appreciated by those skilled in the art that the subsystem 310 need not be FPGA-based, and that term is used herein merely for clarity and simplicity.
In an embodiment, the FPGA-based digital subsystem 310 comprises a field programmable gate array (FPGA), digital-to-analog converters (DACs), analog-to-digital converters (ADCs), and a phase-locked loop (PLL). In the FPGA subsystem 310, crest factor reduction (CFR), digital filtering and predistortion (PD) are implemented, and the FPGA subsystem 310 is SDR-capable. An input/output 340 into the FPGA-subsystem provides bidirectional communication with a remote host, not shown, which can be a web server or other network server, and other suitable hosting system. Feedback subsystem 352 provides to the FPGA subsystem 310 data regarding the operating characteristics of the PA, including temperature, gain, current, voltage, time, time-delay, in-phase and/or quadrature baseband signal (I and Q Signals), coefficients of the PA amplitude-amplitude (AM-AM) and/or amplitude-phase (AM-PM) curves, coefficients of the PD look-up table and/or algorithms, frequency, bandwidth, transistor junction temperatures, non-linearities, and other tangible physical characteristics.
FIG. 2 shows in flow chart form a method for managing communications between a host and a power amplifier in accordance with the present invention. At step 600, the local GUI is started at the host to enable the host/web server to communicate with the PA. Then, at step 605, a check is made to determine whether the PA software needs to be updated. If not, the process advances to step 610 and check is made to determine whether the PA's performance needs to be modified. If the answer is yes at either step 605 or 610, the process advances to step 615 and appropriate software is uploaded from the server to the PA via the communications link 340.
If the answer at both steps 605 and 610 is no, the process jumps to step 620, and the server monitors the PA's performance. In particular, as shown at 625, the server collects, through link 340, PA performance data which, depending upon the particular implementation, can comprise ACPR, temperature, gain, current, voltage, time, time-delay, in-phase and/or quadrature baseband signal (I and Q Signals), coefficients of the PA amplitude-amplitude (AM-AM) and/or amplitude-phase (AM-PM) curves, coefficients of the PD look-up table and/or algorithms, frequency, bandwidth, transistor junction temperatures, non-linearities, and other tangible performance characteristics of the PA. A check is then made at step 630 to determine whether the PA is working properly. If the PA is working properly, the process loops back to step 620, and monitoring continues. If the answer is no, a check is made at step 635 to determine whether a hard failure has occurred. If not, the process loops back to step 610 to determine modify the PA's performance in accordance with the data received from the PA. If a hard failure has occurred, an alarm signal is sent at step 640 to cause a repair/replacement to occur. Either alternatively or in addition to the alarm signal 640, and depending upon the PA's failure mode, the power amplifier may be remotely reconfigured as shown at step 645 to provide limited functionality at least until a repair or replacement can be made. Those skilled in the art will recognize that steps 640 and 645 can occur in either order, or substantially concurrently, and neither necessarily depends upon the other.
Referring next to FIGS. 3 and 4, two alternative embodiments of remotely reconfigurable digital hybrid mode power amplifier systems are shown in block diagram form. Such power amplifier systems are particularly suited to use for base station and repeater applications according to an embodiment of the present invention. In each case, the FPGA-based subsystem, PA subsystem and Feedback subsystem are shown as 103/203, 104/204 and 105/205 respectively. In FIG. 3, a multi-channel input is illustrated, with remote connection 140 providing an I/O link to a remote server, not shown. In FIG. 4, RF input 201 provides an input to a down-converter 206, and again a bi-directional link to a remote server is provided at remote connection 240. It can be appreciated that, in either case, the feedback subsystem is configured to provide to the FPGA-based subsystem appropriate data characterizing the performance of the PA.
As a result, it can be appreciated that the remotely reconfigurable DHMPA system of the present invention communicate with a remote host via any suitable link including the internet, thereby providing capabilities including, depending upon the embodiment, performance monitoring, early warning failure detection, software upgrades, reconfigurability to service providers specifications (ie. # of carriers, modulation of carriers, frequency of carriers, Crest Factor Reduction, Error Vector Magnitude, ACPR, . . . ) and so forth.
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.

## Claims

1. A method for remotely reconfiguring a power amplifier in a wireless communications system comprising the steps of:
providing a power amplifier in a wireless communications system having multiple stages, a microprocessor, and software-defined radio capability,
providing a remote media link between a remote computer and the power amplifier to permit communications therebetween,
monitoring operating characteristics of each of the multiple stages of the power amplifier during normal operation and as a function of time, wherein said operating characteristics comprise transistor junction temperatures and coefficients of power amplifier amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) curves,
detecting changes in nonlinearities of the power amplifier as a function of time based on the operating characteristics of each of the multiple stages of the power amplifier collected during monitoring,
determining an early warning of failure of the power amplifier based on changes in the coefficients of power amplifier amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) curves as a function of time,
reporting the early warning of failure to a remote computer, and
reconfiguring the power amplifier to reduce functionality relative to normal operation as directed by the remote computer.

2. The method of claim 1 wherein the reconfiguring step comprises uploading at least one software patch.

3. The method of claim 1 wherein the operating characteristics further comprise: in-phase and quadrature baseband signals (I and Q Signals), coefficients of a predistortion look-up table, frequency, and bandwidth measurements of the power amplifier.

4. The method of claim 1 wherein monitoring operating characteristics and detecting changes in nonlinearities comprises measuring predistortion look-up table coefficients and updating a digital predistorter coupled to the power amplifier.

5. The method of claim 2 wherein the power amplifier is characterized by a first performance level prior to monitoring operating characteristics of the power amplifier and the at least one software patch reconfigures the power amplifier to operate with limited functionality characterized by a second performance level less than the first performance level.

6. A reconfigurable power amplifier having multiple stages for use in wireless communications systems comprising:
a communications link adapted to communicate with a remote computer system,
at least one detector for monitoring operating characteristics of each of the multiple stages of the power amplifier as a function of time during normal operation, wherein said operating characteristics comprise transistor junction temperatures and coefficients of power amplifier amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) curves,
a memory operable to record multiple values associated with the operating characteristics of each of the multiple stages of the power amplifier during normal operation, and
a microprocessor having software-defined radio capability and responsive to the at least one detector for communicating with the remote computer system via the communications link, operable to determine an early warning of failure of the power amplifier based on changes in the coefficients of power amplifier amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) curves collected by the at least one detector during monitoring as a function of time, and to report the early warning of failure to the remote computer system, and responsive to instructions from the remote computer for reconfiguring the power amplifier for reduced functionality relative to normal operation in response to the early warning of failure.

7. The reconfigurable power amplifier of claim 6 wherein the instructions comprise providing a software patch to the microprocessor via the communications link.

8. The reconfigurable power amplifier of claim 6 wherein the instructions comprise uploading a new operating system to the power amplifier and causing the microprocessor to install the new operating system.

9. The reconfigurable power amplifier of claim 6 further comprising a multi-channel input configurable to interface with a plurality of base stations.

10. The reconfigurable power amplifier of claim 6 further comprising a predistorter coupled to the detector and operable to receive predistortion look-up table coefficients.

11. The reconfigurable power amplifier of claim 7 wherein the power amplifier is characterized by a first performance level prior to monitoring operating characteristics of the power amplifier and the software patch reconfigures the power amplifier to operate with limited functionality characterized by a second performance level less than the first performance level.

12. The reconfigurable power amplifier of claim 9 wherein the multi-channel input is further configurable to interface with a plurality of repeater applications.