WO2009046226A1

WO2009046226A1 - Wireless to wireless signal amplification with gain optimization and oscillation prevention

Info

Publication number: WO2009046226A1
Application number: PCT/US2008/078635
Authority: WO
Inventors: Timothy R. Geis; Lawrence Jacob Kovac
Original assignee: Intelligent Wireless Products, Inc.
Priority date: 2007-10-02
Filing date: 2008-10-02
Publication date: 2009-04-09

Abstract

Embodiments of the invention include an apparatus and a method of gain optimization and oscillation prevention for a wireless to wireless signal amplifier. The method includes incrementally increasing a channel gain value until oscillations are detected or a maximum gain threshold is reached. After the channel gain value is increased to a value at which oscillations are detected, the channel gain value is decreased to provide operating margin. The detection of oscillations may include increasing the channel gain value until oscillations are suspected, then decreasing the channel gain value to confirm the presence of oscillations. Gain optimization and oscillation prevention may also be performed for multiple signals and may be performed for unidirectional and/or bidirectional signals.

Description

WIRELESS TO WIRELESS SIGNAL AMPLIFICATION WITH GAIN OPTIMIZATION AND OSCILLATION PREVENTION

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the earlier filing date of U.S. Provisional Application, titled "WIRELESS TO WIRELESS SIGNAL AMPLIFICATION WITH GAIN OPTIMIZATION AND OSCILLATION PREVENTION," Serial No. 60/977,059, filed on October 2, 2007, under 35 U.S. C. § 119(e), the contents of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention is generally directed to the area of signal amplification, and particularly, but not exclusively, to signal amplification in wireless communication systems.

BACKGROUND

Wireless communications are convenient for using mobile devices, such as cellular telephones, laptop computers, personal digital assistants, and the like. However, such mobile devices are often designed with a relatively low maximum transmit power to minimize overall size and increase battery life. Internal amplification is typically included in mobile devices, but is subject to the size and battery parameters. External, or other auxiliary signal amplification can be employed to increase the gain, power, signal-to-noise ratio, and/or the like, of a signal. Auxiliary signal amplification may also be employed to increase the effective range of a communications system, enable wireless communication through materials with high signal attenuation properties, enable wireless communications from mobile devices in areas having poor communication system coverage, and/or the like. Auxiliary signal amplification also typically uses an additional power source, such as an additional battery or a public power source.

It is generally desirable to provide adequate isolation between an output and an input of a wireless signal amplification system. For example, if inadequate isolation is provided, portions of an output signal may be sensed at the amplification system input. This feedback may result in oscillations whereby the amplification system exhibits instability. The isolation between the output and input of a wireless to wireless signal amplification system is based on many factors. These factors include atmospheric conditions, the materials between the output and the input, the separation distance between the output and the input, and/or the like.

Likewise, in wireless to wireless signal amplification systems, the isolation needed to prevent oscillations is based, at least in part, on the gain of the amplification system. For example, in relatively well isolated systems, relatively high gain may be provided without causing oscillations. However, in relatively un-isolated systems, oscillations may occur when relatively lower gains are provided. These oscillations may interfere with or otherwise disrupt the communications of the wireless to wireless signal amplification system and/or other communications such as cellular or other wireless base station communications. To accommodate a variety of possible conditions, and reduce the likelihood of oscillation, gain may not be optimized. Consequently, the effective range or other properties may not be optimized. Embodiments of this invention are directed to these and other aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

Non- limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified. These drawings are not necessarily drawn to scale.

For a better understanding of the present invention, reference will be made to the following Detailed Description, which is to be read in association with the accompanying drawings, wherein:

FIGURE 1 shows a functional block diagram illustrating one embodiment of an environment for practicing the invention;

FIGURE 2 is a block diagram of an embodiment of a unidirectional single-band amplifier circuit according to aspects of the present invention;

FIGURE 3 is a block diagram of an embodiment of a bidirectional multi-band amplifier circuit according to aspects of the present invention; and

FIGURE 4 illustrates a logical flow diagram generally showing one embodiment of a process by which the invention may be practiced. DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific embodiments by which the invention may be practiced. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Among other things, the present invention may be embodied as methods, processes, or devices. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Also, hardware may include digital hardware, analog hardware, and or combinations of digital and analog hardware. The following detailed description is, therefore, not to be taken in a limiting sense.

Throughout the specification and claims, the following terms take at least the meanings explicitly associated herein, unless the context dictates otherwise. The meanings identified below do not necessarily limit the terms, but merely provide illustrative examples for the terms. The meaning of "a," "an," and "the" includes plural reference. References in the singular are made merely for clarity of reading and include plural reference unless plural reference is specifically excluded. The meaning of either "in" or "on" includes both "in" and "on." The term "or" is an inclusive "or" operator, and is equivalent to the term "and/or" unless specifically indicated otherwise. The term "based on" or "based upon" is not exclusive and is equivalent to the term "based, at least in part on," and includes being based on additional factors, some of which are not described herein. The term "coupled" means at least either a direct electrical connection between the items connected, or an indirect connection through one or more passive or active intermediary devices. The term "circuit" means at least either a single component or a multiplicity of components, either active and/or passive, that are coupled together to provide a desired function or functions.

The term "signal" means at least one current, voltage, electromagnetic, optical, charge, temperature, data, or other signal and may include one or more data stream(s). The term "band" means a range of frequencies in the electromagnetic spectrum. A band may be in the radio frequency spectrum, microwave frequency spectrum, infrared spectrum, visible light spectrum, X-ray spectrum, gamma ray spectrum, and/or the like. The term "signal component" means a portion of a signal which includes a data stream. A signal component may be part of a multi-band or signal-band signal. The term "multi-band signal" means a signal that is employed to communicate signal components from more than one band. A multi-band signal may include signal components from two bands, three bands, and/or more bands. The term "single-band signal" means a signal that is employed to communicate signal components from less bands than the multi-band signal from which it is derived, or into which it is combined. The term "signal path" means the path through which a data stream travels. A signal path may travel through active or passive elements, along a signal, as a signal component along a signal, and/or the like. A "signal" may be used to communicate using frequency modulation, amplitude modulation, phase modulation, active high, active low, time multiplexed, synchronous, asynchronous, differential, single-ended, or any other analog or digital signaling or modulation techniques. The phrase "in one embodiment," as used herein does not necessarily refer to the same embodiment, although it may.

Briefly stated, the invention includes embodiments for gain optimization and oscillation prevention for wireless to wireless signal amplification. A method embodiment includes incrementally increasing a channel gain value until oscillations are detected or a maximum gain threshold is reached. After the channel gain value is increased to a value at which oscillations are detected, the channel gain value is decreased to provide operating margin. The detection of oscillations may include increasing the channel gain value until oscillations are suspected, then decreasing the channel gain value to confirm the presence of oscillations. Gain optimization and oscillation prevention may also be performed for multiple signals and may be performed for unidirectional and/or bidirectional signals.

Illustrative Operating Environment

FIGURE 1 shows components of one embodiment of an environment in which the invention may be practiced. Not all the components may be required to practice the invention, and variations in the arrangement and type of the components may be made without departing from the spirit or scope of the invention. As shown, system 190 of FIGURE 1 includes base stations 191 and 192 of a wide-area wireless network 193, separation medium 195, local area wireless network 196 including one or more mobile devices 197 and 198, and wireless to wireless signal amplifier 100. Wireless to wireless signal amplifier 100 may include antennas 150 and 160. Generally, base stations 191 and 192 include virtually any network device capable of receiving and sending a message over a network. Network devices such as, mobile telephony base stations, packet radio base stations, television broadcast transmitters, wireless network access points, amateur or commercial radio repeaters, integrated devices combining one or more of the preceding devices, or the like, are some examples of base stations 191 and 192. Base stations 191 and 192 may communicate with mobile devices 197 and 198 directly or via wireless to wireless signal amplifier 100.

Generally, mobile devices 197 and 198 include virtually any portable computing device capable of receiving and sending a message over a network. Mobile devices 197 and 198 may also be described generally as client devices that are configured to be portable or support portable devices, although they are not so limited. Embodiments of mobile devices 197 and 198 may include virtually any portable computing device capable of connecting to another computing device and receiving information. Such devices include portable devices such as, cellular telephones, smart phones, display pagers, radio frequency (RF) devices, Personal Digital Assistants (PDAs), handheld computers, laptop computers, wearable computers, tablet computers, routers, gateways, access points, integrated devices combining one or more of the preceding devices, or the like. As such, mobile devices 197 and 198 typically range widely in terms of capabilities and features. For example, a cell phone may have a numeric keypad and a few lines of monochrome display on which only text may be displayed. In another example, a web-enabled mobile device may have a touch sensitive screen, a stylus, and several lines of a color display in which both text and graphics may be displayed. Mobile devices 197 and 198 may communicate with base stations 191 and 192 directly or via wireless to wireless signal amplifier 100.

Wide-area wireless network 193 and local area wireless network 196 are configured to enable mobile devices 196 and 197 to communication with each other and with base stations 191 and 192. Wireless networks 193 and 196 may include any of a variety of wireless sub-networks that may further overlay stand-alone ad-hoc networks, and the like, to provide an infrastructure-oriented connection for mobile devices 196 and 197. Such subnetworks may include mesh networks, Wireless LAN (WLAN) networks, cellular networks, and the like.

Wide-area wireless network 193 and local area wireless network 196 may further employ a plurality of access technologies including 2nd (2G), 3rd (3G), and 4th (4G) generation radio access for cellular systems, WLAN, WiMax, Wireless Router (WR) mesh, and the like. Access technologies such as 2G, 3G, 4G, and future wireless access networks may enable wide area coverage for mobile devices, such as mobile devices 197 and 198 with various degrees of mobility. For example, wide-area wireless network 193 and local area wireless network 196 may enable a radio connection through a radio network access such as Global System for Mobile communication (GSM), General Packet Radio Services (GPRS), Enhanced Data GSM Environment (EDGE), Wideband Code Division Multiple Access (WCDMA), Universal Mobile Telephone System (UMTS), and the like. In essence, wide- area wireless network 193 and local area wireless network 196 may include virtually any wireless communication mechanism by which information may travel between mobile devices 197 and 198 and another base station, computing device, network, and the like.

Separation medium 195 provides isolation between antennas 150 and 160 and may be any medium through which a wireless signal is attenuated. For example, separation medium 195 may include air, water, wood, metal, glass, plastic, the atmosphere, and/or the like, and combinations thereof. Separation medium 195 may be of any thickness and may provide any level of signal attenuation. For example, separation medium 195 may provide almost no signal attenuation, or it may substantially attenuate a signal. Also, separation medium 195 may attenuate different signals to different degrees. In one embodiment separation medium comprises a shell of a vehicle, which encloses wireless signal amplifier 100, antenna 160, and one or more of mobile devices 197 and 198. In another embodiment, separation medium comprises a roof or wall of a structure, which separates antenna 150 from wireless signal amplifier 100, antenna 160, and one or more of mobile devices 197 and 198. Wireless signal amplifier 100 may include, or be coupled to a power source separate from mobile devices 197 and 198.

In one embodiment, wireless to wireless signal amplifier 100 is arranged to receive a wireless signal from wide-area wireless network 193 and to transmit an amplified wireless signal to local area wireless network 196. Wireless to wireless signal amplifier 100 may also be arranged to receive a wireless signal from local area wireless network 196 and to transmit an amplified wireless signal to wide-area wireless network 193. In this environment, the maximum gain that can be provided by wireless to wireless signal amplifier 100 before oscillations occur is based, at least in part, on the signal attenuation through separation medium 195. For example, if antennas 150 and 160 are located relatively close together and separation medium 195 is air, oscillations may occur when wireless to wireless signal amplifier 100 provides relatively low gain. However, when antennas 150 and 160 are located relatively far apart or separation medium 195 includes materials with high signal attenuation properties, wireless to wireless signal amplifier 100 may provide relatively high gain without oscillation. The gain optimization and oscillation prevention provided by wireless to wireless signal amplifier is discussed in further detail below.

Illustrative Circuit Embodiments

FIGURE 2 is a block diagram of unidirectional single-band amplifier circuit 200 that may comprise, or be included in wireless signal amplifier 100 of FIGURE 1, according to aspects of the present invention. Circuit 200 is a signal amplifier that is arranged to amplify input signal IN from antenna 250, and to provide output signal OUT to antenna 260. Circuit 200 includes gain circuit 210, sense circuit 220, and gain control circuit 230.

Input signal IN may be either a single-band signal or a multi-band signal. Also, input signal IN may include signal components from any frequency band of the electromagnetic spectrum. For example, input signal IN may include signal components from the RF spectrum, microwave spectrum, audible spectrum, and/or the like. In one example, input signal IN includes cellular band signal components (800MHz) or Personal Communications Services (PCS) band signal components (1800/1900 MHz).

Gain circuit 210 is arranged to amplify input signal IN to provide gained signal GAINED. Gain circuit 210 provides a level of amplification that is based, at least in part, on the value of control signal CONTROL.

In one embodiment, gain circuit 210 includes one or more radio frequency amplifiers or radio frequency power amplifiers, such as a LEE-59 amplifier, available from Mini- Circuits Inc. of Brooklyn, New York. In other embodiments, gain circuit 210 also includes filtering circuitry. For example, passive filters, active filters, analog filters, digital filters, and/or the like, may be suitably employed. These filters may include crystal filters, bulk acoustic wave filters, high-pass filters, low-pass filters, band-bass filters, RC filters, LC filters, RLC filters, and/or the like. Likewise, gain circuit 210 may also include attenuators. For example an AVl 01 -12 attenuator, available from Skyworks Solutions, Inc. of Worburn, Massachusetts, may be employed to control the gain provided by gain circuit 210. However, the gain provided by gain circuit 210 may be controlled by other circuitry. For example, the gain may be controlled by employing amplifiers with gain control inputs, employing discrete attenuators, employing gain circuit feedback circuits having electronically controllable feedback value (e.g., variable resistances, variable capacitance, and variable inductances), employing combination amplifier/attenuators, and/or the like. In one embodiment, gain circuit 210 is arranged to receive a pulse width modulated (PWM) control signal CONTROL which is employed to control the attenuation provided by an attenuator. The PWM control signal is filtered to determine a DC level that is used to drive the attenuator. In an alternate embodiment, a pulse code modulated control (PCM) signal could be used with a digital-to-analog converter to produce the control signal.

Also, other embodiments of gain circuits are described in a U.S. Patent Application to T. Geis, with attorney docket number 21165/0207746-US0, and entitled "Multiplexed Multi- Band Signal Amplification," the entire contents of which are hereby incorporated by reference. These and other gain circuits are within the spirit and scope of the invention.

Sense circuit 220 is arranged to sense a signal strength associated with gained signal

GAINED and to provide sense signal SENSE to indicate the sensed signal strength. For example, sense signal SENSE may be provided based, at least in part, on a sensed RF output power level of gain circuit 210. In one embodiment, a DC voltage is provided on sense signal SENSE to indicate the sensed signal strength. Any suitable circuits, methods, and/or the like, may be employed to provide sense signal SENSE signals based on the output of gain circuit 210.

Gain control circuit 230 is arranged to receive sense signal SENSE and to provide gain control signal CONTROL to control the gain provided by gain circuit 210. Gain control circuit 230 is further arranged to provide gain optimization and to prevent oscillations.

As discussed above, in one embodiment, sense signal SENSE is an analog signal representing a sensed signal strength, and control signal CONTROL is a PWM output signal. In this embodiment, gain circuit 230 may include an analog-to-digital converter that is arranged to digitize sense signal SENSE for digital processing. Also, control signal CONTROL may be provided from a PWM output of a microcontroller or from a general purpose output of a microcontroller. In one embodiment, gain control circuit 230 optimizes gain and prevents oscillation by determining a gain level that can be provided without causing oscillation. For example, gain control circuit 230 may initially control gain circuit 210 such that a relatively low gain is provided. Incrementally higher gains may be subsequently provided, for example, until oscillation of circuit 200 is suspected. In one embodiment, oscillation is suspected when, after an incremental gain increase, sense circuit 220 detects an increase in the output of gain circuit 210 that is substantially greater than the incremental gain increase. However, such an increase may be unrelated to the onset of oscillation. For example, a sudden increase in detected signal strength may result from a transmitter initiating transmissions on a previously idle channel; a transmitter increasing transmission power; a transmitter moving closer to antennas 250 or 260; and/or the like.

Accordingly, in one embodiment, after oscillations are suspected, the gain provided by gain circuit 220 is lowered by a known amount. If the sensed signal strength then decreases by a substantially similar amount, it is assumed that oscillations did not occur. However, if the sensed signal strength decreases by a substantially greater amount, oscillations are assumed to have occurred. If oscillations are assumed to have occurred, the channel gain value may be set to a value that provides operating margin and headroom to prevent oscillations while substantially optimizing gain.

In one embodiment, gain control circuit 230 includes a PIC 16F688 microcontroller, available from Microchip Technology Inc. of Chandler, Arizona. However, other gain circuits may include programmable logic devices, field programmable gate arrays, application specific integrated circuits, digital signal processors, microcontrollers, microprocessors, analog circuitry, and/or the like. Methods of optimizing gain and preventing oscillation for an embodiment of the invention are described in further detail with regards to FIGURE 4.

In other embodiments, circuit 200 may be arranged differently. For example, it may include multiple gain circuits and/or sense circuits; a sense circuit may be arranged to sense a signal strength on input signal IN instead of on gained signal GAINED; and/or the like. In one embodiment, the components of circuit 200 are embodied on a monolithic integrated circuit. In another embodiment, they are discrete components mounted on one or more circuit boards. The circuit board(s) may be FR4, Polymide, PTFE, Phenolic, and/or the like, and may be of laminate or non-laminate construction, and may have any number of layers. In at least one embodiment, components are mounted on a flexible circuit board made of Pyralux, RigidFlex, and/or the like. Also, if multiple circuit boards are employed, the boards may be connected by ribbon cables, thru-board connectors, board-edge connector, and/or the like. In one embodiment, multiple circuit boards, flexible circuits, and/or connectors may be stacked, coupled at angles or otherwise configured to reduce overall size, to fit into another assembly, to fit around existing parts, and/or to otherwise integrate into a desired packaging arrangement. One such embodiment may be a small integrated package in a vehicle. These and other embodiments are within the spirit and scope of the invention.

FIGURE 3 is a block diagram of bidirectional multi-band amplifier circuit 300 that may comprise, or be included in wireless signal amplifier 100 of FIGURE 1, according to aspects of the present invention. Circuit 300 includes IO circuit 341, IO circuit 342, gain circuits 310AD, 310AU, 310BD, and 310BU, sense circuits 320AD, 320AU, 320BD, and 320BU, and gain control circuit 330.

In one embodiment, circuit 300 is arranged to provide signal amplification in a wireless bi-directional communication system such as a mobile telephone system. For example, circuit 300 may be employed as a signal amplifier for increasing the gain of cellular band signal components (800MHz) and Personal Communications Services (PCS) band signal components (1800/1900 MHz) in a multi-band signal. Signal components in these bands may include a Global System for Mobile communication (GSM) data stream(s), General Packet Radio Services (GPRS) data stream(s), Enhanced Data GSM Environment (EDGE) data stream(s), Wideband Code Division Multiple Access (WCDMA) data stream(s), Universal Mobile Telephone System (UMTS) data stream(s), and/or the like. In one embodiment, circuit 300 may be employed to amplify a wireless signal that includes a data stream, such as an EDGE data stream. This EDGE data stream may, for example, be employed to enable communications between a local area network, such as an IEEE 802.11 network, and a wide area network, such as the Internet. However, other embodiments of circuit 300 may be arranged to amplify virtually any multi-band signal.

In one embodiment, circuit 300 is arranged to amplify four signal components. For example, for a mobile telephony system, these signal components may include: BANDA Uplink PCS 1850 - 1910 MHz;

BANDA Downlink PCS 1930 - 1990 MHz;

BANDB Uplink Cellular 0824 - 0849 MHz; and BANDB Downlink Cellular 0869 - 0894 MHz.

Also, as used herein for one embodiment, the letters appended to the reference numbers / signal names in FIGURE 3 refer to the band and direction of the signal components to which the elements / signals correspond. For example, gain circuit 310AD corresponds to the BANDA downlink gain circuit. Also, to optimize gain and to prevent oscillation, gain control may be provided for each separate signal component. In other embodiments, gain control may be provided for less than all signal components.

IO circuit 341 is arranged to interface signals INAD, OUTAU, INBD, and OUTBU to antenna 350 via bidirectional multi-band signal IO1. In one embodiment, IO circuit 341 includes a diplexer that is arranged to separate, in the downlink direction, the BANDA signal components and BANDB signal components from signal 101. And to combine, in the uplink direction, the BANDA signal components with the BANDB signal components onto signal 101. Also, IO circuit 341 may include a BANDA duplexer that is arranged to separate/combine the BANDA downlink signal components from the BANDA uplink signal components. IO circuit 341 may further include a BANDB duplexer that is arranged to separate/combine the BANDB downlink signal components from the BANDB uplink signal components. Such diplexer and duplexers may be any circuits that are suitable for splitting a multi-band signal into its constituent single-band components and for combining multiple single band signals into a multi-band signal. For example, the diplexer and duplexers may each include a high-pass filter and a low-pass filter; two band-pass filters; and/or the like.

IO circuit 342 is arranged to interface signals OUTAD, INAU, OUTBD, and INBU to antenna 360 via bidirectional multi-band signal 102. In one embodiment, IO circuit 342 is the same as, or substantially similar to IO circuit 341. However, the invention is not so limited.

Gain circuits 31 OAD, 31 OAU, 31 OBD, and 31 OBU may be employed as embodiments of gain circuit 210 of FIGURE 2. Also, sense circuits 320AD, 320AU, 320BD, and 320BU may be employed as embodiments of sense circuit 220 of FIGURE 2.

Gain control circuit 330 is arranged to receive sense signals SENSEAD, SENSEAU, SENSEBD, and SENSEBU; and to provide gain control signal CONTROLAD, CONTROLAU, CONTROLBD, and CONTROLBU. Gain control circuit 330 is further arranged to provide gain optimization and to prevent oscillations. In one embodiment, gain control circuit 330 employs substantially similar algorithms and/or circuits to independently control the gain provided by gain circuits 310AD, 310AU, 3 lOBD, and 3 lOBU. However, in other embodiments, the gain control of certain signal paths may be dependent on the sensed signal strength of a different signal path; the sensed signal strengths of multiple signal paths may be averaged; and/or the like. These and other variations are within the spirit and scope of the invention.

Generalized Operation

The operation of certain aspects of the invention will now be described with respect to FIGURE 4. FIGURE 4 illustrates a logical flow diagram generally showing one embodiment of a process by which the invention may be practiced.

As shown, a process 400 begins, after a start block, at block 410, where a preset delay timer is decremented and the value of the delay timer is checked. For example, a delay timer may be employed to control the delay between subsequent gain optimizations. In one embodiment, gain optimizations are performed infrequently so as to minimize disturbances to the operation of gain circuits, such as gain circuit 210 of FIGURE 2. In another embodiment, gain optimizations are performed at system power-up and are not repeated until the next power-up. Also, different delay timers may be used for each signal path. For example, it may be advantageous to perform gain optimizations for certain signal paths more frequently than for other signal paths.

In other embodiments, other methods may be employed to control the start of gain optimizations. For example, a user input, power-on reset circuit, an automatic reset after a threshold condition, and/or the like may be used to initiate a gain optimization. Likewise, a gain optimization may be performed when no wireless communications is detected, when a change in the relative positions of antennas, such as antennas 150 and 160 of FIGURE 1, is detected, and/or the like.

If no timeout is detected after the delay timer is decremented, processing remains at block 410. If a timeout is detected, processing moves to block 420.

At block 420, a channel gain value is initialized to a startup value. This startup value may correspond to an initial gain value for the gain circuit and may be defined in hardware or in software. In one embodiment, the startup value is defined such that the gain provided by a gain circuit, such as gain circuit 210 of FIGURE 2, is relatively low, and such that oscillation is unlikely at this gain.

Processing then continues to block 430 where the channel power is sensed and compared to an oscillation threshold. In one embodiment, the oscillation threshold is a constant value that represents a sensed power level or signal strength at which the gain circuit is nearly saturated. If the channel power is less than this oscillation threshold, processing progresses to block 440. However, if the channel power is greater or equal to this oscillation threshold, processing progresses to block 460.

In another embodiment, the oscillation threshold represents a change in the sensed power level or sensed signal strength which is substantially greater than the incremental gain increase provided by block 450. As discussed above, a rapid increase in signal strength may be unrelated to the onset of oscillation. Accordingly, in one embodiment, after oscillation is suspected (e.g., oscillation threshold exceeded), block 430 may lower the channel gain value by a known amount and recompare the sensed signal strength. If the sensed signal strength decreases by a substantially similar amount, processing continues at block 440. However, if the sensed signal strength decreases by a substantially greater amount, oscillation is assumed to have occurred and processing continues to block 460.

In yet another embodiment, other methods may be employed to ascertain whether a rapid increase in signal strength is unrelated to the onset of oscillation. For example, an input signal or a sense signal may be integrated to determine a rate of increase over time and compare with expected rates. The integration may be short-term integration and/or long term integration.

At block 440, the channel gain value is compared to a maximum gain value. This maximum gain value may be defined to characterize the maximum gain provided by a gain circuit. For example, it may be defined based on heat dissipation requirements, maximum effective radiated power considerations, input power limitations, and/or the like. If the channel gain is less than the maximum gain value, processing continues at block 450. If the channel gain is greater or equal to the maximum gain value, process 400 returns.

At block 450, the channel gain value is incremented. The value by which the channel gain value is incremented may be any suitable value. For example, the channel gain value may be incremented by a constant amount each time block 450 is entered. In one embodiment, the channel gain value is increased such that the gain is increased by 0.86 decibels each time block 450 is entered. However, the invention is not limited to this embodiment. For example, the amount that the channel gain is incremented does not have to be constant. In one embodiment, the increase to the channel gain value is inversely proportional to the difference between the channel power and the oscillation threshold. In another embodiment, the increase to the channel gain value is inversely logarithmically proportional to the difference between the channel power and the oscillation threshold. These and other variations are within the spirit and scope of the invention.

At block 460, the channel gain value is decremented by a margin to determine the operating value for the gain circuit. The value by which the channel gain value is decremented may be any suitable value. For example, the channel gain value may be decremented to provide an operating margin or headroom for the gain circuit. In one embodiment, the channel gain value is decreased such that gain is decreased by 0.86 decibels. From block 460, process 400 returns.

The above specification, examples and data provide a description of the method and applications, and use of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, this specification merely set forth some of the many possible embodiments for the invention.

Claims

CLAIMSWhat is claimed as new and desired to be protected by Letters Patent is:

1. An method for optimizing a signal amplification gain, comprising: initializing a channel gain value to an initial value; comparing a channel power level to an oscillation threshold; comparing the channel gain value to a maximum gain threshold; increasing the channel gain value by an incremental value, if the channel power level is less than the oscillation threshold and is less than the maximum gain threshold; and decreasing the channel gain value by a decrement value, if the channel power level is greater than or equal to the oscillation threshold.