Radiated power control systems and methods in wireless communication devices

Embodiments include systems and methods for controlling radiation of radio frequency (RF) energy by a wireless communication device that includes a transmitter, an antenna, a vector field sensor, and a processing system. The transmitter produces an analog RF signal, and the antenna radiates the analog RF signal into an environment. The vector field sensor senses an intensity of a vector field resulting from the analog RF signal radiated by at least the antenna (and possibly other portions of the device). The processing system determines whether a value representing the intensity is greater than a first threshold, and when the value is greater than the first threshold, the processing system causes the radiated RF energy produced by the wireless communication device to be decreased.

TECHNICAL FIELD

The inventive subject matter relates generally to wireless communications, and more particularly to methods and systems for controlling power radiated by a wireless communication device.

BACKGROUND

An antenna system of a wireless telephone (e.g., a cellular telephone) provides a means by which radio frequency (RF) energy may be radiated into the environment. Governmental agencies (e.g., the United States Federal Communications Commission (FCC)) impose limitations on the intensity of RF energy that a wireless telephone is permitted to radiate. For example, the FCC requires wireless telephone manufacturers to ensure that wireless telephones manufactured or imported for use in the United States do not radiate quantities of RF energy that exceed objective limits for human RF energy exposure, which limits have been deemed to be “safe” by the FCC. These limits are given in terms of a unit referred to as the Specific Absorption Rate (SAR), which is a measure of the amount of RF energy absorbed by the head of a wireless telephone user.

In addition to SAR requirements, the Hearing Aid Compatibility Act of 1988 (HAC Act) requires that the FCC ensure that wireless telephones are compatible with hearing aids and cochlear implants. The term “compatible,” in this context, means that electric and magnetic fields produced by a wireless telephone have local intensities that will not cause appreciable interference with hearing aids or cochlear implants, as such interference may lead to audible noise. A wireless telephone may be considered to be compliant with HAC regulations when the maximum field strength within a measurement grid (referred to herein as the “HAC grid”) is controlled to fall below specified limits. During the design and testing phase of a wireless telephone, the HAC grid is virtually transposed above and centered over the wireless telephone's earpiece speaker. The telephone is placed in a “free-space” condition, is activated to emit RF energy, and the electric and magnetic fields within the HAC grid are measured. When the measured electric and/or magnetic fields exceed HAC requirements, the device may be modified to reduce the emitted RF energy. HAC requirements tend to be more difficult to meet than SAR requirements. In other words, power control apparatus and algorithms that result in compliance with HAC requirements are highly likely also to result in compliance with SAR requirements. Accordingly, some wireless device manufacturers ensure compliance with both SAR and HAC requirements by controlling RF signal power and/or the efficiency of their antenna emissions so that the electric and magnetic fields do not exceed the specified limits within the HAC grid, along with verifying SAR compliance.

Compliance with HAC and SAR regulations are two important wireless device design considerations. However, these considerations tend to be in conflict with a common user desire, which is to maximize radiated RF energy (within safe limits) in order to have more reliable and higher quality communications. For example, during use of a wireless telephone, environmental conditions may decrease the radiation efficiency of the telephone, when compared with the radiation efficiency in a free-space condition. As a more specific example, the degree of contact between a wireless telephone and a user's body (e.g., the user's hand and head) may significantly and detrimentally affect the radiation efficiency of the wireless telephone. This may cause the telephone to produce electric and magnetic fields having intensities even further below HAC thresholds than intensities that may be produced during operation in a free-space condition. However, the reduced radiation efficiency also may decrease communications quality.

Although manufacturers readily design wireless telephones that comply with HAC and SAR regulations, current wireless telephone designs are not configured to optimize radiated RF power (within HAC and SAR limits) when environmental factors are present that may reduce radiation efficiency. Accordingly, what are needed are methods and apparatus for controlling the RF power radiated by a wireless telephone, which ensure compliance with prevailing regulations and which allow for increased RF power radiation under various environmental conditions. Other desirable features and characteristics of the present inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit the inventive subject matter or the application and uses of the inventive subject matter. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

As discussed previously, the United States Federal Communications Commission (FCC) imposes restrictions on manufacturers of wireless telephones. These restrictions include limits imposed on radio frequency (RF) emissions, and more specifically include limits on radiated RF power. Other governmental bodies may impose analogous restrictions on radiated RF power by a wireless telephone (or other wireless device), and/or wireless device manufacturers may self-impose their own limitations. Although the description, below, discusses RF power radiation control in the context of Specific Absorption Rate (SAR) or Hearing Aid Compatibility Act of 1988 (HAC Act) restrictions, it is to be understood that these particular regulations are discussed for example purposes, and are not meant to limit the scope of the embodiments to RF power radiation control based specifically on SAR and/or HAC regulations. Embodiments also may be used to control RF power radiation based on other regulations or limitations.

As discussed previously, during the testing of a wireless device design, vector field measurements associated with determining compliance of the device with HAC regulations are taken when the wireless device is in a free-space condition. However, the degree of contact between a wireless telephone and a user's body (e.g., the user's hand and head) may significantly and detrimentally affect the radiation efficiency of energy-radiating components of the telephone. Accordingly, an antenna that is tuned to radiate RF power at a level at or just below HAC compliant levels in a free-space condition will become detuned, and thus radiate significantly less RF power, when the wireless telephone is held in a user's hand and/or up against a user's head. Current methods of antenna tuning are driven by feedback data received from the device's RF system (e.g., measurements of load impedance, current, and/or forward power). Embodiments discussed below, however, utilize sensed and/or determined information regarding the actual vector fields produced as a result of the radiated RF power during “in the field” device operations. Based on that information, embodiments include adjusting various component values and/or transmit power parameters that affect the radiated RF power, in order to drive the radiated RF power toward, but not exceeding, pre-defined limits (e.g., limits associated with HAC and/or SAR regulations).

Embodiments include radiated RF power control methods and apparatus implemented in wireless communication devices.FIG. 1illustrates a simplified block diagram of a wireless communication device100within which adaptive radiated power control is implemented, in accordance with an example embodiment. According to an embodiment, wireless device100is a wireless telephone that is configured to communicate with a terrestrial-based, satellite-based, airborne or vehicle-borne base station. This may include, for example, wireless device100transmitting signals to a base station and receiving signals from the base station. In other embodiments, wireless device100may wirelessly communicate with other types of remote devices (e.g., Bluetooth-compatible devices, relays, and so on).

Device100may be a wireless telephone (e.g., a cellular telephone), according to an embodiment, although device100may be some other type of wireless communication apparatus, in other embodiments. Although embodiments are discussed in detail that are incorporated in wireless telephones, it is to be understood that embodiments also may be implemented in other types of devices that emit RF energy (e.g., one-way or two-way radios, computers, personal data assistants (PDAs), pagers, wireless personal area network (WPAN) compatible devices, or other types of wireless communication apparatus). Accordingly, it is to be understood that embodiments are not limited only to wireless telephones.

According to an embodiment, device100includes a processing system102, one or more transceivers104, one or more matching circuits106, one or more antennas108, one or more tuning circuits110,111, an earpiece speaker112, one or more vector field sensors113,114,115, data storage116, one or more ground planes118,120(located on one or more printed circuit boards, not illustrated), and a housing122, among other things. According to further embodiments, device100also may include a voltage standing wave ratio (VSWR) detector130. AlthoughFIG. 1illustrates only a single transceiver104, matching circuit106, and antenna108, it is to be understood that a device may include a plurality of any one or more of these components. In addition, althoughFIG. 1illustrates two tuning circuits110,111and two ground planes118,120, other devices may have only a single tuning circuit or ground plane or more than two tuning circuits or ground planes.

Device100may be, for example, a foldable type of wireless communication device. In such an embodiment, ground plane118may be located on a printed circuit board in the “base” of the telephone, and ground plane120may be located on a printed circuit board in the “cover” of the telephone. A hinge168enables the base and the cover to be rotated, with respect to each other, in order to open and close the telephone. In such a case, the housing122would include two portions: one associated with the base, and one associated with the cover. Alternatively, device100may be, for example, a slide type of wireless communication device, which has similarly separated ground planes118,120and separate portions of housing122. Rather than a hinge168, however, a slide type of cellular telephone instead includes a slide mechanism, also indicated with reference numeral168, to enables the base and cover of the telephone to be re-oriented, with respect to each other. In yet another embodiment, device100may be a “candy bar” type of wireless communication device. In such an embodiment, hinge or slide168may be excluded from the device100. In addition, the device100may include a single ground plane (and a single printed circuit board), rather than multiple ground planes118,120. In such an embodiment, tuning circuit110and vector field sensor114, discussed later, may be excluded from device100.

Processing system102may include, for example, one or more general-purpose or special-purpose microprocessors, application specific integrated circuits (ASICs), digital-to-analog converters (DACs), analog-to-digital converters (ADCs), reference generators, clocks, and/or associated circuitry. According to an embodiment, processing system102is adapted, during operation, to control the functionality of matching circuit106, tuning circuit110, and/or tuning circuit111by determining one or more component values for one or more variable, impedance matching components of matching circuit106, tuning circuit110, and/or tuning circuit111. Once the component values are determined, processing system102provides control signals150,151to matching circuit106, tuning circuit110, and/or tuning circuit111, which cause matching circuit106, tuning circuit110, and/or tuning circuit111to set the associated components to the indicated component values (e.g., to “tune” matching circuit106, tuning circuit110, and/or tuning circuit111). According to an embodiment, processing system102also or additionally may determine power control parameters, and provide control signals153to transceiver104, which may affect the output power of signals produced by transceiver104(e.g., by controlling the amplification applied by the transceiver's power amplifier, not illustrated). The component values and/or power control parameters may be computed by processing system102, or the component values and/or power control parameters may be selected from pre-defined component values and/or power control parameters, which may be stored within data storage116, for example.

As will be described in more detail below, determination of the component values and/or power control parameters is performed based on the intensity of one or more vector fields (e.g., electric and/or magnetic fields), as sensed at one or more points by vector field sensors113-115and/or as indicated by measurements made by transceiver104. More particularly, the component values and/or power control parameters are determined so that, under environmental conditions that cause the radiated RF power to decrease (as indicated by information provided by vector field sensors113-115or transceiver104), the device100may increase the radiated RF power toward, but not exceeding, pre-defined limits. These pre-defined limits may be related to HAC Act requirements, SAR requirements, or other requirements or limits. For example, current FCC HAC requirements stipulate that, for transmissions having frequencies below 1 gigahertz (GHz), the electric field is not to exceed 48.5 decibel volts per meter (dBV/m), and the magnetic field is not to exceed −1.9 decibel amps per meter (dBA/m), within a HAC measurement grid (e.g., HAC grid170) that is virtually overlaid over a wireless telephone (e.g., device100). For transmissions having frequencies above 1 GHz, the electric field is not to exceed 38.5 dBV/m, and the magnetic field is not to exceed −11.9 dBA/m. In addition to HAC requirements, FCC limits for human exposure from wireless telephones also are restricted to a SAR level of 1.6 watts per kilogram (1.6 W/kg). According to various embodiments, processing system102receives vector field information from vector field sensors113-115and/or transceiver104, and based on the vector field information, determines component values and/or power control parameters so that the RF power radiated by device100does not produce vector fields that exceed the pre-defined HAC and/or SAR limits.

Vector field sensors113-115may include electric field sensors, magnetic field sensors, or both, according to various embodiments. At the physical location at which it is positioned, each vector field sensor113-115is configured to sense an electric field and/or a magnetic field corresponding to RF energy that is radiated by device100. According to an embodiment, measurement signals160,161that include information representing the sensed electric and/or magnetic fields are provided by vector field sensors113,114to processing system102. In such an embodiment, processing system102analyzes the measured signals and may adjust radiated RF energy, accordingly. According to another embodiment, measurement signals162that include information representing the sensed electric and/or magnetic fields are provided by vector field sensor115to transceiver104. In such an embodiment, transceiver104may analyze the measured signals and may adjust radiated RF energy and/or provide signals157to processing system102to enable the processing system102to adjust radiated RF energy. Each of these embodiments will be discussed in more detail later.

For the purpose of simplicity of description, embodiments described in more detail herein will discuss vector field sensors113-115in the form of electric field sensors, and various determinations that may affect radiated RF power being made based on electric field measurements produced by such electric field sensors. It is to be understood, however, that embodiments also or alternatively may include magnetic field sensors, and various determinations that may affect radiated RF power may be made based on magnetic field measurements produced by magnetic field sensors. In addition, althoughFIG. 1illustrates three vector field sensors113-115, other devices may include as few as one vector field sensor, two vector field sensors, or more than three vector field sensors.

According to an embodiment, each vector field sensor113-115may include a probe (e.g., probe402,FIG. 4, discussed later) that corresponds to an electric field probe or a magnetic field probe. For example, an electric field probe may include two conductive entities that are physically proximate to each other, but electrically insulated from each other across an air gap or a non-electrically conductive material (e.g., a dielectric). For example, the conductive entities included in a vector field sensor113-115corresponding to an electric field probe may include any two items selected from a group that includes a portion of a ground plane118,120, a transmission line164,165, a miscellaneous metallic component166(e.g., a battery, mechanical part, vibrator, and so on), a floating capacitor167, a portion of a hinge or slide168(e.g., in a foldable phone or a slide type phone, respectively), a portion of housing122, or another conductive entity. Alternatively, a magnetic field probe may include a looped conductive element169. For example, a looped conductive element included in a vector field sensor113,115corresponding to a magnetic field probe may include a conductor selected from a group that includes an inductor, a portion of a transformer, or another looped conductive element. According to still other embodiments, an antenna or antenna element (e.g., an auxiliary antenna such as a Bluetooth, Global Positioning System (GPS), diversity or other antenna), when not being used for other purposes, may be used to perform the function of one or more of vector field sensors113-115. Accordingly, such an antenna element, at times may be considered a “vector field sensor” as that term is to be interpreted in the description and claims.

Vector field sensors113-115may be positioned in various physical locations within wireless device100. For example, as shown inFIG. 1, vector field sensor114is positioned in proximity to hinge or slide168, and vector field sensor115is positioned in proximity to ground plane118(e.g., in the base of a foldable or slide type phone, or on the lower half of a candy bar type phone). In contrast, vector field sensor113is positioned in proximity to ground plane120and earpiece speaker112. More particularly, vector field sensor113is positioned in a portion of device100over which HAC grid170is transposed, according to an embodiment. Any of vector field sensors113-115may be electrically coupled to processing system102and/or transceiver104, in various embodiments.

HAC grid170is used to define the maximum allowable field strength for FCC HAC conformance, and its positioning may vary from one device design to another. HAC grid170includes a three-by-three (3×3) array of measurement areas (e.g., squares), with a central measurement area172positioned above earpiece speaker112(e.g., about 1.5 centimeters (cm) above the highest surface of the device100). According to an embodiment, vector field sensor113is not only positioned in a portion of device100over which HAC grid170is transposed, but is further positioned in a portion of device100over which a particular measurement area173of HAC grid170is located. The “particular” measurement area173corresponds to a measurement area within which a vector field intensity measurement taken during device testing was highest, when compared with intensity measurements taken during the device testing within measurement areas of the HAC grid170other than the particular measurement area173. Accordingly, measurement area173may be referred to as a “highest intensity measurement area.” AlthoughFIG. 1shows vector field sensor113being located within measurement area173(i.e., the left, central measurement area of HAC grid170), a highest intensity measurement area may be a different measurement area, as well. In addition, in an alternate embodiment, a vector field sensor may be located in a measurement area other than the highest intensity measurement area. In still other embodiments, more than one vector field sensor may be located within a portion of the device over which HAC grid170is transposed. Locations of vector field sensors according to various embodiments will be described in more detail in conjunction withFIGS. 2 and 3, later.

Matching circuit106may include, for example but not by way of limitation, a matching network, a balun, an antenna tuner, a transmatch or an antenna tuning unit (ATU). Matching circuit106is coupled with antenna108, and is adapted, during operation, to provide an input impedance to antenna108, where the input impedance may be varied by adjusting the values of one or more passive or active impedance matching components (not illustrated inFIG. 1) of matching circuit106. More particularly, matching circuit106includes one or more reactive components (e.g., capacitors, inductors, or other components), which have values that may be varied under the command or control of processing system102(via control signals150). Matching circuit106also may include one or more transformers, switchable elements (e.g., transistors), and/or resistive components (e.g., resistors). According to an embodiment, the component values of matching circuit106are determined by processing system102so that the input impedance of matching circuit106closely matches the load impedance of antenna108, in order to drive the radiated RF power toward, but not exceeding, pre-defined limits (e.g., limits associated with HAC and/or SAR regulations)

Tuning circuit110may include, for example but not by way of limitation, a tunable circuit that is located in proximity to or on the hinge or slide168of a foldable or slide type phone, respectively. Tuning circuit110is coupled between the first and second ground planes118,120, and is adapted, during operation, to produce a resonance between the ground planes118,120. The resonance may be produced by providing components that inductively and/or capacitively couple the ground planes118,120. One or more of the tuning circuit component values may be varied, according to an embodiment, in order to adjust the resonance between the ground planes118,120, resulting in an adjustment to the radiation efficiency of the ground planes118,120. More particularly, tuning circuit110includes one or more variable components (e.g., capacitors, inductors, or other components), which have values that may be varied under the command or control of processing system102(via control signals151). According to an embodiment, the component values of tuning circuit110are determined by processing system102in order to drive the radiated RF power toward, but not exceeding, pre-defined limits (e.g., limits associated with HAC and/or SAR regulations).

Tuning circuit111may include, for example but not by way of limitation, a tunable circuit and a parasitic tuning element (not illustrated). Tuning circuit111is coupled with antenna108, and is adapted, during operation, to drive the parasitic tuning element, thus affecting the frequency characteristics of antenna108. One or more of the tuning circuit component values may be varied, according to an embodiment, in order to vary those frequency characteristics. More particularly, tuning circuit111includes one or more variable components (e.g., capacitors, inductors, or other components), which have values that may be varied under the command or control of processing system102(via control signals152). According to an embodiment, the component values of tuning circuit111are determined by processing system102so that the frequency characteristics of antenna108are such that the radiated RF power is driven toward, but not exceeding, pre-defined limits (e.g., limits associated with HAC and/or SAR regulations).

Transceiver104is coupled between processing system102and matching circuit106, and includes a transmitter and a receiver, according to an embodiment. In accordance with providing a transmit function, transceiver104receives baseband digital signals154from processing system102, and the transmitter portion of transceiver104filters and processes the digital signals, converts the resulting digital signals to analog signals, and amplifies and upconverts the analog signals to produce a radio frequency (RF) analog signal155intended for transmission. In conjunction with the amplification process, the transmitter may include a power amplifier (not illustrated), whose amplification may be adjusted based on control signals153from processing system102, according to an embodiment.

In accordance with providing a receive function, transceiver104receives RF analog signals156, amplifies and downconverts the analog signals, converts the resulting analog signals to digital signals, and processes the digital signals to produce a baseband digital signal158that is ready for further processing by processing system102. During the receive process, the receiver may determine a Received Signal Strength Indicator (RSSI) and/or another indication of the strength of a received signal. According to an embodiment, transceiver104may provide an information signal157that indicates the received signal strength (e.g., the RSSI) to processing system102during times that device100is transmitting a signal (rather than while device100is receiving a signal, as is typically done). Processing system102may use this information to estimate the radiated RF power, and may vary the component values of matching circuit106, tuning circuit110, and/or tuning circuit111and/or vary power control parameters associated with the transmitter of transceiver104, in order to drive the radiated RF power toward, but not exceeding, pre-defined limits (e.g., limits associated with HAC and/or SAR regulations). In such an embodiment, processing system102may use indications of received signal strength, instead of or in addition to information provided by vector field sensors113-115, in order to estimate or determine the radiated RF power of device100.

As indicated above, processing system102may determine, based on information from vector field sensors113-115and/or transceiver104, component values for matching circuit106, tuning circuit110, and/or tuning circuit111, and the component values of each of these circuits106,110,111may affect the RF power that is radiated by device100. In addition or alternatively, processing system102or transceiver104may determine, based on information from vector field sensors113-115and/or transceiver104, power control parameters for the transmitter of transceiver104(or more particularly the transmitter's power amplifier), and these power control parameters also may affect the RF power that is radiated by device100. According to one embodiment, processing system102may determine component values only for matching circuit106, based on information from vector field sensors113-115and/or transceiver104, in order to ensure HAC and/or SAR compliance. According to another embodiment, processing system102may determine component values only for tuning circuit110, based on information from vector field sensors113-115and/or transceiver104, in order to ensure HAC and/or SAR compliance. According to yet another embodiment, processing system102may determine component values only for tuning circuit111, based on information from vector field sensors113-115and/or transceiver104, in order to ensure HAC and/or SAR compliance. According to yet another embodiment, processing system102may determine only power control parameters, based on information from vector field sensors113-115and/or transceiver104, in order to ensure HAC and/or SAR compliance. And according to still other embodiments, processing system102may determine power control parameters and/or component values for one, two or all three of matching circuit106, tuning circuit110and/or tuning circuit111, based on information from vector field sensors113-115and/or transceiver104, in order to ensure HAC and/or SAR compliance.

Antenna108is coupled with matching circuit106and tuning circuit111, and may include, for example, a single antenna element or a plurality of antenna elements. Upon receipt of an analog signal161from matching circuit106, antenna108will radiate RF power corresponding to the analog signal into the environment. In addition, antenna108is adapted to detect RF power from the environment, and to provide corresponding analog signals162to matching circuit106. According to an embodiment, antenna108is completely contained within housing122, although antenna108may partially or completely extend outward from housing122, in other embodiments. Along with antenna108, housing122and ground planes118,120may function to radiate RF power into the environment. Antenna108is illustrated inFIG. 1as being positioned toward a bottom of housing122. In other embodiments, antenna108may be positioned elsewhere within or extending from housing122.

VSWR detector130is coupled between the output of matching circuit106and the input to antenna108. VSWR detector130is adapted, during operation, to monitor actual forward and reflected RF power from the analog signals161at the input of antenna108, in order to calculate a VSWR measurement182, that VSWR detector130may provide to processing system102. VSWR measurements182may be expressed using S-parameters (scattering parameters), for example. According to an embodiment, VSWR detector130includes a 4-port directional coupler, with a main line input and output ports being connected to the output of matching circuit106and the input to antenna108, respectively. Both coupled ports of the coupler are connected to corresponding RF power sensors, which provide data about measured forward and reflected RF power levels. As will be described in more detail later, VSWR measurements182may be evaluated by processing system102during its determination of component values and/or power control parameters.

Data storage116may include, for example, one or more data storage devices that are separate from or integral with processing system102. Data164may be stored by processing system102within data storage116, or retrieved by processing system102from data storage116. For example, data storage116may include a combination of various types of non-volatile and volatile read only memory (ROM) and random access memory (RAM). According to an embodiment, data storage116is adapted to store information that enables processing system102to evaluate information produced by vector field sensors113-115and/or transceiver104. For example, this information may include one or more thresholds and a HAC reading comparison table, as will be discussed in more detail later. According to another embodiment, data storage116also may be adapted to store pre-defined component values for at least those impedance matching components of matching circuit106, tuning circuit110, and/or tuning circuit111that are variable.

AsFIG. 1indicates, vector field sensors113-115may be located in various positions within housing122or on the surface of housing122.FIG. 2illustrates various possible sensor locations transposed on an example of an electric field contour plot200associated with lowband transmissions, in accordance with an example embodiment. Plot200depicts varying intensities of an electric field measured approximately 15 mm above the front surface of a wireless communication device (e.g., device100,FIG. 1) at a time when the device is radiating RF energy associated with a wireless signal transmission at a lowband frequency. For purposes of example, the term “lowband” means frequencies in a range of about 800-900 MHz.

Each of contour lines201-210represents a continuum of points at which a particular electric field intensity is measured. For example, contour line201, which borders region220, may represent points at which an electric field intensity of about 51 dBV/m is measured. Accordingly, the measured electric field intensities within region220would be 51 dBV/m or higher. Similarly, contour line202may represent points at which an electric field intensity of about 50 dBV/m was measured, and region221(between contour lines220and221) would correspond to measured electric field intensities between 50 and 51 dBV/m. As a final example, contour lines203may represent points at which an electric field intensity of about 48.6 dBV/m is measured. One of contour lines203borders region222.

The wireless device that was used to produce the RF radiation associated with plot200includes a primary antenna (e.g., antenna108,FIG. 1) toward the bottom of the device housing (or in the base of a foldable or slide type of telephone), as depicted by rectangle224(in proximity to region220). The earpiece speaker (e.g., earpiece speaker112,FIG. 1) is located toward the top of the device housing (or in the cover of a foldable or slide type of telephone), as depicted by square225. A HAC grid230is shown transposed over plot200, and the location225of the earpiece speaker is below and within the central measurement area of HAC grid230. Plot200is shown divided into four quarters240,241,243,244. The highest electric field intensity above the surface of the device corresponds to region220, which occurs within the bottom quarter240of plot200, where the antenna is located. Proceeding upward from the location of the antenna, the electric field intensity first decreases, and then increases again to another region of relatively high intensity, which is region222. Region222occurs within HAC grid230and within the top quarter244of the device.

As discussed previously in conjunction withFIG. 1, embodiments include sensing (e.g., by one or more of sensors113-115,FIG. 1) a vector field resulting from radiation of RF energy, and setting power control parameters and/or the values of one or more variable components in order to ensure that the vector field does not exceed pre-defined limits. As plot200indicates, the intensity of a vector field may vary significantly over the surface of a device, and accordingly a measured reading of vector field intensity depends on the location of a vector field sensor. Circles250,251,252,253,254indicate five example locations of vector field sensors. Circle250is present within the bottom quarter240of plot200, and corresponds to a sensor location in the bottom quarter of a device's housing (e.g., in the base of a foldable or slide type phone). Circle251is present within the second-to-bottom quarter241of plot200, and corresponds to a sensor location in the second-to-bottom quarter of the device's housing (e.g., also in the base of a foldable or slide type phone). Circle252is present within the second-to-top quarter242of plot200, and corresponds to a sensor location in the second-to-top quarter of the device's housing (e.g., in the cover of a foldable or slide type phone). Finally, circles253,254are present within the top quarter244of plot200, and correspond to sensor locations in the top quarter of the device's housing (e.g., also in the cover of a foldable or slide type phone). Circles253,254also coincide with HAC grid230. Circle253more particularly coincides with the highest intensity region222within the top half of plot200and within the HAC grid230.

According to an embodiment, at least one vector field sensor is located in a portion of a device over which a HAC grid is transposed (e.g., in portions of the device corresponding to circles253,254). According to a further embodiment, at least one vector field sensor is located in a portion of a device corresponding to a highest intensity region (e.g., region222) within a HAC grid transposed over the device (e.g., over circle253). The portion of the device corresponding to the highest intensity region222within the HAC grid230may be determined during device design, for example. According to yet another embodiment, a distance (e.g., distance260) of at least one vector field sensor from the antenna is at least one half the length (i.e., the longest dimension) of the device, although the distance may be shorter, as well. In the case of a foldable or slide type of device, this would be the length when the device is in an open (i.e., unfolded) or extended position.

FIG. 3illustrates various possible sensor locations transposed on an example of an electric field contour plot300associated with highband transmissions, in accordance with an example embodiment. Once again, plot300depicts varying intensities of an electric field measured approximately 15 mm above the front surface of the same wireless communication device as inFIG. 2at a time when the device is radiating RF energy associated with a wireless signal transmission at a highband frequency. For purposes of example, the term “highband” means frequencies in a range of about 1800-1900 MHz. A comparison of plots200(FIG. 2) and 300(FIG. 3) shows that a particular wireless device may produce significantly differently contoured electric fields for transmissions in different frequency bands. More particularly, for example, contour line301, which borders region320, may represent points at which an electric field intensity of about 37 dBV/m is measured. Within HAC grid230, region320represents a region of highest intensity for highband transmissions. Once again, circle253(which is also present inFIG. 2) coincides with the highest intensity region320within the top half of plot300and within the HAC grid230. According to an embodiment, at least one vector field sensor is located in a portion of a device corresponding to highest intensity regions (e.g., regions222,320) for multiple frequency bands, which occur within a HAC grid transposed over the device (e.g., over circle253). Again, the portion of the device corresponding to the highest intensity regions222,320within the HAC grid230may be determined during device design. As discussed previously, vector field sensors also or alternatively may be located in portions of the device corresponding to lower intensity regions, within or outside of the HAC grid, according to various embodiments.

The contour plots200,300ofFIGS. 2 and 3are given for example purposes only, in order to facilitate descriptions of various embodiments. It is to be understood that various wireless devices may produce electric fields having similar or significantly different contour plots. In addition, although contour plots were produced for transmissions at frequencies between 800-900 MHz and 1800-1900 MHz, respectively, it is to be understood that embodiments may be implemented in devices that transmit at higher, lower, and/or intermediate frequencies, as well.

FIGS. 4-7illustrate various types of vector field sensors (e.g., vector field sensors113-115,FIG. 1) and other transceiver apparatus that may be used to sense vector fields and/or to produce an indication of a vector field intensity. More particularly,FIG. 4illustrates an example of a vector field sensor400, in accordance with an example embodiment. Vector field sensor400includes at least a probe402and a rectifier404, according to an embodiment. Probe402may include any apparatus that is configured to produce an analog indication of a vector field intensity410(e.g., an electric or magnetic field). The analog indication410may be a voltage, a current, or a capacitive charge, for example. As discussed previously, for example, probe402may correspond to an electric field probe, and thus may include two conductive entities of a device that are physically proximate to each other, but electrically insulated from each other across an air gap or a non-electrically conductive material (e.g., any two of ground planes118,120, transmission lines164,165, a miscellaneous metallic component166, a floating capacitor167, a portion of a hinge or slide168, a portion of housing122, or another conductive entity of device100,FIG. 1). Alternatively, probe402may correspond to a magnetic field probe, and thus may include a looped conductive element (e.g., looped conductive element169,FIG. 1, which may be an inductor, a portion of a transformer, or another looped conductive element).

Rectifier404may include, for example, a diode detector or another type of rectifier. Rectifier404is configured to receive the analog indication of the vector field intensity410, and to rectify the received analog indication in order to produce an analog, rectified vector field intensity indication412. According to an embodiment, this indication412may be provided to a processing system (e.g., processing system102,FIG. 1) for analysis. According to another embodiment, vector field sensor400may also include an amplifier406, which is configured to amplify the rectified vector field intensity indication412in order to produce an analog, amplified vector field intensity indication414. The amplified vector field intensity indication414may thereafter be provided to the processing system (instead of rectified vector field intensity indication412). Amplifier406may be excluded, however, in embodiments in which amplification is not important to signal analysis. According to a further embodiment, vector field sensor400also may include an analog-to-digital converter408(ADC), which is configured to convert the amplified vector field intensity indication414(or the rectified vector field intensity indication412) into a digital vector field intensity indication416. In such an embodiment, the digital vector field intensity indication416may be provided to the processing system for analysis.

FIG. 5illustrates an example of a configuration of a portion of a device500that includes a vector field sensor502and a transceiver504, which together are adapted to generate a vector field intensity indication, in accordance with another example embodiment. Device500includes vector field sensor502, transceiver504, and antenna506. Transceiver504includes a transmit chain510, a receive chain512, and a processor514. Transceiver504may be, for example, a transceiver configured to communicate using a GSM (Global System for Mobile communications) communication protocol, according to an embodiment. A typical GSM protocol implements Time Division Multiplexing (TDM), which involves alternatively configuring the device in a transmit mode or a receive mode. While in the receive mode, the receive chain512is interconnected with antenna506through a transmit (TX)/receive (RX) switch522. Conversely, while in the transmit mode, the transmit chain510is interconnected with antenna506through TX/RX switch522. The receive chain512essentially is idle during times that device500is in the transmit mode.

According to an embodiment, portions of receive chain512are utilized while device500is in the transmit mode to determine an indication of a vector field intensity associated with the device's RF transmissions. More particularly, during at least part of the time that the TX/RX switch522is configured to interconnect transmit chain510with antenna506, a sensor switch524is configured to provide an analog vector field intensity indication530produced by vector field sensor502to the receive chain512. Vector field sensor502may include an electric field sensor and/or a magnetic field sensor. For example, vector field sensor502may include a probe (e.g., probe402,FIG. 4) and a rectifier (e.g., rectifier404,FIG. 4). Vector field sensor502also may include an attenuator (not illustrated) or an amplifier (e.g., amplifier406,FIG. 4), in various embodiments.

Receive chain512receives the vector field intensity indication530. According to an embodiment, receive chain512may process the received vector field intensity indication530in order to produce a Received Signal Strength Indicator (RSSI)532and/or another indication of the strength of the vector field intensity indication530. Processor514may include a baseband processor, and may form a portion of a larger processing system (e.g., processing system102,FIG. 1). According to an embodiment, processor514analyzes the RSSI532to determine a relationship between the vector fields from the device's transmissions and pre-defined limits on RF radiation (e.g., HAC and/or SAR limits). As will be described in more detail in conjunction withFIG. 8, based on the relationship between the measured vector fields and the pre-defined limits, processor514(or processing system102,FIG. 1) may produce control signals (e.g., signals534and/or signals150-153,FIG. 1) that cause adjustments in the component values within tunable circuits (e.g., circuits106,110,111,FIG. 1) and/or that cause adjustments in the amplification produced by the transmit chain510. Each of these adjustments may affect the level of RF power radiated by the device. According to an embodiment, the adjustments are made in order to drive the radiated RF power toward, but not exceeding, the pre-defined limits (e.g., limits associated with HAC and/or SAR regulations).

FIG. 6illustrates an example of a configuration of a portion of a device600that includes a vector field sensor602and multiple transceivers604,606, which together are adapted to generate a vector field intensity indication, in accordance with another example embodiment. Transceiver604may be, for example, a transceiver configured to communicate using a GSM communication protocol, and transceiver606may be a transceiver configured to communicate using a Wideband Code Division Multiple Access (WCDMA) protocol, according to an embodiment. Either transceiver604,606may be activated to transmit and receive RF signals. However, only one transceiver604,606would be activated at any given time. Accordingly, one transceiver may be idle while the other transceiver is activated. According to an embodiment, portions of one transceiver604or606are utilized to determine an indication of a vector field intensity while the other transceiver606or604is producing RF transmissions. Transceiver and TX/RX switch620may be configured either to connect the receive chain612of transceiver604to antenna608, to connect the transmit chain610of transceiver604to antenna608, or to connect transceiver606to antenna608, at any given time. When transceiver606is activated, it is connected with antenna608through transceiver and TX/RX switch620. Conversely, when transceiver604is activated, either transmit chain610or receive chain612is connected with antenna608through transceiver and TX/RX switch620.

As mentioned above, transceiver606may communicate using a WCDMA protocol. Unlike communications using a GSM protocol, communications using a WCDMA protocol may involve simultaneous transmission and receipt of RF signals (at different carrier frequencies). Transceiver606includes a transmit chain640, a receive chain642, and a processor644. In addition, transceiver606may include a level detector646, which may or may not form a portion of the transmit chain640. During normal operations, level detector646is adapted to determine the power level of transmitted signals originating from transmit chain640by sensing the transmit power level using a coupler648. Level detector646provides signals656indicating the transmit power level to processor644, which may use the information to adjust the amplification performed by the power amplifier of transmit chain640. According to an embodiment, when transceiver606is inactive and/or when transceiver604is active (and transmitting an RF signal), sensor switch624and level detector switch650may be configured to provide an analog vector field intensity indication630produced by vector field sensor602to the level detector646. Level detector646may process the received vector field intensity indication630in order to produce an indication of the power level of transmitted signals originating from transmit chain610of transceiver604. Once again, level detector646provides signals656indicating the transmit power level to processor644.

Processor644may include a baseband processor, and may form a portion of a larger processing system (e.g., processing system102,FIG. 1). According to an embodiment, processor644analyzes the signals656from level detector646to determine a relationship between the vector fields from the device's transmissions and pre-defined limits on RF radiation (e.g., HAC and/or SAR limits). As will be described in more detail in conjunction withFIG. 8, based on the relationship between the measured vector fields and the pre-defined limits, processor644(or processing system102,FIG. 1) may produce control signals (e.g., signals654or signals150-153,FIG. 1) that cause adjustments in the component values within tunable circuits (e.g., circuits106,110,111,FIG. 1) and/or that cause adjustments in the amplification produced by the transmit chain610of transceiver604. Each of these adjustments may affect the level of RF power radiated by the device. According to an embodiment, the adjustments are made in order to drive the radiated RF power toward, but not exceeding, the pre-defined limits (e.g., limits associated with HAC and/or SAR regulations).

Operation of a GSM type of transceiver (e.g., transceiver604) was discussed previously in conjunction withFIG. 5. Similar to the previously discussed operation, while transceiver604is activated and is in the receive mode, the receive chain612of transceiver604is interconnected with antenna608through a transceiver and TX/RX switch620. Conversely, while in the transmit mode, the transmit chain610of transceiver604is interconnected with antenna608through transceiver and TX/RX switch620. According to an embodiment, portions of receive chain612may be utilized while transceiver604is activated and is in the transmit mode to determine an indication of a vector field intensity associated with the device's RF transmissions. More particularly, during at least part of the time that the transceiver and TX/RX switch620is configured to interconnect transmit chain610with antenna608, sensor switch624is configured to provide the analog vector field intensity indication630produced by vector field sensor602to the receive chain612, as discussed previously. Receive chain612may process the received vector field intensity indication630in order to produce an RSSI632and/or another indication of the strength of the vector field intensity indication630, as also discussed previously. According to another embodiment, receive chain612may be utilized to produce an RSSI632or other indication while the other transceiver (i.e., transceiver606) is activated and is transmitting RF energy. In other words, receive chain612may be utilized when transceiver604is considered inactive (i.e., the transmit chain610is not being used to transmit RF signals).

The example embodiment described in conjunction withFIG. 6includes transceiver606, which is adapted to communicate using a GSM communications protocol, and transceiver604, which is adapted to communicate using a WCDMA communications protocol. Other embodiments may include one or more additional or different transceivers that are adapted to communicate using one or more other types of standards-based and/or proprietary communications protocols (e.g., any second generation (2G), third generation (3G), fourth generation (4G), and/or other communications protocol or standard defined by the International Telecommunication Union). Regardless of the types of transceivers implemented, embodiments include using resources (e.g., hardware, firmware, software) of a transmitter of a first transceiver within a device to transmit an RF signal, while simultaneously using resources of a receiver of a second transceiver within the device to determine information (e.g., an RSSI or other information) that is related to the vector field intensity of the transmissions.

FIG. 7illustrates an example of a configuration of a portion of a device700that includes multiple vector field sensors702,704and multiple receive chains706,708, which together are adapted to generate a vector field intensity indication, in accordance with another example embodiment. Device700includes multiple vector field sensors702,704, transceiver710, and multiple antennas716,718. Transceiver710is configured to implement receive and/or transmit diversity, and accordingly includes one or more transmit chains712, multiple receive chains706,708, and a processor714, according to an embodiment. Transceiver710may be configured to implement a GSM communications protocol, and the description below discusses such an implementation in detail. It is to be understood, however, that embodiments may include other types of transceivers (e.g., transceivers that implement other communications protocols) that are configured to implement receive and/or transmit diversity, and such embodiments are intended to be included in the scope of the inventive subject matter.

As discussed in conjunction withFIG. 5, a typical GSM protocol implements TDM, which involves alternatively configuring the device in a transmit mode or a receive mode. Accordingly, while device700is in a receive mode during which device700is receiving an RF signal from a remote device (e.g., a base station or another device), a primary receive function includes configuring TX/RX switch720to connect main antenna716to receive chain706, detecting the RF signal using main antenna716, and processing the signal using receive chain706and processor714. In addition, and according to an embodiment, a diversity receive function includes configuring sensor/antenna switch724to connect diversity antenna718to diversity receive chain708, redundantly detecting the RF signal using diversity antenna718, and processing the redundantly detected signal using diversity receive chain708and processor714. Details regarding redundant processing in conjunction with receive diversity will not be discussed herein, as such processing techniques are known to those of skill in the art. According to another embodiment, transceiver710also may be configured to implement transmit diversity, as well. However, a detailed discussion of transmit diversity is outside the scope of this description.

While device700is in the transmit mode, receive chain706and diversity receive chain708essentially are idle. According to an embodiment, portions of receive chains706,708are utilized while device700is in the transmit mode to determine an indication of a vector field intensity associated with the device's RF transmissions. More particularly, during at least part of the time that the TX/RX switch720is configured to interconnect transmit chain712with main antenna716, sensor switch722is configured to provide a first analog vector field intensity indication730produced by a first vector field sensor702to the receive chain706. In order to provide additional information that may improve accuracy, sensor/antenna switch724simultaneously may be configured to provide a second analog vector field intensity indication732produced by a second vector field sensor704to diversity receive chain708. According to an alternate embodiment, device700may be configured to provide only second analog vector field intensity indication732to diversity receive chain708, without providing the first analog vector field intensity indication730to receive chain706. For example, when device700is not in an operational mode in which receive diversity is being implemented, sensor/antenna switch724may be configured to provide analog vector field intensity indication732produced by vector field sensor704to diversity receive chain708, and provision of vector field intensity indication730may be excluded.

According to an embodiment, receive chains706,708may process the received vector field intensity indications730,732in order to produce RSSIs734,736and/or other indications of the strength of the vector field intensity indications730,732. Processor714may include a baseband processor, and may form a portion of a larger processing system (e.g., processing system102,FIG. 1). According to an embodiment, processor714analyzes either or both RSSIs734,736to determine a relationship between the vector fields from the device's transmissions and pre-defined limits on RF radiation (e.g., HAC and/or SAR limits). When both first and second RSSIs734,736are received, processor714may, for example, use the larger of the received RSSIs734,736during its analysis, and/or may use a combination of the received RSSIs734,736during its analysis (e.g., an average or some other mathematical combination of the RSSIs734,736). When only a single RSSI (e.g., either RSSI734or736) is received, processor714may use the single RSSI during its analysis, according to an alternate embodiment.

As will be described in more detail in conjunction withFIG. 8, based on the relationship between the measured vector fields and the pre-defined limits, processor714(or processing system102,FIG. 1) may produce control signals (e.g., signals738and/or signals150-153,FIG. 1) that cause adjustments in the component values within tunable circuits (e.g., circuits106,110,111,FIG. 1) and/or that cause adjustments in the amplification produced by the transmit chain712. Each of these adjustments may affect the level of RF power radiated by the device. According to an embodiment, the adjustments are made in order to drive the radiated RF power toward, but not exceeding, the pre-defined limits (e.g., limits associated with HAC and/or SAR regulations).

FIG. 8illustrates a flowchart of a method for performing radiated power control based on sensed information, in accordance with an example embodiment. According to an embodiment, the method may be performed within the context of a “call,” where a “call” refers to any type of communication session in which a wireless device transmits RF signals (e.g., a voice communication session or a data communication session) to a base station or to another device. The method may run continuously for a duration of the call, or may be executed periodically, aperiodically or in response to a triggering event.

Embodiments of the method may be performed by a processing system (e.g., processing system102,FIG. 1) in conjunction with one or more vector field sensors (e.g., sensors113-115,400,502,604,702,704, FIGS.1and4-7), tunable circuits (e.g., matching circuit106, tuning circuit110, and/or tuning circuit111,FIG. 1), transceivers (e.g., transceivers102,504,604,606,710, FIGS.1and5-7), and various other system elements. For enhanced understanding, an example embodiment will be discussed in which electric fields are sensed by vector field sensors, and the corresponding sensed values are analyzed to determine whether the sensed values indicate compliance with HAC Act regulations. For purposes of example, assume that the transmission frequency is below 1 GHz. Accordingly, current, relevant HAC Act regulations stipulate that the electric field is not to exceed 48.5 dBV/m. It is to be understood that the above example, which will be used throughout the description ofFIG. 8, is not to be construed as limiting. Instead, modifications to the below described embodiment may be made to ensure compliance with other HAC Act regulations (e.g., regulations relating to magnetic fields, regulations associated with different transmission frequencies, and/or future-defined regulations), SAR regulations, other regulations stipulated by governmental entities, and/or limitations on RF emissions that are voluntarily implemented by device manufacturers. Thus, the below discussion relating to sensing electric fields and comparing values to specific HAC related values is not intended to be limiting, but is provided for example and explanation purposes only.

According to an embodiment, the method may begin, in block802, when the processing system receives one or more vector field intensity indications. The term “vector field intensity indication,” as used herein, means any type of indication of an electric field or a magnetic field that is produced by components incorporated into a device (as opposed to external test equipment). For example, a vector field intensity indication may be an analog or digital representation of a sensed vector field produced by a vector field sensor (e.g., sensors113-115,400,502,604,702,704, FIGS.1and4-7). For example, but not by way of limitation, the analog or digital representation of a sensed vector field produced by a vector field sensor may be an analog or digital representation of a voltage, current or charge, according to various embodiments. Alternatively, a vector field intensity indication may be a processed (e.g., amplified, attenuated, filtered, and/or analyzed) version of an analog or digital representation of a sensed vector field produced by a vector field sensor. For example, as discussed previously, a vector field intensity indication may be an RSSI or other indicator of the strength of a signal that is transmitted by the device, as determined by a receive chain (e.g., receive chains512,612,706,708,FIGS. 5-7) or other component (e.g., level detector646,FIG. 6) within a transceiver (e.g., transceivers504,604,606,710,FIGS. 5-7).

In block804, the vector field intensity indication(s) are analyzed to determine a threshold comparison value. According to an embodiment, the threshold comparison value may be equal to a single received vector field intensity indication. For example, when the vector field intensity indication includes a voltage value received from an electric field sensor, the threshold comparison value may equal the voltage value. Alternatively, the vector field intensity indication and the threshold comparison value may be in the units of current, charge, power, RSSI or some other measurable quantity, in various embodiments.

In other embodiments, the threshold comparison value may be different from the vector field intensity indication (e.g., it may be in different units), or may be calculated based on multiple received vector field intensity indications. For example, when multiple vector field intensity indications are received (e.g., vector field intensity indications730,732,FIG. 7), the threshold comparison value may be calculated based on a mathematical relationship between the received vector field intensity indications (e.g., a maximum received value, an average, or some other relationship). As yet another example, when one or more RSSIs (or other signal power measurements) are received as vector field intensity indications, the threshold comparison value may equal the value of an RSSI (or a mathematical relationship between multiple RSSIs). In still another example embodiment, the vector field intensity indication(s) may be converted to different units (e.g., units associated with HAC or SAR regulations or other units). For example, during testing of a device or a device design, a table may be populated and stored within the device (e.g., in data storage116,FIG. 1), which correlates (for each frequency band of interest) HAC and/or SAR values with voltages produced by one or more electric field sensors, currents produced by one or more magnetic field sensors, RSSI values, and/or other types of vector field intensity indications. Table 1, below, illustrates an example of such a table for correlating voltages with electric field-related HAC values for a particular device. Additional fields could be included for vector field intensity indications in the form of currents, RSSI, magnetic field-related HAC values, and so on:

In an embodiment in which the vector field intensity indication is a voltage and in which the voltage is converted to a HAC value in block804, a table such as Table 1 above may be used to perform the conversion, and the threshold comparison value thus may be determined in the same units as the HAC Act regulations (e.g., dBV/m) (or some other unit). For example, when a voltage of 0.95 volts is produced by an electric field sensor, the processing system may convert the voltage to a HAC value of 48.0 dBV/m using Table 1. As will be described below, a table such as Table 1, above, also or alternatively may be used during device design and testing to determine various thresholds (e.g., first and second thresholds, discussed below). For purposes of example only, a threshold comparison value in the units of voltage (e.g., a voltage derived from vector field intensity indications from one or more electric field sensors) will be described below. It is to be understood that alternate embodiments may include threshold comparison values in different units.

In block806, the threshold comparison value is compared with a first threshold to determine whether the threshold comparison value is less than (or less than or equal to) the first threshold. According to an embodiment, the first threshold is a value in the same units of measurement as the threshold comparison value. For example, when the threshold comparison value is in the unit of voltage, the first threshold is in the unit of voltage. Alternatively, when the threshold comparison value is in some other unit (e.g., amps, watts, dBV/m, dBA/m or some other unit), the first threshold is in the same type of unit.

According to an embodiment, the first threshold corresponds to a pre-defined limit that the device is controlled (as will be described more fully below) not to exceed in conjunction with RF transmissions. For example, the first threshold may correspond to an upper HAC Act defined limit on electric fields that may be produced by the device (e.g., 48.5 dBV/m for transmissions under 1 GHz). In such a case, the first threshold may coincide precisely with the upper HAC Act defined limit. Alternatively, the first threshold may have a value that coincides with a HAC value that is higher or lower than the HAC Act defined limit by some margin (e.g., 5 percent of the upper HAC Act defined limit or some other margin). Alternatively, the first threshold may correspond to a HAC Act defined limit associated with magnetic fields, a SAR limit, and/or another limit. During the design and/or testing process, the first threshold may be defined and stored within the device (e.g., in data storage116,FIG. 1). For example, the first threshold may be determined during design and testing using a table such as Table 1, above. As a more specific example, the first threshold may be defined to correspond with the upper HAC Act limit on electric fields (or magnetic fields). Assuming, for example, that Table 1 accurately reflects the correlation between HAC values and voltages produced by an electric field sensor, a voltage of 1.0 volts corresponds with a HAC value of 48.5 dBV/m (e.g., the current upper limit for electric fields defined by the HAC Act). Accordingly, the first threshold may equal 1.0 volts.

When the threshold comparison value is not less than (or less than or equal to) the first threshold (i.e., the threshold comparison value is greater than or equal to (or simply greater than) the first threshold), adjustments are made to decrease the radiated power produced by the device, in block808. According to an embodiment, a decrease in the radiated power may be achieved by adjusting one or more values of tunable components (e.g., components of circuits106,110,111,FIG. 1) that affect the radiation efficiency of the device. For example, the impedance provided by one or more tunable circuits (e.g., one or more of circuits106,110,111,FIG. 1) may be increased via component value adjustments, when such an increase is known to cause a decrease in radiated power, or the impedance provided by one or more tunable circuits may be decreased via component value adjustments, when such a decrease is known to cause a decrease in radiated power. According to another embodiment, decreasing the radiated power may be achieved by reducing the amplification applied by the device's transmitter (or more particularly the amplification applied by the transmitter's power amplifier). These various types of adjustments were discussed in detail, above. After performing block808, the process may iterate as shown inFIG. 8. A single iteration of block808may not result in a radiated power decrease that is sufficient to pull the threshold comparison value below the first threshold. If not, blocks802-808will be repeated one or more times until the threshold comparison value does drop below the first threshold.

When the threshold comparison value is less than (or less than or equal to) the first threshold, as determined in block806, the threshold comparison value may be compared with a second threshold to determine whether the threshold comparison value is less than (or less than or equal to) the second threshold, in block810. According to an embodiment, the second threshold has a value that is less than the first threshold. For example, the second threshold may have a value that is 10 to 20 percent less than the first threshold, although the second threshold may have a value that is closer to or further from the first threshold, as well.

According to an embodiment, the second threshold corresponds to a pre-defined limit that the device is controlled (as will be described more fully below) not to fall below in conjunction with RF transmissions. For example, the second threshold may have a value that corresponds to a defined number of dBV/m below an upper HAC Act defined limit on electric fields that may be produced by the device (e.g., 10 to 20 percent below 48.5 dBV/m for transmissions under 1 GHz). Alternatively, the second threshold may have a value that corresponds to a defined number of dBA/m below a HAC Act defined limit associated with magnetic fields, a value that corresponds to a value below a SAR limit, and/or a value that corresponds to a value below some other limit. During the design and/or testing process, the second threshold may be defined and stored within the device (e.g., in data storage116,FIG. 1). Assume, for example, that Table 1 accurately reflects the correlation between HAC values and voltages produced by an electric field sensor, the first threshold equals a voltage of 1.0 volts (which corresponds with a HAC value of 48.5 dBV/m), and the second threshold is defined to be 10 percent lower than the first threshold. In such a case, the second threshold equals 0.9 volts (which corresponds with a HAC value of 47.5 dBV/m).

When the threshold comparison value is not less than (or less than or equal to) the second threshold (i.e., the threshold comparison value is greater than or equal to (or simply greater than) the second threshold), the method iterates as shown, and a radiated RF power adjustment is not made. Conversely, when the threshold comparison value is less than the second threshold, adjustments are made to increase the radiated power produced by the device, in block812. According to an embodiment, an increase in the radiated power may be achieved by adjusting one or more values of tunable components (e.g., components of circuits106,110,111,FIG. 1) that affect the radiation efficiency of the device. For example, the impedance provided by one or more tunable circuits (e.g., one or more of circuits106,110,111,FIG. 1) may be decreased via component value adjustments, when such a decrease is known to cause an increase in radiated power, or the impedance provided by one or more tunable circuits may be increased via component value adjustments, when such an increase is known to cause an increase in radiated power. According to another embodiment, increasing the radiated power may be achieved by increasing the amplification applied by the device's transmitter (or more particularly the amplification applied by the transmitter's power amplifier). These various types of adjustments were discussed in detail, above. After performing block812, the process may iterate as shown inFIG. 8. A single iteration of block812may not result in a radiated power increase that is sufficient to pull the threshold comparison value above the second threshold. If not, blocks802,804,810,812will be repeated one or more times until the threshold comparison value rises above the second threshold.

AsFIG. 8and the associated description indicate, embodiments enable the radiated RF power of a wireless device to be controlled, based on sensed vector fields, to have values that fall between a first threshold and a second threshold. Accordingly, the system is configured and adapted to maintain the radiated RF power at a level that may be close to, but not exceeding, a pre-defined limit (e.g., the first threshold that may correspond with an upper HAC or SAR limit), rather than allowing the radiated RF power level to drift excessively far below the pre-defined limit. In addition, comparison of the threshold comparison value with a second threshold establishes system hysteresis, thus avoiding rapid switching between power increases and decreases around a single threshold.

The sequence of process blocks illustrated inFIG. 8represent just one example of an order in which the process blocks may be performed, and the depicted sequence is not intended to limit the scope of the inventive matter only to the depicted order. Instead, it is to be understood that, in alternate embodiments, some or all of the process blocks illustrated inFIG. 8may be performed in different orders, may be performed in parallel, may be combined together, may be expanded into multiple sub-processes, and/or may include one or more intermediate processes that are not illustrated.

FIGS. 9 and 10are provided to illustrate the effects of varying a component value of a circuit (e.g., one of circuits106,110,111,FIG. 1) on the RF power radiated by a device. More particularly,FIGS. 9 and 10assume that the variable component is a capacitor of such a circuit. It is to be understood that, in other embodiments, the values or states of other types of components may be varied, and/or the values or states of multiple components may be varied, and/or power control parameters may be adjusted to affect the RF power radiated by a device.

FIG. 9illustrates an electric field measurement chart902and a radiated RF power chart904for a wireless communication device in a free-space condition. In both charts902,904, the horizontal axis corresponds to the value of a capacitor (in pF) of a matching or tuning circuit (e.g., one of circuits106,110,111,FIG. 1). Radiated RF power chart904illustrates that, as the value of the capacitor is increased, the radiated RF power also increases. Similarly, electric field measurement chart902illustrates that, after a value of approximately 0.3 pf, as the value of the capacitor (and thus the radiated RF power) is increased, the electric field also increases. At a capacitor value of about 0.72 pF, as indicated by dashed vertical line906, the electric field coincides with an upper HAC limit of 48.5 dBV/m. This corresponds with a radiated power value of about 0.83 W. Accordingly, in order not to exceed the upper HAC limit of 48.5 dBV/m, the capacitor value should not be adjusted to exceed 0.72 pF, and the radiated power should not be permitted to exceed 0.83 W, as such excesses may cause the RF radiation to exceed the upper HAC limit.

As discussed previously, the degree of contact between a wireless telephone and a user's body (e.g., the user's hand and head) may significantly and detrimentally affect the radiation efficiency of energy-radiating components of the telephone. Accordingly, an antenna that is tuned to radiate RF power at a level at or just below HAC compliant levels in a free-space condition will become detuned, and thus radiate significantly less RF power, when the wireless telephone is held in a user's hand and/or up against a user's head. Such a phenomenon is illustrated inFIG. 10.

More particularly,FIG. 10illustrates a HAC measurement chart1002and a radiated RF power chart1004for the same wireless communication device as was characterized inFIG. 9, but in a hand held condition rather than a free-space condition. Once again, radiated RF power chart1004illustrates that, as the value of the capacitor is increased, the radiated RF power also increases. Similarly, electric field measurement chart1002illustrates that, as the value of the capacitor (and thus the radiated RF power) is increased, the electric field also increases. However, at a capacitor value of about 0.72 pF, as indicated by dashed vertical line1006, the electric field only coincides with a HAC value of about 44.5 dBV/m, which is significantly below the upper HAC limit of 48.5 dBV/m. Accordingly, the capacitor value may be adjusted to exceed 0.72 pF without causing the RF radiation to exceed the upper HAC limit. Embodiments of methods and apparatus for controlling the radiated RF power of a wireless device enable the device to respond to environmental conditions that cause a decrease in radiated RF power, by sensing the decrease in radiated power, and adjusting the radiated power toward, but not exceeding, pre-defined limits (e.g., HAC and/or SAR limits).

Thus, various embodiments of radiated RF power control systems and methods in wireless communication devices have been described. An embodiment includes a method for controlling radiation of RF energy by a wireless communication device that includes a transmitter and an antenna. The method is performed by the wireless communication device and includes the steps of producing radiated RF energy by the wireless communication device, sensing, by a vector field sensor of the wireless communication device, an intensity of a vector field resulting from the radiated RF energy, and determining whether the intensity is greater than a first threshold. When the intensity is greater than the first threshold, the method includes decreasing the radiated RF energy produced by the wireless communication device.

Another embodiment includes a wireless communication device with a transmitter, an antenna, a vector field sensor, and a processing system. The transmitter is configured to produce an analog RF signal. The antenna, which is operably coupled with the transmitter, is configured to radiate the analog RF signal into an environment. The vector field sensor is configured to sense an intensity of a vector field resulting from the analog RF signal radiated by at least the antenna. The processing system, which is operably coupled with vector field sensor, is configured to determine whether the intensity is greater than a first threshold, and when the intensity is greater than the first threshold, to cause radiated RF energy produced by the wireless communication device to be decreased.

While the principles of the inventive subject matter have been described above in connection with specific systems, apparatus, and methods, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the inventive subject matter. Further, the phraseology or terminology employed herein is for the purpose of description and not of limitation. For example, the term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner.

The foregoing description of specific embodiments reveals the general nature of the inventive subject matter sufficiently that others can, by applying current knowledge, readily modify and/or adapt it for various applications without departing from the general concept. Therefore, such adaptations and modifications are within the meaning and range of equivalents of the disclosed embodiments. The inventive subject matter embraces all such alternatives, modifications, equivalents, and variations as fall within the spirit and broad scope of the appended claims and their legal equivalents.