Patent Application
20110090126
The present invention generally relates to telecommunications, and more particularly to wireless communication devices and cancellation of portions of electric fields generated by such devices.
Wireless communication devices (i.e., cellular phones, digital wireless phones, wireless terminals, etc.) communicate with base-stations using radio-frequency (RF) transmissions. Wireless communication devices emit electromagnetic energy from the antennas and backlights or other components and hence can exhibit a relatively strong electromagnetic (EM) field. In particular, RF transmissions from antennas can cause EM fields to radiate around the wireless communication device that can sometimes interfere with other electrical devices operating nearby.
For instance, emissions from a wireless communication device can interfere with operation of a hearing aid (or cochlear implant). Such emissions are undesirable since they are rectified by the hearing aid causing a hum, whistle or buzzing sound to be emitted by the hearing aid's speaker. When the user of a hearing aid experiences such interference this makes it difficult or impossible for them to hear conversations taking place over the wireless communication device. In this regard, manufacturers of digital wireless communication devices will soon be obliged to produce digital wireless communication devices for the hearing impaired. For example, in the United States, the Federal Communications Commission (FCC) recently modified the previous exemption to the Hearing Aid Compatibility (HAC) Act of 1988 and established rules for the hearing aid compatibility of digital wireless telephones. Specifically, the FCC required that that digital wireless telephone manufacturers and digital wireless service providers make certain numbers of models or percentages of all digital wireless phones accessible to individuals who use hearing aids. Wireless phones which meet this new requirement are sometimes referred to as HAC-compliant terminals.
Accordingly, it is desirable to reduce the incidence of an electric near-field generated by a digital wireless communication device against a hearing aid to thereby reduce or mitigate undesirable signal interference with hearing aid components when in use, and thus provide improved digital wireless communication equipment that are HAC-compliant. It is also desirable to provide digital wireless communication devices that control near-field emissions absorbed by a user of a wireless communication device to comply with Specific Absorption Rate (SAR) requirements set for wireless communication devices by various government entities. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures.
As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of apparatus components related to controlling electric fields radiated by a wireless communication device. The wireless communication device implements transmit diversity techniques and includes apparatus components designed to actively cancel at least a portion (e.g., the near-field component) of an electric field generated by a main transmit antenna. This can, for example, reduce the specific absorption rate experienced by a user of the device, and can reduce undesirable signal rectification on hearing aid components. Signal rectification refers to the situation where RF energy transmitted by a cellular telephone is received by the circuitry in a hearing aid and such energy is audio rectified across a non-linear junction resulting in a “buzz” produced by the hearing aid.
As used herein, the term “near-field” refers to a portion or region of an EM field in the immediate vicinity of the source of the emission, such as the area immediately adjacent the antenna, and may for example refer to the area where the angular field distribution is dependent upon the distance from the antenna. Those skilled in the art will recognize that the size of the near field will depend upon the wavelength of the emission and the geometry of the source. By way of example, the near-field may be thought of as a relatively intense field impacting a user in physical contact with the wireless communication device proximate the area of physical contact with the wireless communication device.
By contrast, the far-field region is a region outside the near-field region. As used herein, the term “far-field” refers to a portion or region of an EM field relatively far from the source of the emission and in which the radiation pattern does not change shape with distance. For example, the far field could be thought of as a field impacting a person at a point a meter away from a wireless communication device's emission source.
In accordance with some of the disclosed embodiments, a method of operating a wireless communication device is provided. A “first” magnitude of an amplified RF signal is reduced to generate a drive signal having a “second” magnitude that is less than the first magnitude. The phase of the drive signal is shifted to generate a phase-shifted drive signal having an angle that is phase shifted with respect to the amplified RF signal. A main antenna is driven with the amplified RF signal to radiate a first electric field having a “first” near-field component with a “first” magnitude and having a maximum intensity at a hot spot location, and an auxiliary antenna structure is driven with the phase-shifted drive signal to radiate a second electric field having a “second” near-field component with a “second” magnitude that reduces the first magnitude of the first electric field at the hot spot location. In other words, the second near-field component can reduce and/or cancel the first near-field component of the first electric field at the hot spot location. As used herein, the term “hot spot location” refers to a region, area or volume where the near-field component of an electric field has its maximum intensity.
In accordance with other disclosed embodiments, a wireless communication device is provided that includes a housing, an RF front end module designed to generate an amplified RF signal having a first magnitude, a main antenna disposed inside the housing, a coupler, a phase shifter, an auxiliary antenna structure disposed inside the housing, and a an earpiece speaker integrated within the housing. The coupler reduces the magnitude of the amplified RF signal to generate a drive signal having a second magnitude that is less than the first magnitude, and the phase shifter shifts the phase of the drive signal to generate a phase-shifted drive signal having an angle that is phase shifted with respect to the amplified RF signal. In response to the amplified RF signal, the main antenna radiates a first electric field having a maximum intensity at a hot spot location, and the auxiliary antenna structure radiates a second electric field in response to the phase-shifted drive signal. The auxiliary antenna structure can be oriented to radiate the second near electric field having a second near-field component that is in the same orientation as the first near-field component of the first electric field generated by the main antenna. The second near-field component of the second electric field has sufficient magnitude at the hot spot location such that when it is superposed on the first near-field component of the first electric field, the first near-field component of the first electric field that is incident at the hot spot location is reduced and/or cancelled. In other words, the second near-field component of the second electric field destructively interferes with the first near-field component of the first electric field generated by the main antenna to reduce the first near-field component of the first electric field at the hot spot location. In one implementation, the auxiliary antenna structure can be disposed in close proximity to the earpiece speaker and beneath or underneath the hot spot location. In one particular implementation, the auxiliary antenna structure can be a non-resonant auxiliary antenna structure, and the phase shifter can be an adjustable phase shifter that allows the phase shift applied to the drive signal to be adjusted so that intensity of the second electric field radiated by the auxiliary antenna can be pre-set and/or controlled by a user.
Exemplary Wireless Communication Device
The wireless computing device 100 comprises an antenna 160, an RF front end module and HAC unit 130, a baseband processor 105, a processor 101, a coder/decoder (CODEC) 113, a display 107, input devices 108 (keyboards, touch screens, etc.), a program memory 103, 105 for storing operating instructions that are executed by the processor 101, a buffer memory 111, a removable storage unit 115, a microphone 125 and an earpiece speaker 127 (i.e., a speaker used for listening by a user of the device 100). The various blocks are coupled to one another as illustrated in
The processor 101 controls an overall operation of the wireless computing device 100. The processor 101 can include one or more microprocessors, microcontrollers, DSPs (digital signal processors), state machines, logic circuitry, or any other device or devices that process information based on operational or programming instructions. Such operational or programming instructions can be, for example, stored in the program memory that may be an IC (integrated circuit) memory chip containing any form of RAM (random-access memory) or ROM (read-only memory), a floppy disk, a CD-ROM (compact disk read-only memory), a hard disk drive, a DVD (digital video disc), a flash memory card or any other medium for storing digital information. In one implementation, the Read Only Memory (ROM) 103 stores microcodes of a program for controlling the processor 101 and a variety of reference data, and the Random Access Memory (RAM) 105 is a working memory of the processor 101 and temporarily stores data that are generated during the execution of the program. The buffer memory 111 may be any form of volatile memory, such as RAM, and is used for temporarily storing received information packets. The removeable storage 115 stores a variety of updateable data, and can be implemented using Flash RAM. One of ordinary skill in the art will recognize that when the processor 101 has one or more of its functions performed by a state machine or logic circuitry, the memory 103, 105 containing the corresponding operational instructions may be embedded within the state machine or logic circuitry.
The coder-decoder (CODEC) 113 communicates with the processor 101 over a bus 104. The speaker 127 and the microphone 125 connected to the codec 313 serve as an audio input/output block for communication. The CODEC 113 converts digital data from the processor 101 into analog audio signals and outputs the analog audio signals through the speaker 127. Also, the CODEC 113 converts audio signals received through the microphone 125 into digital data and provides the digital data to the processor 101.
Working together the RF front end module 130 and baseband processor 105 enable the wireless computing device 100 to communicate information packets over the air and acquire information packets that are processed at the processor 101. In this regard, the RF front end module 130 and baseband processor 105 include conventional circuitry to enable transmissions over a wireless communication channel. The implementations of the RF front end module 130 and baseband processor 105 depend on the implementation of the wireless computing device 100. In general, the baseband processor 105 processes the baseband signals that are transmitted/received between the RF front end module 130 and the processor 101. The RF front end module 130 down-converts the frequency of an RF signal received through an antenna 190 and provides the down-converted RF signal to a baseband processor 105.
The baseband processor 105 receives digital baseband data (originally generated at the CODEC 113) from the processor 101 and converts the baseband data into real (I) and imaginary (Q) data streams. Although not shown, RF front end module 130 can also include conventional transmitter circuitry including a modulator, an upconverter module and a power amplifier. The modulator (not shown) is designed to modulate information from the baseband processor 105 onto a carrier frequency. The frequency of the modulated carrier is upconverted by the upconverter module to an RF frequency to generate an RF signal. The RF signal is amplified by a power amplifier (not shown) to a sufficient power level for radiation into free space and transmitted via the antenna 190. Although not shown, the RF signal is provided from the power amplifier to the antenna 190 over a transmission path between the power amplifier and antenna 190. In one embodiment, the transmission path is a hardwired path that includes one or more connectors and one or more sections of coaxial cable (e.g., 50 ohm RF transmission cable).
The main antenna 160 comprises any known or developed structure for radiating and receiving electromagnetic energy in the frequency range containing the wireless carrier frequencies. The antenna 160 is coupled and matched to the electronic circuitry of the communication device 100 as is known in the art. As such, other elements (not shown) such as an antenna switch, duplexer, circulator, or other highly isolative means can also be present.
Prior to describing that HAC unit with reference to
The communication device 100 can include a user interface such as one or more of a display 107 (not shown in
The movable flip housing 110 has a width dimension extending in an x-direction, a thickness dimension extending in a y-direction, and a length dimension extending in a z-direction.
When the wireless communication device is in use and user is speaking, the main antenna generates an electric field having an x-component (ExMA) that is substantially aligned with the x-direction, a y-component (EyMA) that is substantially aligned with the y-direction, and a z-component (EzMA) that is substantially aligned with the z-direction.
In many common designs, the wireless communication device 100 will have a size on the order of approximately 50 mm by 100 mm by 20 mm, when in a closed position. There is constant effort to reduce this volume and make dimensions of the overall size of the device smaller. The continual reduction in housing dimensions has direct impact on how the user will interact with the wireless communication device, and in many cases this necessarily means that antennas will be closer to biologic tissue during use of the wireless communication device.
Although not illustrated in
The coupler 362 receives the amplified RF signal 160 and reduces its magnitude to generate a drive signal 364 having a “second” magnitude that is less than the first magnitude of the first drive signal 160 (e.g., by 10 dB or less). The coupler 362 should couple at −10 dB or less so that the reduction in magnitude does not significantly impact the Total Radiated Power (TRP) of main antenna. Although not illustrated, those skilled in the art will readily appreciate that the coupler 362 is a passive device used to couple part of the transmission power in a transmission line by a known amount out through another port, often by using two transmission lines set close enough together such that energy passing through one is coupled to the other.
The coupler 362 is coupled to a phase shifter 366. The phase shifter 366 is a device that provides a discrete phase shift to the input signal, which in this case is the drive signal 364, to shift to a desired angle. The phase shifter 366 can be implemented using either a passive or active phase shifter device either of which can be analog or digital. In one embodiment, the phase shifter 366 can be a passive phase shifter device. In general, at any particular instant, the phase-shifted drive signal 370 will have a lower magnitude than the first drive signal 160 and will be phase shifted with respect to the first drive signal 160. As will be described below, this allows a near-field component of the electric field (EAA) generated by the auxiliary antenna structure 390 to destructively interfere with the near-field component of electric field (EMA) generated by the main antenna 190.
In some embodiments, the optimal phase shift applied to the drive signal 370 can be determined by conducting a phase sweep of the auxiliary antenna structure during antenna system development. This way, an optimal phase shift can be determined. The optimal phase shift will cause the auxiliary antenna structure 390 to generate an optimal destructive electric field (EAA) having a near-field component designed for cancellation of the near-field component of electric field (EMA) generated by the main antenna 190 at a hot spot location. As will be explained below, the optimal phase shift is determined on a frequency-band-by-frequency-band basis (i.e., for a particular band of transmit frequencies). In this regard, the angle of the phase shift applied by the phase shifter 366 will depend on the frequency band that the transmitter is operating in; however, the angle of the phase shift applied by the phase shifter 366 for a particular frequency band will generally be the same for different sub-frequencies within same frequency band, and will allow a near-field component of the electric field (EAA) generated by the auxiliary antenna structure 390 to destructively interfere with a near-field component of the electric field (EMA) generated by the main antenna 190. For example, in the context of a radio (e.g., CDMA radio) that operates over 800 MHz and 1900 MHz bands, the phase shifter 366 will apply a particular phase shift angle to the drive signal 364 to reduce the intensity of the near-field component of the electric field (EMA) generated at a hot spot location (by the main antenna 190) for all frequencies in the 800 MHz frequency band. By contrast, the phase shifter 366 applies a different phase shift angle to the drive signal 364 to mitigate a hot spot (associated with the near-field component of the electric field (EMA) generated by the main antenna 190) for all frequencies in the 1900 MHz frequency band. In one non-limiting implementation, the optimal phase shift applied to the drive signal 364 was determined to be 140 degrees at a transmit frequency of 836 MHz.
In other embodiments, the phase shifter 366 can be an adjustable phase shifter device that allows the user of the wireless communication device to adjust the amount of phase shift that is applied to the drive signal 364 in real time during a call, which in turn allows for the intensity of a net near-field component of the electric field (i.e., sum of the near-field component of the electric field from main antenna 190 and the near-field component of the electric field from the auxiliary antenna 390) radiated by the wireless communication device to be controllable.
The main antenna 190 can be disposed inside the housing. The main antenna can be any known antenna including a microstrip or patch antenna that can be printed directly onto a circuit board. In one exemplary implementation, the main antenna 190 can be a Planar Inverted F Antenna (PIFA). The main antenna 190 is designed to generate/radiate a first near-field component of the electric field (EMA) in response to the first drive signal 160. The near-field component of first electric field (EMA) has a maximum intensity at a hot spot location. For instance, under the HAC Act, RF Emission ratings are based on peak field strength as measured at various points within a plane (e.g., a 5×5 cm grid) in the region that is located at a distance above the earpiece speaker. The hot spot location is a near-field component of the electric field that has the highest intensity and is represented by the region or area on a HAC sub-grid or sub-grids that has the highest intensity electric field. As will be described below, the near-field component of the first electric field (EMA) has an x-component (ExMA), a y-component (EyMA) and a z-component (EzMA), which will be referred to below as a first x-component (ExMA), a first y-component (EyMA) and a first z-component (EzMA) to differentiate them from components of a near-field component of the electric field generated by the auxiliary antenna structure 390. The relative field strength of radio signals can be measured in free space by sampling one near-field component of the electric field. The intensity or strength of the first electric field (EMA) is measured in volts per meter (V/m) or a fractional unit such as millivolt per meter (mV/m) or microvolt per meter (μV/m) is equal to 10−6 V/m. In some implementations (e.g., wireless communication handsets), it has been observed that a majority of the near-field component of the first electric field (EMA) at the hot spot location is attributable to the first z-component (EzMA). In other implementations (e.g., two-way radios, etc.), the majority of the near-field component of the first electric field (EMA) at the hot spot location can be attributable to the first z-component (EzMA) and/or one or more of the other components (ExMA, EyMA). In these other implementations, the similar techniques can be applied to mitigate the near-field components in other orientations.
The auxiliary antenna structure 390 can be an implemented using any known resonant or non-resonant structure for radiating electromagnetic energy in the frequency range containing the wireless carrier frequencies. As used herein, the term “non-resonant” refers to an antenna which does not have natural frequencies of oscillation, and responds equally well to radiation over a broad range of frequencies. A non-resonant antenna has approximately constant input impedance over a wide range of frequencies, and does not have natural resonance on frequency bands over which the main antenna transmits. The non-resonant auxiliary antenna structure 390 does not significantly degrade radiated performance of with the main antenna 190 due good isolation and therefore minimal coupling. The non-resonant structure does not have natural resonance in the same frequency band of the main antenna, therefore, increasing natural isolation between both structures, therefore minimizing the amount of energy that one structure will couple from each other. Use of non-resonant auxiliary antenna structure 390 may be preferable in some implementations since resonant structures can create other design constraints that are wavelength dependent, and also require isolation to minimize coupling with the main antenna 190. As such, the non-resonant structure is as effective as resonant structures without additional design constrains associated with in band resonance.
The auxiliary antenna structure 390 can be coupled and matched to the phase shifter using one or more transmission lines (not illustrated) and one or more sections of coaxial cable (not illustrated) as is known in the art.
The auxiliary antenna structure 390 is driven by the phase-shifted drive signal 370, which is a sample of main antenna drive signal 160 after having a phase shift applied and its magnitude reduced (e.g., 10 dB lower or more) with respect to the first drive signal 170. The phase shift of the phase-shifted drive signal 370 can be selected such that the auxiliary antenna structure 390 generates enough destructive interference to reduce the magnitude of the near-field component of the first electric field (EMA) at the hot spot location.
The auxiliary antenna structure 390 can have any known shape that will allow it to generate a destructive electric field with respect to the near-field component of the first electric field (EMA) generated by the main antenna 190. In some embodiments, the shape and orientation of the auxiliary antenna structure 390 are designed to generate a second electric field (EMA) having a near-field component in the same orientation of the near-field component of the first electric field (EMA) generated by the main antenna 190. In such embodiments, in response to the phase-shifted drive signal 370, the auxiliary antenna structure 390 generates/radiates a second electric field having a near-field component that has a second x-component (ExAA) that is substantially oriented with the first x-component (ExMA), a second y-component (EyAA) that is substantially oriented with the first y-component (EyMA), and a second z-component (EzAA) that is substantially oriented with the first z-component (EzMA).
When considering the principle of superposition, the total near-field component of the electric field (ETotal) at any point is equal to the vector sum of the respective near-field components of the electric fields that each antenna would create in the absence of the others, and can be defined in Equation 1 as:
E
Total
=E
MA
+E
AA (Equation 1)
The near-field component of the total electric field (ETotal) can also be written in Equation 2 as:
E
Total=(ExMA+EyMA+EzMA)+(ExAA+EyAA+EzAA) (Equation 2)
The near-field component of the total electric field (ETotal) can also be defined in Equation 3 as:
E
Total(x,y,z)=jωμ∫∫∫vJ(xA,yA,zA)G(xA,yZ,zA)e−jωt+jωμ∫∫∫vJ(xW,yW,zW)G(xW,yW,zW)e−jω(t−φ)dxdzdz (Equation 3)
where ω is angular velocity (radians/second), μ is permeability (H/m), J is the electric current density, G is the three-dimensional homogeneous Green's function, t is time and φ is the phase shift of phase-shifted drive signal 370. Equation 3 shows that the electric near-field destructive interference, takes into account the phase shift of phase-shifted drive signal 370 transmitted by the auxiliary antenna 390 in relation to first drive signal 160 transmitted by the main antenna 190.
As illustrated in
Taken together
Thus, by utilizing the principle of superposition, at least part of the first electric field (EMA) generated by main antenna 190 is actively cancelled by the second electric field generated that is generated by the auxiliary antenna structure 390. As such, the disclosed embodiments can be used to reduce or mitigate undesirable electric near-field radiation against a user of a wireless communication device. For example, the incidence of an electric near-field on biologic tissue or a hearing aid can be reduced. In such implementations, the disclosed embodiments can be used to reduce biologic tissue energy absorption (e.g., as evidenced by Specific Absorption Rate (SAR) levels), and/or can be used to reduce undesirable signal rectification on hearing aid components (e.g., as evidenced via Hearing Aid Compatibility (HAC) levels defined in the FCC's HAC Act).
It should be appreciated that the exemplary embodiments described with reference to
Those of skill will appreciate that the various illustrative logical blocks, modules, circuits, and steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. Some of the embodiments and implementations are described above in terms of functional and/or logical block components (or modules) and various processing steps. However, it should be appreciated that such block components (or modules) may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. As used herein the term “module” refers to a device, a circuit, an electrical component, and/or a software based component for performing a task. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. For example, an embodiment of a system or a component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that embodiments described herein are merely exemplary implementations
The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
Furthermore, the connecting lines or arrows shown in the various figures contained herein are intended to represent example functional relationships and/or couplings between the various elements. Many alternative or additional functional relationships or couplings may be present in a practical embodiment.
In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical.
Furthermore, depending on the context, words such as “connect” or “coupled to” used in describing a relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other manner, through one or more additional elements.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
