United States Patent (19)
`Lindell
`
`||||III
`US005524275A
`11) Patent Number:
`(45) Date of Patent:
`
`5,524,275
`Jun. 4, 1996
`
`54 AVERAGED RF EXPOSURE CONTROL
`
`(75) Inventor: Bo K. Lindell, Lidingo, Sweden
`73) Assignee: Ericsson GE Mobile Communications
`Inc., Research Triangle Park, N.C.
`
`(21) Appl. No.: 168,151
`22 Filed:
`Dec. 17, 1993
`6
`(51) Int. Cl. ....................................................... H04B 1/04
`(52) U.S. Cl. .......................... 455/117; 455/115 455/127;
`340/635
`58 Field of Search ..................................... 455/127, 115,
`455/117, 126; 340/635, 657
`
`56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,034,297 7/1977 Giorgi et al. ........................... 455/117
`... 455/17
`4,114,108 9/1978 Faulkenberry et al.
`330/207 P
`4,165,493 8/1979 Harrington ..............
`375/70
`4,242,753 12/1980 Dolikian et al. ...
`45.5/17
`4,313,210
`1/1982 Hume et al. ........
`... 455/103
`4,373,206 2/1983 Suzuki et al. ...
`455/115
`4,521,912 6/1985 Franke et al. .......
`4,939,786 7/1990 McCallum et al. .
`- - - - - - 455/67
`... 5538.3
`5,193,212 3/1993 Son ....................
`5,241,690 8/1993 Larsson et al. ........................ 555,
`FOREIGN PATENT DOCUMENTS
`2-39634 2/1990 Japan.
`
`1427578 9/1988 U.S.S.R..
`2198912 6/1988 United Kingdom ..................... 455/79
`OTHER PUBLICATIONS
`
`IEEE Standard for Safety Levels with Respect to Human
`Exposure to Radio Frequency Electromagnetic Fields, 3 kHz
`to 300 GHz,” IEEE C95.1-1991, Institute of Electrical and
`Electronics Engineers, Inc., New York, N.Y., USA, Apr. 27,
`1992.
`Federal Communications Commission (FCC), Notice of
`Proposed Rulemaking, "Guidelines for Evaluating the Envi
`ronmental Effects of Radiofrequency Radiation,' ET Docket
`No. 93-62, Apr. 8, 1993, pp. 1-26.
`Primary Examiner-Reinhard J. Eisenzopf
`Assistant Examiner-Doris To
`Attorney, Agent, or Firm-Burns, Doane, Swecker & Mathis
`57
`ABSTRACT
`
`A radio transmitter output power controller which automati
`cally restricts the maximum transmitting time during an
`averaging time so that the average power remains below an
`acceptable level. Additionally or alternatively, the maximum
`transmitter output power may be automatically reduced to a
`lower level if and when a predetermined average power
`level is approached. A warning signal may be generated to
`inform a user that the maximum permitted power output is
`being approached.
`
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`US. Patent
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`Jun. 4, 1996
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`Sheet 1 of 4
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`|PR2018—O1473
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`US. Patent
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`Jun. 4, 1996
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`Sheet 2 of 4
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`|PR2018—O1473
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`U.S. Patent
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`Jun. 4, 1996
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`US. Patent
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`Jun. 4, 1996
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`Sheet 4 of 4
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`5,524,275
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`1.
`AVERAGED RF EXPOSURE CONTROL
`
`5,524,275
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`2
`The present invention achieves these ends by automati
`cally restricting the maximum transmitting time during a
`predetermined averaging time so that the average power
`remains below an acceptable level. Additionally or alterna
`tively, the maximum transmitter output power can be auto
`matically reduced to a lower level if and when a certain
`average power is approached. Further, a warning signal may
`be generated to inform a user that the MPE is being
`approached.
`By implementation of this invention, higher power levels
`than the maximum power output that would otherwise be
`permitted without averaging can be used, thus increasing the
`quality and reliability of the radio link. Further, the present
`invention can be implemented in preexisting system designs
`through an easily made software modification or through a
`slight circuit modification, such as the inclusion of an
`integrator circuit.
`The present invention thus avoids possible detrimental
`effects implied by the newly proposed power restrictions and
`assures users that the exposure guidelines, and particularly
`the MPE guidelines, cannot be exceeded by a device in
`accordance with the present invention. Also, radio transmit
`ters incorporating the present invention can be exempted
`from the proposed FCC requirements.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The present invention will now be described in detail with
`reference to the accompanying drawings wherein like ele
`ments are given like reference numbers, in which,
`FIG. 1 is a functional diagram of a first embodiment of the
`present invention;
`FIG. 2 is a functional diagram of a second embodiment of
`the present invention;
`FIG. 3 is a functional diagram of a third embodiment of
`the present invention;
`FIG. 4 is a program flow diagram of some of the features
`of the first embodiment of the present invention;
`FIG. 5 is a program flow diagram of some additional
`features of the first embodiment of the present invention;
`and
`FIG. 6 is a program flow diagram of the second and third
`embodiment of the present invention.
`With reference to FIGS. 4-6, the rectilinear blocks rep
`resent states and the circles represent activities or events.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODEMENTS
`Several examples of where and how the present invention
`can be implemented will be offered.
`
`Handheld Simplex Radios
`For purposes of illustration, with respect to professional
`handheld simplex radio systems, it is assumed that it has
`been found by measurements that allowed specific absorp
`tion rate (SAR) levels permit a continuous output over an
`averaging time of 1 W. During normal use of a handheld
`simplex radio, due to the customer usage profile, it can be
`expected that only a few short transmissions will take place
`during any six minute period, which corresponds to the
`permitted averaging time. However, a normal handheld
`radio for this system would preferably have 3 watt output
`power. This kind of system may use a transmitter timing
`control to limit any transmission period to one minute, for
`
`10
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`20
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`25
`
`BACKGROUND OF THE INVENTION
`1. Technical Field
`The present invention relates to a method and apparatus
`for assuring that the average RF-exposure levels from radio
`transmitters, particularly cellular, hand-held radio tele
`phones, do not exceed a predetermined level.
`2. Background Art
`In recent years there has been an increasing concern over
`the environmental effects of radio frequency radiation. For
`instance, the American National Standards Institute (ANSI)
`in association with the Institute of Electrical and Electronic
`15
`Engineers, Inc. (IEEE) have adopted new standards for RF
`exposure. ANSI/IEEE C95.1-1992. The Federal Communi
`cations Commission (FCC) has proposed adopting these
`new guidelines. Notice of Proposed Rulemaking, "Guide
`lines for Evaluating the Environmental Effects of Radio
`frequency Radiation,” ET Docket No. 93-62, Apr. 8, 1993.
`The new guidelines are generally more restrictive than the
`previously adopted guidelines and encompass land-mobile
`systems, such as cellular radio, pocket and hand-held radio
`telephones. The guidelines provide for exclusions to the
`regulations if it can be shown through laboratory procedures
`that exposure conditions do not exceed a certain specific
`absorption rate (SAR) or, alternatively, if the radiated power
`is below a certain level. The FCC has proposed that hand
`held devices such as cellular telephones must either comply
`30
`with or be exempted from the requirements specified for
`uncontrolled environments.
`The Maximum Permissible Exposure (MPE) for uncon
`trolled environments, the factors of which include electric
`field strength E (Win), magnetic field strength H (A/m) and
`power density S (mW/cm), are related to the frequency
`range (MHz) of the radio signal. The averaging time, e.g., 6
`or 30 minutes, for MPE under the new standard is also
`related to the frequency range of the radio signal. The RF
`40
`exposure can be correlated to output power of a transmitter
`provided that environmental factors can be assumed, such as
`the transmitter radiating points being within a range of
`distance from a user (e.g., 2.5 cm from a user's head in a
`mobile telephone). Thus, the MPE can be correlated to a
`maximum permitted power.
`45
`Keeping within the guidelines by lowering the maximum
`power output to a level which cannot exceed the MPE at any
`instant may lead to unnecessary and undesirable results. For
`instance, in order to maintain a radio link, a mobile cellular
`transmitter may need to momentarily increase power output
`as the mobile transmitter passes obstructions in the path of
`the radio link. Exceeding a maximum power output would
`not, however, necessarily exceed the MPE because of the
`permitted averaging time.
`
`35
`
`50
`
`SUMMARY OF THE INVENTION
`The present invention is designed to assure that a trans
`mitter does not exceed a MPE over the permitted averaging
`time while concurrently permitting a greater range of power
`output to maximize the transmitter's ability to broadcast at
`a level sufficient to establish or maintain a radio link.
`An assurance that a radio system can not exceed the MPE
`will likely increase consumer confidence and thereby
`65
`increase the marketability of products incorporating the
`present invention.
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`5,524,275
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`3
`example. There is, however, no limit on the number of
`transmissions, so the average output power P. might well
`approach or exceed the maximum allowed power P. In
`FIG. 3 the maximum allowed average power P may be a
`digital or analog representation of decided maximum aver- 5
`age power for cutting of the transmitter.
`In this case a safety device in accordance with the present
`invention is useful. Such a safety device can take the form
`of an integrating circuit or a software equivalent thereof for
`estimating the average output power P. during an averag- 10
`ing time T, e.g., the last six minute period. The safety
`device will either stop or disable a transmission until a new
`transmission can take place without exceeding the maximum
`allowed power P, and/or give a warning that one more
`transmission is allowed, as explained further infra. Normal 15
`use will not cause radio links to be interrupted very often.
`Burst Mode Transmitters
`Another example is a burst mode transmitter where the
`duty cycle is usually low. In this case a high peak power can
`be used, and the safety device can delay transmissions when
`necessary without much influence on system performance,
`since interruptions will be rare.
`
`4
`sion power cannot be exceeded. When the average power
`during the preceding averaging time (e.g., 6 minutes or 30
`minutes) passes a threshold below or equal to the maximum
`power P allowed by the MPE, the transmission is cut-off.
`With reference to FIG.1, an apparatus in accordance with
`this aspect of the present invention involves an average
`power determining circuit 11 for determining an average
`power by which a radio transmitter has transmitted during a
`preceding time period. This might take the form of an
`integrating circuit. The preceding time period may be the
`maximum averaging time T or a portion thereof. The
`average power determining circuit may determine, as a
`measure of average power P, a maximum continuous
`transmission time based on past transmission time within an
`averaging time period T when the transmission power
`P is at a fixed level.
`The apparatus also includes a comparator 12 for compar
`ing the average power P to a first, predetermined thresh
`old P. The first threshold may correspond to a maximum
`allowed average power P for a given averaging time T,
`which can be set by a first threshold setting circuit 13. The
`output of the comparator 12 activates a transmitter disable
`circuit 14 which disables the radio transmitter when the
`comparator 12 determines that the first threshold P.
`has
`been exceeded.
`In addition to the above structure, the apparatus may
`include a second comparator 15 for comparing the average
`power P at which a radio transmitter has transmitted
`during a preceding time period T (including a time period
`in which the transmitter has been disabled) to a second
`predetermined threshold P. The second threshold P is the
`average power P where power is restored and/or blocking
`is removed. The second threshold P. may correspond to a
`maximum allowed average powerfor a given averaging time
`T plus a margin sufficient to permit significant transmis
`sion time prior to re-exceeding the first threshold. In other
`words, an hysteresis effect is introduced to prevent rapid
`cycling of the power cut-off function. The second threshold
`P may be set by a second threshold setting circuit 16.
`The transmitter disabling circuit 14 may enable the
`resumption of radio transmission after being disabled when
`the average power P has diminished to be equal or be
`below the second threshold P.
`The possible parameter settings thus include averaging
`time T and maximum allowed average power P, as
`well as the transmission re-enable threshold P. One addi
`tional possible parameter setting is the useful time T
`which will be allowed prior to re-exceeding the maximum
`averaged power P.
`In its simplest form with a fixed output power, the power
`cut-off criteria will be a measurement of what proportion of
`the past averaging time that has been used for transmission,
`and setting a maximum output time according to that pro
`portion (e.g., setting a maximum output time to be the ratio
`of the allowed average power divided by the current output
`power).
`These functions can be implemented through software or
`hardware. FIG. 4 is a flow diagram in accordance with an
`implementation of the present invention. In FIG. 4, the
`rectilinear blocks represent states, and the circles activities
`Or events.
`With reference to FIG. 4, the present invention is illus
`trated by the program flow diagram thereof. State 46 is the
`state where the transmitter can be used, e.g., be switched on.
`The average power P is below the maximum allowed
`average power P. In step 41, the average power P
`
`ave
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`25
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`Cellular Radio
`The situation for cellular radios is different than handheld
`simplex or burst mode transmitters. The maximum power
`output is often in the order of 0.6 W. For purposes of
`illustration, it is assumed that it has been found that a certain 30
`type of cellular radio might be used continuously with 0.2W
`output without exceeding the SAR limits. Normally cellular
`systems use power control depending on propagation con
`ditions, hence the power of the mobile unit, for instance, will
`vary during use. In this case a warning signal could be given 35
`when a few minutes of transmission is allowed to continue
`at the same average power P as used during the averaging
`time T, e.g., the last few minutes of the ongoing trans
`mission. If the power limit P is reached, the transmitter
`will be automatically switched off for a time period. A
`40
`nuance can involve allowing at least one additional useful
`transmission (for a sufficient time) if the unit is manually
`switched on again.
`Alternatively, the transmission power P could be
`reduced to a lower level at or shortly after the warning
`instant to permit non-interrupted (or at least a longer)
`transmission time. In FIG. 3 the instantaneous power P.
`may be digital numerical value, or analog voltage represent
`ing actual transmitter output power. This is appropriate if
`there is margin in the normal power control system so that
`some additional reduction of power will only result in
`degradation of quality, not in total loss of communication.
`
`45
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`Transmitter Cut-Off Embodiment
`In a first embodiment illustrated in FIGS. 1 and 4, the
`invention acts analogously to a fuse wherein when the
`maximum power duration is exceeded, the transmission is
`simply shut-off. This embodiment is useful for most appli
`cations such as handheld simplex radios because the aver- 60
`aging time generally exceeds the typical duration of a radio
`link. Thus, the transmission powerP never approaches the
`maximum output power P, as averaged over the averag
`ing time T. However, in rare instances wherein the
`reception conditions are particularly poor and/or the radio 65
`transmission link duration relatively long, the first embodi
`ment of FIGS. 1 and 4 assures that the maximum transmis
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`5
`determined to be greater than or equal to the maximum
`allowed power P. If it is greater, then transmission is
`blocked, as shown at step 42 resulting in the state 43. In state
`43 the transmitter can no longer transmit, so the average
`power P will inevitably drop as time passes. Provided that
`the average power P
`is less than or greater than the
`maximum allowed power P
`while the transmitter is
`blocked (state 43), then it is determined whether the average
`power P is less than or equal to a second threshold P as
`shown in step 44. When the average power P. drops below
`the second threshold P, then, as shown at step 45, the
`transmitter is re-enabled and therefore free to transmit. As
`shown in state 46, when the transmitter is free to transmit
`and the average power P is less than or equal to the
`maximum allowed power P then the program return to
`step 41. Thus this aspect of the invention acts as a fuse to
`cut-off transmission and then re-enable transmission once
`the average power P. drops below the maximum allowed
`power P plus a margin as represented by the second
`threshold P.
`This mechanism assures that the user will not be exposed
`to an average transmission power greater than permitted
`over the averaging time T, while allowing renewed com
`munication of an interrupted call as quickly as possible.
`Thus, when average power P.
`during past averaging
`time T has decreased below the limit P by an amount that
`will allow some additional useful operating time T at an
`expected power level, the transmitter can be re-activated
`after having been cut-off.
`It is assumed that the transmitter is allowed to be turned
`on in its usual way, manually or through system request and
`not automatically, by a protective circuit in accordance with
`the present invention, when the past averaging time has
`decreased below the limit P.
`An apparatus in accordance with the present invention
`may include a circuit or program for setting a threshold P.
`allowing the transmitter to be turned on when the average
`power P.
`during the past time period T (decreasing)
`passes the threshold P, and estimating this threshold level
`P. from the expected power level P. and a decided useful
`operating time T, and estimating the expected power
`level.
`This embodiment may include a device for blocking the
`transmitter from being used when the average power P.
`45
`passes the allowed limit P. When the transmitter is
`blocked the average power necessarily goes down, since no
`more energy is integrated. When P. passes the threshold
`P, the transmitter blocking is removed and the transmitter
`is allowed to be used again. The threshold Pis set to a value
`that will give some useful transmission time T, if the
`transmitter is switched on after removal of the blocking.
`When the average power P is likely to exceed a
`predetermined limit P if transmission is continued at
`expected power level P. for more than a decided suitable
`time, a warning signal may be generated.
`With reference to the phantom lines of FIG. 1, an appa
`ratus suitable for implementing the invention can include the
`average power determining circuit 11 for determining an
`average power P by which a radio transmitter has trans
`mitted during a preceding time period. The apparatus also
`includes a comparator 17 for comparing the average power
`P to an warning threshold P. The inventive apparatus
`may include warning threshold setting circuit 23 for setting
`the warning threshold P. The warning threshold P. may be
`a representation of decided level of average power P to
`give warning signal and/or to reduce transmitter power. The
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`warning threshold setting circuit 18, in one embodiment,
`predicts when the average power is likely to exceed an
`allowed maximum average power P according to the
`expected power level P. and determine a warning thresh
`old P sufficiently below the permitted maximum average
`power P output to allow an alarm to be generated within
`a predetermined time, such as a minute, prior to the trans
`mitter exceeding the permitted maximum average power
`P., based on a result of the prediction. This allows the user
`to sign-off without or at least be forewarned of an abrupt
`interruption.
`The inventive apparatus can include a warning generator
`19 for generating a warning when the comparator deter
`mines that the warning threshold P. has been exceeded. The
`warning can be audio or visual or both.
`Thus, one of the possible parameter settings is a suitable
`time prior to generating a warning signal the average power
`level P. exceeding the warning threshold P.
`Awarning signal is initiated when and if the power passes
`the warning threshold P. If transmission is continued long
`enough, the transmitter will be blocked when P is reached
`in this embodiment. The power decreases, and when P is
`passed, the transmission blocking is removed. If transmis
`sion is stopped before P is reached, the average power
`P will decrease without the transmitter being blocked.
`FIG. 5 shows a flow diagram illustrating an embodiment
`of this aspect of the present invention. This embodiment is
`similar to that shown in FIG. 4, wherein like steps are
`provided with like step reference numbers.
`As shown in FIG. 5, in a state 52 when the average power
`is below a threshold value P for generating warning and the
`transmitter is enabled, it is then determined whether the
`average power P equals or exceeds the warning threshold
`value P at step 53. If the warning threshold P is exceeded,
`then a warning is given, as shown at step 54. Step 55 shows
`a state where the average power P is between the maxi
`mum allowed power P and the warning threshold P.
`while the transmitter is free. If the average allowed power
`P is below the warning threshold P, then the program
`flows to step 56, back to step 52 through step 53 and step 54.
`However, when the average power P equals the maximum
`allowed power P, as shown at step 41, then the trans
`mitter is blocked as shown at step 42, thus resulting in the
`state 51 where the average power is between a first threshold
`Pfor re-enabling the transmitter and the maximum allowed
`power P, while the transmitter is blocked. When the
`average power drops below the transmitter re-enabling the
`threshold P., as shown at step 54, then the transmitter is
`re-enabled, as shown at step 45 and the flow proceeds to step
`52 to determine whether the average power is below or
`exceeds the warning threshold P.
`A warning signal is thus initiated when and if the average
`power P. passes the warning threshold P. If the transmis
`sion is continued long enough, the transmitter will be
`blocked when the maximum allowed power P is reached.
`When the average P. decreases, and when the re-enabling
`threshold P, is passed, the transmitter blocking is removed.
`If the transmission is stopped before the maximum allowed
`power P is reached, the average power P will decrease
`and the original state returns without the transmitter being
`blocked.
`This warning can take any suitable form such as audio or
`visual indicators, or a combination of audio and visual
`indicators. Such indicators may optionally pulse and further
`may optionally pulse at an increasing rate as the predicted
`remaining transmission time grows short. Alternatively, the
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`7
`user can be informed of the actual, predicted time remaining
`by either an LCD display or by an artificially generated
`voice.
`Another aspect of the present invention is power reduc
`tion, rather than simple power cut-off. The criteria for power
`reduction is the same as for generating a warning signal.
`With reference to FIG. 2, an apparatus in accordance with
`the present invention includes a circuit 11 for determining an
`average power P by which a radio transmitter has trans
`mitted during a preceding time period T, as in the
`embodiment of FIG. 1, and a comparator 21 for comparing
`the average power P to a first power reduction threshold
`P. This embodiment includes a first reduced power thresh
`old setting circuit 22 for setting the first power reduction
`threshold P. The first reduced power threshold setting
`circuit 22 predicts when the average power is likely to
`exceed a maximum average power P and determines a
`first power reduction threshold P sufficiently below the
`maximum average power P
`to allow for power reduction
`within a predetermined time prior to the transmitter exceed
`ing the maximum average power P, based on a result of
`the prediction.
`This embodiment includes a power control 23 for reduc
`ing the maximum power at which the transmitter can trans
`mit when the first comparator 21 determines that the first
`power reduction threshold P has been exceeded.
`This embodiment may also include a second comparator
`24 for comparing the average power P at which a radio
`transmitter has transmitted during a preceding time period
`T including a time period in which the transmitter maxi
`mum power output has been reduced, to a second predeter
`mined reduced power threshold P2, and the power control
`23 removes the reduced maximum power output restriction
`when the average power has diminished to equal or be below
`the second reduced power threshold P. The second thresh
`old P. corresponds to the first power reduction threshold
`P plus a margin sufficient to permit significant transmis
`sion time prior to re-exceeding the first threshold P. Also
`included may be a second reduced power threshold setting
`circuit 25 for setting the second threshold P.
`Thus a device implementing this aspect of the invention
`includes means for reducing power to suitable level (which
`will then be the expected level), estimating suitable level
`(which could be a fixed reduction in dB or a change of power
`level based on the level used which would be different for
`each level or range of levels).
`FIG. 6 shows an embodiment of this aspect of the
`invention. In FIG. 6, steps analogous to those shown in
`FIGS. 4 and 5 are referred to by like reference numbers.
`In the embodiment shown in FIG. 6, the transmission
`power is limited to a level which should not cause the
`average transmission power P to exceed the maximum
`permitted transmission power P. Thus, in the instance
`where the limited transmission power is insufficient for a
`clear radio communication link, the quality of the radio
`communication link may degrade or result in an interruption
`of the radio communication link when the quality drops
`below a minimum. However, some static on the communi
`cation link, for analog systems, or an increased bit error rate
`(BER) in digital systems, is deemed tolerable when offset
`against the advantages of assuring that the maximum aver
`age transmission power is not exceeded.
`The criteria for removal of the power reduction is when
`estimated average power P will not exceed limit P.
`65
`within suitable time if power returns to system setting. This
`is the same as above for resuming transmission capability in
`
`30
`
`8
`the first embodiment, but a full power range returns auto
`matically.
`Thresholds for warning P. power reduction P1, increase
`of power P and release of blocking P can be set indepen
`dently, giving slightly differing diagrams.
`Reference will now be made to FIG. 6. FIG. 6 illustrates
`the embodiment where power reduction and automatic
`removal of power reduction is introduced. It should be noted
`that the threshold for power reduction P may be equal to
`the warning threshold P., as it is illustrated in FIG. 6. Thus,
`a warning can be generated in addition to the power reduc
`tion. Similarly, the increase in power threshold P and the
`release of transmission blocking threshold P can be made
`equal. This is expedient, for instance, where both the power
`reduction function and the transmission blocking function
`are introduced into one embodiment, as will be discussed
`with reference to FIG. 3, infra. These assumptions simplify
`the illustration. However, if the parameters are made to be
`distinct, FIG. 6 would only be modified by adding appro
`priate states and activities.
`In state 61 wherein the average power P is between the
`maximum allowed power P and the first threshold P.
`while the transmitter is blocked and the power is reduced, it
`is determined whether the average power P has dropped
`to the first threshold P whereupon the transmitter is no
`longer blocked and may transmit at the increased power
`levels, as shown at step 62. As shown at step 63, in a state
`where the transmitter is free to transmit and the average
`power P is below the warning threshold P, the program
`proceeds to step 64 where it is determined whether the
`average power equals or exceeds the warning threshold P.
`and thereupon generates a warning and reduces the maxi
`mum power P at which the transmitter can transmit.
`Thereafter, at state 65 where the average power P is
`between the warning threshold P and the maximum
`allowed power P, the transmitter is not blocked but
`broadcasts at a reduced power. In this state, as shown at step
`66, if the average power drops below the first threshold P.
`the transmitter is permitted to transmit at an increased power
`level. By this step 66, the transmission is not interrupted.
`However, if the average power P equals the maximum
`allowed power P, as shown in step 41, then the trans
`mission is blocked, as shown at state 62, and the program
`flow returns to step 61.
`FIG. 3 shows another embodiment of the present inven
`tion which incorporates the features of the present invention
`including terminating transmission when a threshold corre
`sponding to the maximum average power P is reached,
`give a warning when a warning threshold is reached, and
`provide for power reduction as the maximum average power
`P is approached.
`This embodiment includes an integrator 31 which
`receives a representation of the actual transmitter powerP
`inst
`and a parameter setting representing the averaging time T,
`The integrator 31 integrates the actual transmitter output
`power P over averaging T to output the average power
`P. The average output P is input to three comparators
`32, 33 and 34. The first comparator 32 determines if the
`average power P is greater than the decided maximum
`average power P for cutting-off the transmitter. This
`maximum permitted power P is a parameter which might
`be a constant or variable obtained through other processes
`but preferably corresponds to the MPE for a given set of
`conditions. The output of the comparator 32 is input to a
`flip-flop 35 which outputs a signal to block transmission.
`The flip-flop 35 may be an R/S flip-flop, or equivalent
`
`35
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`40
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`45
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`50
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`55
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`60
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`IPR2018-01473
`Apple Inc. EX1005 Page 9
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`function in processor wherein B=1 will cut off the transmit
`ter power of the transmitter, and B=0 permits normal trans