Efficient antenna system for a personal communication device

An antenna system is installed on a wireless device which is designed to be placed near the ear of a human user. The antenna system has a first antenna configured to transmit and receive signals. The first antenna is located at the end of a boom. The boom rotates so as to displace the first antenna away from the user's head when wireless device is in use in close proximity to the user's head. In one embodiment, the system includes a monopole whip antenna and a switching mechanism to alternatively activate the monopole whip antenna and the first antenna.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention pertains to wireless communication devices. More
 particularly, the invention relates to antenna systems used with such
 devices.
 2. Description of the Related Art
 Wireless communication devices are becoming increasingly prevalent, with
 cellular telephones being a particularly notable example. With these
 devices, radio-frequency (RF) signals are transmitted and received to
 create a communication link to the device.
 Most wireless communication devices contain one or more antennas protruding
 from a surface of the device to facilitate transmission and reception of
 the RF signals. Therefore, the upper surface of the device is usually the
 most efficient location for an antenna because this location provides the
 antenna the clearest path to and from the device. This antenna location
 also allows for some form of extendable whip antenna to be extended
 without interfering with the user's operation of the device. Numerous
 antenna systems exist which contain one or more antennas located on the
 upper surface of a wireless communication device.
 Referring now to FIGS. 1A-1C, one type of prior art wireless communication
 device 90 is illustrated. FIG. 1A illustrates a frontal elevation view of
 a wireless communication device 90. FIG. 1B illustrates a side elevation
 view of the wireless communication device. FIG. 1C illustrates a top
 elevation view of the wireless communication device 90. The device 90 may
 be, for example, a cellular telephone, or other wireless communication
 product. The device 90 shown in FIGS. 1A-1C contains both a monopole whip
 antenna 92 and a helical antenna 94. The monopole whip antenna 92 extends
 through the center of the helical antenna 94. When the monopole whip
 antenna 92 is extended, the helical antenna 94 is disengaged from the
 transceiver and the monopole whip antenna 92 is used to transmit and
 receive RF signals. When the monopole whip antenna 90 is less than fully
 extended, the helical antenna 94 is engaged with the transceiver and the
 helical antenna 94 is used to transmit and receive RF signals.
 Typically, the wireless communication device 90 exchanges wireless link
 signals with a base station. As the signals travel between the wireless
 communication device 90 and the base station, the signal energy of the RF
 signal dissipates exponentially as a function of the distance that the
 signal travels. In addition, the RF signals also dissipate when they pass
 through or reflect off of objects such as buildings, people or cars. In
 addition, when the helical antenna 94 is used, considerable signal loss
 can occur if the user's head disrupts the wireless link path between the
 wireless communication device 90 and the base station. When the monopole
 whip antenna 92 is extended, it extends up past the head of the user.
 However, the helical antenna 94, by nature of its small design, is more
 susceptible to path loss due to the user's head. For this reason,
 generally, the wireless communication device 90 performs better when the
 monopole whip antenna 92 is engaged.
 Many standard wireless devices are sold today with the antenna
 configuration shown in FIG. 1. This configuration allows the user to
 operate the device with the monopole whip antenna 92 less than fully
 extended for the convenience of the user. For example, extending the
 antenna can require additional motion from the user who may wish to answer
 a ringing phone quickly. In addition, in certain operating conditions,
 such as in a crowded area or confined automobile, it is impractical to
 fully extend the monopole whip antenna 92. In these instances, it is
 common for the user to operate the wireless communication device 90 with
 the monopole whip antenna 92 less than fully extended.
 The increase in path loss means that either the performance of the system
 is adversely impacted or that the transmitted signal power must be
 increased. Adverse changes in performance are often intolerable to system
 operation and can result in system failure. Increasing the transmitted
 signal power can result in reduced battery life, large heat dissipation
 problems and difficulty in meeting government signal level limit
 requirements. For this reasons, some systems are designed such that the
 user is unable to use of the helical antenna 94 to establish communication
 in some limited regions of the system.
 It will be appreciated that there is a need in the technology for a means
 and method that minimizes the loss resulting from signals being forced to
 pass through the user's head in these circumstances.
 SUMMARY OF THE INVENTION
 The invention is a novel and improved antenna system for wireless
 communication devices. According to the invention, a helical antenna or
 other low profile antenna is located at the end of a boom. The boom
 protrudes laterally away from the device increasing the distance between
 the user's head and the helical antenna. In one embodiment, the system
 also contains a retractable monopole whip antenna located on the top of
 the wireless communication device. In another embodiment, the boom can
 rotate 90 degrees to be located over the upper surface of the wireless
 communication device for easy storage when the device is not in use. In
 yet another embodiment, the boom telescopically extends away from the
 wireless communication device.
 This system improves the transmission efficiency of the wireless
 communication device when the whip antenna is retracted and the helical
 antenna is used to transmit RF signals or when the device only contains a
 helical antenna. Therefore, by moving the helical antenna a short distance
 away from the user's head, the system improves signal quality by
 minimizing loss near the antenna.

DETAILED DESCRIPTION OF THE INVENTION
 FIGS. 2A-2C illustrate one embodiment of the invention. FIG. 2A is a front
 elevation view of a personal wireless communication device 100 with an
 antenna system according to one embodiment of the invention. This
 embodiment comprises a monopole whip antenna 102, a helical antenna 104
 and a boom 106. The monopole whip antenna 102 extends perpendicularly from
 a top surface 108 of the wireless communication device 100. The boom 106
 is coupled to the top surface 108 of the wireless communication device 100
 and, in one embodiment, is coupled to a standard swivel mechanism 105
 which is configured to rotate the boom 106 around a pivot axis at the
 centerline of the monopole whip antenna 102. In an alternative embodiment,
 the boom 106 has a fixed position and is not configured to rotate. In yet
 another embodiment, the boom telescopically extends away from the wireless
 communication device. As shown in FIG. 2A, in one stop position, the
 rotating boom 106 extends laterally away from a front surface 110 of the
 main body of the wireless communication device 100. In one embodiment, the
 front surface 110 of the main body of the wireless communication device
 100 comprises an ear piece 112 and mouth piece 114 and is intended to be
 placed against the ear of the human user.
 FIG. 2B is a side elevation view of the wireless communication device 100
 more clearly showing the boom 106 extended laterally away from the front
 surface 110 of the device 100. In the embodiment shown, the monopole whip
 antenna 102 travels through the boom's axis of rotation. As such, the
 rotation of the boom 106 does not affect the location of the monopole whip
 antenna 102. The helical antenna 104 extends along the length of the boom
 106 and at the tip of the boom 106 comprises a helical radiating portion
 140 (shown explicitly in FIG. 4). The helical radiating portion 140
 extends in a direction that is perpendicular to the boom 106 and away from
 a top surface 108 of the wireless communication device 100. The helical
 antenna 104 is located on the boom 106 to increase the distance between
 the helical radiating portion 140 and the user's head. In alternative
 embodiments, another type of low profile antenna can be used in place of
 the helical antenna.
 FIG. 2C is a top plan view of the wireless communication device 100 showing
 the boom 106 extended laterally away from the front surface 110 of the
 device 100. From FIG. 2C, the relative location of the monopole whip
 antenna 102 and the helical antenna 104 is clearly shown. In one
 embodiment, the user of the device 100 can manually rotate the boom 106
 ninety (90) degrees counter-clockwise such that the boom 106 extends over
 the top surface 108 parallel to the front surface 110 for easy storage. In
 one embodiment, the boom 106 is also capable of rotating more than ninety
 degrees, such as 180 degrees or more. In yet another embodiment, the boom
 106 can rotate 360 degrees in either a clockwise or counter-clockwise
 direction.
 The monopole whip antenna 102 and the helical antenna 104 are mechanically
 coupled so that at any given time, only one of them is in electrical
 contact with the RF components within the wireless communication device
 100 in any position. When it is fully extended, only the monopole whip
 antenna 102 is in electrical contact with the RF components within the
 wireless communication device 100. When the monopole whip antenna 102 is
 less than fully extended, it is electrically disconnected from the RF
 components within the wireless communication device 100 and the helical
 antenna 104 is in electrical contact with the RF components within the
 wireless communication device 100. The rotation of the boom 106 does not
 affect connection of either the monopole whip antenna 102 or the helical
 antenna 104 to the RF components within the wireless communication device
 100. The preferred position of the boom 106 during operation is the
 extended configuration shown in FIGS. 2A-2C, although the device 100 can
 be configured to operate in any boom position. Alternatively, the device
 100 can be disabled when the monopole whip antenna 102 is less than fully
 extended and the boom 106 is in the storage position. The details of the
 switching mechanism used in this embodiment are described in more detail
 with reference to FIG. 4.
 The present invention solves the need in the industry for an antenna system
 that minimizes the loss resulting from signals being forced to pass
 through the user's head. This problem is solved by placement the helical
 antenna 104 on the boom 106 that laterally protrudes away from the
 wireless communication device 100, thereby increasing the distance between
 the user's head and the helical antenna 104 and reducing the loss
 experienced by the signal. In addition, in one embodiment, the ability to
 move the location of the helical antenna 104 by rotation of the boom more
 than 90 degrees also allows the user to position the helical antenna 104
 to adjust for current operating conditions.
 FIGS. 3A-3C illustrate another embodiment of the invention that does not
 include a monopole whip antenna. In this embodiment, when a user activates
 a wireless communication device 200, the helical antenna 104 is utilized
 for all transmissions.
 In FIGS. 3A-3C, a boom 112 is shown to have the same general configuration
 as the boom 106 in FIGS. 2A-2C except that its length has been increased
 so as to increase the distance between the user's head and the helical
 radiating portion 140 of the helical antenna 104, and no provision has
 been made for the inclusion of a monopole whip antenna. As distance
 between the user's head and the helical radiating portion 140 of the
 helical antenna 104 is increased, the path loss attributable to the user's
 head decreases on average. Thus, increasing length of the boom 112
 increases the performance of the wireless communication device 100. In one
 embodiment, the length of the boom 112 is limited by the length of the top
 surface 108 of the wireless communication device 100 so that the boom 112
 does not extend past the edge of the top surface 108 of the device 200
 when the boom 112 is in the storage position.
 FIG. 4 illustrates a cross-sectional view taken along line 4--4 of FIG. 2C
 showing more clearly a switching mechanism 120 which controls the antenna
 coupling. The monopole whip antenna 102 is shown to comprise a radiating
 portion 122, a shaft portion 126 and a stopper 124. The radiating portion
 122 has an elongated rod shape and is typically encapsulated in a
 mechanically protective polymer material. The encapsulating material also
 acts to conductively isolate the radiating portion 122 from the shaft
 portion 126 when the monopole whip antenna 102 is less than fully
 extended. In one embodiment, the radiating portion 122 comprises a helical
 or other configuration which functions to minimize its physical length
 while retaining suitable radiating properties. The shaft portion 126
 defines a channel which extends longitudinally through the interior of the
 shaft portion 126 and through which the radiating portion 122 is slidably
 mounted. The length of the shaft portion 126 is less than the length of
 the monopole whip antenna 102. Accordingly, a storage channel (not shown)
 extends downward past the end of the shaft portion 126 within the device
 housing. Thus, when the monopole whip antenna 102 is disposed in the fully
 retracted position, its lower portion lie within at least a portion of the
 storage channel.
 The stopper 124 is located at the lower end of the radiating portion 122
 and is electrically coupled thereto. The stopper 124 is formed from
 conductive fingered material. A distended portion 128 of the stopper 124
 has a slightly larger diameter than the radiating portion 122. When the
 monopole whip antenna 102 is fully extended, the distended portion 128 of
 the stopper 124 becomes electrically coupled to an antenna connector 130
 via a contact protrusion 132 on the interior surface of the top portion of
 the shaft 126. For example, in one embodiment, the shaft portion 126 is
 constructed of conductive material. The interior diameter of the contact
 protrusion 132 is slightly smaller than the exterior diameter of the
 distended portion 128. The fingered material of the stopper 124 compresses
 inward when disposed within the shaft portion 126. When the monopole whip
 antenna 102 is fully extended, the distended portion 128 is seated within
 the contact protrusion 132 so as to mechanically secure the monopole whip
 antenna 102 in place and so as to provide a reliable electrical connection
 between the shaft portion 126 and the monopole whip antenna 102.
 FIG. 5 is a bottom plan view of the stopper 124 showing the fingered nature
 of its construction. From this view, a set of fingers 134 are apparent. In
 one embodiment, the set of fingers 134 is constructed of beryllium copper
 or other conductive material capable of flexing without breaking. Each
 finger of the set of fingers 134 is connected to a common mounting area
 (not shown) at the top of the stopper 124. The fingers 134 extend downward
 from the mounting area parallel to one another longitudinally along the
 length of the stopper 124 defining gaps 138 between the fingers 134. Each
 of the set of fingers 134 is spring-like and thus, can move inward toward
 one another in response to an application of force. When the stopper 124
 is disposed within the shaft portion 126, the set of fingers 134 deforms
 and moves inward toward one another decreasing the side of the gaps 138
 due to the pressure exerted on the distended portion 128. When the
 distended portion 128 is fully seated in the contact protrusion 132, the
 set of fingers 134 remains under inward pressure from the contact
 protrusion 132 and deforms inward causing a reliable mechanical and
 electrical connection between the contact protrusion 132 and the distended
 portion 128.
 Referring again to FIG. 4, in one embodiment, the antenna connector 130
 includes a threaded portion on the outside surface of the shaft 126. When
 installed in device 100, the antenna connector 130 is threadably coupled
 to the top surface 108 of the wireless communication device 100. When
 installed, the antenna connector 130 is also electrically coupled to the
 RF components within the wireless communication device 100 and, thereby,
 provides the coupling between the switching mechanism 120 and the RF
 components. For example, in one embodiment, the antenna connector 130 is
 coupled to a threaded conductive receptacle when installed on the wireless
 communication device 100 and the threaded conductive receptacle is coupled
 to the RF components within the wireless communication device 100.
 In general, the helical antenna 104 is made up of the helical radiating
 portion 140 having a spiral or helical shape and a boom conductor 142
 which, in one embodiment, is also configured to radiate and receive signal
 energy. In one embodiment, the radiating portion 140 is encapsulated in a
 mechanically protective polymer material. The conductive radiating portion
 140 may comprise another configuration which functions to reduce its
 physical length while retaining suitable radiating properties such as a
 meandering line antenna, a ceramic or dielectrically loaded antenna or a
 patch antenna.
 The switching mechanism 120 (FIG. 4) is used to activate either the
 monopole whip antenna 102 or the helical antenna 104. The monopole whip
 antenna 102 is activated in "whip mode" when the monopole whip antenna 102
 is fully extended as shown in FIG. 4. In "whip mode", the stopper 124
 physically displaces a dielectric plate 146 away from the monopole whip
 antenna 102. In the illustrated embodiment, the dielectric plate 146 is
 slidably disposed between the boom 106 and a conductive portion 150. The
 conductive portion 150 is disposed on an opposite side of the dielectric
 plate 146 from the boom 106 and is slidably coupled with the dielectric
 plate 146. The conductive portion 150 is electrically coupled to the shaft
 portion 126 and the antenna connector 130. The conductive portion 150 is
 mechanically coupled at one end to the boom 106 such that it remains in
 the same relative position with respect to the boom 106 as the boom 106
 rotates. For example, in one embodiment, the conductive portion 150 is
 mechanically coupled to the boom 106 by a protective casing that encases
 the boom 106 and the conductive portion 150. The conductive portion 150 is
 slidably coupled to the shaft portion 126 such that the conductive portion
 150 is free to rotate with the boom 106. In another embodiment, the
 dielectric plate 146 may be comprised of a material other than a
 dielectric.
 When displaced by the stopper 124, the dielectric plate 146 presses upon a
 boom contact 144. In one embodiment, the boom contact 144 is a straight
 spring mechanically coupled to the boom 106 and electrically coupled to
 the boom conductor 142. The boom contact 144 is biased toward the shaft
 portion 126 against the dielectric plate 146. The boom contact 144 bends
 under the pressure of the displaced dielectric plate 146 and physically
 and electrically separates from an antenna connector contact 148. In one
 embodiment, the antenna connector contact 148 is a simple conductive pad
 disposed at the distal end of the conductive portion 150 so as to couple
 with the boom contact 144 when the dielectric plate 146 is not displaced
 by the stopper 124. When the dielectric plate 146 is displaced, a physical
 separation electrically disconnects the helical antenna 104 from
 electrical coupling with the antenna connector 130 via the conductive
 portion 150 and, hence, disconnects the helical antenna 104 from
 electrically coupling with the RF components within the wireless
 communication device 100. Therefore, in "whip mode" the monopole whip
 antenna 102 is activated and the helical antenna 104 is dormant.
 When the monopole whip antenna 102 is less than fully extended, the stopper
 124 does not displace the dielectric plate 146 nor make electrical contact
 with the contact protrusion 132. The biased boom contact 144 presses
 against the dielectric plate 146 and the dielectric plate 146 slides
 toward the shaft portion 126 into its natural position. In this
 embodiment, the boom contact 144 contacts the antenna connector contact
 148. In this "helical mode", the helical antenna 104 is activated.
 Like most common antenna designs, the configuration of FIG. 4 is not
 properly activated in either whip mode or helical mode when the stopper
 124 is partially disposed within the shaft portion 126 but is not fully
 seated in the contact protrusion 132. Common operating instructions
 caution the user from operating the device with the monopole whip antenna
 in the less than the fully extended or less than fully retracted states.
 FIG. 6 is a cross-sectional view of an alternative embodiment of the
 invention, taken along line 6--6 of FIG. 3C. The embodiment of FIG. 6 does
 not contain a monopole whip antenna. The embodiment of FIG. 6 comprises
 the helical antenna 104 and an electrical connection mechanism 160. The
 helical antenna 104 is located on the boom 112. The electrical connection
 mechanism 160 comprises the conductor 142 and the antenna connector 130.
 This embodiment does not contain a switching device because there is only
 one antenna and, therefore, no need to switch between multiple antennas.
 In one embodiment, the helical antenna 104 is always coupled to the
 antenna connector 130.
 The invention improves the transmission efficiency of the personal wireless
 communication device when the low profile antenna is used to transmit RF
 signals. By moving the low profile antenna away from the user's head, the
 system improves system operation by minimizing the average path loss due
 to the user's head.
 One common design used for personal communications is the "clam shell"
 design. In a clam shell device, the housing is constructed of two portions
 coupled together by a hinge. In the closed position, the two portions fold
 together such that an inner surface of both portions is placed in close
 proximity to one another and the profile of the device is reduced. In the
 open position, the inner surfaces of the two portions rotate apart from
 one another. Typically, the ear piece in a clam shell device is located on
 the upper inner surface of device. In such design, a whip antenna can be
 attached to the hinge area of the device such as shown in U.S. Pat. No.
 5,905,966 entitled PORTABLE RADIO APATUS CAPABLE OF KEEPING THE ANTENNA
 WAY FROM USER WHEN CALLING. According to the present invention, a boom and
 low profile antenna as described above can be connected to the hinge area
 of the device.
 Many alternate embodiments of the invention will be readily apparent to one
 of skill in the art. For example, other switching mechanism differing from
 the one shown may be incorporated into the invention.
 The invention may be embodied in other specific forms without departing
 from its spirit or essential characteristics. The described embodiments
 are to be considered in all respects only as illustrative and not
 restrictive and the scope of the invention is, therefore, indicated by the
 appended claims rather than by the foregoing description. All changes
 which come within the meaning of equivalency of the claims are to be
 embraced within their scope.