Wireless device reconfigurable radiation desensitivity bracket systems and methods

A wireless communications device reconfigurable radiation desensitivity bracket, and associated reconfigurable radiation desensitivity method are provided. The method includes: generating a radiated wave at a first frequency; in response to generating the radiated wave at the first frequency, creating a maximum current per units square (I/units2) through a minimal area of an electrical circuit groundplane; generating a radiated wave at a second frequency; in response to generating the radiated wave at the second frequency, maintaining the maximum I/units2 through the minimal area of the groundplane. Alternately stated, the method controls the distribution of current flow through a groundplane, responsive to radiated emissions, as the wireless device changes operating frequency or communication band. More specifically, the method maintains the maximum I/units2 through the minimal area of the groundplane by coupling the groundplane to a bracket having a selectable effective electrical length.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to wireless communication and, more particularly, to wireless communication antennas.

2. Description of the Related Art

The size of portable wireless communications devices, such as telephones, continues to shrink, even as more functionality is added. As a result, the designers must increase the performance of components or device subsystems and reduce their size, while packaging these components in inconvenient locations. One such critical component is the wireless communications antenna. This antenna may be connected to a telephone transceiver, for example, or a global positioning system (GPS) receiver.

Wireless communications devices are known to use simple cylindrical coil or whip antennas as either the primary or secondary communication antennas. Inverted-F antennas are also possible. Many conventional wireless telephones use a monopole or single-radiator design with an unbalanced signal feed. This type of design is dependent upon the wireless telephone printed circuit board groundplane or housing or both to act as the counterpoise. A single-radiator design acts to reduce the overall form factor of the antenna. However, the counterpoise is susceptible to changes in the design and location of proximate circuitry, and interaction with proximate objects when in use, e.g., placed on a metallic desk, or the manner in which the telephone is held. As a result of the susceptibility of the counterpoise, the radiation patterns and communications efficiency can be detrimentally impacted. Even if a balanced antenna is used, so that the groundplanes of proximate circuitry are not required as an antenna counterpoise, radiation pattern and radiation-susceptible circuitry issues remain.

This problem is compounded when an antenna, or a group of antennas operate in a plurality of frequency bands. State-of-the-art wireless telephones are expected to operate in a number of different communication bands. In the US, the cellular band (AMPS), at around 850 megahertz (MHz), and the PCS (Personal Communication System) band, at around 1900 MHz, are used. Other communication bands include the PCN (Personal Communication Network) and DCS at approximately 1800 MHz, the GSM system (Groupe Speciale Mobile) at approximately 900 MHz, and the JDC (Japanese Digital Cellular) at approximately 800 and 1500 MHz. Other bands of interest are GPS signals at approximately 1575 MHz, Bluetooth at approximately 2400 MHz, and wideband code division multiple access (WCDMA) at 1850 to 2200 MHz.

To dampen the effects of radiation upon proximate circuitry it is known to attach so-called bracket, or radiation-parasitic, elements to a groundplane. Typically, these “brackets” are used to evenly distribute current through the groundplane associated with a radiated wave. Alternately stated, the brackets are used to prevent any particular spot on a circuit board, housing, or keyboard from becoming too sensitive to radiation-induced current. It is difficult, if not impossible, to design a wireless device to minimize the interaction between antenna radiation and susceptible circuitry in every one of its communication bands. As a result, a conventional design must be optimized for one particular communication band, or the design must be compromised to in one or more communication bands of interest.

It would be advantageous if the radiation-induced current sensitivity of a wireless communications device groundplane could be minimized for every frequency of operation.

It would be advantageous if the radiation-induced current sensitivity of a wireless communications device groundplane could be tuned in response to changes in frequency, or in response to one particular groundplane area becoming too sensitive.

It would be advantageous if wireless communication device radiation desensitivity brackets could be made reconfigurable, to minimize the sensitivity of proximate circuitry at every frequency of radiation.

DETAILED DESCRIPTION

The present invention describes a wireless communications device with a reconfigurable radiation desensitivity bracket that can be added to the groundplane of a circuit proximate to a radiation source such as an antenna, to minimize the effects of radiation-induced current. The bracket can be selectively tuned or switched in response to changes in frequency. Alternately considered, the bracket is space-reconfigurable to selectively redistribute current flow through the groundplane associated with radiated waves.

Accordingly, a method is provided for reconfigurable radiation desensitivity in a wireless communications device. The method comprises: generating a radiated wave at a first frequency; in response to generating the radiated wave at the first frequency, creating a maximum current per units square (I/units2) through a minimal area of an electrical circuit groundplane; generating a radiated wave at a second frequency; in response to generating the radiated wave at the second frequency, maintaining the maximum I/units2through the minimal area of the groundplane. Alternately stated, the method controls the distribution of current flow through a groundplane, responsive to radiated emissions, as the wireless device changes operating frequency or communication band. The method is applicable to wireless device electrical circuitry such as a printed circuit board (PCB) with mounted components, a display, a connector, or a keypad.

More specifically, the method maintains the maximum I/units2through the minimal area of the groundplane by coupling the groundplane to a bracket having a selectable effective electrical length. The coupling mechanism may be through a transistor, p/n junction coupling through a PIN diode, selectable capacitive coupling through a varactor diode or ferroelectric capacitor, or mechanically bridging through a switch or microelectromechanical system (MEMS).

Typically, the bracket has a fixed physical length section, in addition to the selectable effective electrical length section to provide a combined effective electrical length responsive to the fixed physical length and the selectable effective electrical length. Further, the bracket may include a plurality of selectable electrical length sections, a plurality of fixed physical length sections, or a plurality of both section types. The sections may be connected to the groundplane, series connected, parallel connected, or combinations of the above-mentioned connection configurations.

FIG. 1is a schematic block diagram of the present invention wireless communications device with a reconfigurable radiation desensitivity bracket. The device100comprises a transmitter102and an antenna104connected to the transmitter102. The wireless device100includes an electrical circuit106having a groundplane108. A reconfigurable radiation desensitivity bracket108is coupled to the groundplane106. Examples of the electrical circuit represented by reference designator104include components, such as integrated circuits (ICs), transistors, resistors, capacitors, inductors, and the like, mounted on a printed circuit board (PCB). Electrical circuit104can also be a display, a connector, or a keypad. The invention is not limited to any particular type of electrical circuit. In some aspects, the groundplane106can be the wireless device housing110. Although the antenna104is typically the primary radiation source, the bracket108may also be used to control radiation-induced current from a source such as a transistor, resistor, inductor, integrated circuit, or the like (not shown).

Two primary uses of the present invention bracket are for use in a portable or base station wireless communications device, where circuitry is susceptible to radiating elements such as an antenna, transmitter, transmitter component such as a transistor, inductor, resistor, or changes in the environment around a radiating element, to list a few examples. Receiver circuitry, for example, may be susceptible to radiating elements. Another use for the bracket is in microprocessor-driven computing devices, such as a personal computer. Here, susceptible circuitry can be protected, using the present invention bracket, from a radiation source such as a power supply, high-speed ICs, or network interfaces.

One general purpose of the bracket108is to evenly distribute groundplane currents that are generated as a result of radiated emissions. For this reason, the bracket108is termed a radiation desensitivity bracket, as radiation-generated current flow through a groundplane often makes wireless device transceiver and antenna circuitry susceptible to proximate objects that interrupt and modify current flow patterns. That is, the bracket acts to distribute current flow so as make the groundplane less susceptible to proximate objects. In other aspects, the bracket can be used to intentionally direct radiation-induced current flow to particular areas of the groundplane, for example, to a shielded area of the groundplane that is not susceptible to proximate objects such as a user's hand or to a wall that may temporarily be in close proximity (within the near-field).

FIG. 2is a schematic block diagram of the bracket108ofFIG. 1. Generally, the bracket108has a selectable effective electrical length200. The electrical length200is the measurement of wavelength, or wavelength portion. The electrical length is directly proportional to frequency, and is modified by the dielectric constant of the material through which the radiated wave travels to reach the bracket108. For example, the bracket may be tuned to have either an electrical length200aor electrical length200b. As can be appreciated by those skilled in the art, the bracket, in combination with the attached groundplane, forms parasitic element that has a radiation susceptance or sensitivity that is dependent upon the frequency of radiation. That is, the interaction of a radiated wave with the groundplane/bracket combination is dependent upon the electrical length of the bracket. Every bracket108includes a selectable electrical length section204having a distal end206, a proximal end208, a control input on line210to accept control signals, and a selectable effective electrical length200responsive to the control signals on line210. The bracket is termed configurable in that it may include switch elements, tunable elements, or both. As explained in detail below, the electrical length of the bracket can be manipulated using either the switchable or tunable elements.

The selectable electrical length section (SELS)204can be a coupling element such as FET, bipolar transistor, PIN diode, ferroelectric capacitor, varactor diode, or microelectromechanical system (MEMS) switch. The electric length of the SELS204is dependent upon more than just the physical length212of the section. That is, the coupling action of the SELS204includes a reactance or imaginary impedance component that can be varied to change the electrical length. Note, a MEMS switch can be used a variable air-gap capacitor by partially closing the switch.

Returning toFIG. 1, a desensitivity control circuit111has an input on line113to accept frequency selection commands and an output on line210, connected to the selectable effective length section204. The desensitivity control circuit111supplies control signals in response to the frequency selection commands. That is, the desensitivity control circuit111tracks the frequency selection commands sent to the transceiver112on line113and provides control signals to the bracket accordingly.

In one aspect, the transmitter102is a wireless telephone transmitter, part of transceiver112that additionally includes a receiver114. As noted above, the transmitter (and receiver114), or a set of transceivers112(not shown), may operate in a number of different communications bands, such as AMPS or PCS to name just a couple of examples. Further, the transmitter102may operate in number of channels within a particular communication band. Advantageously, the bracket108can be configured for every frequency of operation.

For example, the transmitter102may selectively operate at a first frequency and a second frequency. Then, the bracket108selectable electrical length section has a first effective electrical length, selected in response to the transmitter operating at the first frequency. The first effective electrical length may operate to evenly distribute radiation-induced ground current when the transmitter102operates at the first frequency. Likewise, the bracket108SELS has a second effective electrical length, selected in response to the transmitter102operating at the second frequency. The second effective electrical length may operate to evenly distribute radiation-induced current in the groundplane when the transmitter operates at the second frequency.

FIG. 3is a schematic block diagram of a first variation of the bracket108ofFIG. 1. In this variation, the bracket108further includes a fixed electrical length section (FELS)300having a distal end302, a proximal end304, and a fixed physical length306. The combination of the selectable electrical length section204and the fixed electrical length section300provides a combined selectable effective electrical length308responsive to the control signal on line210. That is, the overall electrical length308is a combination of the physical length306of the FELS300and the electrical length200of the SELS204, which may be physical length, if enabled as a MEMS for example, or a reactance, if enabled as a varactor diode for example.

FIG. 4is a schematic block diagram of a second variation of the bracket108ofFIG. 1. The bracket108may include a plurality of selectable electrical length sections204. Although three SELS'204are shown, the invention is not limited to any particular number. As shown, the SELS'204are connected to the groundplane106.

FIG. 5is a schematic block diagram of a third variation of the bracket108ofFIG. 1. As shown, the three SELS'204are series-connected to the groundplane106. Note, although the series of SELS' is shown as open-connected (unterminated), in other aspects both ends of the bracket108may be connected to the groundplane106or other circuitry (not shown). In other shown aspects not shown, the connections between individual SELS'204in the series may be terminated in the groundplane106.

FIG. 6is a schematic block diagram of a fourth variation of the bracket108ofFIG. 1. As shown, the three SELS'204are parallel-connected to the groundplane106. In other aspects not shown, both ends of one or all the SELS'204may be terminated in the groundplane.

FIG. 7is a schematic block diagram illustrating a fifth variation of the bracket108ofFIG. 1. Here, SELS204ais connected to the groundplane106, SELS'204band204care series-connected to the groundplane106, and SELS'204dand204eare parallel-connected to the groundplane106. Note, although each configuration of SELS'204is shown as open-connected (unterminated), in other aspects both ends of each configuration may be connected to the groundplane106or other circuitry (not shown).

FIG. 8is a schematic block diagram of a sixth variation of the bracket108ofFIG. 1. In this aspect, the bracket108includes a plurality of fixed electrical length sections300. As shown, two FELS'300are series-connected through an intervening SELS204. Note, although the series of sections is shown as open-connected (unterminated), in other aspects both ends of the bracket may be connected to the groundplane106or other circuitry (not shown), or the connections between sections may be terminated in the groundplane106.

FIG. 9is a schematic block diagram illustrating a seventh variation of the bracket108ofFIG. 1. As shown, FELS300aand300bare parallel-connected to the groundplane106through separate SELS'204aand204b, respectively. Alternately, FELS'300cand300dare parallel-connected through a single SELS204c. Note, although each configuration of sections is shown as open-connected (unterminated), in other aspects both ends of each configuration may be connected to the groundplane106or other circuitry (not shown).

FIG. 10is a schematic diagram illustration some combinations of series-connected and parallel-connected FELS'300.

FIG. 11is a plan view schematic diagram illustrating a bracket design1100where a plurality of fixed electrical length sections form a matrix of adjoining conductive areas1102. For example, the adjoining conductive areas may part of a wireless device keyboard that is mounted overlying PCB groundplane106. The spaces, represented with cross-hatched lines, are the individual keypads. In this aspect, the adjoining conductive areas1102are the FELS'. The bracket1100also includes a plurality of selectable electrical length sections204that are used to couple between fixed electrical length sections1102. A variety of connection configurations are shown, but the examples are not exhaustive of every possible combination. At least one of the selectable electrical length sections204is coupled to the groundplane106. Alternately, a FELS, enabled as a screw or wire (not shown), for example, may connect the bracket1100to the groundplane106.

FIG. 12is a perspective cutaway view illustrating a bracket housing design1200. A housing1202surrounds the electrical circuit104, and functions as a bracket element. A third fixed electrical length section300cis a conductive trace (or conductive paint) formed on the housing1200, coupled to the groundplane106through a SELS204. As shown, SELS204is connected to a first FELS300a, enabled as a conductive trace of a PCB, a second FELS300b, enabled as a screw, connects FELS300ato300c. In other aspects, the FELS300bcan be a spring-loaded clip, pogo pin, or a conductive pillow (gasket). A variety of other bracket configurations are possible that make use of the housing as a bracket element, as would be understood by those skilled in the art in light of the above-mentioned examples.

FIG. 18is a plan view drawing of a wireless device display bracket design. In this aspect the electrical circuit is a liquid crystal display (LCD)1800or other type of display circuit. The bracket108includes a (at least one) selectable electrical length section204coupling between fixed electrical length sections300. A plurality of fixed electrical length sections300form perimeter regions around the LCD1800. The exact shape of the perimeter is determined by using the SELS'204to couple or connect FELS'300. The perimeter need not necessarily be closed. As shown the perimeter has an opening1804. The opening1804placement and electrical length may be tuned used a SELS204in response to changing transmission frequencies, for example. Further, the opening1804may be formed as a result of not switching a SELS204. Although the perimeter regions are shown as series-connected, parallel connections are also possible using a SELS204. Further, a SELS204or FELS300may be used to connect the bracket108to a groundplane, such as a proximate PCB groundplane106.

FIG. 13is a perspective drawing illustrating some exemplary FELS variations. The FELS300can be a conductive metal member that is soldered or tension mounted to a bracket or groundplane. The metal form can be straight1300, L-shaped1302, or O-shaped member1304. Other shapes, or combinations of shapes are possible. Some shapes are dependent upon the surrounding area available. In addition, the FELS may be a wire1306, a fastener, such as screw1308, conductive pillow (gasket)1312, or a conductive element, such as a conductive trace or paint1310formed on a PCB or housing. These are just a few examples of FELS elements. Any element capable of conducting an electrical current is potentially capable of acting as a FELS.

FIG. 14is a schematic block diagram of the present invention portable wireless telephone communications device with a reconfigurable radiation desensitivity bracket. The device1400comprises a telephone transceiver1402and an antenna1404connected to the transceiver1402. The portable device1400includes an electrical circuit1406having a groundplane1408. A reconfigurable radiation desensitivity bracket1410is coupled to the groundplane1408. As in the more generic wireless device described inFIG. 1, the portable device electrical circuit1406may be components mounted on a printed circuit board (PCB), a display, a connector, or a keypad. The details of bracket1410are essentially the same as the brackets described inFIGS. 1 through 13and18, above, and will not be repeated in the interest of brevity.

FIG. 15is a schematic block diagram of the present invention wireless communications base station with a reconfigurable radiation desensitivity bracket. The base station1500comprises a telephone transceiver1502and an antenna1504connected to the transceiver1502. In this case, two antennas marked1504are shown. The base station1500also includes an electrical circuit1506having a groundplane1508. A reconfigurable radiation desensitivity bracket1510is coupled to the groundplane1508. As in the more generic wireless device described inFIG. 1, the base station electrical circuit1506may be components mounted on a printed circuit board (PCB), a display, a connector, or a keypad. The details of bracket1510are essentially the same as the brackets described inFIGS. 1 through 13and18, above, and will not be repeated in the interest of brevity.

Functional Description

FIGS. 16A and 16Bare diagrams illustrating the present invention bracket redistributing radiation-induced current flow in a groundplane. The vertical dimension illustrates current flow (I). The current through an area (unit2) is one possible measure of current distribution, for example, A/in2. However, other measurements of current or current distribution can be used to illustrate the invention. InFIG. 16A, a relatively high current flow in shown in one particular region as a result of a source radiating at 890 MHz. In response to enabling the bracket108, the current flow is redistributed, as shown inFIG. 16B. The bracket may be considered frequency reconfigurable, as a different electrical length may be used for different radiated frequencies. Alternately, the bracket may be considered space-reconfigurable, as it can be used to redistribute current flow to different regions of the groundplane. For example, the bracket108may be tuned to redistribute current (as shown inFIG. 16A) after device is moved near a proximate object, to create the current pattern shown inFIG. 16B.

FIG. 17is a flowchart illustrating the present invention method for reconfigurable radiation desensitivity in a wireless communications device. Although the method is depicted as a sequence of numbered steps for clarity, no order should be inferred from the numbering unless explicitly stated. It should be understood that some of these steps may be skipped, performed in parallel, or performed without the requirement of maintaining a strict order of sequence. The method starts at Step1700.

Step1702generates a radiated wave at a first frequency. Alternately stated, Step1702transmits at a first frequency. Step1704in response to generating the radiated wave at the first frequency, creates a maximum current per units square (I/units2) through a minimal area of an electrical circuit groundplane. That is, current flow is induced as a result of the wave radiated in Step1702. Step1706generates a radiated wave (transmits) at a second frequency. Alternately stated, the wireless device changes the frequency of transmission between Steps1702and1706. Step1708, in response to generating the radiated wave at the second frequency, maintains the maximum I/units2through the minimal area of the groundplane. Alternately stated, with respect to a groundplane area with a predetermined (minimal) size, radiation-associated current flow is not allowed to exceed a predetermined (maximum) level.

The groundplane may be associated with an electrical circuit such as components mounted on a printed circuit board (PCB), a display, a connector, or a keypad. However, the invention is not limited to any particular type of electrical circuit or groundplane. The choice of the current-related measurement is somewhat arbitrary, and the invention can also be expressed in other units of measurement related to current, energy, or field strength

Typically, maintaining the maximum I/units2through the minimal area of the groundplane (Step1708) includes coupling the groundplane to a bracket having a selectable effective electrical length. The coupling mechanism may be transistor coupling, where the transistor acts as a switch, buffer, current amplifier, voltage amplifier, or reactance element. In other aspects, the coupling mechanism is p/n junction coupling through a PIN diode, selectable capacitive coupling through a varactor diode or ferroelectric capacitor, variable gap coupling using a MEMS, or mechanically bridging through a switch or MEMS. The same analysis applies to Step1704.

In one aspect, Step1708(or Step1704) additionally couples the groundplane to a bracket with a fixed physical length section to provide a combined effective electrical length responsive to the fixed physical length and the selectable effective electrical length. Further, the groundplane may be coupled to a bracket with a plurality of selectable electrical length sections. The plurality of selectable electrical length sections may be connected in a configuration such as groundplane connected, series-connected, parallel-connected, or combinations of the above-mentioned connection configurations. The invention is not limited to any particular connection configuration type.

In another aspect, Step1708(Step1704) couples the groundplane to a bracket with a plurality of fixed physical length sections. The plurality of fixed electrical length sections can be connected to a selectable electrical length section in a configuration such as connected to the groundplane, series-connected, parallel-connected, or combinations of the above-mentioned connection configurations.

A wireless communications device with a reconfigurable radiation desensitivity bracket, and corresponding reconfigurable radiation desensitivity method have been provided. Some examples of specific bracket shapes and schematic arrangements have been presented to clarify the invention. Likewise, some specific physical implementations and uses for the invention have been mentioned. However, the invention is not limited to just these examples. Other variations and embodiments of the invention will occur to those skilled in the art.