System and method for providing a quasi-isotropic antenna

[0002] This application is a Continuation in Part of patent application Ser. No. 09/881,611 filed Jan. 14, 2001 now U.S. Pat. No. 6,441,790.

[0003] The present invention generally relates to a system and a method for providing an antenna and, more specifically, to a system and a method for providing a quasi-isotropic antenna.

[0004] In an increasingly mobile working environment, short-range communications standards were developed to help in eliminating wires and cables between stationary devices, mobile devices and combinations thereof. Examples of short-range communications standards include, for example, IEEE 802.11 and HyperLan. Another example of a short-range communications standard is the global standard called Bluetooth. Bluetooth is a relatively short-ranged wireless technology that has found application in ranges under approximately 100 yards and has proven popular in providing personal area networks (PANs) located in homes and small offices. Unlike other conventional wireless techniques such as infrared (e.g., IrDA), Bluetooth does not require a direct line of sight for communications. In addition, Bluetooth can provide, for example, point-to-point and/or point-to-multipoint connections in piconet and scatternet configurations.

[0005] Bluetooth generally includes hardware components, software and interoperability requirements. Bluetooth hardware includes a 2.4 GHz Bluetooth radio and provides spread spectrum techniques such as frequency hopping. For example, Bluetooth may operate in a 2.4 GHz to 2.48 GHz range in which signal hops may occur among 79 frequencies at 1 MHz intervals. Furthermore, at present, Bluetooth can support voice channels, for example, of 64 kb/s and asynchronous data channels of, for example, 723.2 kb/s asymmetric or 433.9 kb/s symmetric.

[0006] In theory, Bluetooth technology can be installed in handheld wireless communications devices such as, for example, cellular phones or personal digital assistants (PDAs). For example, a Bluetooth antenna can be mounted on a handheld device in addition to the cellular antenna. However, in general, Bluetooth technology tends to interfere with the cellular transceivers including cellular antennas. Furthermore, the converse is true that cellular transceivers including cellular antennas tend to interfere with Bluetooth technology. Accordingly, neither the Bluetooth antenna nor the cellular antenna works effectively.

[0007] In another conventional device, a Bluetooth patch antenna is placed on the back of the cellular phone with additional shielding between the Bluetooth antenna and the back of the cellular phone. However, such a device performs poorly if, for example, the cellular phone is disposed on its back while lying on a table. In this position, the shielding and the table block effective communications with the Bluetooth antenna.

[0008] The consequences become exacerbated in situations in which the Bluetooth technology is used for automated communications. For example, the Bluetooth technology may be configured to transfer e-mail messages from a local wireless network in an office to a handheld device carried by the user when the user is in Bluetooth range (e.g., in the office) of the local wireless network. If the user places the handheld device in such an orientation as to effectively shield the Bluetooth antenna from the local wireless network (despite being in range of the local wireless network), then the e-mail messages will not be transferred to the handheld device, the user will be unaware of communications problems and the user will assume that he or she had no unread e-mail messages on the local wireless network.

[0009] The short-range wireless antennas in known wireless communications devices do not perform well. Specifically, the known wireless antennas have anisotropic radiation patterns. This results in failed short-range wireless communications when the wireless communication device is orientated in certain positions. There exists a need to provide a short-range wireless antenna in a wireless communications device in which the short-range wireless antenna has quasi-isotropic radiation characteristics.

[0010] Briefly, the present invention uses a microstrip, line or trace forming part of the wireless communications device's electrical circuitry to function as a short-range wireless antenna. The microstrip, line or trace is structured to transmit and receive short-range communications signals. The structure of the microstrip, line or trace includes many branches that meander in a plurality of directions to provide the antenna with quasi-isotropic radiation characteristics.

[0011] Advantages of the present invention include forming a short-range wireless antenna in a wireless communications device by using an existing microstrip, line or trace. The present invention also has an advantage in that existing shielding may provide isolation between the existing antenna and the microstrip, line or trace that has been adapted to be a short-range antenna. Therefore, a separate short-range antenna and additional shielding is not needed which results in cost reduction and space savings in an already crowded circuit board of the wireless communications device.

[0012] An additional advantage is that the meandering line shape of the microstrip, line or trace provides an antenna with quasi-isotropic radiation characteristics. Such quasi-isotropic radiation characteristics are further enhanced in configurations in which the microstrip, line or trace is disposed on the front side and the rear side of a printed circuit board of the wireless communications device, or meanders away from the board in a vertical direction. Furthermore, the microstrip, line or trace may operate as a specific absorption rate element that redirects radiation away from the back of the wireless device and the user.

[0013] These and other features and advantages of the present invention will be appreciated by reviewing the following detailed description of the present invention and the accompanying figures.

[0014] FIG. 1 is a schematic representation illustrating an exemplary embodiment of a wireless communications device according to the present invention;

[0015] FIG. 2 is a schematic representation illustrating a plurality of wireless communications devices communicating using short-range antennas according to the present invention;

[0016] FIG. 3A is a schematic representation illustrating an exemplary embodiment of a trace according to the present invention;

[0017] FIG. 3B is a schematic representation illustrating the trace shown in FIG. 3A coupled to other circuitry according to the present invention;

[0018] FIG. 3C is a physical representation illustrating a side view of the trace shown in FIG. 3B coupled to other circuitry according to the present invention;

[0019] FIG. 3D is a physical representation illustrating a top-down view of an exemplary embodiment of a trace according to the present invention;

[0020] FIG. 3E is a physical representation illustrating a side view of an exemplary embodiment of a trace according to the present invention;

[0021] FIG. 4 is a block representation illustrating a short-range wireless communications transceiver according to the present invention; and

[0022] FIG. 5 is a circuit representation of an embodiment of a tuning module according to the present invention.

[0023] FIG. 1 illustrates an exemplary embodiment of a wireless communications device 100 according to the present invention. The wireless communications device 100 may include, for example, a handheld wireless communications device, a mobile phone, a car phone, a cellular or a personal communications services (PCS) phone, a cordless phone, a laptop computer or other computing device with a wireless modem, a pager or a personal digital assistant (PDA). The wireless device 100 may be digital or analog or some combination thereof. Indeed, the present invention contemplates other forms of wireless communications devices known to one of ordinary skill in the art.

[0024] As illustrated in FIG. 1, the wireless communications device 100 includes a first antenna 110, shielding 120 and a second antenna 130. In an exemplary embodiment, the wireless communications device 100 is a cellular phone; the first antenna 110 is code division multiple access (CDMA) antenna; the second antenna 130 includes a short-range antenna (e.g., a Bluetooth antenna or other short-range communications antennas) in accordance with the present invention. The shielding 120 provides isolation between, for example, the Bluetooth antenna 130 and the CDMA antenna 110.

[0025] The first antenna 110 is in two-way wireless communications with a base station 140. The base station 140 may be part of, for example, an array of base stations 140 or cells which are part of a wireless communications network (e.g., a CDMA cellular network). The second antenna 130 may be in two-way communications with a short-range wireless communications network 150 when the wireless communications device 100 is within a range area 160 of the short-range wireless communications network 150.

[0026] In operation, a user may access the base station 140 via the first antenna 110. Thus, for example, the user may make a wireless CDMA telephone call using the first antenna 110 of the wireless communications device 100. Furthermore, if the user enters the range area 160 of the short-range wireless communications network 150, then the second antenna 130 may be used to automatically and seamlessly establish two-way communications with the short-range communications network 150.

[0027] In an exemplary embodiment, the short-range wireless communications network 150 includes or is part of an office network which may include devices or networks coupled by short-range wireless communications (e.g., using Bluetooth technology) or devices coupled by, for example, local area networks via cables. When the user enters the range area 160 (e.g., the office building), the wireless communications device 100 and the office network 150 automatically and seamlessly establish two-way communications. Thus, for example, the user may print out a hardcopy of an e-mail, that has been loaded onto the wireless communications device 100, to a printing device that is coupled to or a part of the office network 150. In another example, the user may wirelessly access the Internet via the office network 150, which itself is connected to the Internet via, for example, a cable modem. The user may use the wireless communications device 100 to call or to interact with others devices or users that are coupled to or part of the office network 150. Conversely, devices or users that are coupled to or part of the office network 150 may call or interact with the wireless communications device 100.

[0028] Furthermore, information transfers between the wireless communications device 100 and the office network 150 can be automatic and seamless. This is particularly advantageous where, in the range area 160, the device 100 and the office network 150 automatically locate and interact with each other. For example, when the wireless communications device 100 enters the range area 160 of the office network 150, the office network 150 is notified that the wireless communications device 100 is within the range area 160 and automatically transmits unread e-mails to the wireless communications device 100 via the second antenna 130. The wireless communications device 100 and the office network 150 can automatically synchronize information stored in the device 100 and the office network 150. Thus, updates made to, for example, the calendar or other databases of the user stored in the wireless communications device 100 may be transferred to the calendar or other databases of the user stored in the office network 150. In another example, files or information updated on the office network 150 can be transferred to the wireless communications device 100 to update the files or information stored in the wireless communications device 100.

[0029] FIG. 2 illustrates three wireless communications devices 100a-c, which are in wireless communications via second antennas 130a-c. Although the wireless communications devices 100a-ccan be coupled via a short range wireless network 150 (e.g., an office network) (FIG. 1), the wireless communications devices 100a-ccan be coupled directly or form a short-range wireless network themselves. In an exemplary embodiment, the first wireless communications device 100ais in direct and simultaneous two-way communications with the second wireless communications device 100band the third wireless communications device 100c. Accordingly, the second wireless communications device 100band the third wireless communications device 100care in direct two-way communications with each other, or are in two-way communications via the first wireless communications device 100a. The present invention contemplates other numbers of wireless communications devices 100 in two-way communications directly or indirectly. Furthermore, the present invention also provides that other devices or networks can be coupled to this ad hoc network 170 by coupling (e.g., wirelessly coupling) with any of the three wireless communications devices 100a-c.

[0030] FIGS. 3A and 3B are schematic representations illustrating a trace 300 disposed on a printed circuit board (PCB) 310. It will be appreciated that a microstrip or line may be substituted for the trace 300. The trace 300 may be disposed on a plurality of sides and edges of the PCB 310. Thus, for example, the trace 300 may be disposed on a front side and a back side of the PCB 310. The trace 300 is illustrated as meandering in a plurality of directions with numerous branches. Furthermore, the trace 300 is spread substantially throughout the PCB 310.

[0031] FIG. 3B shows the trace 300 connected to electrical components and electrical circuitry 320 of the wireless communications device 100 (FIGS. 1 and 2). It will be appreciated that a microstrip or line may be substituted for the trace 300. For example, the trace 300 may be a signal trace, power trace or ground line. The trace 300 may be disposed on a plurality of sides or edges of the printed circuit board 310. Thus, for example, the trace 300 may be disposed on a front side and a back side of the printed circuit board 310. The trace 300 is illustrated as meandering in a plurality of directions with numerous branches 330a-d. The branches 330a-dare electrically connected together to form the trace 300. The trace 300 may use any conducting material present on the printed circuit board 310.

[0032] The trace 300 is typically a data line or signal line that forms part of the wireless communications device's electrical circuitry. The electrical components and circuitry 320 form signal sources and signal sinks. In operation, the electrical components and circuitry 320 drive and receive signals on trace 300 via branches 330a-d. For example, the electrical components and circuitry 320 may drive a power signal on the trace 300. Alternatively, the electrical components and circuitry 320 may drive data and control signals on the trace 300.

[0033] Furthermore, the trace 300 may be a ground line electrically connecting the electrical control and circuitry 320 to a ground plane. When the trace 300 is connected to a ground plane, the trace 300 provides a common return path for electromagnetic signals forming a part of the wireless device's electrical control and circuitry 320. In this manner, the trace 300 carries signals essential to the operation of the wireless communications device 100 (FIGS. 1 and 2).

[0034] FIG. 3C is a physical depiction showing a side view of the trace 300 disposed on the printed circuit board 310. The trace 300 and electrical components and circuitry 320 are disposed on a front side 340 of the printed circuit board 310. However, trace 300 and electrical components and circuitry 320 may be disposed on a back side 350 or edges 360 of the printed circuit board 310. The electrical components and circuitry 320 are electrically connected through the trace 300. The branches 330aand 330bof the trace 300 are electrically connected together forming the trace 300.

[0035] FIG. 3D is a physical depiction showing an embodiment of the trace 400 in which one branch 430aof the trace 400 is a specific absorption rate (SAR) element. The SAR element branch 430ais disposed on the front side 440 of printed circuit board 410 and is electrically connected to the electrical components and circuitry 420 and other branches 430b-dof the trace 400. The SAR element branch 430aredirects electromagnetic signals away from the wireless communication device 110 (FIGS. 1 and 2) and away from a user. It will be appreciated that the SAR element branch 430amay lie flatly against the front surface 440 of the printed circuit board 410. The SAR element branch 430amay also extend away from the printed circuit board 410. It will also be appreciated that more than one branch 430a-dmay form an SAR element in the wireless communications device 110 (FIGS. 1 and 2). Furthermore, the SAR element branch 430amay extend to other conductive elements of the wireless communications device 10, such as the shielding 120 (FIGS. 1 and 2).

[0036] FIG. 3E illustrates another embodiment of the trace 500 in which the SAR element branch 530ais an extension of the trace 500 and extends in a vertical direction away from the printed circuit board 510. For example, the SAR element branch may be a specific absorption rate bracket. Typically, the SAR element branch 530aof the trace 500 is spaced away from other electrical components and circuitry 520 on the printed circuit board 510. The trace 500 and electrical components and circuitry 520 are disposed on a front side 540, back side 550 and edges 560 of the printed circuit board 510. The electrical components and circuitry 520 are electrically connected through the branches 530a-dof the trace 500. The vertically extending SAR element branch 530ais mounted to branch 530band electrically coupled to branches 530b-dforming the trace 500. The vertically extending SAR element branch 530amay use any conducting material present on the printed circuit board 510. The SAR element branch 530aand other branches 530b, 530cand 530dform part of the wireless communications device's 100 (FIGS. 1 and 2) electrical circuitry.

[0037] In this manner, the trace 500 operates both as an additional short-range antenna and as an SAR element. A separate short-range antenna or additional SAR element is not needed resulting in cost and space savings in the wireless communications device 100 (FIGS. 1 and 2).

[0038] FIG. 4 is a block representation of the wireless communications device 100 including a short-range radio transceiver 260 according to the present invention. The short-range radio transceiver 260 includes a radio-frequency integrated circuit (RFIC) 220, a compensation module 230 and the second antenna 130. The compensation module 230 also includes an optional matching impedance module 240 and a tuning module 250. The second antenna 130 includes a microstrip, line or trace 190. For example, the microstrip, line or trace 130 may be a power microstrip, signal trace, ground signal trace, signal line or ground line.

[0039] As illustrated, the RFIC 220 is connected to the matching impedance module 240 which, in turn, is connected to the tuning module 250. The tuning module 250 is connected to the microstrip, line or trace 190. In operation, the RFIC 220 transmits to or receives from the second antenna 130 a signal that has been tuned and possibly impedance matched by the compensation module 230.

[0040] In an exemplary embodiment, the RFIC 220 includes conventional Bluetooth technology including corresponding hardware, software and combinations thereof. The compensation module 230 includes an optional matching impedance module 240 which matches an impedance of the RFIC 220 as seen from the impedance module 240 to an impedance of the second antenna 130 as seen from the impedance module 240. The matched impedance may be a particular value having real or imaginary values. In an exemplary embodiment, the matched impedance value is the impedance of the RFIC 220 which is, for example, approximately 50 Ω, approximately 75 Ω or other impedance values.

[0041] The compensation module 230 also may include a tuning module 250. The tuning module 250 may compensate for non-linear responses of the second antenna 130. For example, the tuning module 250 may be a tuning circuit that compensates for frequency dependent impedance variations. FIG. 5 illustrates an embodiment of the tuning module 250, which includes inductors 252, 254 and capacitor 258 in a particular tuning configuration according to the present invention. Clearly, the present invention contemplates other more complex tuning arrangements and their dual equivalents and may include passive elements, active elements or some combination thereof. Such tuning arrangements, configurations and their dual equivalents would be available without undue experimentation to one of ordinary skill in the art.

[0042] In an exemplary embodiment, the present invention implements a lossy transmission line approach. The microstrip, line or trace 190 is adapted to provide an antenna that is electrically long and convoluted which tends to promote a quasi-isotropic radiation pattern. Although not well suited for cellular use due to its lossy nature, the microstrip, line or trace 190, by optimizing the loss, may act as a low gain antenna, which finds application in, for example, Bluetooth technology.

[0043] By using the microstrip, line or trace 190 as a short-range radio frequency antenna (e.g., a Bluetooth antenna), the present invention accrues a number of advantages. For example, since the microstrip, line or trace 190 meanders throughout the PCB 180 in numerous directions and may be present on a front and a back side of the PCB 180, the microstrip, line or trace 190, when used, for example, as a Bluetooth antenna, has quasi-isotropic radiation characteristics. Therefore, because of the approximately omni-directional coverage, there is an enhanced probability that no matter what position and orientation the user places the wireless communications device 100, the Bluetooth antenna will be able to have or to maintain two-way communications with, for example, the office network 150 when within the range area 160.

[0044] Furthermore, since the present invention employs the microstrip, line or trace 190 in the wireless communications device 100, no additional antenna is needed. An additional advantage of the present invention is that an existing shielding 120, which normally isolates the first antenna (e.g., the CDMA antenna) 110 from the microstrip, line or trace 190, can be employed to isolate the first antenna 110 from the second antenna 130 (e.g., the Bluetooth antenna). In an exemplary embodiment, by using the existing shielding 120 and adapting the existing microstrip, line or trace 190 as described above for use in the second antenna 130, the present invention minimizes the number of additional parts which are added to the wireless communications device 100 and, in particular, to the PCB 180.

[0045] Thus, it is seen that a system and method for wireless communications are provided. One skilled in the art will appreciate that the present invention can be practiced by other than the preferred embodiments which are presented in this description for purposes of illustration and not of limitation, and the present invention is limited only by the claims that follow. It is noted that equivalents for the particular embodiments discussed in this description may practice the present invention as well.