Reconfigurable Multi-Mode Active Antenna System

Abstract

A reconfigurable antenna system is described which combines active and passive components used to impedance match, alter the frequency response, and change the radiation pattern of an antenna. Re-use of components such as switches and tunable capacitors make the circuit topologies more space and cost effective, while reducing complexity of the control signaling required. Antenna structures with single and multiple feed and/or ground connections are described and active circuit topologies are shown for these configurations. A processor and algorithm can reside with the antenna circuitry, or the algorithm to control antenna optimization can be implemented in a processor in the host device.

Claims

1-9. (canceled)

10. An antenna system, comprising: an antenna comprising a feed point; a parasitic element positioned in proximity to the antenna; and a matching circuit coupled to the feed point, the matching circuit comprising: a tunable capacitor; and a transmission line coupled to the tunable capacitor and the parasitic element, wherein the tunable capacitor is operable to alter impedance of the matching circuit at the feed point and impedance of the parasitic element at a parasitic-ground junction on the parasitic element based at least in part on a change in capacitance of the tunable capacitor.

11. The antenna system of claim 10, wherein the tunable capacitor is operable to simultaneously alter the impedance of the matching circuit and the impedance of the parasitic element based at least in part on the change in the capacitance of the tunable capacitor.

12. The antenna system of claim 10, wherein the tunable capacitor is operable to adjust a frequency response of the antenna based at least in part on simultaneous alteration of the impedance of the matching circuit and the impedance of the parasitic element based at least in part on the change in the capacitance of the tunable capacitor.

13. The antenna system of claim 10, wherein the tunable capacitor is coupled to the matching circuit in a shunt configuration.

14. The antenna system of claim 10, further comprising: a tunable inductor positioned between the feed point and the antenna, wherein the tunable inductor is coupled to the feed point, the antenna, and the matching circuit, and wherein the matching circuit is coupled to the feed point via the tunable inductor.

15. The antenna system of claim 10, wherein a first end of the transmission line is coupled to the tunable capacitor and a second end of the transmission line is coupled to the parasitic element.

16. The antenna system of claim 10, wherein the antenna comprises at least one of a modal antenna or an isolated magnetic dipole antenna.

17. An antenna system, comprising: an antenna comprising a feed point; a parasitic element positioned in proximity to the antenna; an inductor positioned on the parasitic element; and a matching circuit coupled to the feed point, the matching circuit comprising: a tunable capacitor; and a transmission line coupled to the tunable capacitor and the inductor, the transmission line coupled to the inductor at a junction of the transmission line and the parasitic element, wherein the tunable capacitor and the inductor are operable to alter impedance of the matching circuit and impedance of the parasitic element based at least in part on a change in capacitance of the tunable capacitor.

18. The antenna system of claim 17, wherein the tunable capacitor and the inductor are operable to alter the impedance of the matching circuit at the feed point and the impedance of the parasitic element at a parasitic-ground junction on the parasitic element based at least in part on the change in the capacitance of the tunable capacitor.

19. The antenna system of claim 17, wherein the tunable capacitor and the inductor are operable to simultaneously alter the impedance of the matching circuit and the impedance of the parasitic element based at least in part on the change in the capacitance of the tunable capacitor.

20. The antenna system of claim 17, wherein the tunable capacitor and the inductor are operable to adjust a frequency response of the antenna based at least in part on simultaneous alteration of the impedance of the matching circuit and the impedance of the parasitic element based at least in part on the change in the capacitance of the tunable capacitor.

21. The antenna system of claim 17, wherein the tunable capacitor is coupled to the matching circuit in a shunt configuration.

22. The antenna system of claim 17, further comprising: a tunable inductor positioned between the feed point and the antenna, wherein the tunable inductor is coupled to the feed point, the antenna, and the matching circuit, and wherein the matching circuit is coupled to the feed point via the tunable inductor.

23. The antenna system of claim 17, wherein a first end of the transmission line is coupled to the tunable capacitor and a second end of the transmission line is coupled to the inductor at the junction of the transmission line and the parasitic element.

24. The antenna system of claim 17, wherein the antenna comprises at least one of a modal antenna or an isolated magnetic dipole antenna.

25. A method to operate an antenna system, the method comprising: adjusting a capacitance of a tunable capacitor located in a matching circuit coupled to a feed point of an antenna of the antenna system, the matching circuit comprising a transmission line coupled to the tunable capacitor and a parasitic element positioned in proximity to the antenna; and altering impedance of the matching circuit and impedance of the parasitic element based at least in part on a change in the capacitance of the tunable capacitor.

26. The method of claim 25, further comprising: adjusting a frequency response of the antenna based at least in part on alteration of the impedance of the matching circuit at the feed point and the impedance of the parasitic element at the parasitic-ground junction on the parasitic element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 illustrates a reconfigurable active antenna system utilizing a modal antenna and antenna tuning module (ATM) in accordance with an embodiment.

[0011] FIG. 2 illustrates a reconfigurable active antenna system utilizing a modal antenna and ATM in accordance with another embodiment.

[0012] FIG. 3 illustrates a reconfigurable active antenna system utilizing a modal antenna and ATM, with the algorithm resident in the ATM.

[0013] FIG. 4 illustrates a reconfigurable active antenna system comprising a modal antenna which utilizes two parasitic elements: parasitic 1 is positioned beneath the multi-band antenna and is used to alter the frequency response of the antenna; parasitic 2 is positioned in proximity to the antenna and is used to alter the radiation pattern of the antenna.

[0014] FIG. 5 illustrates a reconfigurable antenna system comprising a modal antenna which utilizes multiple parasitic elements, a plurality of which being positioned beneath the antenna structure for altering the frequency and a plurality of parasitic elements being in proximity to the antenna to alter the radiation mode.

[0015] FIG. 6 illustrates a reconfigurable antenna system comprising a modal antenna which utilizes a first parasitic element positioned beneath the antenna structure for altering the frequency, and a second parasitic element in proximity to the antenna to alter the radiation mode.

[0016] FIGS. 7(A-F) illustrate three active antenna techniques that can be implemented individually or combined to assemble a more capable antenna system, including an antenna configured for beam steering, an antenna with active elements, and an active matched antenna.

[0017] FIGS. 8(A-B) illustrate an n-port ATM wherein the feed and ground connections can be dynamically altered to optimize antenna performance.

[0018] FIGS. 9(A-C) illustrate a reconfigurable antenna topology wherein a multi-port switch is coupled to a radiator to form a planar inverted f-antenna (PIFA) or isolated magnetic dipole (IMD) element.

[0019] FIGS. 10(A-C) illustrate a reconfigurable antenna topology wherein two ground connections are configured on an antenna with a tunable capacitor coupled to ground G1.

[0020] FIG. 11 illustrates a four antenna system configured to use the same tunable capacitor to tune the antenna.

[0021] FIG. 12 illustrates a two antenna system configured to use the same tunable capacitor to tune the antenna.

[0022] FIGS. 13(A-B) illustrate a reconfigurable antenna topology wherein a multi-port switch provides the capability of connecting or disconnecting a ground connection to the antenna, resulting in a monopole or PIFA type radiators.

[0023] FIGS. 14(A-B) illustrate a reconfigurable antenna topology wherein a multi-port switch provides the capability of varying the length of a radiating element, resulting in an antenna that is optimized at several frequencies.

[0024] FIGS. 15(A-B) illustrate a reconfigurable antenna topology wherein a multi-port switch is coupled to the antenna to provide the capability of varying electrical length of the ground connection.

[0025] FIGS. 16(A-B) illustrate a reconfigurable antenna topology wherein a two-port switch is coupled to the antenna to provide the capability of selecting two feed locations.

[0026] FIGS. 17(A-C) illustrate a technique which provides dual use of a tunable capacitor.

[0027] FIGS. 18(A-C) illustrate the technique shown in FIGS. 16(A-B) with the addition of an inductor at the junction of the transmission line and the parasitic element beneath the IMD antenna.

[0028] FIG. 19 illustrates a method of dielectric loading the antenna in the region between the antenna and the parasitic elements positioned beneath the antenna.

[0029] FIG. 20 illustrates a method of dielectric loading the antenna in the region between the antenna and the parasitic elements positioned beneath the antenna.

[0030] FIG. 21 illustrates an integrated method of fabricating an active antenna wherein the module containing active and passive components is attached directly to the dielectric support structure of the antenna.

[0031] FIG.22 shows an antenna architecture including an antenna, and ST Module at a first ground connection, a second ground connection; and a tunable component for matching the feed point of the antenna.

[0032] FIG.23 shows the ST Module of FIG.22 in further detail.

[0033] FIG.24 illustrates an STT Module.

[0034] FIG.25 illustrates the STT Module in further detail.

DESCRIPTION OF EMBODIMENTS

[0035] A reconfigurable active antenna system is provided. The antenna system is adapted to incorporate one or more dynamic impedance matching, band switching, and beam steering techniques in a variable feed and ground connection geometry sufficient to provide improved communication link performance by minimizing mismatch loss at the antenna/front end module interface.

[0036] In one embodiment, a modal antenna comprises passive and active components to enable multiple functions to include open and closed loop impedance matching, band switching of the antenna structure, a null steering function where multiple radiation patterns can be generated from the single antenna, and an algorithm to control and optimize the antenna system. The active elements are assembled into an antenna tuning module (ATM). The tuning functions incorporated into the modal antenna provide for a reconfigurable antenna that can be optimized for a wide variety of devices and form factors. The number of feed and ground connections on the antenna structure can be varied by the ATM to extend the frequency bandwidth of the antenna system or improve communication link performance.

[0037] A microprocessor is integrated into the antenna module to allow for full control of the tuning functions required of the antenna system. Alternately, the microprocessor can operate in conjunction with the processors in baseband and other portions of the host wireless device.

[0038] The tuning functions designed into the module provide an antenna system that adapts to environmental changes such as head and hand effects. A Modal antenna function which results in beam steering is incorporated into the antenna to provide multiple radiation pattern states for link quality improvement. Alternatively, the beam steering function can be used to modify antenna parameters to improve isolation between pairs of antennas or to reduce SAR (Specific Absorption Rate) and/or HAC (Hearing Aid Compatibility).

[0039] The antenna module is capable of both open and closed loop operation. For example, band switching, where the frequency response of the antenna is changed to allow the antenna to operate in another band, can be implemented open loop, with no correction for environmental effects. An example of closed loop operation is when the active matching circuit in the ATM is adjusted based upon metrics related to environmental effects such as reflected power monitored in the ATM and commands sent to the active component in the matching circuit to correct for impedance mismatch of the antenna. Additionally, information from proximity sensors can be used by the algorithm to alter antenna performance to better optimize the antenna to the current use condition.

[0040] The antenna tuning module can be configured for antenna topologies that contain a single feed point and single ground point or multiple feed and ground point locations. One example of the use of multiple ground points is an antenna topology wherein one ground point on the antenna is connected directly to ground and a second ground point is connected to a switch, with the switch connecting or disconnecting the antenna to ground. One or multiple passive or tunable components can be connected to the antenna ground point and the switch, or between the antenna switch port and the ground. By activating the switch the second ground point can be varied to shift the frequency response of the antenna. Alternately, the antenna impedance can be altered by activating the switch on the second ground point to tune the antenna for the frequency of interest or the current use condition.

[0041] In another embodiment, a two feed point configuration can be implemented wherein the first feed point and second feed points are coupled to a multi-port switch. The common port of the switch is connected to the transceiver and a tunable capacitor can be implemented on the first feed point and a fixed, passive matching circuit can be implemented on the second feed point. The feed point locations on the antenna element can be selected to optimize antenna performance for specific frequency bands or groups of bands, with the passive or tunable matching circuits optimized for these frequency bands. Alternately, tunable capacitors can be implemented on both the first and second feed points, with the tunable capacitor characteristics optimized for the frequency bands serviced by each feed point.

[0042] In another embodiment, a novel technique can be implemented wherein a single tunable capacitor is configured to provide both a tunable matching circuit and a band switching function on an antenna. This can be realized by locating a tunable capacitor in a matching circuit at the feed point of an antenna. One end of a transmission line can be coupled to the tunable capacitor, with the other end of the transmission line coupled to a parasitic element positioned in proximity to the antenna to band switch the antenna. Changing the capacitance of the tunable capacitor will result in a change in impedance of the matching circuit at the antenna feed point as well as a change in impedance at the parasitic/ground junction on the parasitic coupled to the antenna element. Proper design of the matching circuit is required to synchronize the impedance requirements of the matching circuit with the impedance requirements for the band switching function. A tunable inductor can be used in place of the tunable capacitor or in conjunction with the tunable capacitor.

[0043] Now turning to the drawings, FIG. 1 illustrates a block diagram of a reconfigurable active antenna system utilizing a Modal antenna and Antenna Tuning Module (ATM). Multiple feed lines connect the ATM to the antenna structure and multiple parasitic elements are coupled to the antenna structure to alter the frequency response of the antenna. Additionally, multiple parasitic elements are positioned in proximity to the antenna to alter the radiation mode of the antenna to provide a variable radiation pattern. ATM modules are used to populate the ATM to provide a repeatable, systemic approach to activating a large number of feed and ground connections. An algorithm to control the reconfigurable active antenna system resides in the processor with control signals being supplied from the processor to the ATM.

[0044] FIG. 2 illustrates a reconfigurable active antenna system utilizing a Modal antenna and ATM (Antenna Tuning Module). An algorithm to control the active antenna system resides in the processor with control signals being supplied from the processor to the ATM.

[0045] FIG. 3 illustrates a reconfigurable active antenna system utilizing a Modal antenna and ATM, with the algorithm resident in the ATM. Input signals from the baseband processor are supplied to the ATM.

[0046] FIG. 4 illustrates a reconfigurable active antenna system comprising a Modal antenna which utilizes two parasitic elements: parasitic 1 is positioned beneath the IMD antenna and is used to alter the frequency response of the antenna; parasitic 2 is positioned in proximity to the IMD antenna and is used to alter the radiation pattern of the IMD antenna. A multi-port RF switch with various impedance loadings on the ports is connected to each parasitic element. An active component, in this case a tunable capacitor, is attached to the feed point of the IMD antenna, between the IMD antenna and the transceiver, and is used to alter the impedance match of the IMD antenna. An algorithm embedded in the processor sends control signals to the active components to adjust the tuning of the antenna.

[0047] FIG. 5 illustrates a generalized reconfigurable antenna system comprising a Modal antenna which utilizes multiple parasitic elements, positioned both beneath the antenna structure for altering the frequency and in proximity to the antenna to alter the radiation mode. ATM modules are connected to each parasitic to provide dynamic tuning of the impedance at the parasitic. Multiple feeds are integrated into the antenna design and connected to the transceiver with tunable components at the feed points to provide dynamic tuning of the antenna impedance. An algorithm embedded in the processor sends control signals to the active components to adjust the tuning of the antenna.

[0048] FIG. 6 illustrates a generalized reconfigurable antenna system comprising a Modal antenna which utilizes a first parasitic element positioned both beneath the antenna structure for altering the frequency, and a second parasitic element in proximity to the antenna to alter the radiation mode. Both first and second parasitic elements have multiple active components which are used to separate sections of the conductor forming the parasitic element. The active components are used to connect or disconnect sections of the conductor, providing a capability to increase or decrease the length of the parasitic element. The active components can be switches, tunable capacitors, tunable inductors, diodes, or other components. Multiple feeds are integrated into the antenna design and connected to the transceiver with tunable components at the feed points to provide dynamic tuning of the antenna impedance. An algorithm embedded in the processor sends control signals to the active components to adjust the tuning of the antenna.

[0049] FIGS. 7(A-F) illustrate three active antenna techniques that can be implemented individually or combined to assemble a more capable antenna system. A modal antenna is shown which provides the ability to change the radiation pattern of the Modal antenna. A band-switched antenna configuration is shown which provides the ability to dynamically tune the antenna radiator. An active matched antenna is shown wherein the impedance characteristics of the antenna can be dynamically altered.

[0050] FIGS. 8(A-B) illustrate a generalized n-port ATM where the feed and ground connections can be dynamically altered to optimize antenna performance. Control signals from algorithm drive the ATM function.

[0051] FIGS. 9(A-C) illustrate a reconfigurable antenna topology wherein a multi-port switch is coupled to a radiator to form a Pifa or IMD element. Coupling a component at G2 provides a fixed ground connection; G1 is an active ground connection that can be altered dynamically. Both G1 and G2 can be active ground connections that can tune to alter antenna performance.

[0052] FIGS. 10(A-C) illustrate a reconfigurable antenna topology wherein two ground connections are configured on an antenna with a tunable capacitor coupled to ground G1. The tuning module contains a tunable capacitor and 4 port switch.

[0053] FIG. 11 illustrates a four antenna system configured to use the same tunable capacitor to tune the antenna. A four port switch connects the antenna intended for use to the tunable capacitor and the transceiver.

[0054] FIG. 12 illustrates a two antenna system configured to use the same tunable capacitor to tune the antenna. A two port switch connects the antenna intended for use to the tunable capacitor and the transceiver.

[0055] FIGS. 13(A-B) illustrate a reconfigurable antenna topology wherein a multi-port switch provides the capability of connecting or disconnecting a ground connection to the antenna, resulting in a monopole or Pifa type radiators. Additional ports of the switch can be reactively loaded to tune the antenna to different frequency bands or impedance states. A tunable capacitor is included to provide optimization of the antenna.

[0056] FIGS. 14(A-B) illustrate a reconfigurable antenna topology wherein a multi-port switch provides the capability of varying the length of a radiating element, resulting in an antenna that is optimized at several frequencies. An example use case is a combination GPS and Bluetooth antenna, where an additional length of conductor is connected to an existing conductor to reduce the frequency of operation of an antenna for GPS functions. Additional ports of the switch can be reactively loaded to tune the antenna to different frequency bands or impedance states. A tunable capacitor is included to provide optimization of the antenna.

[0057] FIGS. 15(A-B) illustrate a reconfigurable antenna topology wherein a multi-port switch is coupled to the antenna to provide the capability of varying electrical length of the ground connection. A tunable capacitor is coupled to the antenna at the feed point to provide for dynamic tuning of the antenna.

[0058] FIGS. 16(A-B) illustrate a reconfigurable antenna topology wherein a two-port switch is coupled to the antenna to provide the capability of selecting two feed locations. A tunable capacitor is coupled to the ground connection of the antenna; a passive connection is also available to provide two options for affecting a ground connection.

[0059] FIGS. 17(A-C) illustrate a technique which provides dual use of a tunable capacitor. The tunable capacitor is attached to the matching circuit in a shunt configuration; a transmission line is connected across the ends of the tunable capacitor, with the opposing end of the transmission line connected to portions of a parasitic element positioned beneath an IMD antenna. The tunable capacitor, when connected in this fashion, will provide the capability of altering the impedance of the matching circuit connected to the feed point of the IMD antenna while simultaneously altering the impedance loading of the parasitic element, which will in turn adjust the frequency response of the IMD antenna.

[0060] FIGS. 18(A-C) illustrate the technique shown in FIGS. 16(A-B) with the addition of an inductor at the junction of the transmission line and the parasitic element beneath the IMD antenna. The addition of an inductor of the proper value provides the capability of shifting the frequency response of the IMD antenna in an opposite fashion compared to the antenna configuration shown in FIGS. 17(A-C).

[0061] FIG. 19 illustrates a method of dielectric loading the antenna in the region between the antenna and the parasitic elements positioned beneath the antenna. Implementing a solid block of dielectric also provides a method of mechanical support of both the antenna element and parasitic elements. A separate dielectric block is used to support an offset parasitic element used to alter the radiation patterns of the antenna. A single module contains all active and passive components to provide the active antenna functions of the antenna.

[0062] FIG. 20 illustrates a method of dielectric loading the antenna in the region between the antenna and the parasitic elements positioned beneath the antenna, wherein two different dielectrics are used to. Changing dielectric constant of the material in portions of the region between the antenna and the parasitic elements provides an additional parameter for optimizing the antenna performance. Implementing a solid block of dielectric wherein two or more different dielectric constants are implemented also provides a method of mechanical support of both the antenna element and parasitic elements. A separate dielectric block is used to support an offset parasitic element used to alter the radiation patterns of the antenna. A single module contains all active and passive components to provide the active antenna functions of the antenna.

[0063] FIG. 21 illustrates an integrated method of fabricating an active antenna wherein the module containing active and passive components is attached directly to the dielectric support structure of the antenna. The dielectric support for the antenna has two different dielectric materials in the region between the antenna and the parasitic elements positioned beneath the antenna. Changing dielectric constant of the material in portions of the region between the antenna and the parasitic elements provides an additional parameter for optimizing the antenna performance. Implementing a solid block of dielectric wherein two or more different dielectric constants are implemented also provides a method of mechanical support of both the antenna element and parasitic elements. A separate dielectric block is used to support an offset parasitic element used to alter the radiation patterns of the antenna. A second module, which contains active and/or passive components used with the offset parasitic element, is attached directly to the dielectric support structure of the parasitic element.

[0064] In another embodiment, an antenna is coupled to a module configured for switching and tuning the impedance of the antenna ground connection, the module can be referred to herein as an “ST Module” referring to the ability to switch and tune the antenna ground connection. FIG.22 shows an antenna architecture including an antenna, and ST Module at a first ground connection, a second ground connection; and a tunable component for matching the feed point of the antenna. The ST Module itself can be configured in accordance with a myriad of architectures as can be understood by those having skill in the art, for example two, three, four, or “N” switchable ports can be provided with each port having a distinct load. The switch selects the port of the plurality of ports for providing the desired load. A tunable component, for example a tunable capacitor, is configured in shunt to the antenna port of the switch for tuning the reactance at the module. Thus, the ST module provides a switchable and tunable antenna ground connection.

[0065] FIG.23 shows the ST Module of FIG.22 in further detail. In the illustrated embodiment, the ST Module comprises a five port switch, wherein one of the ports is configured to terminate the antenna with a 50 ohm load, effectively turning the antenna off. This load will disconnect the antenna from the transceiver.

[0066] In yet another embodiment, an antenna is coupled to a module configured for switching and tuning the antenna ground connection similar to the ST Module, and is further configured with an additional tunable component capable of servicing a variety of additional applications, such as impedance matching the antenna, or tuning an additional antenna; this module can be referred to herein as an “STT Module”. FIG.24 illustrates an example antenna architecture wherein an antenna is coupled to an STT Module in a similar fashion as described above, and a second ground or reference. In the illustrated example, the second tunable component is configured for tunable matching, though it would be recognized by those having skill in the art that this additional tunable component may be used for any purpose, including tuning the illustrated antenna, another antenna, or any other device or component which can utilize a tunable cap. The second tunable component is contained within the STT Module and configured for coupling with the antenna feed point during installation within a communication device.

[0067] Thus, FIG.24 illustrates an STT Module, similar to the ST Module, above, and further configured with a second tunable capacitor within the module to provide the capability of tuning the antenna impedance at the feed point as well as provide a switchable and tunable capacitor circuit for altering the impedance of the ground connection. This provides an additional degree of freedom compared to a typical tunable matching circuit where one or two tunable capacitors are configured to impedance match the antenna. The topology proposed here provides the ability to tune both the feed and ground connections of an antenna simultaneously. The result is an RFIC where band switching (alter impedance of the ground connection) and impedance matching (the tunable capacitor for the feed connection) are implemented.

[0068] FIG.25 illustrates the STT Module in further detail, which comprises a five port switch having four distinct ports (labeled RF ports) and a termination load (50 Ohms) for terminating connection with the transceiver; a first tunable component, for example a tunable capacitor, coupled to the switch and the antenna in shunt; and a second tunable component with an open lead for connecting to the antenna feed point, another antenna, or another device requiring a tunable reactance

[0069] Thus, in an embodiment an antenna with one or more feed connections and one or more ground connections is described. A single integrated circuit configured to provide a tunable capacitor which can be connected to the feed connection of the antenna. A multi-port switch is configured to connect to one or more of the ground connections of the antenna. A tunable capacitor is connected to one of the switch ports to provide the capability of altering the impedance of the switch port.