Agile and adaptive wideband MIMO antenna isolation

The disclosed invention relates to a MIMO (multiple input, multiple output) wideband transceiver. In some cases, the MIMO wideband transceiver comprises a signal processor that outputs or receives a plurality of distinguishable data streams. A first data stream is provided to a first antenna port connected to a plurality of wideband antennas, while a second data stream is provided to a second antenna port connected to a wideband antenna. A spatial filter element configured to assign antenna weights to the plurality of wideband antennas, which cause the wideband antennas to operate in a manner that attenuates wireless signals, at a frequency range at which the wideband transmit wideband radiate, in the direction of the wideband antenna without attenuating the wireless signals in other directions. By attenuating signals extending between the plurality of wideband antennas and the wideband antenna, wideband decoupling between first and second antenna ports is achieved.

BACKGROUND

Many modern wireless communication devices (e.g., cell phones, wireless sensors, PDAs, RFID readers, etc.) utilize transceivers having both a transmitter section configured to transmit data and a receiver section configured to receive data over radio frequencies.

For example,FIG. 1illustrates a wireless communication transceiver100comprising a transmission path102and a reception path104. To achieve high data rates, transceiver100may be configured to operate in full-duplex mode, wherein both transmission path102and reception path104operate at the same time. During full-duplex mode operation, transmission path102typically uses one carrier frequency while reception path104uses another carrier frequency (e.g., an adjacent frequency band). In order to provide isolation between transmission path102and reception path104, a duplexer106may couple both transmission path102and reception path104to a common antenna108.

Despite using different frequencies, intermodulation distortion may arise during operation of transceiver100. One of the most common sources of intermodulation distortion occurs when a transmitted signal110leaks into reception path104due to limited isolation between transmission path102and reception path104. Once intermodulation distortion appears within reception path104, there is no way of distinguishing it from the desired signal and transceiver sensitivity is degraded.

DETAILED DESCRIPTION

Wireless communication devices are configured to wirelessly transmit and receive an RF signal by exciting one or more radiators (e.g., antennas) with the RF signal. To ensure that a signal is properly transmitted or received, a degree of isolation is present between the signal to be transmitted and other signals in the wireless communication system. Without such isolation, performance of the wireless communication system is degraded. For example, MIMO (multi-input multi-output) antenna arrays comprise a plurality of antennas configured to respectively convey separate data streams collectively corresponding to an overall data signal. Isolation between the plurality of antennas ensures that the separate data streams remain independent of one another. Without such isolation, one or more of the data streams may become distorted such that the overall data signal cannot be recovered by a receiver.

Accordingly, in some cases, a transceiver system is disclosed herein that utilizes a spatial filter to achieve a high degree of isolation between antennas of a MIMO antenna array. In some embodiments, the transceiver system comprises a signal processor that outputs or receives a plurality of distinguishable data streams. A first data stream is provided to a first antenna port connected to a plurality of wideband antennas, while a second data stream is provided to a second antenna port connected to a wideband antenna. A spatial filter element configured to assign antenna weights to the plurality of wideband antennas, which cause the wideband antennas to operate in a manner that attenuates wireless signals, at a frequency range at which the wideband transmit radiators radiate, in the direction of the wideband antenna without attenuating the wireless signals in other directions. By attenuating signals extending between the plurality of wideband antennas and the wideband antenna, wideband decoupling between first and second antenna ports is achieved.FIG. 2illustrates an exemplary block diagram of a transceiver system200configured to provide a high degree of transmitter-receiver isolation by attenuating transmitted and/or received signals.

The transceiver system200comprises a mobile communication device220having a reception path and a transmission path. The reception path comprises a receive antenna array202comprising one or more receive antennas202a-202nconfigured to receive a first RF signal (a received signal). The received signal is provided to a reception chain204configured to demodulate and down-convert the received signal. The down-converted, demodulated signal is provided to a digital signal processor (DSP)206. The transmission path comprises transmission chain208configured to modulate data received from the DSP206onto a carrier wave and then to up-convert the modulated data from a baseband frequency to a radio frequency (RF), thereby generating a second RF signal. The second RF signal is provided to a transmit antenna array210comprising a plurality of transmit antennas210a-210n,which are configured to wirelessly transmit the second RF signal (a transmitted signal).

A spatial filter element212is configured to operate the transmit and/or receive antennas in a manner that attenuates RF signals directed between local antennas comprised within the same mobile communication device220(i.e., signals transmitted from a transmit antenna array210and received by a receiver antenna array202). In particular, the spatial filter element212operates the transmit/receive antennas in a manner that attenuates transmitted/received RF signals over a null angle that is in the direction of the receive/transmit antennas. By attenuating RF signals directed between local antennas a high degree of isolation is achieved between the transmission path and the reception path.

For example, in some embodiments, the spatial filter element212is configured to operate the plurality transmit antennas210a-210nin a manner that attenuates transmitted signals over a null angle that is in the direction of the local receive antennas202a-202n(i.e., to attenuate signals transmitted to receive antennas comprised within the same mobile communication device220as transmit antennas210a-210n) without attenuating the transmitted signals over other angles. In other embodiments, the spatial filter element212is configured to operate the plurality of receive antennas202a-202nin a manner that attenuates received signals over a null angle that is in the direction of a local transmit antennas210a-210n(i.e., to attenuate signals received from transmit antennas comprised within the same mobile communication device220as receive antennas202a-202n) without attenuating the received signals over other angles. By attenuating transmitted signals in the direction of the receive antennas202a-202nor received signals in the direction of the transmit antennas210a-210n,a high degree of isolation is achieved between transmission and reception paths.

In some embodiments, the spatial filter element212comprises a local channel determination unit214and a beamforming element216. The local channel determination unit214is configured to determine an environment of local communication channels218extending between the transmission path and the reception path. In other words, the local channel determination unit214determines an effect of transmitted signals on a receive antenna202. In some embodiments, the local channel determination unit214may comprise a memory element configured to store data (e.g., programmed by the DSP) corresponding to a static environment of local communication channels218. In other embodiments, the local channel determination unit214may be configured to actively monitor the environment of local communication channels between the transmission path and the reception path. For example, in some embodiments, the local channel determination unit214is configured to actively measure local communication channels218within the transceiver system200(e.g., using one or more sensors). In other embodiments, the local channel determination unit214is configured to detect an amount of a transmitted signal that has leaked into the reception path.

The local channel determination unit214provides data corresponding to an environment of local communication channels218to the beamforming element216. The beamforming element216is configured to enable beamforming functionality within the transmit antenna array210and/or the receive antenna array202by applying antenna weights to the transmit and/or receive antennas. For example, the beamforming element216enables beamforming functionality for transmitted signals by weighing the transmit antennas210a-210nwith transmit antenna weights in a manner that causes the transmit antennas210a-210nto attenuate the transmitted signal in the direction of the receive antenna202.

The beamforming element216may weigh the receive antennas202a-202nwith analog complex weights to achieve a response of the received signal that has a reduced amplitude (e.g., a null) in the direction of the transmit antennas210a-210n.For example, the beamforming element216can apply analog weights to the receive antennas202a-202nby way of phase-shifters, and then combine the phase shifted signals before the received signal moves to a downstream LNA. By determining the receive antenna weights based upon the local communication channel environments, the amplitude of a received signal can be reduce over one or more null angles in the direction of local transmit antennas.

Similarly, the beamforming element216may weigh the transmit antennas210a-210nwith digital baseband complex weights (i.e., introducing transmit antenna weights in the baseband section of the transmission path) or analog complex weights (e.g., using variable vector modulators in the RF section of the transmission path) to achieve a response of the transmitted signal that has a reduced amplitude (e.g., a null) in the direction of the receive antennas202a-202n.

For example, in some embodiments, the beamforming element216weighs transmit antennas210a-210nby introducing a phase and/or amplitude shift into a transmitted signal provided to each of the transmit antennas210a-210n.Concurrently providing transmitted signals with specific phases and/or amplitudes to the plurality of transmit antennas210a-210ncauses the transmitted signals to be superimposed upon one another to constructively interfere in some locations and to destructively interfere in other locations. By determining the transmit antenna weights based upon the local communication channel environments, the interference can be set to result in a transmitted signal that is output according to a specific radiation pattern having a reduced amplitude over one or more null angles in the direction of local receive antennas.

Since the disclosed spatial filter element212is configured to provide for isolation by attenuating the transmitted/received signal in the direction of the receive antennas202a-202n/transmit antennas210a-210n,a high degree of isolation can be achieved even if the frequencies of the receive antennas202a-202nand transmit antennas210a-210noverlap one another. Therefore, in some embodiments, the receive antennas202a-202nand the transmit antennas210a-210nmay comprise wideband antennas.

In some embodiments, the beamforming element216is configured to dynamically vary the antenna weights. By dynamically varying the antenna weights (e.g., the phases and/or amplitudes of the transmitted signals) changes in the local communication channels218can be accounted for and/or the direction and/or size of a null angle can be adjusted. For example, if the phases of the RF signal transmitted from antennas210a-210nare the same, the resulting transmitted signal will have a first null angle, while if the phases of the RF signal transmitted from antennas210a-210nare different, the resulting transmitted signal may be steered to have a second null angle.

It will be appreciated that the proposed method and apparatus are not limited to providing isolation between a transmission path and reception path in an FDD mode of operation. Rather the proposed method and apparatus can provide isolation in many different situations. For example, the proposed method and apparatus can provide isolation between a transmission path that belongs to a first wireless communication standard (e.g., WiFi TX) and a reception path that belongs to another second wireless communication standard (e.g., a Bluetooth Rx) when both the transmission path and reception path are collocated in a same handset.

To enhance the readers understanding of the disclosed methods and apparatus,FIGS. 3A-5are described in regards to operating transmit antennas in a manner that attenuates a transmitted signal to form a null angle comprising one or more receive antennas. However, one of ordinary skill in the art will appreciate that the disclosed method and apparatus are not limited to such cases, but may be alternatively applied to operating receive antennas in a manner that attenuates a received signal to form a null angle comprising one or more transmit antennas.

FIG. 3Aillustrates an exemplary block diagram of a top view of a transceiver system300having a plurality of transmit antennas configured to provide a high degree of transmitter-receiver isolation by reducing an amplitude of transmitted signals in the direction of one or more receive antennas.

The transceiver system300comprises a mobile communication device312having transmit antennas302a-302band a receive antenna308. The transmit antennas302a-302bare configured to transmit first RF signals (transmitted signals304), while the receive antenna308is configured to receive second RF signals (received signals310). The transmitted signals304interfere with one another to collectively form a radiation pattern306over which the transmitted signals304are transmitted. By properly weighting the transmit antennas302a-302bwith proper transmit antenna weights (e.g., baseband complex weights or analogue complex weights) the transmitted signals304output by the transmit antennas302a-302bdestructively interfere so as to jointly zero-force the near-field over a null anglenthat is in the direction of the receive antenna308.

For example, transmitted signals304from transmit antennas302a-302bconstructively interfere with one another to form a radiation pattern306that maintains a given amplitude until a radius R1, which extends from a center point of the transmit antennas302a-302b.However, along the null anglenthe transmitted signals304destructively interfere with one another to from a radiation pattern306that maintains the given amplitude until a radius R2that is less than the radius R1.

In other words, the power of the transmitted signals304are reduced over the null anglenrelative to the power of the transmitted signals304in other directions. For example,FIG. 3Bis a graph314showing a transmitted signal amplitude as a function of angle, at a radius R1. As shown in graph314, the amplitude of the transmitted signal is reduced along the null anglenwith respect to the amplitude of the transmitted signal at other angles. Because the strength of the radiation pattern is reduced along the direction of the null anglen, a high degree of isolation between the transmit antennas and receive antennas is achieved.

While a mobile communication device312having two transmit antennas302aand302bcan be operated to achieve a single null anglen, it will be appreciated that as the number of transmit antennas present within a transceiver system increases the number of null angles that can be achieved also increases. Therefore, in some embodiments, the number of transmit antennas is greater (e.g., by at least one) than the number of receive antennas, so that the transmit antennas can generate a null angles for receive antennas located at discrete angles.

For example,FIG. 3Cillustrates an exemplary block diagram of a top view of a transceiver system316having a plurality of transmit antennas302a-302cconfigured to reduce an amplitude of transmitted signals along separate null anglesn1-n2. In particular, the transceiver system316comprises a mobile communication device318having three transmit antennas302a-302cand two receive antennas308a-308b.The three transmit antennas302a-302callow the mobile communication device318to be operated to generate a radiation pattern320having a first null anglen1extending from1to2and a second null anglen2extending from3to4. The different null anglesn1andn2reduce an amplitude of transmitted signals in the directions of two receive antennas,308aand308b,which are located at discrete angles.

FIGS.4and5A-5B illustrate a specific embodiment of a transceiver system having transmit antennas configured to attenuate transmitted signals towards a receive antennas. The transceiver system comprises an environment where there is no or limited user interaction with the wireless device, allowing for the transmit antenna weights to be constant (e.g., to be programmed by the DSP or designed once using fixed phase-shifts and fixed gains). It will be appreciated that the transceiver system in FIGS.4and5A-5B is not limited to the number of transmit and receive antennas shown.

FIG. 4illustrates a top view of a more detailed example of a transceiver system400having a transmit antenna array configured to attenuate transmitted signals towards one or more receive antennas.

The transceiver system400comprises a mobile communication device402comprising a first transmit antenna404aand a second transmit antenna404bconfigured to radially transmit an RF signal. A receive antenna406is located along an axis of symmetry408of first and second transmit antennas404aand404b.In alternative embodiments, more than one receive antenna can be located along the axis of symmetric and receive similar strong isolation levels.

A phase-shift splitter410is configured to provide a first signal to first transmit antenna404aand a second signal to second transmit antenna404b.The first and second signals are equal but antipodal versions of the same signal. For example, the first signal may be 180° phase-shifted version of the second signal. In some embodiments, the phase-shift splitter410may comprise a balun configured to receive single ended signal and to output differential signals having a 180° phase shift therebetween. In various other embodiments, the phase-shift splitter may comprise a power divider together with a 180° phase-shifter or other circuitry that provides a similar functionality. By providing transmit antennas404aand404bwith antipodal version of the same signal the local communication channels output from the transmit antennas404a,404bform a transmitted signal having a null vector along the axis of symmetry408, which corresponds to the location of the receive antenna406.

FIG. 5Aillustrates an embodiment of a disclosed transceiver system500implemented using a three port antenna array comprising PIFA antennas. Transceiver system500is a non-limiting embodiment of a disclosed transceiver system, and one of ordinary skill in the art will appreciate that the transmit and receive antennas may comprise various types of antennas. In some embodiments, the transmit and receive antennas may comprise planar inverted-F wideband antennas (PIFA) and/or multiple-input/multiple-output (MIMO) wideband antennas. In some embodiment, the transmit antennas may comprise MIMO wideband antennas and the receive antenna may comprise a wideband PIFA, for example.

Transceiver system500comprises a transmit channel TX and a receive channel RX. The transmit channel TX is connected to a first antenna port TXport—1and a third antenna port TXport—3by way of a balun502. The balun502is configured to receive a signal to be transmitted from the transmit channel TX and to generate first and second output signals, Sout1and Sout2, having a phase-shift therebetween. The first and second output signals, Sout1and Sout2, are provided to the first antenna port TXport—1and the third antenna port TXport—3, respectively. In some embodiments, the first output signal Sout1may have a 180° phase shift with respect to the second output signal Sout2. The receive channel RX is connected to a second antenna port RXport—2.

The antenna ports are connected to three PIFA antennas506a-506cby way of antenna feeds504a-504c.In particular, the first and third antenna ports TXport—1, TXport—3are connected to the first and third PIFA antennas506aand506c,while the second antenna port RXport—2is connected to the second PIFA antenna506b.The first and third PIFA antennas506aand506care configured to operate as transmit antennas, while the second PIFA antenna506bis configured to operate as a receive antenna located in a symmetric topology with respect to the two transmit antennas506aand506c.

The symmetric topology of the PIFA antennas allows for out of phase transmit signals to be provided to transmit antennas506aand506cin a manner that forms a transmitted signal having a reduced amplitude at receive antenna506b.For example, in some embodiments the first and third antenna ports, TXport1and TXport3, can be driven with a 180° out-of-phase signal by using baseband DSP weights of [0.707-0.707] to enable beamforming. In such an example, strong isolation is achieved between the transmit antennas506a,506cand the receive antenna506bdue to the deep null in the near-fields.

FIG. 5Billustrates a graph508showing a frequency response of the antenna array shown inFIG. 5A.

In particular, graph508shows signal responses for a reception path510, a transmission path512, and an isolation514between the transmission and reception paths at 1.3 GHz. The non-zero response of the reception path510and the transmission path512show that the transmission and reception paths are operating properly (i.e., receiving and radiating at 1.3 GHz), while the isolation514shows that there is isolation between them. Accordingly, the operational bandwidth of the reception paths510and transmission path512are not traded for isolation.

The results shown in graph508can be illustrated mathematically by defining a scattering matrix SAcorresponding to the transmit and receive channels (See,FIG. 5A) and a matrix SB, which represents the power division and phase shift operation.

ST=⁢SBT⁢SA⁢SB=⁢[S1100S22-S23],
wherein the zeros along the diagonals indicate an isolation between the reception path and the transmission path.

It will be appreciated that in practice integrated antennas are sensitive to external use cases where there is user interaction with the wireless device (e.g., whether a hand is positioned on the phone, the position of a hand on the phone, etc.). Such external use cases alter the impedance of the integrated antenna, thereby altering the local communication channels between transmission and reception paths. Therefore, in environments having external influences, transmit antenna weights may vary in time to account for dynamic local communication channels.

FIG. 6Aillustrates a disclosed transceiver system600configured to dynamically adapt antenna weights to account for changes in local communication channels between a reception path and a transmission path.

Transceiver system600comprises a mobile communication device602having a beamforming element604configured to apply transmit antenna weights to RF signals provided to different transmit antennas210and/or receive antenna weights to RF signals received at different receive antennas202. The beamforming element604comprises an adaptive operating unit606configured to vary the transmit antenna weights that are applied by the beamforming element604in real time. In some embodiments weighting of the antennas is performed periodically according to the coherence time of the local communication channels. For example, if there is no or limited user proximity effect, the isolation can be made once at the design stage (e.g., as in wireless sensor transceivers), but if the local communication channels are time-varying due to user interaction and other proximity effects, vary the transmit antenna weights is performed periodically.

By dynamically adjusting the antenna weights, the adaptive operating unit606can account for changes in the local communication channels (e.g., due to external use cases) or to steer the null angle of transmitted and/or received signals. For example, at a first time period a first transmit antenna210aoutputs a signal having an amplitude A1,1and a phase a1,1, and a second transmit antenna210boutputs a signal having an amplitude of A2,1and a phase2,1, resulting in a transmitted signal having a null angle φ1. At a second time period a change in external use cases causes the local communication channels to change. By adjusting the first transmit antenna210ato output a signal having an amplitude A1,2and a phase1,2and the second transmit antenna210bto output a signal having an amplitude A3,2and a phase3,2the null angle φ1can remain the same despite changes in the local communication channels.

It will be appreciated that changes to the receive antenna weights can be implemented by the beamforming element604in analog (e.g., by phase shifters), while changes to the transmit antenna weights can be implemented by the beamforming element604either digitally or in analog. In some embodiments, changes in the transmit antenna weights can be implemented in analog by using vector modulators in an RF stage of the transmit chain208. The vector modulators are configured to vary the amplitude and/or phase of the RF signal provided to transmit antennas210a-210n.In other embodiments, changes in the transmit antenna weights can be implemented in digital by using an algorithm (e.g., zero forcing algorithm, SVD algorithm) that gives an excitation of transmit antennas210a-210nthat generates a null in the direction of a receive antenna202. For example, the adaptive operating unit606may use a zero forcing algorithm to invert a measured local communication channel to achieve a null in the direction of a receive antenna202.

In yet other embodiments, changes in the transmit antenna weights can be implemented through parasitic antennas attached to tunable reactive loads. For example, in some embodiments transmit antennas210a-210nare connected to one or more parasitic elements having a reactance value associated therewith. Feed circuits are configured to feed signals having different phases to the transmit antennas210a-210n.By changing the reactance values associated with the parasitic elements, electrical lengths of the parasitic elements can be changed, causing the transmitted signal to change its direction.

In some embodiments, the adaptive operating unit606is configured to determine the transmit and/or receive antenna weights using an iterative algorithm to change transmit and/or receive antenna weights until a local channel determination unit608detects that a null is achieved towards a receive antenna202and/or a transmit antenna. For example, the adaptive operating unit606can use an algorithm that converges blindly without knowing the local communication channels by changing transmit antenna weights applied to transmit antennas and by detecting a power of the transmitted signal (via local channel determination unit608) at a receive antenna, until a minimum energy of the transmitted signal is achieved.

Alternatively, the adaptive operating unit606can receive data about local communication channels from the local channel determination unit608and determine transmit and/or receive antenna weights therefrom. For example, in some embodiments, the adaptive operating unit606is configured to adaptively change transmit antenna weights based upon the detected changes in the local communication channels (i.e., the transmitted signals between transmit and receive antennas). In some embodiments, one or more sensors610located within the mobile communication device602are configured to measure data corresponding to the local communication channels (e.g., including changes in the local communication channels due to the presence or absence of external use cases) and to provide the data to the local channel determination unit608.

In some embodiments, the transceiver system600comprises a training unit612configured to account for the dynamic changes in local communication channels by performing a local training sequence to determine transmit and/or receive antenna weights. In some embodiments, the training unit612is configured to perform a local training sequence to determine the local communication channels extending between the transmitter chain208and the receiver chain204. The local communication channels are then provided to the beamforming element604, which can invert the local communication channels to get null towards receive antenna202.

FIG. 6Billustrates a flow diagram614of an exemplary training sequence that may be implemented to account for the dynamic changes in the local communication channel.

Furthermore, the disclosed methods may be implemented as a apparatus, or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof to control a computer to implement the disclosed subject matter (e.g., the circuits shown inFIG. 2,6A, etc., are non-limiting examples of circuits that may be used to implement the disclosed methods). The term “article of manufacture” as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. Of course, those skilled in the art will recognize many modifications may be made to this configuration without departing from the scope or spirit of the claimed subject matter.

At602, the method operates to determine an estimated channel matrix h.

At604, a singular value decomposition of the estimated channel matrix h is taken. According to the singular value decomposition theorem, the singular value decomposition of the estimated channel matrix h gives ΣVH(i.e. ζ(h)=ΣVH), where V=[vsvn] and vnis the vector that lies in the null space of h.

At606, antennas are weighted with vnto attenuate signals directly between local receive and transmit antennas.

Although illustrated above in relation to narrow-band isolation between a transmission chain and a reception chain, it will be appreciated that the disclosed method of isolation is not limited to such narrow-band isolation between transmission and reception chains. For example, in some cases, the proposed isolation method and apparatus can be employed for achieving wideband decoupling within a wideband MIMO (Multiple-Input/Multiple-Output) antenna setup (e.g., instead of tunable narrow-band isolation between a transmitter and receiver). Such wideband decoupling provides isolation over a broad frequency band used by wideband radiators (i.e., antennas), so as to prevent a signal being provided to one port of a MIMO from interfering with a signal provided to another port of the MIMO.

For example,FIG. 7illustrates a MIMO wideband transceiver system700comprising a spatial filter708configured to provide wideband decoupling between antennas in a wideband MIMO antenna array704. In contrast to the narrow-band isolation between transmit and receive antennas, wideband MIMO performance can be enabled with a lower degree of port-to-port isolation. For example, instead of having isolation at a specific frequency (e.g., 50-60 dB over a 10 MHz frequency band), MIMO wideband transceiver system700is configured to have a lower average isolation over a wider band (e.g., 10-20 dB over a 20-300 MHz frequency band).

The MIMO wideband transceiver system700comprises a mobile communication device702having a signal processor706(e.g., a signal generator) that is connected to a MIMO antenna array704by way of first and second antenna ports, TRXport1and TRXport2. In some embodiments, the signal processor702is configured to output a signal-to-be-transmitted as a plurality of distinguishable data streams. In other embodiments, the signal processor702is configured to receive a plurality of distinguishable data streams corresponding to a received signal. The MIMO antenna array704comprises a plurality of wideband antennas704a, . . . ,704cwith substantially equal operating characteristics (e.g., gain, radiation pattern, etc.) over a wide range of frequencies (e.g., a frequency band over 20 MHz wide). In some cases, the plurality of wideband antennas704a,. . . ,704care configured to separately transmit the distinguishable data streams from the mobile communication device702to a remote mobile terminal (not shown). In other cases, the plurality of wideband antennas704a,. . . ,704care configured to separately receive distinguishable data streams from a remote mobile terminal (not shown).

The first antenna port TRXport1is connected to MIMO wideband antennas704aand704bby way of a spatial filter708. The spatial filter708has an input node connected to the first antenna port TRXport1and output nodes connected to wideband antennas704aand704b. The second antenna port TRXport2is connected to wideband antenna704c.During transmission, the first antenna port TRXport1is configured to convey a first data stream DS1between the signal processor706and wideband antennas704aand704b, while the second antenna port TRXport2is configured to convey a second data stream DS2between the signal processor706and wideband antenna704c. The spatial filter708is configured to operate wideband antennas704aand704bin a manner that provide isolation between the antenna ports by operating wideband antennas704aand704bto perform beamforming that attenuates the first data stream DS1in a direction of wideband antenna704c. By attenuating the first data stream DS1in the direction of wideband antenna704c,a high degree of port-to-port isolation is achieved between antenna ports of the MIMO antenna array704, thereby providing for wideband decoupling between the first and second antenna ports, TRXport1and TRXport2.

In some embodiments, the spatial filter708further comprises a beamforming element714configured to operate an adjustment network710to introduce a phase shift and/or amplitude shift into the first data stream DS1, so that the wideband antennas704aand704breceive phase and/or amplitude shifted versions of the first data stream DS1. The phase and/or amplitude shift causes wireless signals output by wideband antennas704aand704bto interfere in a manner that provides for a shallow isolation over a wide frequency band in the direction of wideband antenna704c. In some embodiments, the values of the phase shift and/or the amplitude shift are optimized so that the maximum or average leakage from TRXport1to TRXport2over an entire target band is minimized, thereby achieving wideband decoupling (instead of tunable narrow-band isolation) within the wideband MIMO setup. In various embodiments, the adjustment network710may comprise a network of phase shifters (e.g., digital or analog phase shifters) or a network of lossless components (e.g., inductors and capacitors) and/or shunt components.

In some embodiments, the spatial filter708comprises a MIMO channel determination unit712. The MIMO channel determination unit712is configured to determine data corresponding to a leakage between the antenna ports TRXport1and TRXport2. For example, in some embodiments, the MIMO channel determination unit712is configured to determine data corresponding to the leakage between antenna ports TRXport1and TRXport2by detecting an environment of communication channels716extending between antenna ports (e.g., by detecting an effect of one transmitted data stream on another transmitted data stream). The data corresponding to the leakage is provided to the beamforming element714, which is configured to optimize the phase shift and/or amplitude shift introduced by the adjustment network710to attenuate the data stream output from wideband antennas704aand704bin the direction of wideband antenna704cover a bandwidth at which the wideband antennas704aand704bradiate at (e.g., a 10-20 MHz bandwidth). In some embodiments, the MIMO channel determination unit712may be configured to actively monitor the environment of communication channels716extending between wideband antennas within the MIMO antenna array704(e.g., using one or more sensors).

The mobile communication device702may comprise an LTE-A mobile communication device. The LTE-A mobile communication device uses a wideband MIMO antenna array operate over a bandwidth of approximately 20 MHz. To provide for isolation in such a mobile communication device, the beamforming element714is operated to adjust the operating parameters of the adjustment network710to have values that provide for an isolation of 15-20 dB to be maintained over a 20 MHz bandwidth.

FIG. 8Aillustrates an embodiment of a disclosed MIMO wideband transceiver system800implemented using a MIMO antenna array comprising a plurality of PIFA antennas. The wideband transceiver system800comprises a first antenna port TRXAand a second antenna port TRXB. Although described below as transmit antenna ports (i.e., antenna ports configured to provide a signal to be transmitted to transmit antennas), one of ordinary skill in the art will appreciated that the first and second antenna ports, TRXAand TRXB, may both comprise transmit antenna ports or may both comprise receive antenna ports.

The first antenna port TRXAis connected to first and third PIFA antennas804aand804cand is configured to provide a first data stream DS1to the first and third PIFA antennas,804aand804c. An adjustment network802(e.g., a balun) is located between the first antenna port TRXAand the first and third PIFA antennas,804aand804c.The adjustment network802is configured to introduce a phase shift and/or amplitude shift into a same version of the first data stream DS1to generate first and second adjusted data streams, DS1′ and DS1″, which are respectively provided to the first and third PIFA antennas,804aand804c.The second antenna port TRXBis connected to a second PIFA antenna804band is configured to provide a second data stream DS2to the second PIFA antenna804b.

The first and third PIFA antennas804aand804coperate to transmit data stream DS1′ and DS1″, while the second PIFA antenna804bis configured to operate to transmit data stream DS2. The symmetric topology of the PIFA antennas804a-804callows for data streams DS1′ and DS1″, provided to PIFA antennas804aand804c, to form a transmitted signal having a reduced amplitude in the direction of PIFA antenna804b, thereby achieving wideband isolation between PIFA antennas804a,804cand the PIFA antenna804b.

FIG. 8Billustrates a graph806showing the frequency response of a wideband MIMO setup having a first and second antenna port shown inFIG. 8A. The graph806illustrates the attenuation of signals between the first and second antenna ports (y-axis) as a function of frequency (x-axis).

Trend line808illustrates the reflected power that a signal processor (e.g., signal generator) is attempting to deliver to a second antenna by way of the second antenna port (e.g., S-parameterS22in a transmission matrix). Trendline810is the reflected power that the signal processor (e.g., signal generator) is attempting to deliver to first and third antennas by way of the first antenna port. Trendline812is the power transferred from a first antenna port to a second antenna port (e.g., S-parameterS21in a transmission matrix) for a transceiver system configured to provide for wideband decoupling between MIMO antenna ports.

As illustrated by trendline812, the disclosed wideband decoupling between MIMO antenna ports provides for an isolation of 10-40 dB that spans a wide-spectrum band ISOWBof approximately 500 MHz, from approximately 1.0-1.5 GHz. Therefore, graph800illustrates that the disclosed wideband decoupling provides for a shallower isolation over a broader frequency band than the disclosed narrow-band isolation.

FIG. 9illustrates a more detailed example of a MIMO wideband transceiver system900comprising an adjustment network902comprising one or more circuit elements configured to introduce a phase shift or an amplitude shift into a data stream.

In some cases, the adjustment network902comprising a phase shift splitter having a splitter904configured to receive the first data stream DS1and to provide the first data stream DS1to a first path906aand to a second path906b.The first path906acomprise a first phase shifter908aconfigured to introduce a phase shift into the first data stream DS1so as to generate a first phase shifted version of the first data stream DS1′. The first phase shifted version of the first data stream DS1′ is provided to a first wideband antenna704a.The second path906bcomprise a second phase shifter908bconfigured to introduce a phase shift into the first data stream DS1so as to generate a second phase shifted version of the first data stream DS1″. The second phase shifted version of the first data stream DS1″ is provided to a second wideband antenna704b.

In other cases, the adjustment network902may comprise a plurality of lossless components (e.g., inductors and capacitors) with some possible shunt components. The lossless components are configured to introduce a phase shift and/or amplitude shift into the first data stream to generate the first and second phase shifted version of the first data stream.

The beamforming element712is configured to optimize components values (corresponding to antenna weights) of the adjustment network902to minimize leakage between antenna ports TRXport1and TRXport2. For example, in some embodiments, the beamforming element712is configured to optimize inductance/capacitance values in the adjustment network902so that the maximum (or average) leakage from the first antenna port TRXport1to the second antenna port TRXport2over a target frequency band is minimized, thereby achieving wideband decoupling (instead of tunable narrow-band isolation) within the wideband MIMO setup.

In some embodiments, the beamforming element712is configured to optimize components of the adjustment network902using an iterative algorithm to change component values until the MIMO channel determination unit710detects that a sufficient level of attenuation has been achieved between antennas704of the MIMO antenna array. For example, the beamforming element712can use an algorithm that converges blindly by changing component values (e.g., antenna weights) applied to antennas704and by detecting a power of the first data stream DS1at the second antenna port TXport2, until a minimum energy of the first data stream DS1is achieved.

FIG. 10illustrates some embodiments of a transceiver system1000comprising a wideband MIMO setup (e.g., a LTE-A system) having a mobile communication device1002. The transceiver system1000is described below in regards to a transmission functionality, however it will be appreciated that the transceiver system1000may operate to have a receiver functionality also.

The mobile communication device1002comprises a signal processor1004configured to generate data to be transmitted. The data is provided to transceiver chain1006comprising a frequency interleaver1008and a plurality of RF front ends1010aand1010b.The frequency interleaver1008is configured to separate the data to be transmitted into a plurality of separate data streams that collectively correspond to the signal-to-be-transmitted. The separate data streams are provided to separate RF front ends. For example, a first data stream DS1is provided to a first RF front end1010a,while a second data stream DS2is provided to a second RF front end1010b.

In various embodiments, the front ends1010a,1010bmay comprise one or more of a power amplifier, a filter, a digital to analog converter, etc. The first front end1010ais configured to convey the first data stream DS1between the frequency interleaver1008and a first adjustment network1012a,while the second front end1010bis configured to convey the second data stream DS2between the frequency interleaver1008and a second adjustment network1012b.

The first and second adjustment networks are configured to provide the first and second data streams to separate antenna arrays within a MIMO antenna array1014. For example, the first adjustment network1012ais configured to operate a first directional antenna array1014ato transmit the first data stream in a manner that provides for shallow wideband isolation between the first data stream and a second antenna port TXport2. Similarly, the second adjustment network1012ais configured to operate a second directional antenna array1014bto transmit the second data stream in a manner that provides for shallow wideband isolation between the second data stream and a first antenna port TXport1.

In some embodiments, a MIMO channel determination unit1016is configured to detect one or more characteristics of the first or second data stream output from the first or second MIMO antenna arrays,1014aor1014b,and to compare the detected characteristics to a data stream input into a respective adjustment network,1012aor1012b.Deviations between the output data stream and the input data stream indicate a leakage is present. In response to the leakage, the channel determination unit1016can generate a signal that adjusts operation of a beamforming element1018to decrease coupling between the first antenna port TXport1and the second antenna port TXport2.

It will be appreciated that disclosed method and apparatus of wideband decoupling (e.g., between antenna ports of a MIMO antenna array) may be implemented in transceiver systems along with the disclosed method of narrow-band isolation (e.g., between a transmit antenna and a receive antenna). For example, MIMO antenna arrays comprising three or more wideband antennas can generate a radiation pattern having a first null angle at which a wideband decoupling is provided and a second null angle at which a narrow-band isolation is provided. The first null angle has a shallow suppression in the direction of the second directional antenna array. The second null angle has a deeper suppression in the direction of the receive antenna. Therefore, the three or more antennas allow for a disclosed MIMO wideband transceiver to provide for both narrow-band isolation and wideband decoupling.

FIG. 11illustrates a flow diagram of a method1100for achieving a wideband decoupling (i.e., isolation) between ports of a MIMO wideband antenna array.

At1102, the method operates to provide a MIMO wideband transceiver having a wideband antenna array. The wideband transceiver comprises a first antenna port configured to convey a first data stream between a signal processor and a plurality of wideband antennas. A second antenna port is configured to convey a second data stream between the signal processor and a wideband antenna within the MIMO wideband antenna array. In some embodiments, a first data stream is provided to the first antenna port and a second data stream is provided to the second antenna port, wherein the first and second data streams collectively correspond to a signal-to-be transmitted by the MIMO antenna array.

At1104, the method operates to determine a leakage between the first and second antenna ports. The leakage may comprise a leakage of the first data stream into a second antenna port and/or a leakage of the second data stream into a first antenna port. In some cases, the leakage is determined by measuring a transmit communication channel environment between antenna ports of the antenna array.

At1106, the method operates the plurality of wideband transmit antennas to attenuate transmit strength of the first data stream in a direction of wideband transmit antenna without attenuating transmit strength of the first data stream in other directions. For example, in some cases (act1108) the method determines antenna weights (e.g., phase values, capacitance or inductance values that correspond to a phase value, etc.), based upon the leakage, which reduce the amplitude of the first data stream in the direction of the wideband antenna. By reducing the amplitude of the first data stream in the direction of the wideband antenna, leakage between the first antenna port and the second antenna port is reduced over a frequency band at which the MIMO wideband transceiver radiates. The method then applies the antenna weights to associated wideband antennas to enable beamforming functionality that attenuates the leakage between antenna ports (act1110).

At1112, the method may operate the plurality of wideband antennas to transmit a separate data streams.

At1114, the method operates to dynamically adjust antenna weights in response to changes in the local communication channel environment.

FIG. 12illustrates an exemplary block diagram of a transmission path1200configured to implement analog beamforming in an RF stage of the transmission path1200.

Transmission path1200comprise a transmit module1202having a signal generator1204and a first hybrid coupler1206configured to provide a single ended signal to a balanced power amplifier1208. By outputting a single ended signal, the transmit module1202is compatible with conventional power amplifiers which are configured to receive a single ended signal.

The balanced power amplifier1208utilizes a first hybrid coupler1210to split the received single ended signal into a differential signal, which is provided to first and second power amplifiers1212a,1212b.By splitting the received single ended signal into two parts, the balanced power amplifier1208operates more efficiently (e.g., at lower power). A second hybrid coupler1214receives the amplified differential signals and generates a single ended signal that is output from the balanced power amplifier1208to a variable hybrid coupler1216.

The variable hybrid coupler1216is configured to generate a first and second output signals, having a phase shift therebetween, which are provided to first and second transmit antennas1218and1218b,respectively. The phase shift between the first and second output signals enables a beamforming functionality in the signal transmitted by first and second transmit antennas1218aand1218b,which provides for a reduction in the amplitude of the transmitted signal in the direction of local receive antennas (i.e., receive antennas within a same transceiver system).

FIG. 13illustrates an exemplary block diagram of a transmission path1300configured to implement digital beamforming in a baseband stage of the transmission path1300.

Transmission path1300comprises a transmit module1302configured to provide a differential signal to a balanced power amplifier1308by way of a first and second differential branches,1306aand1306b.The transmit module1302comprises a digital signal generator1304configured to generate differential signals having a phase shift introduced into one branch relative to the other. The phase shift can be introduced in a relatively simple manner by a register shift operation, for example.

The differential signal output from the transmit module1302, containing signals to which digital weighting has been applied to achieve a transmitted signal having a null in the direction of a local receive antenna, are provided directly from the transmit module1302to separate power amplifiers1310aand1310b, and to first and second transmit antennas1312aand1312b. By using the transmit module1302to perform beamforming digitally, a transmitted signal having a null angle in the direction of local receive antennas (i.e., receive antennas within a same transceiver system) is generated without using a tunable balun/hybrid, resulting in a significant reduction in insertion loss and cost.

FIG. 14illustrates an exemplary block diagram of a transmission path1400configured to implement analog beamforming in a baseband stage of the transmission path1400.

Transmission path1400comprises a transmit module1402having a signal generator1404configured to output a differential signal to a hybrid coupler1406. Hybrid coupler1406provides a single ended signal to a balanced power amplifier1408. By outputting a single ended signal, the transmit module1402is compatible with conventional power amplifiers which are configured to receive a single ended signal.

The balanced power amplifier1408utilizes a hybrid coupler1410to split the received single ended signal into a differential signal. The differential signal is provided to a first power amplifier and a second power amplifier within the balanced power amplifier1408, and to first and second transmit antennas1414aand1414b.

In some embodiments, although analog devices are used in beamforming some elements of the transmission path may be controlled digitally. For example, in some embodiments the signal generator1404is configured to output a differential signal to which digital weighting has already been applied. Therefore, signals that are properly weighted to achieve a transmitted signal having a null in the direction of a local receive antenna are provided from the transmit module1402to first and second transmit antennas1414aand1414b.

In other embodiments, the first or second power amplifiers1412aand1412bare configured to selectively provide a variable phase shift, which can be used to phase shift the signal at one transmit antenna (e.g.,1414a) relative to the other (e.g.,1414b). By adjusting the relative phase shift of the transmitted signal between antennas it is possible to adjust the relative phase of the two versions of the transmitted signal. Moreover, it is possible to adjust the power level of each transmitted signal by use of independent power control of the two transmitted signals. By adjusting both phase and amplitude it is possible to achieve a transmitted signal having a null in the direction of a local receive antenna.

FIG. 15illustrates a flow diagram of a method for achieving a high degree of TX-RX isolation between a transceiver chain and a reception chain.

At1502the method operates a power supply to provide power to a transceiver unit having a transmission path comprising plurality of transmit antennas and a reception path comprising one or more receive antennas. In some embodiments, the number of transmit antennas is greater than the number of receive antennas.

At1504the method operates to determine a local communication channel environment. The local communication channel environment describes the communication channels between the plurality of transmit antennas and the one or more receive antennas.

At1506the method operates to determine antenna weights, based upon the local communication channel environment, which attenuate signals between the plurality of transmit antennas and the one or more receive antennas. In various embodiments, the antennas weights may comprise transmit antenna weights, which are chosen to attenuate a transmitted signal in the direction of the one or more receive antennas, or receive antenna weights, which are chosen to attenuate a received signal in the direction of the plurality of transmit antennas.

At1508the method operates to apply antenna weights to associated antennas to enable beamforming functionality that reduces the amplitude of signals between the plurality of transmit antennas and the one or more receive antennas. In some embodiments, receive antenna weights may be applied to the one or more receive antennas to reduce the amplitude of received signals over a null angle comprising the plurality of transmit antennas without reducing the amplitude of received signals over other angles. In some embodiments, transmit antenna weights may be applied to the plurality of transmit antennas to reduce the amplitude of the transmitted signal over a null angle comprising the one or more receive antennas without reducing the amplitude of the transmitted signal over other angles.

At1510the method may operates the one or more receive antennas to receive a first radio frequency (RF) signal, in some embodiments.

At1512the method may operate the plurality of transmit antennas to transmit a second RF signal, in some embodiments. In some embodiments, the method operates plurality of transmit antennas may transmit the second RF signal concurrent with operating the one receive antennas to receive a first RF signal.

At1514the method operates to dynamically adjust antenna weights in response to changes in the local communication channel environment.

FIG. 16and the following discussion provide a brief, general description of a suitable mobile communication device1600to implement embodiments of one or more of the provisions set forth herein. This mobile communication device1600is merely one possible device on which second order intermodulation noise attenuation techniques as set forth above may be implemented, and it will be appreciated that the noise attenuation techniques may also be used with other devices (e.g., individual digital chip sets, mixed-signal chip sets, and/or analog chip sets). Therefore, the mobile communication device1600ofFIG. 16is only one example of a suitable operating environment and is not intended to suggest any limitation as to the scope of use or functionality of the operating environment. Example mobile communication devices include, but are not limited to, mobile devices (such as mobile phones, Personal Digital Assistants (PDAs), media players, and the like), tablets, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, consumer electronics, mini computers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like.

FIG. 16illustrates an example of a mobile communication device1600, such as a mobile phone handset for example, configured to implement one or more embodiments provided herein. In one configuration, mobile communication device1600includes at least one processing unit1602and memory1604. Depending on the exact configuration and type of mobile communication device, memory1604may be volatile (such as RAM, for example), non-volatile (such as ROM, flash memory, etc., for example) or some combination of the two. Memory1604may be removable and/or non-removable, and may also include, but is not limited to, magnetic storage, optical storage, and the like. In some embodiments, computer readable instructions in the form of software or firmware1606to implement one or more embodiments provided herein may be stored in memory1604. Memory1604may also store other computer readable instructions to implement an operating system, an application program, and the like. Computer readable instructions may be loaded in memory1604for execution by processing unit1602, for example. Other peripherals, such as a power supply1608(e.g., battery) and a camera1610may also be present.

Processing unit1602and memory1604work in coordinated fashion along with a transmitter1612and receiver1616to wirelessly communicates with other devices by way of a wireless communication signal. To facilitate this wireless communication, a plurality of transmit antennas1614are coupled to transmitter1612, and one or more receive antennas1618are coupled to receiver1616. During wireless communication, transmitter1612and receiver1616may use frequency modulation, amplitude modulation, phase modulation, and/or combinations thereof to communicate signals to another wireless device, such as a base station for example.

To provide a high degree of isolation between transmitter1612and receiver1616, a local channel determination unit1620is configured to determine an environment of local communication channels between the transmitter1612and receiver1616. In some embodiments, the local channel determination unit1620provides data corresponding to the environment of local communication channels to a beamforming element1622configured to enable beamforming functionality within the transmit antennas1614(e.g., by weighting the transmit antennas using analog or digital weights to introduce a phase and/or amplitude shift into the transmitted signal provided to different transmit antennas) so to attenuate the transmitted RF signal in the direction of the receive antenna(s)1618. In other embodiments, the local channel determination unit1620provides data corresponding to the environment of local communication channels to a beamforming element1622configured to enable beamforming functionality within the receive antennas1618(e.g., by weighting the receive antennas using analog weights to introduce a phase and/or amplitude shift into the receives signal received at different receive antennas) so to attenuate received RF signal in the direction of the transmit antennas1614. By attenuating transmitted and/or received RF signals between the transmit antennas1614and the receive antenna(s)1618, a high degree of isolation is achieved between transmitter1612and receiver1616.

To improve a user's interaction with the mobile communication device1600, the mobile communication device1600may also include a number of interfaces that allow the mobile communication device1600to exchange information with the external environment. These interfaces may include one or more user interface(s)1624, and one or more device interface(s)1626, among others.

If present, user interface1624may include any number of user inputs1628that allow a user to input information into the mobile communication device1600, and may also include any number of user outputs1630that allow a user to receive information from the mobile communication device1600. In some mobile phone embodiments, the user inputs1628may include an audio input1632(e.g., a microphone) and/or a tactile input1634(e.g., push buttons and/or a keyboard). In some mobile phone embodiments, the user outputs1630may include an audio output1636(e.g., a speaker), a visual output1638(e.g., an LCD or LED screen), and/or tactile output1640(e.g., a vibrating buzzer), among others.

Device interface1626allows a device such as camera1610to communicate with other electronic devices. Device interface1626may include, but is not limited to, a modem, a Network Interface Card (NIC), an integrated network interface, a radio frequency transmitter/receiver, an infrared port, a USB connection, or other interfaces for connecting mobile communication device1600to other mobile communication devices. Device connection(s)1626may include a wired connection or a wireless connection. Device connection(s)1626may transmit and/or receive communication media.

FIG. 17illustrates one embodiment of a wireless network1700over which a mobile communication device (e.g., mobile communication device1600inFIG. 16) in accordance with this disclosure may communicate. The wireless network1700is divided into a number of cells (e.g.,1702a,1702b, . . . ,1702d), wherein each cell has one or more base stations (e.g.,1704a,1704b, . . . ,1704d, respectively). Each base station may be coupled to a carrier's network1706(e.g., a packet switched network, or a circuit switched network such as the public switched telephone network (PSTN)) via one or more wirelines1708.

A mobile device1710(e.g., mobile communication device1100) or other mobile device, having a transmit antenna array configured to operate as a spatial filter that generates a null in the direction of receive antenna(s), may establish communication with the base station within that cell via one or more of frequency channels used for communication in that cell. The communication between a mobile handset or other mobile device1710and a corresponding base station often proceeds in accordance with an established standard communication protocol, such as LTE, GSM, CDMA or others. When a base station establishes communication with a mobile handset or other mobile device, the base station may establish communication with another external device via the carrier's network1706, which may then route communication though the phone network.

Those skilled in the art will realize that mobile communication devices such as mobile phones may in many instances upload and download computer readable instructions from a network through the base stations. For example, a mobile handset or other mobile device1710accessible via network1706may store computer readable instructions to implement one or more embodiments provided herein. The mobile handset or other mobile device1710may access a network and download a part or all of the computer readable instructions for execution.

The term “computer readable media” as used herein includes computer storage media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions or other data. Memory (e.g.,1104inFIG. 11) is an example of computer storage media. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVDs) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which may be used to store the desired information. The term “computer readable media” may also include communication media. Communication media typically embodies computer readable instructions or other data in a “modulated data signal” such as a carrier wave or other transport component and includes any information delivery media. The term “modulated data signal” may include a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal.

Although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. Further, it will be appreciated that identifiers such as “first” and “second” do not imply any type of ordering or placement with respect to other elements; but rather “first” and “second” and other similar identifiers are just generic identifiers. In addition, it will be appreciated that the term “coupled” includes direct and indirect coupling. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components (e.g., elements and/or resources), the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the disclosure. In addition, while a particular feature of the disclosure may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. In addition, the articles “a” and “an” as used in this application and the appended claims are to be construed to mean “one or more”.

Furthermore, to the extent that the terms “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”