Tunable diplexer for carrier aggregation applications

A tunable diplexer includes a high pass filter, a low pass filter, a high band port, a low band port, and an antenna port. The high pass filter is adapted to pass high band signals falling within a high pass band between the high band port and the antenna port, while attenuating signals outside of the high pass band. The low pass filter is adapted to pass low band signals falling within a low pass band between the low band port and the antenna port, while attenuating signals outside of the low pass band. The low pass filter includes a low stop band zero, which is adapted to attenuate signals within a low stop band. The low stop band zero is tunable, such that the low stop band can be adjusted to selectively attenuate signals within a given frequency band in the low pass band.

FIELD OF THE DISCLOSURE

The present disclosure relates to diplexer filters for use in a mobile device. Specifically, the present disclosure relates to diplexer filters that are tunable to allow the pass and stop bands of the diplexer to be changed.

BACKGROUND

Modern mobile telecommunications standards continue to demand increasingly greater rates of data exchange (data rates). One way to achieve a high data rate in a mobile device is through the use of carrier aggregation. Carrier aggregation allows a single mobile device to aggregate bandwidth across one or more operating bands in the wireless spectrum. The increased bandwidth achieved as a result of carrier aggregation allows a mobile device to obtain higher data rates than have previously been available.

FIG. 1shows a table describing a number of wireless communications bands in the wireless spectrum. One or more of the wireless communications bands may be used, for example, in a CDMA, GSM, LTE, or LTE-advanced equipped mobile device. The first column indicates the operating band number for each one of the operating bands. The second and third columns indicate the uplink and downlink frequency bands for each one of the operating bands, respectively. Finally, the fourth column indicates the duplex mode for each one of the operating bands. In non-carrier aggregation configurations, a mobile device will generally communicate using a single portion of the uplink or downlink frequency bands within a single operating band. In carrier aggregation applications, however, a mobile device may aggregate bandwidth across a single operating band or multiple operating bands in order to increase the data rate of the device.

FIG. 2Ashows a diagram representing a conventional, non-carrier aggregation configuration for a mobile device. In the conventional configuration, a mobile device communicates using a single portion of the wireless spectrum10within a single operating band12. Under the conventional approach, the data rate of the mobile device is constrained by the limited available bandwidth.

FIGS. 2B-2Dshow diagrams representing a variety of carrier aggregation configurations for a mobile device.FIG. 2Bshows an example of contiguous, intra-band carrier aggregation, in which the aggregated portions of the wireless spectrum14A and14B are located directly adjacent to one another and are in the same operating band16.FIG. 2Cshows an example of non-contiguous intra-band carrier aggregation, in which the aggregated portions of the wireless spectrum18A and18B are located within the same operating band20, but are not directly adjacent to one another. Finally,FIG. 2Dshows an example of inter-band carrier aggregation, in which the aggregated portions of the wireless spectrum22A and22B are located in different operating bands24,26. A modern mobile device should be capable of supporting each one of the previously described carrier aggregation configurations.

The use of carrier aggregation may pose unique problems for the front end circuitry in a mobile device. For instance, a mobile device using carrier aggregation may require two or more antennas. The use of more than one antenna may complicate the design of the front-end switching circuitry within the mobile device. Additionally, the use of carrier aggregation across certain operating bands may cause undesirable interference between transmit and receive circuitry in a mobile device front end that renders the mobile device unusable in these operating bands.

FIG. 3shows conventional front end circuitry28for use in a mobile terminal. The front end circuitry28includes antenna switching circuitry30, a diplexer32, and an antenna34. The antenna switching circuitry30includes low band switching circuitry36and high band switching circuitry38. The low band switching circuitry36is adapted to couple one of a first plurality of RF front end ports40to the antenna34through the diplexer32. The high band switching circuitry38is adapted to couple one of a second plurality of RF front end ports42to the antenna34through the diplexer32. The diplexer32includes a low band port44coupled to the low band switching circuitry36, a high band port46coupled to the high band switching circuitry38, and an antenna port48coupled to the antenna34. The diplexer32is adapted to pass high band signals falling within a high pass band between the high band port46and the antenna port48, pass low band signals falling within a low pass band between the low band port44and the antenna port48, and attenuate signals outside of the high and low pass bands. Although effective at selectively placing the antenna34in communication with the appropriate RF front end port, the conventional front end circuitry28shown inFIG. 3is not suitable for carrier aggregation applications that require multiple antennas.

FIG. 4shows conventional front end circuitry50for use in a mobile terminal with two antennas. The front end circuitry50includes antenna switching circuitry52, a first diplexer54A, a second diplexer54B, a first antenna56A, and a second antenna56B. The antenna switching circuitry52includes first antenna switching circuitry52A and second antenna switching circuitry52B. The first antenna switching circuitry52A includes first low band switching circuitry58, first high band switching circuitry60, second low band switching circuitry62, and second high band switching circuitry64. The first low band switching circuitry58and the first high band switching circuitry60are adapted to selectively couple one of a first plurality of RF front end ports66to the second antenna switching circuitry52B through the first diplexer54A. The second low band switching circuitry62and the second high band switching circuitry64are adapted to selectively couple one of a second plurality of RF front end ports68to the second antenna switching circuitry52B through the second diplexer54B. The second antenna switching circuitry52B includes antenna selection circuitry70, which is adapted to selectively place the first antenna56A and the second antenna56B in communication with either the first diplexer54A or the second diplexer54B.

The antenna switching circuitry52may comprise a plurality of transistors and other assorted passive components. As is well known in the art, non-linearity of the transistors and other passive components within the antenna switching circuitry52may generate harmonic distortion about a passing signal. In certain carrier aggregation configurations, the generated harmonic distortion can cause desensitization of receive circuitry in the conventional front end circuitry50illustrated inFIG. 4. For example, the conventional front end circuitry50may be unusable in a carrier aggregation configuration using bands 3 and 8 (CA 3-8). In a CA 3-8 configuration, the conventional front end circuitry50will couple one of the second plurality of RF front end ports68corresponding with the band 8 transmit port to the antenna selection circuitry70in order to transmit a carrier signal between 880-915 MHz. As the carrier signal passes through the first low band switching circuitry58, harmonic distortion is generated. The carrier signal and harmonic distortion travel through the first diplexer54A, where the harmonic distortion is effectively filtered. However, as the carrier signal travels through the antenna selection circuitry70, additional harmonic distortion is generated.

Because at least a portion of the second harmonic of the band 8 uplink band (1760-1830 MHz) falls within the band 3 downlink band (1805-1880 MHz), components of the harmonic distortion about the second harmonic are within the high pass band of the first diplexer54A, and a portion of the harmonic distortion will be delivered to the first high band switching circuitry60. Further, because the front end circuitry50is configured to simultaneously transmit on band 8 and receive on band 3, one of the first plurality of RF front end ports66corresponding with the band 3 receive port will be coupled to the first diplexer54A through the first high band switching circuitry60. Accordingly, a portion of the distorted band 8 transmit signal about the second harmonic will be delivered to the band 3 receive circuitry, where it will cause desensitization. Additionally, the harmonic distortion in the carrier signal will be presented to the antennas56A and56B, thereby degrading the quality of the wireless signal. As a result of the desensitization of the receiver circuitry, the performance of the front end circuitry50illustrated inFIG. 4may suffer in a CA 3-8 configuration.

As an additional example, the conventional front end circuitry50will also experience problems in carrier-aggregation applications using bands 4 and 17 (CA 4-17), because the third harmonic of a band 17 transmit signal (2112-2148 MHz) falls within a band 4 receive signal (2110-2155 MHz). The problem with the conventional front end circuitry50may occur in any carrier aggregation configuration using operating bands in which the harmonic components of the carrier signal fall within the frequency band of the receive signal. The limited combination of operating bands usable in a carrier aggregation configuration by the conventional front end circuitry50illustrated inFIG. 4may impede the performance and versatility of a mobile device. Accordingly, front end switching circuitry for a mobile device with two or more antennas is needed that is suitable for carrier aggregation applications across all bands.

FIG. 5shows a conventional diplexer72for use in the front end circuitry28and50shown inFIGS. 3 and 4. The conventional diplexer72is based on a fourth order Butterworth response, and includes an antenna port74, a low band port76, a high band port78, a high pass filter80, and a low pass filter82. The high pass filter80includes a first high band inductor L1_HB coupled between the high band port78and ground, a first high band capacitor C1_HB coupled between the high band port78and a first high band node81, a second high band inductor L2_HB coupled between the first high band node81and ground, and a second high band capacitor C2_HB coupled between the first high band node81and the antenna port74. The low pass filter82includes a first low band capacitor C1_LB coupled between the low band port76and ground, a first low band inductor L1_LB coupled between the low band port76and a first low band node83, a second low band capacitor C2_LB coupled between the first low band node83and ground, and a second low band inductor L2_LB coupled between the first low band node83and the antenna port74. The conventional diplexer72is designed to pass high band signals falling within a high pass band between the antenna port74and the high band port78, pass low band signals falling within a low pass band between the antenna port74and the low band port76, and attenuate signals outside of the high and low pass bands.

The conventional diplexer72allows a mobile terminal to transmit and receive a high band signal and a low band signal simultaneously, thereby increasing the data rate of the mobile device. Although effective at separating low and high band signals, the conventional diplexer72is limited to fixed pass bands for the low and high band signals. In certain carrier aggregation applications, the rigidity of the conventional diplexer72may degrade the performance of a mobile device into which it is incorporated. Carrier aggregation applications may demand more precise control over the high and low pass bands, greater stop band attenuation, and lower insertion loss. To achieve the desired pass and stop bands, a seventh or eighth order Butterworth response may be required according to the conventional design. Such a high order filter would be complex to implement, and would further introduce a high amount of insertion loss into the signal path to the antenna. Accordingly, a diplexer is needed that is capable of providing the necessary pass bands for the high band and low band signals while maintaining a desirable stop band attenuation and insertion loss for carrier aggregation applications.

SUMMARY

A tunable diplexer includes a high pass filter, a low pass filter, a high band port, a low band port, and an antenna port. The high pass filter is coupled between the high band port and the antenna port. The low pass filter is coupled between the low band port and the antenna port. The high pass filter is adapted to pass high band signals falling within a high pass band between the high band port and the antenna port, while attenuating signals outside of the high pass band. The low pass filter is adapted to pass low band signals falling within a low pass band between the low band port and the antenna port, while attenuating signals outside of the low pass band. The low pass filter includes a low stop band zero, which is adapted to attenuate signals within a low stop band. The low stop band zero is tunable, such that the low stop band can be adjusted to selectively attenuate signals within a given frequency band in the low pass band.

According to one embodiment, the high pass filter also includes a high stop band zero, which is adapted to attenuate signals within a high stop band. The high stop band zero is tunable, such that the high stop band can be adjusted to attenuate signals within a given frequency band in the high pass band.

According to one embodiment, the tunable diplexer is operable in two modes. In the first mode of operation, the tunable diplexer is adapted to adjust one or more stop band zeros in order to minimize or eliminate harmonic distortion. In a second mode of operation, the tunable diplexer is adapted to adjust one or more operating parameters in order to minimize insertion loss.

According to one embodiment, the tunable diplexer is integrated with front end switching circuitry on a single semiconductor to form an integrated tunable diplexer. The integrated tunable diplexer is adapted to alter the termination impedance of one or more switching paths within the front end switching circuitry in order to adjust the high pass band, the low pass band, or both.

DETAILED DESCRIPTION

Turning now toFIG. 6, a first embodiment of antenna switching circuitry84is incorporated into a mobile terminal front end86. The basic architecture of the mobile terminal front end86includes transceiver circuitry88, a plurality of power amplifiers90A-90N, a plurality of low noise amplifiers92A-92N, duplexer circuitry93, antenna switching circuitry84, a first diplexer94A, a second diplexer94B, first antenna tuning circuitry96A, second antenna tuning circuitry96B, a first antenna98A, a second antenna98B, and control circuitry100. When receiving a signal, the mobile terminal front end86receives information bearing radio frequency signals at the first antenna98A and the second antenna98B from one or more remote transmitters provided by a base station (not shown). The radio frequency signals pass through the antenna tuning circuitry96to the diplexers94, where the signals are separated into their low band and high band components and delivered to the antenna switching circuitry84. The antenna switching circuitry84selectively couples one or more terminals of the first diplexer94A, the second diplexer94B, or both, to one or more of the plurality of low noise amplifiers92A-92N through the duplexer circuitry93. One or more of the plurality of low noise amplifiers92A-92N amplify the received components of the radio frequency signals and deliver them to the transceiver circuitry88, where they may be subsequently processed and used by the mobile terminal front end86.

On the transmit side, the transceiver circuitry88receives digitized data, which may represent voice, data, or control information. The encoded data is modulated to produce a carrier signal at a desired transmit frequency. The carrier signal is then delivered to one or more of the plurality of power amplifiers90A-90N, where it is amplified and delivered to the antenna switching circuitry84through the duplexer circuitry93. The antenna switching circuitry84selectively couples one or more output terminals of the duplexer circuitry93to one or more terminals of the first diplexer94A, the second diplexer94B, or both, depending on the mode of operation of the mobile terminal front end86. The carrier signal is then filtered by the first diplexer94A, the second diplexer94B, or both, and delivered through the antenna tuning circuitry96to the first antenna98A, the second antenna98B, or both, depending on the mode of operation of the mobile terminal front end86.

By arranging the antenna switching circuitry84such that a diplexer exists between each one of the antennas98and the antenna switching circuitry84, harmonics of the carrier signal are filtered by the diplexers, thereby avoiding the desensitization of receive circuitry within the transceiver circuitry88. For example, the antenna switching circuitry84illustrated inFIG. 6is usable in a carrier aggregation configuration using bands 3 and 8 (CA 3-8). When transmitting on band 8, the transceiver circuitry88will modulate a carrier signal from 880-915 MHz. The carrier signal will pass through one or more of the plurality of power amplifiers90A-90N, where it will be amplified and delivered to the antenna switching circuitry84. The antenna switching circuitry84will selectively place the carrier signal into communication with the first diplexer94A or the second diplexer94B. Due to non-linearity of the switching components, the antenna switching circuitry84will generate harmonic distortion about the carrier signal. As the carrier signal is passed through either the first diplexer94A, the second diplexer94B, or both, the harmonic distortion is effectively filtered. Accordingly, the signal at the output of the first diplexer94A, the second diplexer94B, or both does not fall within high pass band of each one of the diplexers94, and therefore is not passed back to the antenna switching circuitry84. Accordingly, desensitization of the receive circuitry for band 3 is avoided, and the signal passed to the first antenna98A, the second antenna98B, or both, is virtually free of harmonic distortion as a result of the antenna switching circuitry84. A similar result occurs in carrier aggregation configurations using bands 4 and 17 (CA 4-17), in devices simultaneously using band 13 and the GPS band, in devices simultaneously using band 26 and the 2.4 GHz ISM band, and in devices using GSM900 and GSM850 modes, as well as any other combination of operating bands.

According to one embodiment, the first diplexer94A, the second diplexer94B, or both may be tunable. By using tunable diplexers for the first diplexer94A, the second diplexer94B, or both, harmonic signals about the carrier signal may be further reduced or eliminated. For example, by tuning a stop band in the first diplexer94A, the second diplexer94B, or both, to attenuate harmonic signals about the carrier signal, desensitization of the receive circuitry within the transceiver circuitry88may be further avoided, as will be discussed in further detail below. Additionally, the first diplexer94A, the second diplexer94B, or both, may be tuned to minimize insertion loss in the signal path of the antennas98, as will be discussed in further detail below.

The control circuitry100may be in communication with the antenna switching circuitry84, the transceiver circuitry88, the diplexers94, and the antenna tuning circuitry96in order to control one or more operating parameters of the mobile terminal front end86. For example, the control circuitry100may be adapted to place the mobile terminal front end86into a diversity mode of operation, wherein the mobile terminal front end86is adapted to transmit and receive signals on the first antenna98A while using the second antenna98B as a diversity antenna. The control circuitry100may also be adapted to place the mobile terminal front end86into a multiple input multiple output (MIMO) mode of operation, whereby different signals are transmitted and received by the first antenna98A and the second antenna98B simultaneously. The control circuitry100may be further adapted to control one or more operating parameters of the first diplexer94A, the second diplexer94B, or both. For example, the control circuitry100may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that harmonic distortion about the carrier signal is attenuated. Alternatively, the control circuitry100may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that insertion loss from the diplexers94is reduced.

The antenna tuning circuitry96may be configured to ensure optimal operation of the antennas98over a wide bandwidth. Although the antenna tuning circuitry96may contain one or more switching elements, these switching elements are not adapted to selectively couple the antennas98to one of a plurality of RF front end ports within the mobile terminal front end86.

The duplexer circuitry93may be adapted to separate transmit and receive signals such that transmit signals are passed from the power amplifier circuitry90A-90N to the antenna switching circuitry84, and receive signals are passed form the antenna switching circuitry84to the appropriate low noise amplifier in the plurality of low noise amplifiers92A-92N. The duplexer circuitry93may comprise a plurality of surface acoustic wave (SAW) duplexers, a plurality of bulk acoustic wave (BAW) duplexers, or the like.

According to one embodiment, the antenna switching circuitry84is adapted to perform antenna swapping while introducing minimal distortion into a transmit or receive signal. For example, the antenna switching circuitry84may be adapted to selectively place one or more of the power amplifiers90A-90N in communication with either the first antenna98A or the second antenna98B based upon an efficiency associated with each antenna. The efficiency may be based, for example, on electrical measurements and/or environmental conditions. Examples of electrical measurements include a reflected transmit power measured by one or more directional couplers, a received signal strength measurement, or a transmit power measured by a base station. Examples of environmental conditions include feedback from one or more sensors to detect the orientation of the mobile device and feedback from sensors that detect how the mobile device is being held.

FIG. 7shows a schematic representation of the antenna switching circuitry84according to one embodiment of the present disclosure. For context, the control circuitry100, the first diplexer94A, the second diplexer94B, the first antenna98A, and the second antenna98B are also shown. The antenna switching circuitry84includes low band switching circuitry102, first high band switching circuitry104, second high band switching circuitry106, a plurality of RF front end ports108, and a plurality of antenna selection switches110. The low band switching circuitry102, the first high band switching circuitry104, and the second high band switching circuitry106may comprise single pole multi throw (SPMT) switches adapted to selectively couple one or more of the RF front end ports108to one of the plurality of antenna selection switches110. Each one of the plurality of antenna selection switches110may comprise a single pole dual throw (SPDT) switch adapted to selectively couple one of the RF front end ports108to either the first antenna98A through the first diplexer94A or the second antenna98B through the second diplexer94B.

According to one embodiment, one or more of the antenna selection switches110may be directly coupled to one of the plurality of RF front end ports, such as the RF front end ports112A-112C shown inFIG. 7. The RF front end ports112A-112C may be coupled to further switching circuitry (not shown) in order to implement additional functionality of the mobile terminal front end86(shown inFIG. 6), such as, for example, a diversity or a MIMO mode of operation.

Although 19 RF front end ports are shown inFIG. 7, any number of RF front end ports may be used according to the present disclosure. Further switching circuitry for selectively coupling the additional RF front end ports to the antennas98or for otherwise supporting additional modes of operation may also be included without departing from the principles of the present disclosure. For example, additional high band or low band switching circuitry may be added in order to support extra bands.

According to one embodiment, each one of the switches in the antenna switching circuitry84is coupled to the control circuitry100such that the control system determines the connection path of each one of the switches.

According to an additional embodiment, the first diplexer94A, the second diplexer94B, or both are tunable, as will be discussed in further detail below. The control circuitry100may be coupled to each one of the diplexers94in order to alter one or more operating parameters of the diplexers94. For example, the control circuitry100may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that harmonic distortion about the carrier signal is attenuated. Alternatively, the control circuitry100may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that insertion loss from the diplexers94is reduced.

FIG. 8shows a schematic representation of the antenna switching circuitry84according to an additional embodiment of the present disclosure. For context, the first diplexer94A, the second diplexer94B, the first antenna98A, and the second antenna98B are also shown. The antenna switching circuitry84includes low band switching circuitry114, high band switching circuitry116, low band antenna selection circuitry118A, and high band antenna selection circuitry118B. The low band switching circuitry114and the high band switching circuitry116may comprise SPMT switches adapted to selectively couple one or more of the RF front end ports108to the low band antenna selection circuitry118A or the high band antenna selection circuitry118B, respectively. The low band antenna selection circuitry118A and the high band antenna selection circuitry118B may comprise a dual pole four throw (DP4T) switch adapted to selectively couple one of the RF front end ports108to either the first antenna98A through the first diplexer94A or the second antenna98B through the second diplexer94B.

According to one embodiment, one or more of the antenna selection switches110may be directly coupled to one of the RF front end ports108, such as the RF front end ports120A-120C shown inFIG. 8. The RF front end ports120A-120C may be coupled to further switching circuitry (not shown) in order to implement additional functionality of the mobile terminal front end86(shown inFIG. 6), such as, for example, a diversity or a MIMO mode of operation.

By arranging the antenna switching circuitry84such that a diplexer exists between each one of the antennas98and the antenna switching circuitry84, harmonics about the carrier signal are filtered by the diplexers, thereby avoiding the desensitization of receive circuitry within the transceiver circuitry88(shown inFIG. 6), as is discussed above.

Although 17 RF front end ports are shown inFIG. 8, any number of RF front end ports may be used according to the present disclosure. Further antenna switching circuitry for selectively coupling the additional RF front end ports to the antennas98or for otherwise supporting additional modes of operation may also be included without departing from the principles of the present disclosure. For example, additional high band or low band switching circuitry may be added in order to support extra bands

According to one embodiment, each one of the switches in the antenna switching circuitry84is coupled to the control circuitry100such that the control system determines the connection path of each one of the switches.

According to an additional embodiment, the first diplexer94A, the second diplexer94B, or both, are tunable, as will be discussed in further detail below. The control circuitry100may be coupled to each one of the diplexers94in order to alter one or more operating parameters of the diplexers94. For example, the control circuitry may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that harmonic distortion about the carrier signal is attenuated. Alternatively, the control circuitry100may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that insertion loss from the diplexers94is reduced.

FIG. 9shows a schematic representation of the antenna switching circuitry84according to an additional embodiment of the present disclosure. For context, the first diplexer94A, the second diplexer94B, the first antenna98A, and the second antenna98B are also shown. The antenna switching circuitry84ofFIG. 9is adapted to operate three antennas98. Accordingly, a third antenna98C is shown. The antenna switching circuitry84is substantially similar to that described inFIG. 8, with the addition of third antenna selection circuitry124for operating the mobile terminal front end86(shown inFIG. 6) with three antennas98. The third antenna selection circuitry124may comprise a dual pole multiple throw (DPMT) switch adapted to selectively place one of the plurality of RF front end ports108in communication with the third antenna98C and the high band antenna selection circuitry118B. The third antenna selection circuitry124may be coupled to the control circuitry100such that the control circuitry100determines the selected RF front end port to present to the third antenna98C and the high band antenna selection circuitry118B. By arranging the antenna switching circuitry84such that a diplexer exists between each one of the antennas98and the antenna switching circuitry84, the desensitization of receive circuitry within the transceiver circuitry88(shown inFIG. 6) can be avoided in carrier aggregation applications across all bands, as discussed above.

Although 24 RF front end ports are shown inFIG. 9, any number of RF front end ports may be used according to the present disclosure. Further switching circuitry for selectively coupling the additional RF front end ports to the antennas98or for otherwise supporting additional modes of operation may also be included without departing from the principles of the present disclosure. For example, additional high band or low band switching circuitry may be added in order to support extra bands.

According to one embodiment, each one of the switches in the antenna switching circuitry84is coupled to the control circuitry100such that the control system determines the connection path of each one of the switches.

According to an additional embodiment, the first diplexer94A, the second diplexer94B, or both are tunable, as will be discussed in further detail below. The control circuitry100may be coupled to each one of the diplexers94in order to alter one or more operating parameters of the diplexers94. For example, the control circuitry may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that harmonic distortion about the carrier signal is attenuated. Alternatively, the control circuitry100may be adapted to operate the first diplexer94A, the second diplexer94B, or both, such that insertion loss from the diplexers94is reduced.

According to an additional embodiment, the antenna switching circuitry84may further include a plurality of directional couplers122A-122F in order to direct the flow of RF signals between the antenna switching circuitry84and the antennas98. The plurality of directional couplers122may be connected between each port of the first diplexer94A and the antenna switching circuitry84, between each port of the second diplexer94B and antenna switching circuitry84, and between the third antenna98C and the antenna switching circuitry84. Each one of the plurality of directional couplers122may be connected to the control circuitry100such that the control circuitry100determines the direction of the signal flow through each one of the plurality of directional couplers122.

FIG. 10shows a schematic representation of a tunable diplexer126according to the present disclosure. The tunable diplexer126is based at least in part on an elliptical response, and includes a high pass filter128, a low pass filter130, a high band port132, a low band port134, and an antenna port136. The high pass filter128includes a first high band inductor L1_HB coupled between the high band port132and ground, a first high band capacitor C1_HB coupled between the high band port132and a first high band node138, a second high band inductor L2_HB coupled between the first high band node138and ground, a second high band capacitor C2_HB coupled between the first high band node138and the antenna port136, and a third high band inductor L3_HB coupled between the high band port132and the first high band node138. The low pass filter includes a first low band capacitor C1_LB coupled between the low band port134and ground, a first low band inductor L1_LB coupled between the low band port134and a first low band node140, a second low band capacitor C2_LB coupled between the first low band node140and ground, a second low band inductor L2_LB coupled between the first low band node140and the antenna port136, and a third low band capacitor C3_LB coupled between the low band port134and the first low band node140.

The tunable diplexer126is adapted to pass high band signals falling within a high pass band between the antenna port136and the high band port132, pass low band signals within a low pass band between the antenna port136and the low band port134, and attenuate signals outside of the high and low pass bands. The tunable diplexer126includes a tunable low stop band zero that is controllable by adjusting the capacitance of the third low band capacitor C3_LB. In one mode of operation, the tunable diplexer126is adjusted to selectively attenuate signals passing through the tunable diplexer126. The selective attenuation of signals may be especially useful in certain carrier aggregation applications.

As an example, in a carrier aggregation configuration using bands 8 and 3 (CA 8-3), the tunable low stop band zero can be tuned to the third harmonic of the band 8 transmit signal in order to ensure that any harmonic distortion generated by the antenna switching circuitry will not desensitize the receiver circuitry. Such a tuning configuration may be useful in both carrier aggregation and non-carrier aggregation configurations wherein harmonic distortion generated about a transmission signal may desensitize the receive circuitry or otherwise interfere with the functionality of the device. For example, tuning the low stop band zero to attenuate harmonic distortion may be useful in carrier aggregation configurations using bands 4 and 17 (CA 4-17), in devices simultaneously using band 13 and the GPS band, in devices simultaneously using band26and the 2.4 GHz ISM band, and in devices using GSM900 and GSM850 modes. By tuning the low stop band zero to attenuate troublesome harmonic signals, the tunable diplexer126may prevent desensitization of receiver circuitry within a mobile device, and allow for greater flexibility in the operation of the device.

In an additional mode of operation of the tunable diplexer126, the tunable diplexer126may be adapted to minimize insertion loss at the active transmit or receive frequencies. For example, the low stop band zero may be tuned to minimize insertion loss in a non-carrier aggregation configuration, or in a carrier aggregation configuration in which there are no concerns regarding harmonic distortion and desensitization of the receive circuitry.

According to one embodiment, the control circuitry100is in communication with the third low band capacitor C3_LB in order to control the variable capacitance value of the capacitor. The control circuitry100may be adapted to place the tunable diplexer126in a mode of operation to minimize problematic harmonics. The control circuitry100may also be adapted to place the tunable diplexer126in a mode of operation to minimize insertion loss.

According to one embodiment, the first diplexer94A, the second diplexer94B, or both (shown inFIGS. 6-9) comprise the tunable diplexer126illustrated inFIG. 10.

FIG. 11shows a schematic representation of an additional embodiment of a tunable diplexer142according to the present disclosure. For context, the control circuitry100is also shown. The tunable diplexer142shown inFIG. 11is substantially similar to that shown inFIG. 10, further including a programmable array of capacitors (PAC)144for tuning the low stop band zero. Although three capacitors are shown in the PAC144, any number of capacitors may be used to tune the low stop band zero according to the present disclosure. The PAC144may include a first tuning capacitor C1_TN, a second tuning capacitor C2_TN, and a third tuning capacitor C3_TN. Each of the capacitors may be coupled in series with a switch SW1-SW3. Further, each one of the capacitors and switches may be coupled in parallel with the third low band capacitor C3_LB. By selectively turning the switches SW1-SW3 on and off, the capacitance between the low band port134and the first low band node140can be altered. Accordingly, the low stop band zero can be tuned according to the mode of operation of the tunable diplexer142.

AlthoughFIG. 11shows a PAC144for tuning the low stop band zero, any low band filter circuit topology including any tunable component with a filter response including a tunable zero may be used in the tunable diplexer142, as will be appreciated by those of ordinary skill in the art.

According to one embodiment, the control circuitry100is in communication with the PAC144in order to control the orientation of the switches SW1-SW3. The control circuitry100may be adapted to place the tunable diplexer142in a mode of operation to minimize problematic harmonics. The control circuitry100may also be adapted to place the tunable diplexer142in a mode of operation to minimize insertion loss.

According to one embodiment, the first diplexer94A, the second diplexer94B, or both (shown inFIGS. 6-9) comprise the tunable diplexer126illustrated inFIG. 11.

FIG. 12shows a schematic representation of an integrated tunable diplexer146according to the present disclosure. The integrated tunable diplexer146includes the tunable diplexer142including an antenna port148, a high band port150, and a low band port152, high band switching circuitry154, a plurality of high band RF front end ports156, low band switching circuitry158, a plurality of low band switching ports160, and an antenna162. As discussed above, the tunable diplexer142is adapted to route high band signals falling within a high pass band between the high band switching circuitry154and the antenna162, route low band signals falling within a low pass band between the low band switching circuitry158and the antenna162, and attenuate signals outside of the high and low pass bands.

According to one embodiment, the integrated diplexer is formed on a single semiconductor die. By forming the tunable diplexer142and the switching circuitry on a single semiconductor die, space can be saved in a mobile device into which the integrated tunable diplexer146is integrated. Further, by forming the integrated tunable diplexer146on a single semiconductor die, the high band switching circuitry154and the low band switching circuitry158can be used as adjustable tuning elements to alter the performance of the tunable diplexer142. Generally, the impedance of the unused high band port150and the unused low band port152are terminated by a 50 ohm impedance. However, by adjusting the termination impedance of the high band port150, the low band port152, or both using one or more of the switches in the high band switching circuitry154, the low band switching circuitry158, or both, the high pass band, the low pass band, or both, can be tuned.

For example, by terminating the low band port152of the tunable diplexer142in an open circuit, the high pass band may be shifted slightly lower in frequency. Such a shift in frequency may have a significant impact on the performance and versatility of a mobile device. By terminating the low band port152of the tunable diplexer142in an open circuitry and thus shifting the high pass band slightly lower in frequency, additional operating bands within the mobile spectrum may be accommodated without the need for additional components. Such an approach may reduce insertion loss in the signal path of the antenna162, reduce the cost of a mobile device into which the integrated tunable diplexer146is incorporated, and increase the functionality and usability of the mobile device.

According to an additional embodiment, the integrated diplexer includes a combination of silicon on insulator (SOI) semiconductor devices and surface mount devices (SMDs) integrated onto a low temperature co-fired ceramic (LTCC) module.