# Patent

## Title
Apparatus and methods for reconfigurable directional couplers in an RF transceiver with selectable phase shifters

## Abstract

Provided herein are apparatus and methods for reconfigurable directional couplers in an RF transceiver. Reconfigurable directional couplers can be reconfigured and designed to provide high directivity using configurable capacitors to effect a mutual coupling and using lumped components or delay lines to effect a phase shift. Depending on the embodiment, the reconfigurable directional coupler can include capacitors, inductors, and switching components. The coupler can be designed for multi-band operation with an adjustable coupling factor conducive to semiconductor process integration. The coupler can have variable phase shifters to achieve a desired level of directivity in the coupler.

## Background
BACKGROUND
Field
Embodiments of the invention relate to radio frequency (RF) directional couplers, and more particularly, to reconfigurable directional couplers.
Description of the Related Technology
A directional coupler performs a variety of functions or operations relating to RF power signals. In one non-limiting example application a directional coupler is used to measure power delivered from a power amplifier. Power at the coupling port of the directional coupler is delivered to a power meter. Information from the power meter is used to adjust the power amplifier gain to a suitable level for amplifying a power signal of interest.
In another example application a directional coupler is adapted to monitor the transmitted power and the reflected power in a mobile phone antenna. From this information a power control circuit adjusts a power amplifier (PA) within the cell phone so as to improve a voltage standing wave ratio (VSWR).
SUMMARY
The aforementioned needs are satisfied in one non-limiting embodiment which comprises a directional coupler for a power signal comprising: an input port; an output port that is connected to the input port via a first selectable phase shifter; a coupled port that is connected to the input port via a first capacitive coupling element; an isolation port that is connected to the coupled port via a second selectable phase shifter and is further connected to the output port via a second capacitive coupling element; and a processor that adjusts the first and second selectable phase shifters based upon variations of the power signal to achieve a desired phase shift of the first and second signals received by the isolation port to achieve a desired directivity of the coupler the first and second capacitive coupling elements to achieve a desired coupling level between the input port and the coupled port.
The aforementioned needs are also satisfied in another non-limiting embodiment which comprises a directional coupler for a power signal, the directional coupler comprising: a transmission path that includes an input port and an output port with a first selectable phase shifter interposed therebetween; a coupled path that includes a coupled output port and an isolation port that has a second selectable phase shifter interposed therebetween; a first capacitive coupling element that couples the input port on the transmission path to the coupled port on the coupling path; a second capacitive coupling element that couples the output port on the transmission path to the isolation port on the coupled path, the isolation port on the coupled path configured to receive a first signal from the transmission path and second capacitive coupling element and to receive a second signal from the first capacitive coupling element and the coupled path; and a processor that adjusts the processor adjusts the first and second selectable phase shifters based upon variations of the power signal to achieve a desired phase shift of the first and second signals received by the isolation port to achieve a desired directivity of the coupler.
The aforementioned needs are also satisfied in another non-limiting embodiment which comprises a wireless device for a power signal comprising: an antenna; a transceiver; a power amplifier that amplifies signals between the transceiver and the antenna; a coupler that receives the amplified signal from the power amplifier, the coupler having an input port that receives the signal from the power amplifier, an output port that provides a signal to the antenna and that is connected to the input port via a first selectable phase shifter, a coupled port that is connected to the input port via a first capacitive coupling element and provides a coupled signal to a sensor, and an isolation port that is connected to the coupled port via a second selectable phase shifter and is further connected to the output port via a second capacitive coupling element; and a processor that adjusts the first and second selectable phase shifters based upon variations of the power signal to achieve a desired phase shift of the first and second signals received by the isolation port to achieve a desired directivity of the coupler.
The aforementioned needs are addressed in one non-limiting embodiment which comprises a directional coupler for a power signal comprising: an input port; an output port that is connected to the input port via a first phase shifter; a coupled port that is connected to the input port via a first variable capacitive coupling element; an isolation port that is connected to the coupled port via a selectable phase shifter and is further connected to the output port via a second variable capacitive coupling element; and a processor that adjusts the first and second variable capacitive coupling elements to achieve a desired coupling level between the input port and the coupled port.
The aforementioned needs are also addressed in another non-limiting embodiment which comprises a directional coupler for a power signal, the directional coupler comprising a transmission path that includes an input port and an output port with a first phase shifter interposed therebetween; a coupled path that includes a coupled output port and an isolation port that has a second phase shifter interposed therebetween; a first variable capacitive coupling element that couples the input port on the transmission path to the coupled port on the coupling path; a second variable capacitive coupling element that couples the output port on the transmission path to the isolation port on the coupled path, the isolation port on the coupled path configured to receive a first signal from the transmission path and second variable capacitive coupling element and to receive a second signal from the first variable capacitive coupling element and the coupled path; and a processor that adjusts the first and second variable capacitive coupling elements to achieve a desired coupling level between the transmission path and the coupling path based at least in part on a characteristic of the power signal.
The aforementioned needs are also addressed in another non-limiting embodiment which comprises a wireless device for a power signal comprising: an antenna; a transceiver; a power amplifier that amplifies signals between the transceiver and the antenna; a coupler that receives the amplified signal from the power amplifier, the coupler having an input port that receives the signal from the power amplifier, an output port that provides a signal to the antenna and that is connected to the input port via a first phase shifter, a coupled port that is connected to the input port via a first variable capacitive coupling element and provides a coupled signal to a sensor, and an isolation port that is connected to the coupled port via a second phase shifter and is further connected to the output port via a second variable capacitive coupling element; and a processor that adjusts the first and second variable capacitive coupling elements to achieve a desired coupling level between the input port and the coupled port.



BRIEF DESCRIPTION OF THE DRAWINGS
These drawings and the associated description herein are provided to illustrate specific embodiments of the invention and are not intended to be limiting.
FIG. 1 is a schematic diagram of a wireless device having a reconfigurable directional coupler of the present disclosure.
FIG. 2 is a schematic block diagram of an example wireless or network device that can include one or more of the modules of FIG. 1.
FIG. 3 is a schematic diagram a reconfigurable directional coupler and a sensor which can be used with a power amplifier.
FIG. 4 is a schematic diagram of a reconfigurable directional coupler according to an embodiment of the present disclosure.
FIG. 5 is a schematic diagram of a reconfigurable directional coupler according to another embodiment of the present disclosure.
FIGS. 6A-6D are schematic diagrams of alternative embodiments for realizing a first phase shifter and a second phase shifter of FIG. 4.
FIG. 7 is a flow diagram for configuring a reconfigurable directional coupler according to an embodiment of the present disclosure.



DETAILED DESCRIPTION OF EMBODIMENTS
The following detailed description of embodiments presents various descriptions of specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways as defined and covered by the claims. In this description, reference is made to the drawings in which like reference numerals may indicate identical or functionally similar elements.
A directional coupler is a passive device which couples part of a transmitted signal such as a transmitted radio frequency (RF) power signal, by a known amount to another port. The coupled output from the directional coupler can be used to obtain information, such as frequency and power level, of the transmitted signal without interrupting the power flow. Common properties desired for all directional couplers are wide operational bandwidth, high directivity, and good impedance matching at all ports.
Directivity can be important for accurately measuring the output power of a power amplifier. For example, it can be important for the power measured using a coupling port of a directional coupler to track the output power of the power amplifier as the output load impedance of the amplifier varies. Improving the directivity of a directional coupler can improve the accuracy of power measurements required for power systems. For instance, accurate measurements are important for monitoring the transmitted and reflected power resulting from impedance mismatch of an antenna or other load.
A directional coupler is typically constructed using quarter-wavelength transmission lines or stripline placed in close proximity to form couplers. In this manner the coupling is based upon mutual inductance or inductive coupling, and the desirable properties become layout dependent. In this case the directivity depends upon line width, spacing, and distance between the two couplers. For relatively low frequency, coupler size can become large; and obtaining a relatively high inductive coupling can also lead to a relatively high parasitic, unwanted capacitance. The unwanted capacitance can degrade directivity. Therefore, it can be a design challenge to achieve a balance between having a high mutual coupling and a high directivity in a typical directional coupler using inductive coupling.
Accordingly, using directional couplers based upon inductive coupling can require large area and limit the minimum operating frequency and bandwidth. Therefore, there is a need for directional couplers using alternative coupling elements.
Disclosed herein are apparatus and methods for reconfigurable directional couplers. Reconfigurable directional couplers in accordance with embodiments described herein can be reconfigured and designed to address challenges associated with directional couplers, including fixed bandwidth issues, layout dependency, and issues due to large coupler size leading to problems in integrating couplers into the semiconductor process. Instead of relying on coupler inductive mutual coupling, which is layout dependent, reconfigurable directional couplers according to embodiments described herein can rely exclusively or primarily on capacitive coupling, phase addition, and/or phase cancellation to achieve coupling and directivity.
Depending on the embodiment, the coupler can include capacitors, inductors, and switching components. The coupler can be designed for multi-band operation, to have an adjustable coupling factor, and can have a reduced size that is conducive to semiconductor process integration. The couplers can include phase shift networks including delay line or L-C based networks.
FIG. 1 is a schematic diagram of a wireless device 100 having a reconfigurable directional coupler 108 of the present disclosure.
The wireless device 100 can be a cellular phone, smart phone, tablet, modem, communication network or any other portable or non-portable device configured for voice and/or data communication.
The wireless device 100 includes an antenna 110 that receives and transmits power signals and the reconfigurable directional coupler 108 that can use a transmitted signal for analysis purposes or to adjust subsequent transmissions. For example, the directional coupler 108 can measure a transmitted RF power signal from a power amplifier (PA) module 106 which can have one or more power amplifiers (PA's) to amplify signals from a transceiver 104. Additionally, the transceiver 104 can be configured to receive and transmit signals in a known fashion.
FIG. 2 is a schematic block diagram of an example wireless or network device that can include one or more of the modules of FIG. 1. FIG. 2 illustrates the wireless device 100 in greater detail. As shown, the wireless device 100 can receive and transmit signals from the antenna 110.
The transceiver 104 is configured to generate signals for transmission and/or to process received signals. Signals generated for transmission are received by the PA module 106 which can include one or more PA's to amplify one or more of the generated signals from the transceiver 104.
In some embodiments, such transmission and reception functionalities can be implemented in separate components (e.g. a transmit module and a receiving module), or be implemented in the same module. The antenna switch module 122 can be configured to switch between different bands and/or modes, transmit and receive modes etc. As is also shown in FIG. 2, the main antenna 110 both receives signals that are provided to the transceiver 104 via the antenna switch module 122 and also transmits signals from the wireless device 100 via the transceiver 104, the PA module 106 and the antenna switch module 122 in a known fashion.
The system of FIG. 2 further includes a power management system 112 that is connected to the transceiver 104 that manages the power for the operation of the wireless device. The power management system 112 can also control the operation of a baseband sub-system 118 and other components of the wireless device 100. The power management system 112 provides power to the wireless device 100 via the battery 102 in a known manner and includes one or more processors or controllers that can control the transmission of signals and can also configure the directional coupler 108 based upon the frequency of the signals being transmitted in the manner that will be described in greater detail below.
The baseband sub-system 118 is shown to be connected to a user interface 116 to facilitate various input and output of voice and/or data provided to and received from the user. The baseband sub-system 118 can also be connected to memory 114 that is configured to store data and/or instructions to facilitate the operation of the wireless device, and/or to provide storage of information for the user.
The PA module 106 can be used to amplify a wide variety of RF signals. For example, one or more power amplifiers (PA's) of the PA module 106 can receive an enable signal that can be used to pulse the output of the power amplifier to aid in transmitting a wireless local area network (WLAN) signal or any other suitable pulsed signal. Power amplifiers of the PA module 106 need not amplify the same type of signal. For example, one power amplifier can amplify a WLAN signal, while another power amplifier can amplify, for example, a Global System for Mobile (GSM) signal, a code division multiple access (CDMA) signal, a W-CDMA signal, a Long Term Evolution (LTE) signal, or an EDGE signal.
The power amplifier module 106 can further include one or more amplification paths including corresponding sets of power amplifiers. Each path can be dedicated to a different frequency band, for example. Each path may further include different sub-paths (e.g., low and high power amplification paths) which can be selected via corresponding sets of switches.
In certain embodiments, the power amplifiers and associated components including switches and the like can be fabricated on GaAs substrates using, for example, pHEMT or BiFET transistors, and the switches, power amplifiers, and bias control blocks associated with the die can be fabricated on a Silicon substrate using CMOS transistors.
As is also shown in FIG. 2, the wireless device 100 can also include a directional coupler module 108 having one or more reconfigurable directional couplers for measuring transmitted power signals from the PA module 106 and for providing one or more coupled signals to a sensor module 120. The sensor module 120 can in turn send information to the transceiver 104 and/or directly to the PA module 106 as feedback for making adjustments to regulate the power level of one or more power amplifiers of the PA module 106. In this way the directional coupler module 108 can be used to boost/decrease the power of an RF power signal having a relatively low/high power. It will be appreciated, however, that the coupler 108 can be used in a variety of implementations without departing from the spirit or scope of the present teachings.
When the wireless device 100 is a mobile phone having a time division multiple access (TDMA) architecture, the directional coupler module 108 can advantageously manage the amplification of an RF transmitted power signal from the PA module 106. In a mobile phone having a time division multiple access (TDMA) architecture, such as those found in Global System for Mobile Communications (GSM), code division multiple access (CDMA), and wideband code division multiple access (W-CDMA) systems, a PA from the PA module 106 can be used to shift power envelopes up and down within prescribed limits of power versus time.
For instance, a particular mobile phone can be assigned a transmission time slot for a particular frequency channel. In this case the PA module 106 can be employed to aid in regulating the power level one or more RF power signals over time, so as to prevent signal interference from transmission during an assigned receive time slot and to reduce power consumption. In such systems, the directional coupler module 108 can be used to measure the power of a power amplifier output signal to aid in controlling one or more power amplifiers of the PA module 106. The implementation shown in FIG. 2 is exemplary and should be non-limiting. For example, the implementation of FIG. 2 illustrates the directional coupler 108 being used in conjunction with a transmission of an RF signal, however, it will be appreciated that the directional coupler modules described below can also be used with received RF signals as well.
FIG. 3 is a schematic diagram of a reconfigurable directional coupler 108a and a sensor 120a which can be used with a power amplifier 106a. In FIG. 3 the reconfigurable directional coupler 108a receives an RF transmitted power signal from the PA 106a at a power input port RFIN. The RF transmitted power signal from the PA 106a transmits along a power transmission path within the reconfigurable directional coupler 108a to a power output port RFOUT.
In addition the reconfigurable directional coupler 108a has a power coupling path which couples to a power signal of the power transmission path and provides a coupled RF power signal at a coupling port COUP and an isolated RF power signal at an isolation port ISO. The coupling between the power transmission path and the power coupling path is referred to as mutual coupling. A mutual coupling or mutual coupling factor of the reconfigurable directional coupler 108a is related to the ratio of the coupled RF power signal to the RF power signal at the power input port RFIN.
When the isolation port ISO is terminated with a matched impedance, then the coupled RF power signal can be larger than the isolated RF power signal. A directivity of the reconfigurable directional coupler 108a is related to the ratio of the coupled RF power signal to the isolated RF power signal and differentiates between forward and reverse travelling RF signals. The reconfigurable directional coupler 108a can be designed to have a large directivity with a large mutual coupling or mutual coupling factor. In this way the transmitted power signal at the power input port RFIN is accurately sensed by a power sensor 120a, and information from the power sensor 120a can be sent to the transceiver 104 and/or to the PA 106a to regulate the power level of the PA 106a. 
As is also shown in FIG. 3, the reconfigurable directional coupler 108a receives signals from a processor 107 that can be part of the power management element 112 of the wireless device 100 or can comprise a separate element. The processor 107 receives signals from the sensor 120 and potentially elsewhere and changes the settings of the coupler 108a to achieve the desired directivity and coupling factor. It will be understood that, for example, signals that different frequency signals will require different levels of impedances to achieve the desired coupling factor and directivity and the components of the directional coupler 108a can be modified by the processor 107 in the manner that will be described in greater detail below.
FIG. 4 is a schematic diagram of a reconfigurable directional coupler 208 according to an embodiment of the present disclosure. The reconfigurable directional coupler 208 has a first adjustable phase shifter 210 electrically connected between a power input port RFIN and a power output port RFOUT. A power signal entering the power input port RFIN transmits along a power transmission path delineated from the power input port RFIN to the power output port RFOUT. A power signal arriving at the power output port RFOUT is phase shifted by a first phase shift determined by the first adjustable phase shifter 210. The reconfigurable directional coupler 208 additionally has a second adjustable phase shifter 214 electrically connected between an isolation port ISO and a coupling port COUP. A power coupling path is delineated from the isolation port ISO to the coupling port COUP. In addition, a power signal arriving at the coupling port from the isolation port ISO is phase shifted by a second phase shift determined by the second adjustable phase shifter 214.
The reconfigurable directional coupler 208 further has a first configurable capacitor 216 electrically connected between the power input port RFIN and the coupling port COUP. The first configurable capacitor can be configured to provide a first mutual coupling between a power signal of the power input port RFIN and a power signal of the coupling port COUP. The first mutual coupling can be characterized by a first coupling coefficient relating to the value of capacitance of the first configurable capacitor.
Similarly, the reconfigurable directional coupler 208 has a second configurable capacitor 212 electrically connected between the power output port RFOUT and the isolation port ISO. The second configurable capacitor can be configured to provide a second mutual coupling between a power signal of the power output port RFOUT and a power signal of the isolation port ISO. The second mutual coupling can be characterized by a second coupling coefficient relating to the value of capacitance of the second configurable capacitor.
It will be appreciated that the RF coupler disclosed herein can, in some circumstances work bi-directionally. An example of this circumstance would be when the directional coupler is used to detect reverse transmit signals or reflected signals that may be emanating from the output side of the coupler 208. In this circumstance the output power port RFOUT would function as the input power port RFIN, the coupling port COUP would function as the isolation port ISO port and the input power port RFIN would function as the output power port RFOUT. The input power port RFIN or the isolation port ISO would then provide the reverse reflected signals for further processing. The phase shifters 210 and 214 and the coupler 212 and 216 could then be configured to provide the desired phase shifts of the sensed signals and the desired coupling in the manner that will be described hereinbelow. As such, the coupler 208 can be configured to receive two signals between two ports and provide corresponding coupled signals to a coupled port and an isolation port that will vary depending upon the direction of the signal. As such, the descriptions of input power port RFIN the output power port RFOUT Port, the coupling port COUP and the isolation port ISO can vary based upon the direction of the signal that is being received and should not be limited to the direction of the signal being transmitted on a power transmission path.
FIG. 5 is a schematic diagram of one implementation of a reconfigurable directional coupler 208 according to another embodiment of the present disclosure. In FIG. 5 more circuit details are shown. The first adjustable phase shifter 210 is an adjustable low pass tee network electrically connected between the power input port RFIN and the power output port RFOUT. The second adjustable phase shifter 212 is an adjustable high pass pi network electrically connected between the isolation port ISO and the coupling port COUP. The first configurable capacitor 216 is a switchable capacitor array electrically connected between the power input port RFIN and the coupling port COUP. And the second configurable capacitor 212 is a switchable capacitor array electrically connected between the power output port RFOUT and the isolation port ISO.
The first adjustable phase shifter 210 comprises a first inductor 311a and a second inductor 311b electrically connected in series between the power output port RFOUT and the power input port RFIN. The first adjustable phase shifter 210 also comprises a switchable capacitor array having a first capacitor 310a, a second capacitor 310b, and a third capacitor 310c. The first capacitor 310a, the second capacitor 310b, and the third capacitor are electrically connected between ground and a switching port of a single pole multi-throw switch 320 to allow selection of the capacitor value. The first inductor 311a and the second inductor 311b have fixed inductance values and are electrically connected together at a common node of the single pole multi-throw switch 320.
Having discrete or lumped components such as inductors and capacitors, the first adjustable phase shifter 210 can advantageously be adjusted to provide a specified value for the first phase shift when the RF power signal of the transmission path is of a given frequency band. Having more than one capacitor forming a capacitor array allows the first phase shift to be adjusted as a function of frequency and to be adjusted with low insertion loss (IL). Additionally, the size of the lumped components can be advantageously compact compared to stripline when the center frequency is relatively low.
Although the first adjustable phase shifter 210 shows the capacitor array as having three capacitors, the capacitor array can have a fewer or greater number of capacitors selected by the single pole multi-throw switch 320. Also, it can be appreciated by those practiced in the art of designing lumped element switchable arrays that the single pole multi-throw switch 320 can be realized in different ways. For instance, the single pole multi-throw switch 320 can be realized with more than one switch, and the switch can be a gate-controlled transistor such as an NFET (n-type field effect transistor) or PFET (p-type field effect transistor). Or alternatively, the switch can be realized using transmission gates. The switch 320 is, in one implementation, under the control of the processor 107 in a known manner.
The second adjustable phase shifter 214 comprises a first inductor 315a electrically connected between ground and a common node of a first single pole multi-throw switch 326 and a second inductor 315b electrically connected between ground and a common node of a second single pole multi-throw switch 328, for example, under the control of the processor 107. The first multi-throw switch 326 and the second multi-throw switch 328 can selectively connect one of a plurality of capacitors from a capacitor array comprising a first capacitor 314a, a second capacitor 314b, and a third capacitor 314c under, for example, the control of the processor 107.
Like in the first adjustable phase shifter 210, having an adjustable lumped element array of capacitors in the second adjustable phase shifter 214 offers advantages in selecting a frequency dependent specified value of the second phase shift. Also, as in the first adjustable phase shifter 210, the adjustable lumped element array can have fewer or greater capacitors while the first and second multi-throw switches can be realized using alternative connection schemes including using transmission gates or NFETs or PFETs.
The first configurable capacitor 216 is a switchable capacitor from a first capacitor array comprising a first capacitor 316a, a second capacitor 316b, and a third capacitor 316c. A first single pole multi-throw switch 330 having a common node electrically connected to the power input port RFIN and a second single pole multi-throw switch 332 having a common node electrically connected to the coupling port COUP can select one of the capacitors from the array.
The capacitor can be chosen from the array to provide a capacitance suitable for providing a first mutual coupling between a power signal of the power input port RFIN and a power signal of the coupling port COUP. In addition, the first single pole multi-throw switch 330 and the second single pole multi-throw switch 332 can be realized using alternative connection schemes including using transmission gates or NFETs or PFETs.
Similarly, the second configurable capacitor 212 is a switchable capacitor from a first capacitor array comprising a first capacitor 312a, a second capacitor 312b, and a third capacitor 312c. A first single pole multi-throw switch 322 under, for example the control of the processor 107 having a common node electrically connected to the power output port RFOUT and a second single pole multi-throw switch 324 having a common node electrically connected to the isolation port ISO can select one of the capacitors from the array.
The capacitor can be chosen from the array to provide a capacitance suitable for providing a second mutual coupling between a power signal of the power output port RFOUT and a power signal of the isolation port ISO. In addition, the first single pole multi-throw switch 322 and the second single pole multi-throw switch 324 can be realized using alternative connection schemes including using transmission gates or NFETs or PFETs.
While the first configurable capacitor 216 and the second configurable capacitor 212 show a first capacitor array and a second capacitor array having three capacitors, the first capacitor array and the second capacitor array can have fewer or greater capacitors.
Using capacitors instead of inductors to select the first and the second mutual coupling, the reconfigurable directional coupler 208 advantageously is space efficient while allowing the directivity to be adjusted based upon application. The desired characteristics can be attained first by selecting the first mutual coupling and the second mutual coupling to be large, and then second by selecting the first phase shift and the second phase shift for high directivity based upon the frequency band of interest.
FIGS. 6A-6D are schematic diagrams of alternative possible circuit configurations that can be used to achieve realizing the first adjustable phase shifter 210 and the second adjustable phase shifter 214 of FIG. 4.
FIG. 6A is a high pass tee network 602 comprising a first capacitor 610a, a second capacitor 610b, and an inductor 611a with a first node electrically connected to ground.
FIG. 6B is a high pass pi network 604 comprising a first inductor 613a with a first node electrically connected to ground, a second inductor 613b with a first node electrically connected to ground, and a capacitor 612a. 
FIG. 6C is a low pass tee network 606 comprising a first inductor 615a, a second inductor 615b, and a capacitor 614a with a first node electrically connected to ground. And
FIG. 6D is a low pass pi network 608 comprising a first capacitor 616a with a first node electrically connected to ground, a second capacitor 616b with a first node electrically connected to ground, and an inductor 617a. In implementation, there will be a plurality of different impedances arranged between either the transmission or coupled path and ground or in parallel that are connectable to the transmission path via a switch such as the switches 320 and 328 that can be controlled by the processor 107 (FIG. 3).
The embodiments of FIGS. 6A-6D can be used as adjustable networks for realizing the first adjustable phase shifter 210 and the first adjustable phase shifter 214 of FIGS. 4 or FIG. 5. For instance, the low pass tee network 606 can be used to realize the first adjustable phase shifter 210 of FIG. 5 when the capacitor 614a is replaced with a switchable capacitor array. Similarly, the high pass tee network 604 can be used to realize the second adjustable phase shifter 214 of FIG. 5 when the capacitor 612a is replaced with a switchable capacitor array.
FIG. 7 is a flow diagram 700 for configuring a reconfigurable directional coupler according to an embodiment of the present disclosure. The flow diagram begins with a first configuration step 702 corresponding to selecting the first mutual coupling and the second mutual coupling.
The first mutual coupling and the second mutual coupling provide a desired coupling factor K which is related to the capacitance selected from the first capacitor array of the first configurable capacitor 216 and the second capacitor array of the second configurable capacitor 212 of FIG. 4 and FIG. 5.
Following this step the frequency dependent components are adjusted in a second configuration step 704. Preferably, the frequency dependent components are adjusted so that the combined signal received at the ISO port a first path comprising RFIN to the adjustable lumped component phase shifter 210 and the configurable coupling capacitor array 212 and a second path comprising RFIN to the first configurable coupling capacitor array 216, the COUP port and the adjustable lumped component phase shifter 214 comprises two signals have phases that are offset from each other so that the combined signal at the ISO port is reduced in magnitude. In one specific implementation, the phase shifts on the paths are selected so that the signals at the ISO port are complementary to each other and can substantially cancel each other out. In these implementations, the phase is preferably selected so that the phase of the two signals from the two paths is approximately 180 degrees different.
For example, in the second configuration step 704 the first phase shift can be selected to provide approximately 90 degrees of phase shift between an RF power signal of the input power port RFIN and an RF power signal of the output power port RFOUT. This can correspond to selecting a switched discrete or lumped components such as inductors and capacitors from the first adjustable phase shifter 210, or alternatively to setting a delay of a delay line. The first phase shift is selected to be approximately 90 degrees for the frequency band of the RF power signal of the input power port RFIN and the RF power signal of the output power port RFOUT.
In a third configuration step 706, a similar adjustment is effected to provide approximately 270 degrees of phase shift between an RF power signal of the isolation port ISO and an RF power signal of the coupling port COUP. This corresponds to setting the second phase shift of the second adjustable phase shifter 214.
When the first mutual coupling and the second mutual coupling are commensurate, directivity becomes related to the first phase shift and the second phase shift. When the first phase shift and the second phase shift are complementary, having a sum equal to approximately 360 degrees as described above, then the directivity can be high.
Because the first phase shift and the second phase shift are frequency dependent, a decision step 708 is required. In the decision step 708 the RF power signal of the input port RFIN or of the output port RFOUT can be monitored to determine a frequency band of interest. If the frequency band changes, then the decision step 708 will repeat the second configuration step 704 and the third configuration step 706 to readjust the first phase shift and the second phase shift. If the frequency is stable, then the coupler maintains its present state and no changes are affected as shown in a fourth configuration step 710.
Applications
Devices employing the above described reconfigurable directional couplers can be implemented into various electronic devices. Examples of the electronic devices can include, but are not limited to, consumer electronic products, parts of the consumer electronic products, electronic test equipment, etc.
Such devices can include, but are not limited to, a mobile phone such as a smart phone, a telephone, a television, a computer monitor, a computer system, a modem, a hand-held computer, a laptop computer, a tablet computer, a personal digital assistant (PDA), a wearable computing device such as a smart watch, a healthcare monitoring device, an automobile, a stereo system, a radio, a camcorder, a camera, a digital camera, a portable memory chip, a wrist watch, a clock, etc. Further, the electronic devices can include unfinished products. Examples of the electronic devices can also include circuits of optical networks or other communication networks.
The foregoing description and claims may refer to elements or features as being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one element/feature is directly or indirectly connected to another element/feature, and not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one element/feature is directly or indirectly coupled to another element/feature, and not necessarily mechanically. Thus, although the various schematics shown in the figures depict example arrangements of elements and components, additional intervening elements, devices, features, or components may be present in an actual embodiment (assuming that the functionality of the depicted circuits is not adversely affected).
Although this invention has been described in terms of certain embodiments, other embodiments that are apparent to those of ordinary skill in the art, including embodiments that do not provide all of the features and advantages set forth herein, are also within the scope of this invention. Moreover, the various embodiments described above can be combined to provide further embodiments. In addition, certain features shown in the context of one embodiment can be incorporated into other embodiments as well. Accordingly, the scope of the present invention is defined only by reference to the appended claims. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” “include,” “including,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements.
Likewise, the word “connected”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements.
Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description of Certain Embodiments using the singular or plural number may also include the plural or singular number respectively.
The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.
Moreover, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. For example, while blocks are presented in a given arrangement, alternative embodiments may perform similar functionalities with different components and/or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these blocks may be implemented in a variety of different ways. Any suitable combination of the elements and acts of the various embodiments described above can be combined to provide further embodiments. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.

## Claims

1. A directional coupler for a power signal comprising:
an input port;
an output port that is connected to the input port via a first selectable phase shifter;
a coupled port that is connected to the input port via a first capacitive coupling element;
an isolation port that is connected to the coupled port via a second selectable phase shifter and is further connected to the output port via a second capacitive coupling element; and
a processor that adjusts the first and second selectable phase shifters based upon variations of the power signal to achieve a desired phase shift of the first and second signals received by the isolation port, and to achieve a desired directivity of the coupler.

2. The directional coupler of claim 1 wherein the coupler is bi-directional.

3. The directional coupler of claim 1 wherein the first and second capacitive coupling elements are variable and the processor adjusts the first and second variable capacitive coupling elements to achieve a desired coupling level between the input port and the coupled port.

4. The directional coupler of claim 3 wherein the first and second variable capacitive coupling elements each include a plurality of capacitances forming a first and second array and a switching element that is controllable by the processor so that the processor selects a first capacitance for the first capacitive coupling element that determines a first mutual coupling, and so that the processor selects a second capacitance for the second capacitive coupling element that determines a second mutual coupling.

5. The directional coupler of claim 4 wherein the processor selects the first capacitance to have a value commensurate to the second capacitance so that the phase shift of the first and second signal at the isolation port due to the first and second capacitance is substantially equal.

6. The directional coupler of claim 3 wherein the power signal includes an RF power signal that is being transmitted and the processor adjusts the first and second variable capacitive coupling elements and the first and second selectable phase shifters based upon the frequency of the RF signal being transmitted.

7. The directional coupler of claim 1 wherein the first and second selectable phase shifters have variable impedances that the processor configures so that the phase of the first signal and the phase of the second signal at the isolation port are substantially complementary to each other.

8. The directional coupler of claim 5 wherein the impedances of the first and second selectable phase shifters are selected so that the resulting first and second signals at the isolation port are approximately 180 degrees out of phase.

9. The directional coupler of claim 6 wherein the impedances of the first and second selectable phase shifters are selected so that the resulting first and second signals at the isolation port have respective phase angles of approximately 90 and 270 degrees.

10. A directional coupler for a power signal, the directional coupler comprising:
a transmission path that includes an input port and an output port with a first selectable phase shifter interposed therebetween;
a coupled path that includes a coupled output port and an isolation port that has a second selectable phase shifter interposed therebetween;
a first capacitive coupling element that couples the input port on the transmission path to the coupled port on the coupling path;
a second capacitive coupling element that couples the output port on the transmission path to the isolation port on the coupled path, the isolation port on the coupled path configured to receive a first signal from the transmission path and second capacitive coupling element and to receive a second signal from the first capacitive coupling element and the coupled path; and
a processor that adjusts the first and second selectable phase shifters based upon variations of the power signal to achieve a desired phase shift of the first and second signals received by the isolation port, and to achieve a desired directivity of the coupler.

11. The directional coupler of claim 10 wherein the coupler is bi-directional.

12. The directional coupler of claim 10 wherein the capacitive coupling elements are variable and wherein processor adjusts the first and second variable capacitive coupling elements to achieve a desired coupling level between the transmission path and the coupling path based at least in part on a characteristic of the power signal.

13. The directional coupler of claim 12 wherein the power signal includes an RF power signal that is being transmitted and the processor adjusts the first and second variable capacitance coupling elements and the first and second selectable phase shifters based upon the frequency of the RF signal being transmitted.

14. The directional coupler of claim 13 wherein the first and second selectable phase shifters have variable impedances that the processor configures so that the phase of the first signal and the phase of the second signal at the isolation port are substantially complementary to each other.

15. The directional coupler of claim 14 wherein the impedances of the first and second selectable phase shifters are selected so that the resulting first and second signals at the isolation port are approximately 180 degrees out of phase.

16. The directional coupler of claim 12 wherein the first and second configurable capacitive coupling elements each include a plurality of capacitances forming a first and second array and a switching element that is controllable by the processor so that the processor selects a first capacitance for the first capacitive coupling element that determines a first mutual coupling between the transmission and coupled path, and so that the processor selects a second capacitance for the second capacitive coupling element that determines a second mutual coupling between the transmission and coupled path.

17. The directional coupler of claim 16 wherein the processor selects the first capacitance to have a value commensurate to the second capacitance so that the phase shift of the first and second signal at the isolation port due to the first and second capacitance is substantially equal.

18. A wireless device for a power signal comprising:
an antenna;
a transceiver;
a power amplifier that amplifies signals between the transceiver and the antenna;
a coupler that receives the amplified signal from the power amplifier, the coupler having an input port that receives the signal from the power amplifier, an output port that provides a signal to the antenna and that is connected to the input port via a first selectable phase shifter, a coupled port that is connected to the input port via a first capacitive coupling element and provides a coupled signal to a sensor, and an isolation port that is connected to the coupled port via a second selectable phase shifter and is further connected to the output port via a second capacitive coupling element; and
a processor that adjusts the first and second selectable phase shifters based upon variations of the power signal to achieve a desired phase shift of the first and second signals received by the isolation port, and to achieve a desired directivity of the coupler.

19. The wireless device of claim 18 wherein the processor adjusts the first and second variable capacitive coupling elements to achieve a desired coupling level between the input port and the coupled port.

20. The wireless device of claim 19 wherein the power signal includes an RF power signal that is being transmitted and the processor adjusts the first and second variable capacitance coupling elements and the first and second selectable phase shifters based upon the frequency of the RF signal being transmitted.