Tunable electromagnetic coupler and modules and devices using same

An electromagnetic coupler includes a first transmission line connecting an input port to an output port. A second transmission line adjacent the first transmission line connects a coupled port and an isolation port. The electromagnetic coupler provides a coupled signal at the coupled port, which is representative of an input signal at the input port. The amplitude of the coupled signal is related to the amplitude of the input signal by a coupling factor. A tuning element is provided adjacent to the first or second transmission line and is coupled to an impedance. Varying impedance values cause an adjustment to the coupling factor and reactive impedance values provide frequency filtering effects.

BACKGROUND

Directional couplers are widely used in front end module (FEM) products, such as in radio transceivers, wireless handsets, and the like. For example, a directional coupler can be used to detect and monitor electromagnetic (EM) output power. Additionally, when a radio frequency (RF) signal generated by an RF source is provided to a load, such as to an antenna, a portion of the RF signal can be reflected back from the load. An EM coupler can be included in a signal path between the RF source and the load to provide an indication of forward RF power of the RF signal traveling from the RF source to the load and/or an indication of reverse RF power reflected back from the load. EM couplers include, for example, directional couplers, bi-directional couplers, multi-band couplers (e.g., dual band couplers), and the like.

Referring toFIG. 1, an EM coupler100typically has a power input port102, a power output port104, a coupled port106, and an isolation port108. The electromagnetic coupling mechanism, which can include inductive or capacitive coupling, is typically provided by two parallel or overlapped transmission lines, such as microstrips, strip lines, coplanar lines, and the like. A main transmission line110extends between the power input port102and the power output port104and provides the majority of the signal116from the power input port102to the power output port104. A coupled line112extends between the coupled port106and the isolation port108and may extract a portion114of the power traveling between the power input port102and the power output port104for various purposes, including various measurements. When a termination impedance is presented to the isolation port108, an indication of forward RF power traveling from the power input port102to the power output port104is provided at the coupled port106.

In a forward coupling mode, as inFIG. 1, the portion114is a fraction of the main signal116RF power traveling from the power input port102to the power output port104. EM couplers are typically rated by their coupling factor, usually stated in decibels, which is a measure of the ratio of the power of the portion114coupled from the power of the input signal116. For example, a 20 dB coupler will provide a coupled signal, e.g., a portion114, that is 20 dB lower than the input power, or about 1% of the input power.

It is generally desirable to have a relatively low coupling factor to not overly remove power from the main signal, but it is also desirable for the coupling factor to be certain and consistent, to allow accurate assessments of the power of the main signal.

SUMMARY OF INVENTION

Aspects and embodiments are directed to electromagnetic couplers having structures designed to allow for tuning of coupler parameters and performance. As discussed in more detail below, a tuning element may be formed from various materials, e.g., conductors or semiconductors, in proximity to transmission lines that form a tunable electromagnetic coupler, which may be further combined with various components and features to form modules, devices, and systems. Tunable electromagnetic couplers may allow for selectively adjustable coupling factors and may also advantageously implement filtering effects, as discussed in more detail below.

According to one aspect, an electromagnetic coupler is provided. The coupler includes a first transmission line extending between an input port and an output port, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolation port, a tuning element disposed adjacent at least one of the first transmission line and the second transmission line, and an adjustable impedance coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port responsive to receiving an input signal at the input port. The amplitude of the coupled signal is related to an amplitude of the input signal by a coupling factor, and the adjustable impedance is configured to adjust the coupling factor.

In some embodiments the reference node is ground. Some embodiments include a reactive component in the impedance, while others include only a resistive component. In certain embodiments the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line, e.g., by a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

According to another aspect, an electromagnetic coupler module is provided and includes a substrate with a dielectric layer having a first transmission line disposed thereon and extending between an input port and an output port, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolation port, a tuning element disposed adjacent at least one of the first transmission line and the second transmission line, and an adjustable impedance coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port responsive to receiving an input signal at the input port. The amplitude of the coupled signal is related to an amplitude of the input signal by a coupling factor, and the adjustable impedance is configured to adjust the coupling factor. A protective outer surface may be included that overmolds at least a part of the substrate, the first and second transmission lines, and the tuning element.

In some embodiments the reference node is ground. Some embodiments include a reactive component in the adjustable impedance, while others include only a resistive component. In certain embodiments the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line, e.g., by a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch connected to one of the input port and the output port. Some embodiments include a power amplifier coupled to one of the input port and the output port.

According to another aspect, an electronic device is provided and includes a first transmission line extending between an input port and an output port, a transceiver coupled to the input port and configured to produce a transmit signal, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolation port, a tuning element disposed adjacent at least one of the first transmission line and the second transmission line, and an adjustable impedance coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port responsive to receiving an input signal at the input port. The input signal may be the transmit signal. The amplitude of the coupled signal is related to an amplitude of the input signal by a coupling factor, and the adjustable impedance is configured to adjust the coupling factor.

In some embodiments the reference node is ground. Some embodiments include a reactive component in the adjustable impedance, while others include only a resistive component. In certain embodiments the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line, e.g., by a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch module connected to either the input port or the output port and configured to direct the transmit signal to at least one of the transceiver and an antenna. Some embodiments include a power amplifier connected between the transceiver and the input port, the power amplifier being configured to receive and amplify the transmit signal.

Certain embodiments include an antenna coupled to the output port, the antenna being configured to transmit the transmit signal and to receive a receive signal. The output port may be further configured to receive the receive signal from the antenna and to provide the receive signal at the input port.

Certain embodiments include a sensor coupled to the coupled port and configured to detect a power level of the coupled signal. Some embodiments include a baseband sub-system coupled to the transceiver and configured to provide a baseband signal to the transceiver. In some embodiments, any of a sensor module, a memory, a baseband sub-system, a user interface, and/or a battery may be included.

In yet another aspect an electromagnetic coupler is provided that includes a first transmission line extending between an input port and an output port configured to provide an output signal at the output port responsive to receiving an input signal at the input port, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolation port, a tuning element disposed adjacent at least one of the first transmission line and the second transmission line, and an impedance including a reactive component coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port responsive to receiving the input signal at the input port. The impedance and tuning element are configured to filter a range of frequency components of the output signal.

In some embodiments the reference node is ground. Some embodiments include a resistive component in the impedance. The impedance may be adjustable. In certain embodiments the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line, e.g., by a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

According to another aspect an electromagnetic coupler module is provided and includes a substrate with a dielectric layer having a first transmission line disposed thereon extending between an input port and an output port, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolation port, a tuning element disposed adjacent at least one of the first transmission line and the second transmission line, and an impedance including a reactive component coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port responsive to receiving the input signal at the input port. The impedance and tuning element are configured to filter a range of frequency components of the output signal.

In some embodiments the reference node is ground. Some embodiments include a resistive component in the impedance. The impedance may be adjustable. In certain embodiments the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line, e.g., by a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Some embodiments include an antenna switch connected to one of the input port and the output port. Some embodiments include a power amplifier coupled to one of the input port and the output port.

According to another aspect, an electronic device is provided. The electronic device includes a first transmission line extending between an input port and an output port, a transceiver coupled to the input port and configured to produce a transmit signal, a second transmission line disposed adjacent to the first transmission line and extending between a coupled port and an isolation port, a tuning element disposed adjacent at least one of the first transmission line and the second transmission line, and an impedance including a reactive component coupled between the tuning element and a reference node. The second transmission line is configured to provide a coupled signal at the coupled port responsive to receiving the input signal at the input port. The impedance and tuning element are configured to filter a range of frequency components of the output signal.

In some embodiments the reference node is ground. Some embodiments include a resistive component in the impedance. The impedance may be adjustable. In certain embodiments the tuning element is configured to be selectively decoupled from the first transmission line and the second transmission line, e.g., by a switch.

The second transmission line may be laterally offset from the first transmission line. The second transmission line may be laterally offset from the tuning element. In some embodiments a portion of the second transmission line forms an overlapping region with at least one of the first transmission line and the tuning element.

Certain embodiments include an antenna switch module connected to either the input port or the output port and configured to direct the transmit signal to at least one of the transceiver and an antenna. Some embodiments include a power amplifier connected between the transceiver and the input port, the power amplifier being configured to receive and amplify the transmit signal.

Some embodiments include an antenna coupled to the output port, the antenna being configured to transmit the transmit signal and to receive a receive signal. The output port may be configured to receive the receive signal from the antenna and to provide the receive signal at the input port.

Certain embodiments include a sensor coupled to the coupled port and configured to detect a power level of the coupled signal. Some embodiments include a baseband sub-system coupled to the transceiver and configured to provide a baseband signal to the transceiver. In some embodiments, any of a sensor module, a memory, a baseband sub-system, a user interface, and/or a battery may be included.

DETAILED DESCRIPTION

Traditional multi-layer coupler designs, either implemented in laminate manufacturing processes or semiconductor manufacturing processes, are conventionally designed to have a particular coupling factor at a particular frequency or frequency band. Tunable couplers, modules, and devices in accord with aspects disclosed herein allow for an adjustable coupling factor by including a tuning element and an adjustable grounding impedance associated with the tuning element. Adjustability of the coupling factor may beneficially allow for adapting the coupler to multiple frequency bands and/or multiple applications, each of which may allow fewer stock parts to support a range of products, and allow adjustability to correct for manufacturing variation which in turn increases production yield, all of which reduces cost. For example, a grounded tuning element in accord with various aspects and examples disclosed herein provides compensation for variations in coupling factor caused by variations in dielectric thickness between metal layers forming a main transmission line and a coupled line. An adjustable impedance coupled to the tuning element, i.e., a selectable impedance placed in series in the connection to ground, allows adjustment of this compensating effect and shifts the coupling factor, thus allowing multiple selectable coupling factors and filtering effects based on the selected impedance. The tuning element with a selective impedance coupling to ground forms a variable electromagnetic shunt that affects the capacitive and inductive coupling between the main transmission line110(see, e.g.,FIG. 1) and the coupled line112.

Capacitive and inductive coupling is briefly described with reference toFIG. 2, which shows the power input port102, the power output port104, the coupled port106, and the isolation port108. The main transmission line110and the coupled line112may be considered to be inductors, and there is an inductive coupling between them due to their proximity to one another. Additionally, the proximity of the coupled line112to the main transmission line110forms a capacitor, such that there is also a capacitive coupling between the two lines. Both forms of coupling, inductive and capacitive, vary with proximity between the main transmission line110and the coupled line112, along with other factors such as geometry and material selections. Accordingly, the coupling factor of an EM coupler will vary if the proximity between the main transmission line and the coupled line changes. Modern transmission line couplers may be manufactured using laminate and/or semiconductor techniques, and the transmission lines may be separated from each other by a layer of dielectric material. The coupling factor and other characteristics of an EM coupler may also be varied by other elements, such as a tuning element as disclosed herein, that influence the inductive and capacitive coupling between the main transmission line and the coupled line.

Aspects and embodiments provide a coupler that includes additional elements to influence the inductive and capacitive coupling for the advantage of adjusting the coupling factor and providing frequency dependent filter effects. The coupling factor variation may be further influenced by variation in spacing between the main transmission line and coupled line, such as by variation in dielectric thickness between the lines, spacing between the metal traces forming the lines, or variation in the line widths and heights, all brought about by design differences and by variations during the manufacturing processes. Achieving a specific coupling factor is desirable because the coupled signal may be used to determine the power of the main signal, and thus the ratio of the coupled signal to the main signal, i.e., the coupling factor, may be a key factor to meet challenging performance specifications. In mobile phone applications, the ability to accurately monitor and control signal power can be critical. As devices and components get ever smaller in size and are required to support more or broader frequency bands, adjustability of coupling factor and compensation for variations brought in by the manufacturing process (referred to herein as process variations) may become ever more significant. Embodiments of the EM couplers disclosed herein include additional components acting as tuning stubs to counteract coupling factor variation and to allow adjustability of coupling factor and filter effects.

According to certain embodiments, in an EM coupler, a coupled line may be positioned in various orientations relative to a main transmission line. One or more additional traces or transmission lines may be positioned to affect the coupling between the main transmission line and the coupled line in a manner that will tend to influence the coupling factor, yielding manufactured EM couplers having lower variation in coupling factor than conventional designs and allowing for adjustability of the coupling factor and implementation of filter effects.

Various examples of such arrangements are shown inFIGS. 3A-3E.FIG. 3Ais a top schematic view of an example of an EM coupler, showing the main transmission line110, the coupled line112, and a tuning element118coupled to ground122through one or more impedances124.FIG. 3Bis a corresponding end view of the transmission lines shown inFIG. 3A. In this example, the tuning element118is in the same plane with the main transmission line110, and the coupled line112is located in a different plane below (or above) the tuning element118, separated by a dielectric material120and offset from the main transmission line110. In an alternative example, shown inFIG. 3C, the tuning element118may be in the same plane with the coupled line112, and the main transmission line110may be located in a different plane below (or above) the tuning element118, separated by the dielectric material120and offset from the coupled line112.

The transmission lines110,112, tuning element118, and the dielectric material120may be manufactured by a laminating process or a deposition and etching process, for example. As may be seen inFIGS. 3B and 3C, thickness of the dielectric material120can determine the spacing, or distance, between the first plane and the second plane, and therefore between the tuning element118and either the coupled line112or the main transmission line110. This spacing, the presence of the tuning element118, the value of the impedances124, and other factors all affect the capacitive and inductive coupling among the lines.

The tuning element118in the examples ofFIGS. 3A-3Cinclude a grounding122through an impedance124at each end, forming a partial ground plane and creating an electromagnetic shunt effect with the coupled line112and/or the main transmission line110. The impedance124at each grounding122allows selective and adjustable coupling of the tuning element118to ground. In certain embodiments the tuning element118may include one or more impedances124through which the tuning element118is coupled to a ground122connection. Each impedance124may be an adjustable impedance and may be controlled by various embodiments of elements having variable impedance parameters, e.g., resistance, inductance, capacitance. In certain embodiments an impedance124may be adjustable from zero ohms (i.e., a direct connection to ground122) to infinite impedance (i.e., an open circuit with no connection to ground122), and may include or accommodate any suitable impedance in between, real or complex, i.e., including any of a resistance value and a reactance value. In some examples, an adjustable impedance124may include a number of switched elements interconnected in a manner to be selectively included or excluded in the impedance124. Such an example is discussed in more detail below with reference toFIG. 8. Selective switching of elements may be implemented using transistors as switching elements, such as field effect transistors or bipolar junction transistors, for example, through various fabrication techniques. Alternate embodiments may also include switches to selectively connect the tuning element118to alternate nodes, reference voltages, or otherwise, instead of ground122.

In various embodiments the tuning element118may be adjustably coupled to ground122through the one or more impedances124, including being directly electrically connected to ground122or disconnected from ground122, thereby removing the effect of the tuning element118in cases when it may not be needed. Additionally, the impedances124and the groundings122may be located at differing positions in various embodiments. For example, while the impedances124inFIGS. 3A-3Care shown connected near the ends of the tuning element118, alternate embodiments may include impedances124at additional or alternate positions, such as along the length of the tuning element118, and may be coupled to the tuning element118at its sides, middle, or elsewhere.

In the example embodiment ofFIG. 3B, the coupled line112is substantially below the tuning element118and offset from the main transmission line110. In other embodiments, the coupled line112may be substantially below the main transmission line110and offset from the tuning element118, or the coupled line112may be offset from each of the main transmission line110and the tuning element118, or the transmission lines may be otherwise oriented to each other in any number of ways, such as adjacent each other on the same plane, or otherwise. Additionally, it will be understood that the main transmission line110, the coupled line112, and the tuning element118may have various shapes and may be constructed of various materials. The main transmission line110and the coupled line112may be formed of a conductor, such as a metal, and the tuning element118may also be formed of a conductor, but may alternately be formed of a semiconductor or other material selected based upon its influence on coupling factor.

As discussed above, any of the main transmission line110, the coupled line112, and the tuning element118may have various shapes and, in particular, need not be straight lines nor be limited to a particular plane. Additionally, numerous variations may be made to influence coupling factor or other effects and to tailor the tuning effect of the tuning element118, including but not limited to, material, geometry (width, length, shape, etc.), position, and the like of any of the main transmission line110, the coupled line112, and the tuning element118.

Any physical arrangement of main transmission line110, coupled line112, and tuning element118suitable to perform or function in a tuning manner as described herein may be included in various embodiments. For example,FIGS. 3D and 3Eillustrate alternative physical arrangements of the main transmission line110, the coupled line112, and the tuning element118.FIGS. 3D and 3Eeach illustrate a main transmission line110implemented as a loop, with a coupled line112implemented as a loop adjacent to the main transmission line110and, in this example, in a different plane from the main transmission line110, e.g., on a different layer with a dielectric in between. The example ofFIG. 3Dincludes a tuning element118in the form of a loop in the same plane as the main transmission line110with ends selectively switched124to a grounding122. The example ofFIG. 3Eincludes a tuning element118having a larger continuous form factor, rather than a bent strip, as compared toFIG. 3D. The tuning element118of the example ofFIG. 3Ealso includes an adjustable impedance124coupling to ground122. Alternate embodiments include numerous variations in physical structure, materials, and arrangement of the main transmission line110, coupled line112, and tuning element118.

WhileFIGS. 3A-3Eillustrate various physical shapes and arrangements of the main transmission line110, coupled line112, and tuning element118relative to each other,FIG. 4illustrates an example of locations for these elements within a stackup400.FIG. 4illustrates some aspects of an example construction of any of the EM couplers described herein. The example ofFIG. 4includes a circuit stackup400that includes a laminate substrate410and a die420mounted on and electrically connected to the laminate substrate410via solder bumps412. The substrate410and the die420are each made up of multiple layers of conducting (e.g., metal) or semiconducting materials separated by dielectric, with interconnections between layers through conductive vias. In various embodiments, the die420may be electrically connected to the substrate410by other arrangements, such as pins, sockets, pads, balls, lands, etc. Other embodiments may include only a laminate substrate410and no die420.

In the example ofFIG. 4, the main and coupled line sections of the EM coupler are implemented within the layers of the substrate410.FIG. 4shows an “end view” of the main transmission line110and the coupled line112in that the extent of their length may be perpendicular to the plane of the image. As shown, the coupled line112is formed on a layer below and offset from the main transmission line110, and below and in proximity to the tuning element118, similar to the arrangement ofFIG. 3B. In embodiments and as shown inFIG. 4, the tuning element118may be in the same layer as, and adjacent to, the main transmission line110. As discussed above, the main transmission line110and the coupled line112may be exchanged in the figure, or other physical arrangements of the elements relative to each other may be suitable. Also as discussed above, in certain embodiments, any of the main transmission line110, coupled line112, or tuning element118may include curved or angled sections and may not be straight. Additionally, the main transmission line110, coupled line112, and tuning element118may be implemented in one or more layers of either the substrate410or the die420. Additionally, while the stackup400has been described as a substrate410and a die420, the stackup400could equivalently be described as a circuit board (e.g.,410) and a substrate (e.g.,420), or a stackup may have multiple and/or additional layered structures. For example, a multi-chip module may have a substrate and multiple dies, and a device may include a circuit board having one or more multi-chip modules mounted thereto. The main transmission line110, coupled line112, and tuning element118of any of the EM couplers described herein may be implemented among or across multiple layers of various structures.

Additionally, switches, groundings, filters, impedances (such as impedances124), control circuitry, communication interfaces, and memory, as well as other components, may also be implemented within a stackup, such as the stackup400, at one or more layers of a circuit board, a substrate, or a die, or may be distributed among the various layers or may be external to a stackup, or any combination of these.

As discussed above, the effect of the tuning element118coupled to ground122through an impedance124is to shunt some coupled power away from the other elements, i.e., the main transmission line110and the coupled line112. A resistive component of the impedance124causes the tuning element118to shunt more or less power away, thereby affecting coupling factor. Further including a reactive component in the impedance124may cause the tuning element118to shunt more or less power away based upon frequency, thereby creating filter effects. Certain examples may include only a resistive component, i.e., an impedance having only a real value, and no reactive components, i.e., an impedance without any complex or imaginary value. Such a resistive-only impedance may be implemented to allow adjustment of coupling factor without producing frequency-dependent effects.

Accordingly, electromagnetic couplers having a tuning element118in accord with aspects and embodiments disclosed herein allow for tunable adjustment of coupling factor and for frequency-dependent filtering to accommodate varying needs and applications, and/or to compensate for variations in manufacturing process. The adjustable effect of the tuning element118is discussed with reference to performance graphs illustrated inFIGS. 5 through 7.FIG. 5shows multiple curves of coupling factor on the Y-axis across a range of frequencies on the X-axis. Each curve represents a different resistive value between 0 and 5 Ohms for the impedances124for a tunable coupler similar to that shown in, e.g.,FIGS. 3A-3B. Curve512shows the coupling factor versus frequency for an impedance124of zero Ohms, i.e., a direct connection to ground122. Curve514shows the coupling factor versus frequency for an impedance124of 2 Ohms, while curve516shows coupling factor for an impedance124of 5 Ohms. Intermediate curves show coupling factor for intermediate integer resistive values of impedance124. The coupling factor values at a frequency of 2.00 GHz across resistive impedance124values of 0 to 5 Ohms are tabulated in Table 1, in decibels.

As may be seen with reference to Table 1, coupling factor may be adjusted within an 8 dB range spanning from about 28 dB to 36 dB in this example, by altering a resistive impedance124applied to couple the tuning element118to ground122. Accordingly, varying the resistive coupling to ground of a tuning element118may be advantageously implemented to vary the coupling factor of an electromagnetic coupler. Frequency effects, such as frequency notch filtering, may also be advantageously applied (and varied) by including (and varying) a reactive component in the ground coupling, e.g., impedance124, of the tuning element118, as discussed further below.

Frequency filtering of aspects and embodiments can be described with reference to insertion loss. Insertion loss is a comparison of signal power at the output of the coupler relative to the signal power at the input. The majority of input signal power is typically transferred to the output port, with a relatively small amount of signal power coupled to the coupled port, and thus insertion loss is typically close to zero decibels in the operating frequency range of the coupler. Each ofFIGS. 6 and 7shows multiple curves of insertion loss across a range of frequencies for a tunable coupler similar to that shown inFIGS. 3A-3B. Each curve represents a different capacitive impedance124in the case ofFIG. 6and a different inductive impedance124in the case ofFIG. 7. A reduced signal output, as shown inFIGS. 6 and 7at higher frequencies, represents signal power that is rejected by the coupler, e.g., signal power that is not transferred through to the output port. The tuning element118shunts a portion of the power through the impedance124to ground122, which contributes to signal power being rejected, e.g., not transferred to the output port. This effect is advantageously used to reject, e.g., filter out, unwanted signal power in, e.g., a specific frequency range.

With reference toFIG. 6, the curve610shows insertion loss versus frequency for an impedance124having 10 pico-Farads (pF) capacitance. Curve620shows insertion loss for an impedance124having 6 pF capacitance, and curve630for an impedance124with 3 pF capacitance. Intermediate curves inFIG. 6represent intermediate integer capacitance values. As can be seen with reference toFIG. 6, this example provides a coupler that may be adjusted to produce a peak reduction of about 6 dB in signal power at an adjustable frequency from about 2.8 GHz (at the peak of curve610) to more than 6 GHz (at curve peaks off the scale to the right ofFIG. 6).

With reference toFIG. 7, the curve710shows insertion loss versus frequency for an impedance124having 15 nano-Henries (nH) inductance. Curve720shows insertion loss for an impedance124having 11 nH inductance, and curve730for an impedance124with 8 nH inductance. Intermediate curves inFIG. 7represent intermediate integer inductance values. As can be seen with reference toFIG. 7, this example provides a coupler that may be adjusted to produce a peak reduction of about 15 dB in signal power at an adjustable frequency from about 4.1 GHz (at the peak of curve710) to more than 6 GHz (at curve peaks off the scale to the right ofFIG. 7).

The graphs ofFIGS. 6 and 7illustrate that for various reactive impedances124there is a frequency at which an input signal will be significantly reduced at the output, by action of the tuning element118and the impedance124coupling to ground122. The curves inFIGS. 6 and 7illustrate operation of the coupler as a notch filter that rejects a narrow band or “notch” of frequencies. In the examples shown inFIGS. 6 and 7there is an effective upper limit of frequency passed by the coupler. Higher frequencies are rejected by the coupler, i.e., reduced transfer from the input to the output, which may be useful to filter out sidetones and harmonics above an intended frequency band of operation. Accordingly, an adjustable frequency rejection, or filtering, may be implemented by variably adjusting a reactance of the impedance124. In certain examples, tunable couplers may include various combinations of resistances, impedances, and capacitances to provide various fixed or adjustable impedances124that couple a tuning element118to ground122to advantageously tune the coupling factor and/or frequency-dependent filtering effects, or to advantageously allow adjustability of the coupling factor and/or frequency-dependent filtering effects.

One example of an adjustable impedance124is shown inFIG. 8. The impedance124circuit shown inFIG. 8includes multiple banks810,820,830of impedance elements840that may be selectively switched850into the circuit of impedance124. As shown, each bank810,820,830includes one or more impedances840in parallel, and the banks810,820,830are arranged in series with common nodes812,822,832between the banks810,820,830. In the example shown, at least one of the impedances840in each bank810,820,830has zero impedance so that each bank810,820,830may be selectively bypassed. Further, if all the banks810,820,830are bypassed, the impedance124has overall zero impedance and couples directly to ground122, i.e., provides a zero ohm connection between a tuning element118and ground122. Additionally, if all the switches850are open-circuited, the impedance124provides an open circuit, i.e., disconnects the tuning element118from ground122. Each of the switches850may be formed of one or more transistors, such as field effect transistors, bipolar junction transistors, or other suitable transistor types; or may be formed of micro-electromechanical systems (MEMS) or the like; or any other suitable switching element that enables selective connectivity of the impedance elements840between the nodes812,822,832.

The switches850may be controlled by a control logic providing a signal voltage to, e.g., one or more transistor gates, transistor bases, and the like. Controllers may include memory and store switch settings, e.g., on or off, conducting versus non-conducting, to control the switches850to establish a particular impedance value presented by the impedance124. A controller may be part of a device and may adjust the impedance124to adjust the coupling factor, filter effects, or both, in response to operating parameters of the device, such as frequency band of operation, or feedback from other devices or components, command and control signals from other devices or components, or user-established settings, for example.

The adjustable impedance124shown inFIG. 8is merely one example of an adjustable impedance and any adjustable impedance may be suitable for adjusting the coupling factor and/or filter effects of couplers in accord with aspects and embodiments disclosed herein. Additionally, certain embodiments may include a fixed impedance124to establish a fixed coupling factor and/or filter effect. Additionally, a coupler design may include one or more impedances124provided during one portion of a fabrication process that are selectively wired during another portion of fabrication to produce multiple part numbers having differing coupling factors and/or filter effects. Alternately, multiple impedances124may be provided during one portion of fabrication that are selectively connected or selectively disconnected during another portion of fabrication based upon the results of performance tests or manufacturing variation tests to provide a mass manufacture of parts having a higher yield than would otherwise be the case.

As discussed above, the main transmission line110, coupled line112, and tuning element118may be straight (linear) traces of, e.g., electrical conductors, or may be non-linear and/or made of varying materials. One or more of the main transmission line110, coupled line112, and tuning element118may have bends or curves and may be helical, spiral, or C-shaped, for example. In particular embodiments, any or all of the main transmission line110, coupled line112, and tuning element118may be formed into inductor turns or may be patterned, e.g., mesh, sawtooth, etc. Various embodiments may include any suitable shaping and relative proximity to achieve the desired coupling factor range(s), filtering effect(s), and compensation for manufacturing variability.

Additionally, one or more of the main transmission line110, coupled line112, and tuning element118may be sectioned so as to have selectively adjustable length. For example, a suitable set of switches (e.g., FETs, MEMS) may interconnect various sections of transmission line, and a controller can be programmed to control the switches to selectively connect the various sections in multiple ways to form one or more main transmission lines110, one or more coupled lines112, and one or more tuning elements118, to adjust to changing operational parameters or applications.

As discussed above, various embodiments of tunable couplers disclosed herein may be useful in a wide variety of electronic devices. Examples of such electronic devices can include, but are not limited to, consumer electronic products, parts of consumer electronic products, electronic test equipment, cellular communications infrastructure such as a base station, a mobile phone such as a smart phone, a telephone, a television, a computer monitor, a computer, a modem, a hand held computer, a laptop computer, a tablet computer, an electronic book reader, a wearable computer such as a smart watch, a personal digital assistant (PDA), a microwave, a refrigerator, an automobile, a stereo system, a DVD player, a CD player, a digital music player such as an MP3 player, a radio, a camcorder, a camera, a digital camera, a portable memory chip, a health care monitoring device, a vehicular electronics system such as an automotive electronics system or an avionics electronic system, a washer, a dryer, a washer/dryer, a peripheral device, a wrist watch, a clock, etc. Further, the electronic devices can include unfinished products.

FIGS. 9A-9Cillustrate examples of devices including a tunable EM coupler100aaccording to various embodiments discussed above. The EM coupler100ais configured to extract a portion of power of an RF signal traveling between a transceiver920and an antenna930. In general, the EM coupler100ais a bi-directional coupler. As illustrated, in the forward or transmit direction, a power amplifier940receives an EM signal, such as an RF signal, from the transceiver920and provides an amplified signal to the antenna930via an antenna switch module950and the EM coupler100a. Similarly, in the receive direction, a received signal is provided from the antenna930to the transceiver920via the EM coupler100a, the antenna switch module950, and a low noise amplifier960. Various additional elements may be included in a wireless device, such as the wireless device900ofFIGS. 9A-9C, and/or in some embodiments a sub-combination of the illustrated elements may be implemented.

The power amplifier940amplifies an RF signal. The power amplifier940can be any suitable power amplifier. For example, the power amplifier940can include one or more of a single stage power amplifier, a multi-stage power amplifier, a power amplifier implemented by one or more bipolar transistors, or a power amplifier implemented by one or more field effect transistors. The power amplifier940can be implemented on a GaAs die, CMOS die, or a SiGe die, for example.

The antenna930can transmit the amplified signal, and receive signals. For example, in a cellular phone, wireless base station, or the like, the antenna930can transmit and receive RF signals to and from other devices. In alternate embodiments multiple antennas may be used.

Operating in the forward mode, the EM coupler100acan extract a portion of the power of the amplified signal traveling between the power amplifier940and the antenna930. The EM coupler100acan generate an indication of forward power traveling from the power amplifier940to the antenna930, for example. Operating in the reverse mode, the EM coupler100acan generate an indication of reflected power traveling from the antenna930toward the power amplifier940, or can extract a portion of the power of a signal received by the antenna930from an external source. In either mode, the EM coupler100amay provide the signal portion to a sensor912that provides power feedback by measuring the power of the signal portion.

The examples of wireless device900ofFIGS. 9A-9Cfurther include a power management system904that is connected to the transceiver920that manages the power for the operation of the wireless device. The power management system904can also control the operation of a baseband sub-system906and other components of the wireless device900. The power management system904may manage power within the wireless device900by, for example, providing power to the wireless device900from a battery902or providing power to the wireless device900from a power connector, and controlling a charge level of the battery902by controlling charge and discharge cycles and/or status of the battery902.

In one embodiment, the baseband sub-system906is connected to a user interface908to facilitate various input and output of voice and/or data provided to and received from the user. The baseband sub-system906can also be connected to memory910that is configured to store data and/or instructions to facilitate operation of the wireless device900, and/or to provide storage of information for the user.

The power amplifier940can be used to amplify a wide variety of RF or other frequency-band transmission signals. For example, the power amplifier940can 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. The power amplifier940can be configured to amplify any of a variety of types of signal, including, 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, an EDGE signal, and the like. In certain embodiments, the power amplifier940and associated components including switches and the like can be fabricated on GaAs substrates using, for example, pHEMT or BiFET transistors, or on a Silicon substrate using CMOS transistors, as well as other semiconductor fabrication technologies.

Still referring toFIGS. 9A-9C, the wireless device900can also include a tunable coupler100ahaving one or more directional EM couplers for measuring transmitted power signals from the power amplifier940and for providing one or more coupled signals to a sensor module912. The sensor module912can in turn send information to the transceiver920and/or directly to the power amplifier940as feedback for making adjustments to regulate the power level of the power amplifier940. In this way the tunable coupler100acan be used to boost/decrease the power of a transmission signal having a relatively low/high power. It will be appreciated, however, that the tunable coupler100acan be used in a variety of other implementations.

In certain embodiments of any of the examples of the wireless device900, transmissions from the wireless device900may have prescribed power limits and/or time slots. The power amplifier940may 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 power amplifier940may be required to regulate the power level of 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 tunable coupler100acan be used to measure the power of a power amplifier output signal to aid in controlling the power amplifier940, as discussed above. The implementations shown inFIGS. 9A-9Care intended to be exemplary in nature only and non-limiting.

The example shown inFIG. 9Bincludes a combination module970that includes a tunable coupler in accord with aspects and embodiments described herein combined with an antenna switch module (e.g., ASM950). The example shown inFIG. 9Cincludes a combination module980that incorporates a tunable coupler, an antenna switch module, and a power amplifier (e.g., PA940) together as a front end module (module980). Additional embodiments include a front end module that further incorporates one or more low noise amplifiers (e.g., LNA960) and/or sensors (e.g., sensor912).

Embodiments of the tunable coupler100adescribed herein can be implemented in a variety of different modules including, for example, a stand-alone coupler module, a front-end module, a module combining the tunable coupler with an antenna switching network, an impedance matching module, an antenna tuning module, or the like.FIG. 10illustrates one example of a coupler module that can include any of the embodiments or examples of the tunable coupler discussed herein.

FIG. 10is a block diagram of one example of a module1000that includes an embodiment of the tunable coupler100a. The module1000includes a substrate1002and may include various dies and may include packaging, such as, for example, an overmold to provide protection and facilitate easier handling. An overmold may be formed over substrate1002and dimensioned to substantially encapsulate the various dies and components thereon. The module1000may further include connectivity from the coupler100ato the exterior of the packaging to provide signal interconnections, such as input port connection1004, output port connection1006, coupled port connection1008, and isolation port connection1010. The connections1004,1006,1008, and1010may be wirebonds or solder bumps, for example. Embodiments of the tunable coupler disclosed herein, optionally packaged into a module1000, may be advantageously used in a variety of electronic devices as discussed above.