Multiple coupler placements in advanced transmit architectures

Abstract

To provide access to optimal measurements needed for the entire set of needs for DPD and emission correction right at an output of a PA, and to measurements closer to an antenna for power accuracy and antenna tuning, etc.SOLUTION: A front-end module includes a power amplifier, first and second couplers, an antenna switch, and a switch sub-assembly. The power amplifier has an input to receive a radio frequency signal, and an output to provide an amplified radio frequency signal. The first coupler has an input port coupled to the output of the power amplifier, an output port coupled to an input of the antenna switch, a coupled port, and an isolated port. The second coupler has an input port coupled to an output of the antenna switch, an output port coupled to an antenna port, a coupled port, and an isolated port.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Background Wireless devices typically generate electromagnetic (EM) signals at radio frequencies (RF) within the electromagnetic spectrum that can be propagated to other wireless devices for communication purposes. When an electromagnetic signal generated by a source is applied to a load such as an antenna, a portion of this signal may be reflected back from the load. By including an electromagnetic coupler within the signal path between the source and the load, it is possible to provide an indication of the forward power of the electromagnetic signal traveling from the source to the load and / or an indication of the reverse power reflected back from the load. Electromagnetic couplers include, for example, directional couplers, bidirectional couplers, multi-band couplers (e.g., dual-band couplers), and the like.

Background Art

[0002] An EM coupler typically has an input port, an output port, a coupling port, and a decoupling port. When a termination impedance is applied to the decoupling port, an indication of the forward EM power traveling from the input port to the output port is provided at the coupling port. When a termination impedance is applied to the coupling port, an indication of the reverse EM power traveling from the output port to the input port is provided at the decoupling port. The termination impedance is typically realized as a 50-ohm shunt resistor in various conventional EM couplers.

[0003] An EM coupler has a coupling coefficient that represents how much power is supplied to the coupling port of the EM coupler relative to the power of the EM signal at the input port. EM couplers typically introduce insertion loss into the EM signal path. Therefore, the power of the EM signal received at the input port of an EM coupler is generally lower when supplied at the output port of the EM coupler. The cause of insertion loss can be a portion of the EM signal supplied to the coupling port (or decoupling port), and / or losses associated with the main transmission line of the EM coupler. In addition, conventional EM couplers add insertion loss to the signal path even when not in use. This can degrade the EM signal even when the EM coupler is not being used for power sensing. [Overview of the project] [Means for solving the problem]

[0004] Summary of the Invention According to at least one embodiment, a front-end module is provided, the front-end module comprising a power amplifier configured to amplify a radio frequency signal, the power amplifier having an input configured to receive a radio frequency signal and an output configured to provide an amplified radio frequency signal, further comprising a first coupler having an input port, an output port, a coupling port and a decoupling port, the input port being coupled to the output of the power amplifier, further comprising an input coupled to the output port of the first coupler, and an output, and further comprising a second coupler having an input port, an output port, a coupling port and a decoupling port, the input port of the second coupler being coupled to the output of the antenna switch module, further comprising an antenna port configured to be coupled to an antenna, the antenna port being coupled to the output port of the second coupler, further comprising a first switch subassembly, the first switch subassembly switchably connecting one of the coupling port and decoupling port of the second coupler to the output of the first switch assembly and the other of the coupling port and decoupling port of the second coupler to a first termination impedance.

[0005] In one example, the isolation port of the first coupler is connected to the second termination impedance. In another example, the front-end module further comprises a second switch subassembly, which is switchable to connect one of the coupling and decoupling ports of the first coupler to the output of the second switch subassembly, and the other of the coupling and decoupling ports of the first coupler to a second termination impedance.

[0006] In one example, the front-end module further includes a filter connected between the output port of the first coupler and the input of the antenna switch module.

[0007] In another example, the front-end module further comprises a controller coupled to a first and a second switch subassembly, configured to obtain a first measurement from the output of the second switch assembly by connecting the coupling port of the first coupler to the output of the second switch assembly and the isolation port of the first coupler to the second termination impedance, the first measurement providing an indication of the forward power provided by the power amplifier.

[0008] In one example, the controller is further configured to obtain a second measurement from the output of the first switch assembly by connecting the coupling port of the second coupler to the output of the first switch assembly and the isolation port of the second coupler to the first termination impedance, the second measurement providing an indication of the forward power present on the antenna.

[0009] In another example, the controller is further configured to obtain a second measurement from the output of the first switch assembly by connecting the isolation port of the second coupler to the output of the first switch assembly and the coupling port of the second coupler to the first termination impedance, the second measurement providing an indication of the power reflected from the antenna.

[0010] In one example, the controller is further configured to adjust the antenna impedance based on the power reflected from the antenna.

[0011] In another example, the controller is further configured to acquire a first measurement from the output port of the first coupler and a second measurement from the output port of the second coupler.

[0012] In one example, the controller is further configured to linearize the amplified radio frequency signal by modifying the radio frequency signal received by the power amplifier based on a first measurement and a second measurement.

[0013] In another example, the controller is further configured to determine the amplitude and phase of a transfer function that describes the power change of the amplified radio frequency signal between the power amplifier and the antenna, based on the first and second measurements.

[0014] In one example, the controller is configured to further operate a switch assembly to obtain a measurement of the forward power supplied to the antenna, to operate a switch assembly to obtain a measurement of the reflected power from the antenna, to calculate the ratio between the measurement of the forward power and the measurement of the reflected power, and to adjust the amount of power supplied by the power amplifier based on the calculated ratio.

[0015] In another example, the front-end module further comprises a second power amplifier configured to amplify a second radio frequency signal, the second power amplifier having an input configured to receive a second radio frequency signal and an output configured to provide a second amplified radio frequency signal, and further comprises a third coupler having an input port, an output port, a coupling port and a decoupling port, the input port of the third coupler coupled to the output of the second power amplifier, and the output port of the third coupler coupled to a second input of the antenna switch module, and further comprises a fourth coupler having an input port, an output port, a coupling port and a decoupling port, the input port of the fourth coupler coupled to a second output of the antenna switch module, and further comprises a second antenna port configured to couple to a second antenna, the second antenna port coupled to a second output of the second coupler.

[0016] In one example, a power amplifier, a first coupler, a second coupler, and an antenna port form a first chain, and a second power amplifier, a third coupler, a fourth coupler, and a second antenna port form a second chain, and the amplified radio frequency signal of the first chain is in a different frequency band than the second amplified radio frequency signal of the second chain.

[0017] In another example, an amplified radio frequency signal and a second amplified radio frequency signal are transmitted simultaneously.

[0018] In one example, the radio frequency signal received at the input of the power amplifier has a frequency in one of the following ranges: approximately 600 MHz to approximately 2.5 GHz, approximately 450 MHz to approximately 6 GHz, and approximately 24 GHz to approximately 52 GHz.

[0019] In another example, the first coupler is a unidirectional coupler, and the second coupler is a bidirectional coupler.

[0020] According to at least one embodiment, a front-end module is provided, the front-end module comprising a power amplifier configured to amplify a radio frequency signal, the power amplifier having an input configured to receive a radio frequency signal and an output configured to provide an amplified radio frequency signal, further comprising a first coupler having an input port, an output port, a coupling port and a decoupling port, the input port being coupled to the output of the power amplifier, and further comprising an antenna switch module having an input coupled to the output port of the first coupler and an output, and a second coupler having an input port, an output port and a coupling port and a decoupling port The system comprises a second coupler, the input port of which is coupled to the output of an antenna switch module, and further comprises an antenna port configured to be coupled to an antenna, the antenna port of which is coupled to the output port of the second coupler, and further comprises a first switch subassembly, the first switch subassembly switchably connects one of the coupling and decoupling ports of the second coupler to the output of the second switch subassembly and the other of the coupling and decoupling ports of the second coupler to a second termination impedance, or connects each of the coupling and decoupling ports of the second coupler to a second termination impedance.

[0021] In one example, the isolation port of the first coupler is connected to the second termination impedance. In another example, the front-end module further comprises a second switch subassembly, which is switchable to connect one of the coupling and decoupling ports of the first coupler to the output of the second switch subassembly, and the other of the coupling and decoupling ports of the first coupler to a second termination impedance.

[0022] In one example, the front-end module further includes a filter connected between the output port of the first coupler and the input of the antenna switch module.

[0023] In another example, the front-end module further includes a controller, which is coupled to the first switch sub-assembly and the second switch sub-assembly, and is configured to obtain a first measurement value from the output of the second switch assembly by connecting the coupling port of the first coupler to the output of the second switch assembly and connecting the separation port of the first coupler to the second termination impedance. The first measurement value provides an indication of the forward power provided by the power amplifier.

[0024] Still other aspects, embodiments, and advantages of these specific aspects and embodiments as examples are described in detail below. Embodiments disclosed herein may be combined with other embodiments in any manner consistent with at least one of the principles disclosed herein. When reference is made to "an embodiment", "some embodiments", "alternative embodiments", "various embodiments", "one embodiment", etc., it is not necessarily mutually exclusive, and it is intended that the specific features, structures, or characteristics described may be included in at least one embodiment. The appearance of such terms herein does not necessarily refer to all the same embodiments.

[0025] Various aspects of at least one embodiment are described below with reference to the accompanying drawings, which are not intended to be to scale. The drawings are included to provide examples of various aspects and embodiments and to obtain a further understanding, and are incorporated herein and constitute a part thereof, but are not intended to define the limitations of the invention. In the drawings, each identical or substantially identical component shown in the various drawings is represented by like numerals. For clarity, not all components are labeled in every drawing.

Brief Description of the Drawings

[0026] [Figure 1] FIG is a block diagram of an example of an electronic system including a coupler disposed between a power amplifier and a filter. [Figure 2]A block diagram of an example of an electronic system including a coupler disposed between an antenna switch module and an antenna port. [Figure 3] A block diagram of an example of an electronic system including a first coupler and a second coupler according to an aspect of the present invention. [Figure 4A] A circuit diagram of an example of a switch assembly according to an aspect of the present invention. [Figure 4B] A circuit diagram of an example of a switch assembly according to an aspect of the present invention. [Figure 5A] A block diagram of an example of an electronic system including a plurality of transmission lines each including a first coupler and a second coupler according to an aspect of the present invention. [Figure 5B] A block diagram of an example of an electronic system including a plurality of transmission lines each including a first coupler and a second coupler according to an aspect of the present invention. [Figure 6] A circuit diagram of an example of an electronic system that transmits in two different bands according to an aspect of the present invention. [Figure 7] A circuit diagram of an example of an electronic system that transmits in two different bands according to an aspect of the present invention. [Figure 8] A circuit diagram of an example of an electronic system that transmits in two different bands according to an aspect of the present invention.

Embodiments of the Invention

[0027] Detailed Description <00Radio frequency (RF) couplers or electromagnetic (EM) couplers can be used in modern cellular and connectivity transmit architectures to: 1) accurately measure forward power to optimize uplink transmit radiated power (TRP), signal-to-noise ratio (SNR), DC efficiency, and linearity; 2) as part of a closed-loop power control system to adaptively compensate to maintain known and / or constant power levels; 3) measure reflected power as an indicator of mismatched load variations on a transmitting antenna; 4) measure both forward and reflected power as a means of determining the complex impedance of an antenna in an attempt to adjust and retune it to improve load impedance; and 5) measure out-of-channel radiation of a power amplifier to adaptively compensate for linearity through analog stimulus change techniques and / or digital pre-distortion (DPD) techniques.

[0028] In some cases, couplers can be placed either 1) immediately after the power amplifier (PA) and before the acoustic filtering to take closed-loop / DPD into consideration and to get as accurate a picture as possible of the linearity / radiation / impedance environment of the power amplifier, or 2) close to the antenna to get as close as possible to the exact forward / reflected power present on the antenna. Conventional implementations of couplers introduce insertion loss and size / cost into the entire transmit path.

[0029] The coupling coefficient of the coupler can be further controlled by complex impedance termination on unused ports, which can significantly improve directivity and frequency dependence, thereby optimizing the insertion loss and size of the coupler. Whether integrated into a laminate / FR4 PCB metal trace with switching and termination control within a silicon-on-insulator (SOI) chip of a band-selective switch or antenna switch module (ASM), or integrated entirely within the SOI chip of the band-selective switch or ASM, the coupler can be made smaller and incorporated using lamination and / or 3D packaging techniques to further reduce size and improve the quality factor (Q) and insertion loss. As described in the embodiments presented herein, a multiplexed configuration architecture is provided consisting of two couplers (one immediately after the PA for optimal DPD and power amplifier (PA) linearity adjustment / out-of-band radiation correction, and the other behind the ASM to improve proximity to the load antenna for power accuracy). As insertion loss decreases, it becomes possible to use both of these couplers for different applications, and even simultaneous measurements become possible using the solutions provided herein. Each of these couplers provides access to the optimal measurements needed for the entire set of needs for DPD and radiation correction at the very output of the PA, as well as measurements closer to the antenna for power accuracy and antenna tuning.

[0030] Another advantage of the two-coupler design is that it facilitates a complete understanding of the transfer function describing the transmission path from the PA output to the antenna. Since the transfer function is known, it becomes possible to reliably add a DPD. Every component encountered along the transmission path by the input signal affects or distorts the signal in some way. Therefore, there exists a transfer function for each component that describes how the signal is altered by its components. By knowing the power of the signal in the transmission path in the first and second couplers, the transfer function of the entire transmission path can be estimated by finding the transfer function that describes the power change between the first and second couplers.

[0031] By using both couplers simultaneously, it is possible to: 1) accurately measure the complex transfer function between the power amplifier and the antenna pin of the integrated module, providing accurate measurements of the in-band transmit (Tx) filter contour and S21+ASM insertion loss characteristics for each Tx path in each band (conventional single coupler modules do not provide this signal on an internal node or access to these signals); 2) measure the out-of-band attenuation and harmonic characteristics of the Tx path; 3) measure the complex transfer function characteristics of the entire block between the couplers for RF development and tuning; and 4) enable programmable adjustments to the shunt inductor and LPF / notch that can improve / adjust the filter contour / mismatch insertion loss and out-of-band attenuation. These can be used one at a time, sequentially, or simultaneously for combined data analysis by the feedback receiver and modem baseband, ultimately enabling more dynamic adjustments as the block becomes more programmable and tunable and measurements are required to optimize the tunable transmit component.

[0032] It should be understood that the embodiments of the methods and apparatus described herein are not limited to the details of the structure and arrangement of components described below or shown in the accompanying drawings. The methods and apparatus described above are also achievable in other embodiments and can be implemented or performed in a variety of ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to limit. Furthermore, the expressions and terms used herein are for illustrative purposes only and should not be considered limiting. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof means that they encompass the items listed therein and their equivalents and other items. The “or” statement can be interpreted as comprehensive, meaning that any term described using “or” may refer to one, two or more, or all of the terms described.

[0033] Figure 1 is a schematic block diagram of an example of electronic system 2, in which an EM coupler 10 is configured to extract a portion of the power of the EM signal transmitted between the transceiver 4 and the antenna 22. Electronic system 2 may be contained in a front-end module. In this example, the EM coupler 10 is a bidirectional coupler. As shown, in the forward or transmit direction, a power amplifier 8 receives the EM signal 6 from the transceiver 4 and provides the amplified EM signal to the antenna 22 via the EM coupler 10, filter 12, antenna switch module (ASM) 14, and antenna port 18, which are operating in forward mode. In some examples, the filter 12 is a surface acoustic wave filter. Those skilled in the art will understand that additional elements (not shown) may be included in the electronic system of Figure 1, and / or secondary combinations of the elements shown can be realized. Furthermore, the components of system 2 may be arranged in an order different from the order shown in Figure 1. Electronic system 2 includes a loss 20 between the antenna port 18 and the antenna 22 due to components in the transmission path between the filter 12 and the antenna 22. Some examples of loss 20 include resistive and inductive (or capacitive) shunts connected to antenna port 18 and antenna 22.

[0034] Continuing to refer to Figure 1, the EM coupler 10 typically has a power input port 9 (RF_IN), a power output port 11 (RF_OUT), a coupling port 13 (COUPLED), and a isolation port 15 (ISOLATED). The electromagnetic coupling mechanism, which may include inductive or capacitive coupling, is typically provided by two parallel or overlapping transmission lines, such as microstrips, strip lines, or coplanar lines. The main transmission line extends between the power input port 9 and the power output port 11, providing the majority of the signal from the power input port 9 to the power output port 11. The coupling line extends between the coupling port 13 and the isolation port 15, and can extract a portion of the power transmitted between the power input port 9 and the power output port 11 for various purposes, including various measurements. When a termination impedance is applied to the isolation port 15, an indication of the forward RF power transmitted from the power input port 9 to the power output port 11 is provided to the coupling port 13.

[0035] The antenna switch module 14 can selectively electrically connect the antenna 22 to a selected transmit path Tx or a selected receive path Rx16. The antenna switch module 14 can provide several switching functions. The antenna switch module 14 may include a multi-throw switch configured to provide functions such as switching between transmit mode and receive mode, switching between transmit or receive paths associated with different frequency bands, switching between transmit or receive paths associated with different operating modes, or any combination thereof.

[0036] The power amplifier 8 amplifies the EM signal 6 received from the transceiver. The power amplifier 8 can be any suitable EM power amplifier. For example, the power amplifier 8 may include one or more of the following: 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 amplifier 8 can be mounted on, for example, a GaAs chip, a CMOS chip, or a SiGe chip.

[0037] Antenna 22 can transmit and receive amplified EM signals. For example, if the electronic system 2 is included in a mobile phone, antenna 2 can transmit EM signals from the mobile phone to a base station and can also receive EM signals from the base station.

[0038] When the electronic system shown in Figure 1 is operating in transmit mode, the EM coupler 10 can extract a portion of the RF signal power transmitted between the power amplifier 8 and the antenna 22. The EM coupler 10 can generate a representation of the forward RF power transmitted from the power amplifier 8 to the antenna 22, and / or a representation of the reflected (reverse) power transmitted from the antenna 22 to the power amplifier 8. The forward or reflected power representation at output 30 can be provided to a power detector (not shown). The EM coupler 10 has four ports: an input port 9 (RF_IN), an output port 11 (RF_OUT), a coupling port 13, and a decoupling port 15. In the configuration of system 2 shown in Figure 1, the input port 9 can receive the amplified EM signal from the power amplifier 8, and the output port 11 can provide the amplified EM signal to the antenna 22. The termination impedance can be connected to the decoupling port 15 (for forward operation) or to the coupling port 13 (for reverse operation). When the termination impedance is connected to the isolation port 15, the coupling port 13 can provide a portion of the power of the EM signal transmitted from the input port 9 to the output port 11. Thus, the coupling port 13 can provide a representation of the forward EM power. When the termination impedance is connected to the coupling port 13, the isolation port 15 can provide a portion of the power of the EM signal transmitted from the output port 11 to the input port 9. Thus, the isolation port 15 can provide a representation of the reverse EM power.

[0039] By placing the EM coupler 10 immediately after the power amplifier 8, an optimal measurement of the power supplied by the power amplifier 8 is provided without affecting the Rx signal path. For example, although not shown in Figure 1, the Rx path may be a separate receiving path coupled to the antenna port 18, including a low-noise amplifier (LNA) and optionally with a receiving filter in between, or it may be an independent receiving path coupled to a second port of the ASM. Placing the EM coupler 10 in this position brings other advantages. For example, this arrangement facilitates an accurate adjacent channel leakage ratio (ACLR), which is the ratio of the transmitted power to the measured power after the receiver filter in adjacent channels (multiple channels).

[0040] To switch between generating forward power and reflected (reverse) power, the controller 24 is configured to operate multiple switches in the switch assembly 26 through control lines 28. In some examples, the controller 24 is a general-purpose processor. In other examples, the controller 24 is a customized microcontroller. Other suitable examples of the controller 24 are intended herein. The switch assembly 26 includes a termination impedance, which includes a resistor 17 and an inductor 19 connected in series between the node and ground, as shown in Figure 1. The node is connected to one switchable terminal each of a first single-pole double-throw (SPDT) switch 21 and a second single-pole double-throw (SPDT) switch 23. The other switchable terminal of each SPDT switch is coupled to output 30. To generate reverse power, the controller 24 operates the first switch 21 through one or more control lines 28 to connect the coupling port 13 to the termination impedance, and operates the second switch 23 through one or more control lines 28 to connect the isolation port to output 30. In some examples, output 30 is coupled to a controller 24 and provides the controller with a reverse power indication. In other examples, output 30 is coupled to a separate electronic device (not shown) for processing the data obtained from output 30. To generate a forward power indication, the controller 24 connects the coupling port 13 to output 30 by operating a first switch 21 through a control line 28, and connects the disconnection port 15 to the termination impedance by operating a second switch 23 through the control line 28. Although shown in Figure 1 as having a fixed value, it is understood that a variable termination impedance can be provided by using a variable resistor, variable inductor, and / or variable capacitor connected in series with ground instead of the indicated termination impedance. As a result, a desired termination impedance can be provided to each port by tuning the termination impedance to adjust the resistance, capacitance, inductance, and / or combination thereof. Such tunability can be advantageous for post-design configuration, compensation, and / or optimization.

[0041] Figure 2 is a schematic block diagram of an example of an electronic system 32 in which the EM coupler 10 is coupled so as to be close to the antenna 22. The electronic system 32 may be included in a front-end module. Except for the differences from Figure 1, the remaining features of system 32 are the same as those shown and described earlier in Figure 1, so for brevity, redundant descriptions of the same elements are omitted. As shown in Figure 2, the input port 9 of the EM coupler 10 is coupled to the output of the antenna switch module 14, and the output port 11 of the EM coupler is coupled to the antenna switch port 18.

[0042] By positioning the EM coupler 10 behind the antenna switch module 14 and near the antenna 22, accurate measurement of the power supplied to the antenna 22 is provided, which is useful for impedance matching and voltage standing ratio (VSWR) calculations. VSWR is a measure of how efficiently radio frequency power is transmitted from the power source through the transmission line to the load (e.g., the antenna).

[0043] As shown, in the forward or transmit direction, the power amplifier 8 receives the EM signal 6 from the transceiver 4 and provides the amplified EM signal to the antenna 22 via the filter 12, antenna switch module 14, EM coupler 10, and antenna port 18, which are operating in forward mode. Similarly, in the receive direction, the received EM signal Rx is provided from the antenna 22 to the transceiver 4 via the EM coupler 10 and antenna switch module 14 (which are operating in reverse mode). Those skilled in the art will understand that the electronic system 32 in Figure 2 may include additional elements (not shown) and / or secondary combinations of the elements shown may be realized. Furthermore, the components of this system may be arranged in an order different from the order shown in Figure 2.

[0044] Figure 3 is a block diagram of an example of an electronic system 34, which includes a first EM coupler 36 coupled between or near the output of the power amplifier 4 and the filter 12 in a manner similar to the EM coupler 10 shown in Figure 1, and a second EM coupler 38 positioned between the antenna switch module 14 and the antenna port 18 in a manner similar to the EM coupler 10 shown in Figure 2. The electronic system 34 may be included in a front-end module. As shown in Figure 3, the first EM coupler 36 and the second EM coupler 38 are bidirectional couplers. However, in other embodiments, one or both of the first EM coupler 36 and the second EM coupler 38 may be unidirectional or forward-only couplers. A unidirectional coupler is an example of a forward-only coupler and has three ports: an input port, an output port, and a coupling port.

[0045] By combining the embodiments of the EM couplers shown in Figures 1 and 2 into a single electronic system 34, the system 34 not only incorporates all the advantages of placing the EM couplers closer to the power amplifier and closer to the antenna 22, but also provides advantages specific to the system 34 through this combination.

[0046] The first EM coupler 36 includes an input port (RF_IN) 35, an output port (RF_OUT) 37, a coupling port 39, and a separation port 41. The second EM coupler 38 includes an input port (RF_IN) 41, an output port (RF_OUT) 43, a coupling port 45, and a separation port 47. To control the coupling direction of the first EM coupler 36 and the second EM coupler 38, a controller 48 is connected to the switch assembly 52 through one or more control lines 50. In some examples, the controller 48 is a general-purpose processor. In other examples, the controller 48 is a customized microcontroller. Other suitable examples of the controller 48 are intended herein. The switch assembly 52 includes four terminals, namely a first terminal 40 configured to connect to the coupling port 39 of the first EM coupler 36, a second terminal 42 configured to connect to the disconnection port 41 of the first EM coupler 36, a third terminal 44 configured to connect to the coupling port 45 of the second EM coupler 38, and a fourth terminal 46 configured to connect to the disconnection port 47 of the second EM coupler 38.

[0047] Figure 4A is a schematic diagram of an example of a switch assembly 54. In some examples, switch assembly 54 is identical to switch assembly 52. ​​Switch assembly 54 includes a first terminal 40, a second terminal 42, a third terminal 44, and a fourth terminal 46. As shown in Figure 4A, switch assembly 54 includes a first switch subassembly 56 and a second switch subassembly 58, which operate independently in the same manner as the switch assembly 26 described above. Each of the switch subassemblies is configured to couple either the coupling or decoupling port of its respective EM coupler to an output, such as output 30. The first switch subassembly 56 is configured to couple one of the coupling port 39 and decoupling port 41 to output 60 and the other port to termination impedance 57. The second switch subassembly 58 is configured to couple one of the coupling port 45 and decoupling port 47 to output 62 and the other port to termination impedance 59. Each of the SPDT switches shown in Figure 4A is configured to be operated through one or more control lines 50 connected to a controller (e.g., controller 48).

[0048] In an example where either the first EM coupler 36 or the second EM coupler 38 is a 3-port unidirectional coupler (not shown), the corresponding switch subassemblies 56, 58 would require only one SPDT switch for the 3-port coupler operated by the controller. To save manufacturing costs, in one example, the first EM coupler 36 may be a unidirectional coupler having coupling ports connected to the switch assembly 52 through a single terminal, a first terminal 40 and a second terminal 42. In some examples, one or both of the first EM coupler 36 and the second EM coupler 38 are unidirectional and have no switches. In one example, only the first EM coupler is switchless and unidirectional (forward only), while the second EM coupler 38 is bidirectional and has at least one switch. The second coupler 38 may be a bidirectional coupler. As a result, the first switch subassembly 56 will require only one SPDT switch (not shown) configured to be controlled via a control line 50 for switching between the output 60 and the termination impedance 57.

[0049] Figure 4B is a schematic diagram of an example of a switch assembly 55 that shares some components in common with switch assembly 54, and therefore, for brevity, a detailed explanation of the same comments will not be repeated. Switch assembly 55 differs from switch assembly 54 in that the first terminal 40 is directly coupled to the output 60 and the second terminal 42 is directly coupled to the termination impedance 57. In an example where the first EM coupler 36 is wired to be unidirectional and is therefore a unidirectional coupler without a switch, switch assembly 55 may be used with the unidirectional first coupler 36 and the bidirectional second coupler 38.

[0050] Figure 5A is a block diagram of an example of an electronic system 64 including multiple transmit chains, each transmit chain 68', 70' including multiple EM couplers sharing a single antenna switch module 66 and a switch assembly 76. The switch assembly 76 includes multiple internal switches that are selectively coupled to all or a subset of the electromagnetic (EM) couplers in the electronic system 64. The internal switches are operated by a controller. The electronic system 64 may be contained in a front-end module. The multiple transmit chains shown in Figure 5A include a first transmit chain 68' connected to the antenna switch module 66 at a first antenna switch module input 72, and a second transmit chain 70' connected to the antenna switch module 66 at a second antenna switch module input 74. Each transmit chain includes two EM couplers, thereby providing a first EM coupler 78 and a second EM coupler 80 in the first transmit chain 68', and a third EM coupler 82 and a fourth EM coupler 84 in the second transmit chain 70'. The second EM coupler 80 is coupled to the first antenna port 18A, which is coupled to the first antenna 22A via a filtering loss 20A. The fourth EM coupler 84 is coupled to the second antenna port 18B, which is coupled to the second antenna 22B via a filtering loss 20B. The first EM coupler 78 and the third EM coupler 82 are coupled to the outputs of their respective power amplifiers, resulting in relatively little impact on the transmission path of each transmit chain compared to placing the couplers before each power amplifier. However, as will be described in more detail below, there are also advantages to placing the couplers before the power amplifiers. In some embodiments, one or more of the first transmit chain 68' and the second transmit chain 70' include the same components as the transceiver 4, power amplifier 8, first EM coupler 36, filter 12, second EM coupler 38, antenna port 18, and antenna 22, and the antenna switch module 66 includes additional ports for each transmit chain.The two transmission chains 68' and 70' shown in Figure 5A are merely examples of electronic systems, and it should be understood that embodiments described herein may include electronic systems having three or more transmission chains.

[0051] Figure 5B is a block diagram of an example of an electronic system 65 including multiple transmit chains, which include multiple EM couplers sharing an antenna switch module 66 and a switch assembly 76. The difference between electronic system 65 and electronic system 64 shown in Figure 5A is that electronic system 65 includes a first transmit chain 68'' and a second transmit chain 70'', the first transmit chain 68'' includes a first EM coupler 78 coupled between the transceiver and power amplifier of the first transmit chain 68'', and the second transmit chain 70'' includes a third EM coupler 82 coupled between the transceiver and power amplifier of the second transmit chain 70''. One reason for placing the EM couplers closer to the transceiver is to avoid or at least mitigate the effects of nonlinearity introduced into the RF signal transmission path by the transceiver (and any other upstream equipment), thereby preventing additional noise from being added to the signal when it is amplified, filtered, and processed.

[0052] In both electronic systems 64 and 65, the first EM coupler 78 is located in the first transmit chains 68', 68'', before the antenna switch module 66 and before the signals generated by the power amplifiers in the first transmit chains 68', 68'' are filtered by filter 12A. Similarly, the third EM coupler 82 is located in the second transmit chains 70', 70'', before the antenna switch module 66 and before the signals generated by the power amplifiers in the second transmit chains 70', 70'' are filtered by filter 12B. By arranging the couplers in this manner, the forward power entering the filters and / or power amplifiers can be detected more accurately. When the antennas in the transmit chains become loads and detune due to interaction with RF signals, changes occur in the power amplifiers of the transmit chains. These changes include an increase in the power of the signals supplied to the filters. Each filter may have a specified operating range that includes the maximum input power. If the amount of power supplied to the filters cannot be monitored, the filters may exceed their specified operating range and be consequently damaged. Therefore, to ensure that the forward power does not reach a level that would damage the filter or exceed the maximum temperature limit, for example, electronic systems 64, 65 monitor the forward power via EM couplers 78, 82 placed before the filtering (as shown in Figure 5A), and bandwidth switching occurs in the transmission path of each transmit chain. The forward power can be estimated using EM couplers placed closer to the antennas of the transmit chain, but placing the EM couplers closer to the transceivers and power amplifiers provides relatively more accurate power accuracy and faster response times to prevent damage to the filter. By placing EM couplers 78, 82 immediately before the power amplifiers (as shown in Figure 5B), the power supplied to the power amplifiers can be measured, and if the power reaches an unsafe level, the power amplifiers or the entire transmit chain can be shut down to prevent damage.

[0053] Including EM couplers 80, 84 after the antenna switch module ASM66, in combination with EM couplers 78, 82 placed before the antenna switch module ASM66, offers several advantages. For example, when an Rx signal is picked up by an antenna in the first transmit chain 68'', this Rx signal travels through the first antenna port 18A, the second EM coupler 80, the antenna switch module 66, and the transceiver. Placing the EM couplers 80, 84 after the antenna switch module 66 provides a more accurate measurement of the Tx power supplied by the antenna than if they were placed closer to the power amplifier before the antenna switch module 66. This is because the sampling point after the Tx signal has passed through various components of the transmit chain is closer to the antenna. Ideally, the Rx signal received by the antenna does not interfere with the Tx signal transmitted by the transceiver to the EM coupler 78, the power amplifier, etc. However, in reality, the Rx signal can leak into the Tx path due to coupling between the Rx signal and components along the Tx path. Filters following the power amplifier (e.g., filters 12A and 12B in Figures 5A and 5B) provide at least some rejection capability to block the Rx signal in the Tx path. However, by using a second EM coupler 80 at the location shown in Figure 5B, the transmitted Rx / Tx signal from or reflected from the antenna may be "sniffed" in the Rx path before reaching the power amplifier and potentially damaging or interfering with it. In some examples, the second EM coupler 80 (and likewise the fourth EM coupler 84) is configured to have an Rx-specific termination impedance for shunting signals carrying specific frequencies to ground, thereby preventing damage to the PA. In at least one example, the second EM coupler 80 and / or the fourth EM coupler 84 measure forward power and are configured to have a termination impedance at their reverse coupling ports. Using a fixed termination impedance, each EM coupler 80, 84 is configured to block specific RF frequencies.The controllable variable impedance allows for the selection or modification of specific frequencies to be blocked, which is desirable when the electronic system 65 is located in an environment with signals interfering with the Tx path.

[0054] Multiple transmit chains are beneficial for many applications, including those requiring 5G communication. For example, 5G mobile networks can operate at various frequencies and may require different antennas for different frequency bands. Therefore, for a 5G application of electronic system 64, the first transmit chains 68', 68'' can operate in a first 5G frequency band, and the second transmit chains 70', 70'' can operate in a second 5G frequency band different from the first frequency band. In applications requiring both 4G and 5G communication, an electronic system using at least three transmit chains may be used, in which case, as mentioned earlier, two chains operate for 5G and the third chain operates for 4G communication.

[0055] The switch assembly 76 is configured to receive outputs from each of the EM couplers 78, 80, 82, and 84. In some embodiments, one of the coupling or decoupling ports of each EM coupler 78, 80, 82, and 84 is selected by the switch assembly 76 for sampling, and the other port is shunted to ground by the switch assembly 76, thereby sampling either forward or reverse power from each EM coupler 78, 80, 82, and 84. In some embodiments, the switch assembly 76 includes a separate switch subassembly for each EM coupler that is similar to or identical to that of the switch assembly 26, thereby providing a termination impedance and output for each EM coupler 78, 80, 82, and 84.

[0056] Figure 6 shows an electronic system 86A that includes an antenna switch module 96A, a first B3 (band 3) coupler 89, a second B3 coupler 91, a third B41 (band 41) coupler 93, and a fourth B41 coupler 95. The band 3 couplers may be used to transmit data on bands 3, 4, and 66, each of which occupies a similar frequency band between approximately 1710 MHz and 1785 MHz. In some embodiments, the electronic system 86A is part of a front-end module. Some front-end module applications require or are capable of transmitting and / or receiving at least two different frequency bands simultaneously. For example, some smartphones require transmitting on both the 4G and 5G frequency bands. According to one example, the 4G and 5G frequency bands are both different and do not overlap. In Figure 6, B3 and B41 are examples of different and non-overlapping frequency bands. Bands 2, 3, and 4 are examples of frequency division duplexing (FDD) channels or bands, while bands such as band 41 are examples of time division duplexing (TDD) channels or bands. Frequency bands operating in frequency division duplexing (FDD) mode perform simultaneous transmit (Tx) and receive (Rx) operations over different frequencies. For example, band 3 operates with a transmit signal having a frequency of approximately 2500 MHz to approximately 2570 MHz and a receive signal having a frequency of approximately 2620 MHz to approximately 2690 MHz. This is typically achieved by using a duplexer that couples the Tx and Rx paths to a common terminal. In contrast, frequency bands operating in time division duplexing (TDD) mode have a single frequency band used for both Tx and Rx operations. For example, bandwidths 40 and 41 operate in a single frequency band of approximately 2300MHz to 2400MHz for bandwidth 40 and approximately 2496MHz to 2690MHz for bandwidth 41.It should be understood that the aspects of this disclosure are not limited to any specific frequency band, whether time-division duplex or frequency-division duplex, but are actually applicable to any situation involving both where carrier aggregation can be used.

[0057] Currently, the majority of 5G deployments utilize a non-standalone (NSA) architecture. In NSA 5G deployments, some 5G mobile devices, such as smartphones, remain connected to 4G LTE so that data transfer occurs simultaneously on both 4G LTE and 5G. One radio standard that enables this dual LTE / 5G functionality is E-UTRAN New Radio-Dual Connectivity (ENDC). Electronic systems 64, 65, and 86A, when implemented as an ENDC architecture in wireless devices used to access both 5G and 4G LTE networks simultaneously, can provide additional overall bandwidth compared to standalone (SA) 5G networks.

[0058] System 86A includes a B3 Tx signal 88 that leaks into the signal path of the B41 signal 90 through finite antenna isolation (typically about 12 dB). The dashed line 97 shows an unwanted B3 signal leaking into the B41 signal path due to leakage path 101. Similarly, the dashed line 98 shows an unwanted B41 signal leaking into the B3 signal path due to leakage path 103. Band selection switches 108 and 110 are used to select which band-specific bandpass filters to connect between the couplers 89 and 93 and the ASM 87 for different frequency bands. For example, the band selection switch 108 couples filters between the coupler 89 and the ASM 87 for band 2 transmit (Tx), bands 3 / 4 / and 66 transmit (Tx), band 1 transmit (Tx), and band 40 transmit (Tx). Receiver band filters for bands 2, 1, 4, and 66, and band 40 are provided to the band selection switch 108 and can be appropriately routed to one or more receive low-noise amplifiers (LNAs, not shown). The band selection switch 110 couples transmit and receive filters for band 7 and bands 41, 34, and 39 between the coupler 93 and the ASM87, and each of these filters can be coupled to a suitable LNA (not shown).

[0059] As can be understood in view of Figure 6, if the first B3 coupler 89 and the third B41 coupler 93 are not present behind the power amplifiers in each chain, the coupled output signals are necessarily provided by the coupled outputs of the second B3 coupler 91 and the fourth B41 coupler 95, respectively. Assuming adequate isolation (approximately 12 dB) between the two antennas, the coupled B3 signal from the second B3 coupler 91 contains significant energy from the B41, and the coupled B41 signal from the fourth B41 coupler 95 contains significant energy from the B3. As a result, the detection accuracy in each of the power detectors is significantly impaired.

[0060] Any unwanted B3 signals leaking into the B41 signal path, such as the signal indicated by the dashed line 97, can pass through the ASM 87 and then the B41 transmit filter 105 (which should effectively filter out everything except the B41 signal) before being coupled to the B41 power detector 94. Similarly, any unwanted B41 signals leaking into the B3 signal path, such as the signal indicated by the dashed line 98, can pass through the ASM 87 and then the B3 / 4 / 66 transmit filter 104 (which should effectively filter out everything except the B3 signal) before being coupled to the B3 power detector 92. As a result, forward power detection becomes significantly more accurate than when detected via the second B3 coupler 91 and the fourth B41 coupler 95.

[0061] The switch assembly 96A includes a B3 switch 96A1 and a B41 switch 96A2. The B3 switch 96A1 is coupled to a B3 power detector 92, and the B41 switch 96A2 is coupled to a B41 power detector 94. In addition, the B3 switch 96A1 is configured to switch between power supplied from the coupling port of a first B3 coupler 89 and power supplied from the coupling port of a second B3 coupler 91, and the B41 switch 96A2 is configured to switch between power supplied from the coupling port of a third B41 coupler 93 and power supplied from the coupling port of a fourth B41 coupler 95. In some embodiments, it is understood that the switch assembly 96A includes additional inputs, outputs, and / or switches. The switch assembly 96A also includes a CPL_IN switch 96A3 configured to select either a B3 power detector 92 or a B41 power detector 94.

[0062] The B41 filter 105 provides significant rejection outside of B41 and significantly attenuates the B3 signal 88. Similarly, the B3 / 4 / 66 filter 104 provides significant rejection outside of B3 / 4 / 66 and significantly attenuates the B41 signal 90. However, to further attenuate the B3 signal 88 in power measurements acquired by the B41 power detector 94 and to further attenuate the B41 signal 90 in power measurements acquired by the B3 power detector 92, one or more notch filters can be coupled to the isolation ports of the second B3 coupler 91 and the fourth B41 coupler 95. One or more notch filters may also be included in the switch assembly, or one or more notch filters may be included in the switch assembly instead.

[0063] Figure 7 shows an electronic system 86B that includes a switch assembly 96B but does not include a first B3 coupler 89 and a third B41 coupler 93. Each of the isolation ports of the second B3 coupler 91 and the fourth B41 coupler 95 is selectively coupled to one of a pair of notch filters arranged in parallel between ground and a switch coupled to the respective isolation port. The notch filters are arranged in parallel with a resistor. In at least one example, the resistor is a 50-ohm resistor. The isolation port of the second B3 coupler 91 is selectively coupled via switch 91C to one of a pair of notch filters, including a first notch filter 91A and a second notch filter 91B. Similarly, the isolation port of the fourth B41 coupler 95 is selectively coupled via switch 95C to one of a pair of notch filters, including a third notch filter 95A and a fourth notch filter 95B. For each pair of notch filters, one of the two notch filters in the pair provides a notch to B3, and the other notch filter provides a notch to B41. Since the electronic system 86B supports B3 and B41 from either antenna, two notch filters are provided for each of the couplers 91, 95. In one example, the first notch filter 91A and the third notch filter 95A provide a notch at B3, and the second notch filter 91B and the fourth notch filter 95B provide a notch at B41. By selecting specific notch filters, unwanted signals (e.g., dashed line 97 or dashed line 98) are isolated from reaching the switch assembly 96B (and therefore one of the power detectors 92, 94), or at least significantly reduced. Each notch filter may have an insertion loss of 20 dB or more. The notch filter configurations described herein are not limited to bands B3 and B41, but may be applied to other bands, and it is understood that the notch filters may be appropriately modified to exclude or reduce the appropriate bands as needed.

[0064] The switch assembly 96B includes a B3 switch 96B1 and a B41 switch 96B2. The B3 switch 96B1 is coupled to a B3 power detector 92, and the B41 switch 96B2 is coupled to a B41 power detector 94. The B3 switch 96B1 is configured to select the coupling port of a second B3 coupler 91, and the B41 switch 96B2 is configured to select the coupling port of a fourth B41 coupler 95. The switch assembly 96B also includes a CPL_IN switch 96B3 configured to select either a B3 power detector 92 or a B41 power detector 94.

[0065] In another embodiment, instead of selecting either notch filter to reject a particular bandwidth, a selectable open connection is provided for the switch (e.g., switch 91C or switch 95C) associated with each pair of notch filters, such that the only component coupled between the isolation port and ground when the switch is coupled to the open connection is a resistor. Choosing resistor termination rather than either B3 or B41 filtered termination may be desirable when transmitting only over a single bandwidth rather than over multiple bandwidths.

[0066] Figure 8 shows an electronic system 86C that includes a switch assembly 96C but does not include a first B3 coupler 89 and a third B41 coupler 93. The switch assembly 96C includes a fifth notch filter 96E and a sixth notch filter 96F. In one example, the fifth notch filter 96E is configured to eliminate or reduce unwanted B3 signals reaching the B41 power detector 94, and the sixth notch filter 96F is configured to eliminate or reduce unwanted B41 signals reaching the B3 power detector 92. Providing selectable notch filters in the switch assembly 96C provides each power detector with a trade-off: (i) select each notch filter to reduce unwanted signals at the cost of additional losses, or (ii) bypass each notch filter at the cost of unwanted signals detected by the power detector.

[0067] To select or bypass specific notch filters, the switch assembly 96C includes a B3 filter selection switch 96C1 and a B41 filter selection switch 96C2. The B3 filter selection switch 96C1 is configured to select either a path including a sixth notch filter 96F or a bypass path 96G that bypasses both the fifth notch filter 96E and the sixth notch filter 96F. The B41 filter selection switch 96C2 selects either a path including the fifth notch filter 96E or the bypass path 96G. The switch assembly 96C also includes a CPL_IN switch 96C3 configured to select either a B3 power detector 92 or a B41 power detector 94. The switch assembly 96C also includes a B41 power detector switch 96C4 coupled to a B41 power detector 94 and configured to select either a fifth notch filter 96E or a bypass path 96G, and a B3 power detector switch 96C5 coupled to a B3 power detector 92 and configured to select either a sixth notch filter 96F or a bypass path 96G.

[0068] In one example of the operation of the electronic system 86C, during SA / single-band operation, the outputs of the second B3 coupler 91 and the fourth B41 coupler 95 are routed from the couplers to the bypass path 96G and to their respective power detectors. During NSA(ENDC) operation, each EM coupler is routed to the required filter and then to the selected power detector.

[0069] By incorporating a notch filter into the above configuration, cross-contamination of different frequency bands in different power measurements is significantly reduced, while the advantages of placing the coupler both immediately after the power amplifier and immediately after the antenna switch module, as described in the embodiments provided herein, are still maintained. For example, the power measurements from chains 68' and 70' shown in Figure 5A show less signal loss and / or corruption due to the addition of the notch filter described above. It is understood that the concepts and techniques described herein are extendable to other bands and other ENDC combinations.

[0070] Some of the embodiments described above provide examples relating to power amplifiers and / or mobile devices. Specifically, each of the electronic systems 2, 32, 34, 64, 65, 86A, 86B, and 86C described herein may be included in the front-end module of a mobile device such as a smartphone. However, the principles and benefits of the embodiments can be used in any other system or device, such as any uplink cellular device, which can benefit from any of the circuits described herein. Any of the principles and benefits described herein can be realized in electronic systems where there is a need to detect and / or monitor power levels associated with EM signals, such as forward EM power and / or reverse EM power. Any of the switch networks and / or switch circuits described herein can be realized, either alternatively or additionally, by any other suitable logically equivalent and / or functionally equivalent switch network. The teachings herein are applicable to a variety of power amplifier systems, including systems having multiple power amplifiers, such as multiband and / or multimode power amplifier systems. The power amplifier transistors described in this specification may be, for example, gallium arsenide (GaAs), complementary metal oxide semiconductor (CMOS), or silicon germanium (SiGe) transistors. Furthermore, the power amplifiers described in this specification can be realized by bipolar transistors such as FETs and / or heterojunction bipolar transistors.

[0071] The aspects of this disclosure can be realized in various electronic devices. Examples of electronic devices may include, but are not limited to, consumer electronic products, components of consumer electronic products, electronic test equipment, and cellular communication infrastructure such as base stations. Examples of electronic devices may include, but are not limited to, mobile phones such as smartphones, telephones, televisions, computer monitors, computers, modems, handheld computers, laptop computers, tablet computers, e-book readers, wearable computers such as smartwatches, personal digital assistants (PDAs), microwave ovens, refrigerators, automobiles, stereo systems, DVD players, CD players, digital music players such as MP3 players, radios, camcorders, cameras, digital cameras, portable memory chips, medical monitoring devices, automotive electronic systems such as automotive electronic systems and avionics electronic systems, washing machines, dryers, washing machine / dryer systems, peripherals, wristwatches, and clocks. Furthermore, electronic devices may include unfinished products.

[0072] While several aspects of at least one embodiment have been described, it should be understood that those skilled in the art will readily conceive of various changes, modifications, and improvements. Such changes, modifications, and improvements are intended to be part of this disclosure and within the scope of the invention. Thus, the foregoing description and drawings are merely illustrative, and the scope of the invention should be determined from the appropriate configuration of the appended claims and their equivalents.

Claims

1. A front-end module, the front-end module comprising: a power amplifier configured to amplify a radio frequency signal, the power amplifier having an input configured to receive the radio frequency signal and an output configured to provide an amplified radio frequency signal; and a first combiner having an input port, an output port, a coupled port, and an isolated port, the input port coupled to the output of the power amplifier; an antenna switch module having an input coupled to the output port of the first coupler and an output; a second combiner having an input port, an output port, a coupled port, and an isolated port, the input port of the second combiner being coupled to the output of the antenna switch module; and an antenna port configured to be coupled to an antenna, the antenna port being coupled to the output port of the second coupler; and a first switch subassembly that switchably connects one of the coupled port and the isolated port of the second coupler to an output of the first switch assembly and connects the other of the coupled port and the isolated port of the second coupler to a first termination impedance.

2. 2. The front-end module of claim 1, wherein the isolated port of the first coupler is connected to a second termination impedance.

3. 2. The front-end module of claim 1, further comprising a second switch subassembly that switchably connects one of the coupled port and the isolated port of the first coupler to an output of the second switch assembly and connects the other of the coupled port and the isolated port of the first coupler to a second termination impedance.

4. The front-end module of claim 3 , further comprising a filter connected between the output port of the first coupler and the input of the antenna switch module.

5. 5. The front-end module of claim 4, further comprising: a controller coupled to the first switch subassembly and the second switch subassembly, the controller configured to obtain a first measurement value from the output of the second switch assembly by connecting the coupled port of the first coupler to the output of the second switch assembly and connecting the isolated port of the first coupler to the second termination impedance, the first measurement value providing an indication of forward power provided by the power amplifier.

6. 6. The front-end module of claim 5, wherein the controller is further configured to obtain a second measurement from the output of the first switch assembly by connecting the coupled port of the second coupler to the output of the first switch assembly and connecting the isolated port of the second coupler to the first termination impedance, the second measurement providing an indication of forward power present on the antenna.

7. 6. The front-end module of claim 5, wherein the controller is further configured to obtain a second measurement from the output of the first switch assembly by connecting the isolated port of the second coupler to the output of the first switch assembly and connecting the coupled port of the second coupler to the first termination impedance, the second measurement providing an indication of power reflected from the antenna.

8. The front end module of claim 7 , wherein the controller is further configured to adjust the impedance of the antenna based on the indication of power reflected from the antenna.

9. 6. The front-end module of claim 5, wherein the controller is further configured to obtain a first measurement from the output port of the first coupler and a second measurement from the output port of the second coupler.

10. 10. The front-end module of claim 9, wherein the controller is further configured to linearize the amplified radio frequency signal by modifying the radio frequency signal received by the power amplifier based on the first measurement value and the second measurement value.

11. 10. The front-end module of claim 9, wherein the controller is further configured to determine, based on the first measurement value and the second measurement value, an amplitude and a phase of a transfer function describing a change in power of the amplified radio frequency signal between the power amplifier and the antenna.

12. The controller further comprises: operating the switch assembly to obtain a measurement of forward power provided to the antenna; operating the switch assembly to obtain a measurement of reflected power from the antenna; calculating a ratio between the measured forward power and the measured reflected power; adjusting the amount of power provided by the power amplifier based on the calculated ratio The front-end module according to claim 5 , configured as follows:

13. a second power amplifier configured to amplify a second radio frequency signal, the second power amplifier having an input configured to receive the second radio frequency signal and an output configured to provide a second amplified radio frequency signal; and a third combiner having an input port, an output port, a coupled port, and an isolated port, the input port of the third combiner being coupled to the output of the second power amplifier and the output port of the third combiner being coupled to a second input of the antenna switch module; and a fourth combiner having an input port, an output port, a coupled port, and an isolated port, the input port of the fourth combiner being coupled to a second output of the antenna switch module; 2. The front-end module of claim 1, comprising a second antenna port configured to be coupled to a second antenna, the second antenna port coupled to the second output of the second coupler.

14. the power amplifier, the first combiner, the second combiner, and the antenna port form a first chain; the second power amplifier, the third combiner, the fourth combiner, and the second antenna port form a second chain; 14. The front-end module of claim 13, wherein the amplified radio frequency signal of the first chain is in a different frequency band than the second amplified radio frequency signal of the second chain.

15. The front-end module of claim 14 , wherein the amplified radio frequency signal and the second amplified radio frequency signal are transmitted simultaneously.

16. 2. The front-end module of claim 1, wherein the radio frequency signal received at the input of the power amplifier has a frequency within one of a range of about 600 MHz to about 2.5 GHz, a range of about 450 MHz to about 6 GHz, and a range of about 24 GHz to 52 GHz.

17. 2. The front-end module of claim 1, wherein the first coupler is a unidirectional coupler and the second coupler is a bidirectional coupler.

18. A front-end module, the front-end module comprising: a power amplifier configured to amplify a radio frequency signal, the power amplifier having an input configured to receive the radio frequency signal and an output configured to provide an amplified radio frequency signal; and a first combiner having an input port, an output port, a coupled port, and an isolated port, the input port coupled to the output of the power amplifier; an antenna switch module having an input coupled to the output port of the first coupler and an output; a second combiner having an input port, an output port, a coupled port, and an isolated port, the input port of the second combiner being coupled to the output of the antenna switch module; and an antenna port configured to be coupled to the antenna, the antenna port being coupled to the output port of the second coupler; and a first switch subassembly that switchably connects one of the coupled port and the isolated port of the second coupler to an output of the second switch assembly, connects the other of the coupled port and the isolated port of the second coupler to a first termination impedance, or connects each of the coupled port and the isolated port of the second coupler to the first termination impedance.

19. 20. The front-end module of claim 18, wherein the isolated port of the first coupler is connected to a second termination impedance.

20. 20. The front-end module of claim 18, further comprising a second switch subassembly that switchably connects one of the coupled port and the isolated port of the first coupler to an output of the second switch assembly and connects the other of the coupled port and the isolated port of the first coupler to a second termination impedance.

21. 21. The front end module of claim 20, further comprising a filter connected between the output port of the first coupler and the input of the antenna switch module.

22. 22. The front-end module of claim 21, further comprising: a controller coupled to the first switch subassembly and the second switch subassembly, the controller configured to obtain a first measurement value from the output of the second switch assembly by connecting the coupled port of the first coupler to the output of the second switch assembly and connecting the isolated port of the first coupler to the second termination impedance, the first measurement value providing an indication of forward power provided by the power amplifier.

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