Patent Application
20200252036
Aspects of the present disclosure relate generally to power amplifiers, and more particularly, to a power amplifier using a multi-mode distributed active transformer.
Power amplifiers are used in transmitters to amplify radio frequency (RF) signals for transmission. In one power amplifier architecture, a distributed active transformer (DAT) is used to combine the output powers of multiple power amplifiers.
The following presents a simplified summary of one or more implementations in order to provide a basic understanding of such implementations. This summary is not an extensive overview of all contemplated implementations and is intended to neither identify key or critical elements of all implementations nor delineate the scope of any or all implementations. Its sole purpose is to present some concepts of one or more implementations in a simplified form as a prelude to the more detailed description that is presented later.
A first aspect relates to a multi-mode power amplifier. The multi-mode power amplifier includes first primary inductors, second primary inductors, and switches configured to selectively couple each of the second primary inductors with a respective one of the first primary inductors. The multi-mode power amplifier also includes power amplifiers coupled to the first primary inductors, and a secondary inductor magnetically coupled to the first primary inductors.
A second aspect relates to a method for multi-mode operation using a reconfigurable transformer including first primary inductors, second primary inductors, and a secondary inductor. The method includes, in a first mode of operation, driving the first primary inductors to induce a first output voltage on the secondary inductor. The method also includes, in a second mode of operation, coupling each of the second primary inductors with a respective one of the first primary inductors, and driving the first and second primary inductors to induce a second output voltage on the secondary inductor.
A third aspect relates to a multi-mode transformer. The multi-mode transformer includes a first primary side comprising a first plurality of inductors, a second primary side comprising a second plurality of inductors, a plurality of switches configured to selectively couple the second plurality of inductors with respective ones of the first plurality of inductors, and a secondary side.
A fourth aspect relates to an apparatus for multi-mode operation using a reconfigurable transformer including first primary inductors, second primary inductors, and a secondary inductor. The apparatus includes, in a first mode of operation, means for driving the first primary inductors to induce a first output voltage on the secondary inductor. The apparatus also includes, in a second mode of operation, means for coupling each of the second primary inductors with a respective one of the first primary inductors, and means for driving the first and second primary inductors to induce a second output voltage on the secondary inductor.
To the accomplishment of the foregoing and related ends, the one or more implementations include the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more implementations. These aspects are indicative, however, of but a few of the various ways in which the principles of various implementations may be employed and the described implementations are intended to include all such aspects and their equivalents.
The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.
Each of the power amplifiers 130-1 to 130-4 is a push-pull amplifier including a pair of n-type metal semiconductor (NMOS) transistors driven by a differential RF signal. In certain aspects, the power amplifiers 130-1 to 130-4 are driven by the same input differential RF signal.
Each of the primary inductors 120-1 to 120-4 is coupled between two neighboring power amplifiers. More particularly, each of the primary inductors 120-1 to 120-4 has a first end (i.e., terminal) coupled to an output of the one of the power amplifiers 130-1 to 130-4 and a second end (i.e., terminal) coupled to an output of opposite phase (i.e., opposite polarity) of another one of the power amplifiers 130-1 to 130-4. In the example shown in
Each of the primary inductors 120-1 to 120-4 has a center tap coupled to the supply voltage VDD, which provides a direct current (DC) bias current for neighboring power amplifiers 130-1 to 130-4. Because each of the primary inductors 120-1 to 120-4 is coupled between amplifier outputs of opposite phase, a virtual alternating current (AC) ground is created at the center tap of each of the primary inductors 120-1 to 120-4.
The DAT power amplifier 110 also includes capacitors 140-1 to 140-4 used for impedance matching, in which each of the capacitors 140-1 to 140-4 is coupled across the differential output of a respective one of the power amplifiers 130-1 to 130-4. In the example shown in
The capacitors 140-1 to 140-4 and the primary inductors 120-1 to 120-4 form an output matching network that is used to provide impedance matching with the outputs of the power amplifier 130-1 to 130-4. In this regard, the capacitances of the capacitors 140-1 to 140-4 and/or the inductances of the primary inductor 120-1 to 120-4 may be chosen such that the load impedance of the output matching network seen by each of the power amplifiers 130-1 to 130-4 approximately matches the output impedance of the power amplifier 130-1 to 130-4. The impedance matching increases power efficiency.
In operation, the power amplifiers 130-1 to 130-4 are driven by an input differential RF voltage. The power amplifiers 130-1 to 130-4 convert the differential RF voltage into drive currents that drive the primary inductors 120-1 to 120-4, inducing voltages on the secondary inductor 115. The induced voltages are summed at the output of the DAT power amplifier 110 to provide an output voltage VOUT across a load (not shown).
A limitation of the DAT power amplifier 110 is that the output matching network may only be optimized for one operation mode. For example, for a wireless device with a low-power mode and a high-power mode, the output matching network of the DAT power amplifier 110 may only be optimized for one of these modes. In this example, optimizing the output matching network for the high-power mode sacrifices power efficiency for the low-power mode, and vice versa. This is because the capacitances of the capacitors 140-1 to 140-4 and/or the inductances of the primary inductors 120-1 to 120-4 are tuned in the design phase to optimize the output matching network for a single operation mode. Once the DAT power amplifier 110 is fabricated, the capacitors 140-1 to 140-4 and the primary inductors 120-1 to 120-4 are fixed. Thus, the DAT power amplifier 110 is limited to a single operation mode. In addition, the layout of the DAT power amplifier 110 occupies a relatively large chip area, especially for low-gigahertz (low-GHz) frequency designs.
The multi-mode DAT power amplifier 310 is discussed below using the example of two operation modes (e.g., power modes). However, it is to be appreciated that the present disclosure is not limited this example, and that the multi-mode DAT power amplifier 310 may be extended to three or more operation modes, as discussed further below.
In the example shown in
The first and second power amplifiers 330-1 and 330-2 are driven by an input differential RF signal. Each of the power amplifiers 330-1 and 330-2 may be configured to operate in two different power modes (e.g., a low-power mode and a high-power mode). In this example, the output impedance of each of the power amplifiers 330-1 and 330-2 is different for the different power modes. More particularly, the output impedance is lower in the high-power mode to deliver more power. Each of the power amplifiers 330-1 and 330-2 has a differential output comprising two outputs of opposite phase (e.g., opposite polarity). Each of the power amplifiers 330-1 and 330-2 may be implemented with a push/pull amplifier (e.g., a differential NMOS transistor pair). However, it is to be appreciated that the present disclosure is not limited to this example, and that the power amplifiers 330-1 and 330-2 may be implemented with other types of amplifiers. Further, although two power amplifiers 330-1 and 330-2 are shown in the example in
Each of the first primary inductors 320-1 and 320-2 is coupled between the first and second power amplifiers 330-1 and 330-2. More particularly, each of the first primary inductors 320-1 and 320-2 has a first end (i.e., terminal) coupled to an output of the first power amplifier 330-1 and a second end (i.e., terminal) coupled to an output of opposite phase (i.e., opposite polarity) of the second power amplifier 330-2.
The switches 340-1, 340-2, 345-1 and 345-2 are configured to selectively couple the second primary inductors 325-1 and 325-2 in parallel with respective ones of the first primary inductors 320-1 and 320-2. In certain aspects, the switches 340-1, 340-2, 345-1 and 345-2 couple the second primary inductors 325-1 and 325-2 in parallel with the respective ones of the first primary inductors 320-1 and 320-2 when the switches 340-1, 340-2, 345-1 and 345-2 are closed (i.e., turned on).
In the example shown in
Switch 340-2 is coupled between the first end (i.e., terminal) of first primary inductor 320-2 and a first end (i.e., terminal) of second primary inductor 325-2, and switch 345-2 is coupled between the second end (i.e., terminal) of first primary inductor 320-2 and a second end (i.e., terminal) of second primary inductor 325-2. Thus, when the switches 340-2 and 345-2 are closed (i.e., turned on), second primary inductor 325-2 is coupled in parallel with first primary inductor 320-2. When switches 340-2 and 345-2 are open (i.e., turned off), second primary inductor 325-2 is decoupled from first primary inductor 320-2.
Each of the first primary inductors 320-1 and 320-2 has a center tap coupled to the supply voltage VDD, and each of the second primary inductors 325-1 and 325-2 has center tap coupled to the supply voltage VDD, as shown in
The DAT power amplifier 110 also includes capacitors 350-1 and 350-2 used for impedance matching. Capacitor 350-1 is coupled across the differential output of the first power amplifier 330-1, and capacitor 350-2 is coupled across the differential output of the second power amplifier 330-2. As discussed above, the differential output of each power amplifier 330-1 and 330-2 comprises outputs of opposite phase (i.e., opposite polarity). Thus, capacitor 350-1 is coupled between the outputs of the first power amplifier 330-1, and capacitor 350-2 is coupled between the outputs of the second power amplifier 330-2.
In operation, the reconfigurable transformer is configured to operate the multi-mode DAT power amplifier 310 in the high-power mode or the low-power mode by controlling the on/off states of the switches 340-1, 340-2, 345-1 and 345-2. In certain aspect, the switches 340-1, 340-2, 345-1 and 345-2 are configured to selectively couple the second primary inductors 325-1 and 325-2 in parallel with the respective ones of the first primary inductors 320-1 and 320-2 based on the power mode of the power amplifiers 330-1 and 330-2. In these aspects, the switches 340-1, 340-2, 345-1 and 345-2 couple the second primary inductors 325-1 and 325-2 in parallel with the respective ones of the first primary inductors 320-1 and 320-2 in the high-power mode, and decouple the second primary inductors 325-1 and 325-2 from the respective ones of the first primary inductors 320-1 and 320-2 in the low-power mode.
To operate the multi-mode DAT power amplifier 310 in the low-power mode, the switches 340-1, 340-2, 345-1 and 345-2 are open (i.e., turned off). In this case, the second primary inductors 325-1 and 325-2 are decoupled from the first primary inductors 320-1 and 320-2. The first primary inductors 320-1 and 320-2 and the capacitors 350-1 and 350-2 form an output matching network that is used to provide impedance matching with the outputs of the power amplifiers 330-1 and 330-2 in the low-power mode. The second primary inductors 325-1 and 325-2 are not part of the output matching network in the low-power mode since the second primary inductors 325-1 and 325-2 are decoupled from the first primary inductors 320-1 and 320-2 in the low-power mode.
In certain aspects, the inductances of the first primary inductors 320-1 and 320-2 are chosen (e.g., in the design phase) such that the load impedance of the output matching network seen by each of the power amplifiers 330-1 and 330-2 approximately matches the output impedance of the power amplifier 330-1 and 330-2 in the low-power mode. The impedance matching provides high power efficiency in the low-power mode.
In the low-power mode, the power amplifiers 330-1 and 330-2 convert the input differential RF voltage into drive currents that drive the first primary inductors 320-1 and 320-2, inducing voltages on the secondary inductor 315. The induced voltages on the secondary inductor 315 are summed at the output of the DAT power amplifier 310 to provide an output voltage VOUT across a load (represented as load resistor RL). The second primary inductors 325-1 and 325-2 are not driven by the power amplifiers 330-1 and 330-2 in the low-power mode.
To operate the multi-mode DAT power amplifier 310 in the high-power mode, the switches 340-1, 340-2, 345-1 and 345-2 are closed (i.e., turned on). In this case, each of the second primary inductors 325-1 and 325-2 is coupled in parallel with the respective one of the first primary inductors 320-1 and 320-2. The parallel combinations of the first and second primary inductors 320-1, 320-2, 325-1 and 325-2 and the capacitors 350-1 and 350-2 form an output matching network that is used to provide impedance matching with the outputs of the power amplifier 330-1 and 330-2 in the high-power mode.
In certain aspects, the inductances of the second primary inductors 325-1 are 325-2 are chosen (e.g., in the design phase) such that the load impedance of the output matching network seen by each of the power amplifiers 330-1 and 330-2 approximately matches the output impedance of the power amplifier 330-1 and 330-2 in the high-power mode. The impedance matching provides high power efficiency in the high-power mode.
Note that the inductances of the first primary inductors 320-1 and 320-2 are chosen to provide output impedance matching for the low-power mode. The inductances of the second primary inductors 325-1 and 325-2 are chosen such that the inductances of the parallel combinations of the first and second primary inductors 320-1, 320-2, 325-1 and 325-2 provide output impedance matching for the high-power mode. Coupling the second primary inductors 325-1 and 325-2 in parallel with the first primary inductors 320-1 and 320-2 reduces the inductances in the output matching network.
In the high-power mode, the power amplifiers 330-1 and 330-2 convert the input differential RF voltage into drive currents that drive the parallel combinations of the first and second primary inductors 320-1, 320-2, 325-1 and 325-2, inducing voltages on the secondary inductor 315. The induced voltages on the secondary inductor 315 are summed at the output of the DAT power amplifier 310 to provide an output voltage VOUT across the load (represented as load resistor RL).
Thus, the multi-mode DAT power amplifier 310 can be reconfigured to support multi-mode operation. In the example discussed above, the reconfigurable transformer can be reconfigured using switches 340-1, 340-5, 345-1 and 345-2 to provide output impedance matching for the low-power mode and the high-power mode. This allows the multi-mode DAT power amplifier 310 to operate with high power efficiency (e.g., at least 40%) in the low-power mode and the high-power mode. In contrast, the signal-mode DAT power amplifier 110 is optimized for a single operation mode.
Although the multi-mode DAT power amplifier 310 is discussed above using the example of two operation modes (i.e., the low-power mode and the high-power mode), it is to be appreciated that the present disclosure is not limited this example. The multi-mode DAT power amplifier 310 may be extended to three or more operation modes, for example, by adding additional inductors and switches to the reconfigurable transformer. The additional inductors and switches allow the reconfigurable transformer to be reconfigured to provide output impedance matching for one or more additional operation modes. Further, although the multi-mode DAT power amplifier 310 has two channels in the example shown in
As discussed above, each of the power amplifiers 330-1 and 330-2 may be configured to operate in the low-power mode or the high-power mode. In this regard, the first power amplifier 330-1 may include a first low-power (LP) power amplifier 410-1 and a first high-power (HP) power amplifier 420-1, an example of which is shown in
The LP power amplifiers 410-1 and 410-2 (i.e., power amplifiers associated with the low-power mode) are coupled to the first primary side of the transformer, which includes the first primary inductors 320-1 to 320-2. In the example shown in
The second LP power amplifier 410-2 has first and second outputs 412-2 and 414-2 of opposite phase (i.e., opposite polarity). The first output 412-2 is coupled to the second end (i.e., terminal) of first primary inductor 320-2, and the second output 414-2 is coupled to the second end (i.e., terminal) of first primary inductor 320-1. In this example, capacitor 350-2 is coupled between the first and second outputs 412-2 and 414-2 of the second LP power amplifier 410-2 to provide impedance matching.
The HP power amplifiers 420-1 and 420-2 (i.e., power amplifiers associated with the high-power mode) are coupled to the second primary side of the transformer, which includes the second primary inductors 325-1 to 325-2. The switches 340-1, 340-2, 345-1 and 345-2 selectively couple the HP power amplifiers 420-1 and 420-2 with the first primary side of the transformer based on the power mode, as discussed further below. The first HP power amplifier 420-1 has first and second outputs 422-1 and 424-1 of opposite phase (i.e., opposite polarity). The first output 422-1 is coupled to the first end (i.e., terminal) of second primary inductor 325-1, and the second output 424-1 is coupled to the first end (i.e., terminal) of second primary inductor 325-2. When switches 340-1 and 340-2 are closed in the high-power mode, capacitor 350-1 is coupled between the first and second outputs 422-1 and 424-1 of the first HP power amplifier 420-1 to provide impedance matching in the high-power mode.
The second HP power amplifier 420-2 has first and second outputs 422-2 and 424-2 of opposite phase (i.e., opposite polarity). The first output 422-2 is coupled to the second end (i.e., terminal) of second primary inductor 325-2, and the second output 424-2 is coupled to the second end (i.e., terminal) of second primary inductor 325-1. When switches 345-1 and 345-2 are closed in the high-power mode, capacitor 350-2 is coupled between the first and second outputs 422-2 and 424-2 of the second HP power amplifier 420-2 to provide impedance matching in the high-power mode.
In the low-power mode, the switches 340-1, 340-2, 345-1 and 345-2 are open (i.e., turned off), which decouples the second primary inductors 325-1 and 325-2 from the first primary inductors 320-1 and 320-2. In the low-power mode, the primary inductors 320-1 and 320-2 are used in conjunction with the capacitors 350-1 and 350-2 to provide output matching network with the outputs of the LP power amplifiers 410-1 and 410-2. In this regard, the inductances of the first primary inductors 320-1 and 320-2 are chosen (e.g., in the design phase) such that the load impedance of the output matching network seen by each of the LP power amplifiers 410-1 and 410-2 approximately matches the output impedance of the LP power amplifier 410-1 and 410-2.
In the low-power mode, the LP power amplifiers 410-1 and 410-2 are driven by an input different RF voltage. The LP power amplifiers 410-1 and 410-2 convert the input differential RF voltage into drive currents that drive the first primary inductors 320-1 and 320-2, inducing voltages on the secondary inductor 315. The induced voltages on the secondary inductor 315 are summed at the output of the DAT power amplifier 310 to provide an output voltage VOUT across a load (represented as load resistor RL). Thus, in the low-power mode, the LP power amplifiers 410-1 and 410-2 drive the first primary side of the transformer.
In the high-power mode, the switches 340-1, 340-2, 345-1 and 345-2 are closed (i.e., turned on), which couples the second primary inductors 325-1 and 325-2 in parallel with the first primary inductors 320-1 and 320-2. This also couples the HP power amplifiers 420-1 and 420-2 with the first primary side of the transformer via the switches 340-1, 340-2, 345-1 and 345-2. In the high-power mode, the parallel combinations of the first and second primary inductors 320-1, 320-2, 325-1 and 325-2 are used in conjunction with the capacitors 350-1 and 350-2 to provide output matching network with the outputs of the HP power amplifiers 420-1 and 420-2. In this regard, the inductances of the second primary inductors 325-1 and 325-2 are chosen (e.g., in the design phase) such that the load impedance of the output matching network seen by each of the HP power amplifiers 420-1 and 420-2 approximately matches the output impedance of the HP power amplifier 420-1 and 420-2.
In the high-power mode, the HP power amplifiers 420-1 and 420-2 are driven by an input different RF voltage. The HP power amplifiers 420-1 and 420-2 convert the input differential RF voltage into drive currents that drive the parallel combinations of the first and second primary inductors 320-1, 320-2, 325-1 and 325-2, inducing voltages on the secondary inductor 315. The induced voltages on the secondary inductor 315 are summed at the output of the DAT power amplifier 310 to provide an output voltage VOUT across a load (represented as load resistor RL). Thus, in the high-power mode, the HP power amplifiers 420-1 and 420-2 drive the second primary side and the first primary side of the transformer, which are coupled in the high-power mode via the switches 340-1, 340-2, 345-1 and 345-2.
In the example shown in
Referring to
The first and second lower coils 515 and 520 and the first and second upper coils 560 and 565 form first primary inductor 320-1. The first center tap 510-1 coupled between the first and second lower coils 515 and 520 provides the center tap for first primary inductor 320-1, and is coupled to the supply voltage VDD. In this example, the structure of first primary inductor 320-1 is symmetric about the first center tap 510-1.
In the example shown in
Referring to
The third and fourth lower coils 525 and 530 and the third and fourth upper coils 570 and 575 form first primary inductor 320-2. The second center tap 510-2 coupled between the third and fourth lower coils 525 and 530 provides the center tap for first primary inductor 320-2, and is coupled to the supply voltage VDD. In this example, the structure of first primary inductor 320-2 is symmetric about the second center tap 510-2.
In the example shown in
The lower layer further includes a second outer metal trace 560 coupled between the second output 414-1 of the first HP power amplifier 420-1 (shown in
Referring to
In the example in
Note that
At block 610, in a first mode of operation, the first primary inductors are driven to induce a first output voltage on the secondary inductor. For example, the first mode of operation may correspond to the low-power mode discussed above. The first primary inductors may be driven using multiple power amplifiers (e.g., power amplifiers 330-1 and 330-2).
At block 620, in a second mode of operation, each of the second primary inductors is coupled with a respective one of the first primary inductors. For example, the second mode of operation may correspond to the high-power mode discussed above. Also, each of the second primary inductors may be coupled in parallel with a respective one of the first primary inductors. At block 630, in the second mode of operation, the first and second primary inductors are driven to induce a second output voltage on the secondary inductor. For the example in which each of the second primary inductors is coupled in parallel with the respective one of the first primary inductors, the multiple power amplifiers (e.g., power amplifiers 330-1 and 330-2) may drive parallel combinations of the first and second primary inductors.
Any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order of those elements. Rather, these designations are used herein as a convenient way of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element.
Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect electrical coupling between two structures.
The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
