Low modulation bandwidth envelope tracking circuit

Abstract

A low modulation bandwidth (LMB) envelope tracking (ET) circuit is provided. The LMB ET circuit is configured to generate an ET modulation voltage at an output node based on a modulation target voltage for amplifying an LMB radio frequency (RF) signal. More specifically, the LMB ET circuit includes: an amplifier configured to generate a modulation amplifier voltage based on the modulation target voltage; and an offset circuit configured to increase the modulation amplifier voltage by the modulation offset voltage at the output node. The offset circuit is configured to generate the modulation offset voltage based on a modulation target offset voltage proportional to the modulation target voltage. As a result, it is possible to maintain the ET modulation voltage at a defined voltage level for a defined duration so that the LMB RF signal can be amplified to a defined power level.

Description

[0001] Related applications

[0002] This application claims the benefit of Provisional Patent Application No. 62 / 658,660, filed April 17, 2018, the disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0003] The technology of this disclosure generally relates to envelope tracking (ET) circuits. Background Art

[0004] Mobile communication devices have become increasingly common in today's society, providing wireless communication services. The popularity of these mobile communication devices is driven in part by the many features now enabled on these devices. Increased processing power in these devices has meant that mobile communication devices have evolved from mere communication tools to sophisticated mobile multimedia centers that enable an enhanced user experience.

[0005] While supporting wide-area wireless communication technologies such as Long Term Evolution (LTE) and Fifth Generation New Radio (5G-NR), mobile communication devices can form the Internet of Things (IoT) with many non-conventional communication devices (e.g., vehicles, home appliances, sensors, etc.) to implement various human-machine interaction applications. Compared to RF signals transmitted in wide-area wireless networks, RF signals transmitted in IoT networks are typically modulated with a lower modulation bandwidth (e.g., less than 180 kHz) and communicate sporadically rather than periodically or continuously.

[0006] Envelope tracking (ET) is a technique whereby an ET modulation voltage is provided to an amplifier circuit to amplify an RF signal. The ET modulation voltage is associated with a time-varying voltage envelope that closely tracks the time-varying amplitude envelope of the amplified RF signal. In this regard, the peaks and valleys of the ET modulation voltage can be generated based on the peaks and valleys of the RF signal to help improve the linearity and efficiency of the amplifier circuit. However, maintaining the ET modulation voltage at a peak level for a sufficient duration (e.g., 2 microseconds) to amplify a lower modulation bandwidth (e.g., <180 kHz) RF signal to a defined power level (e.g., +26 dBm) can be challenging, particularly when the ET modulation voltage is generated based on a lower battery voltage (e.g., <3.2 V). Therefore, it may be necessary to maintain the ET modulation voltage at a peak level for a desired duration without compromising the error vector magnitude (EVM) of the amplifier circuit. Summary of the Invention

[0007] Embodiments of the present disclosure relate to a low modulation bandwidth (LMB) envelope tracking (ET) circuit. In the examples discussed herein, the LMB ET circuit is configured to generate an ET modulation voltage at an output node based on a modulation target voltage for amplifying an LMB (e.g., <180 kHz) radio frequency (RF) signal. More specifically, the LMB ET circuit includes an amplifier configured to generate a modulation amplifier voltage based on the modulation target voltage; and an offset circuit configured to increase the modulation amplifier voltage by the modulation offset voltage at the output node. The offset circuit is configured to generate the modulation offset voltage based on a modulation target offset voltage proportional to the modulation target voltage. In this regard, both the ET modulation voltage and the modulation offset voltage can rise and fall depending on the modulation target voltage. As a result, it is possible to maintain the ET modulation voltage at a defined voltage level for a defined duration, allowing the LMB RF signal to be amplified to a defined power level for transmission, for example, in an Internet of Things (IoT) network.

[0008] In one aspect, a LMB ET circuit is provided. The LMB ET circuit includes an input node configured to receive a modulation target voltage. The LMB ET circuit also includes an output node configured to output an ET modulation voltage corresponding to the modulation target voltage. The LMB ET circuit also includes an amplifier configured to generate a modulation amplifier voltage at an amplifier output terminal based on the modulation target voltage. The LMB ET circuit also includes an offset circuit coupled between the amplifier output terminal and the output node. The offset circuit is configured to receive a modulation target offset voltage proportional to the modulation target voltage. The offset circuit is further configured to generate a modulation offset voltage between the amplifier output terminal and the output node based on the modulation target offset voltage, such that the ET modulation voltage is maintained at a defined voltage level for a defined duration.

[0009] Those skilled in the art will understand the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure and together with the description serve to explain the principles of the disclosure.

[0011] FIG1A is a schematic diagram of an exemplary prior art envelope tracking (ET) circuit that may be unable to maintain the ET modulation voltage at a desired peak level for a duration sufficient to amplify a radio frequency (RF) signal modulated in a lower modulation bandwidth;

[0012] Figure 1B is a diagram providing an exemplary diagram of an ET modulation voltage that decreases over time due to discharge of an offset capacitor in the prior art ET circuit of FIG. 1A ;

[0013] Figure 2 is a schematic diagram of an exemplary low modulation bandwidth (LMB) ET circuit configured to maintain an ET modulation voltage at a defined voltage level for a defined duration sufficient to amplify an LMB radio frequency (RF) signal to a defined power level according to one embodiment of the present disclosure; and

[0014] Figure 3 Except Figure 2 FIG2 is a schematic diagram of an exemplary circuit including a second ET circuit in addition to the LMB ET circuit. DETAILED DESCRIPTION

[0015] The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode for practicing the embodiments. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically set forth herein. It should be understood that these concepts and applications all fall within the scope of the present disclosure and the appended claims.

[0016] It should be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of this disclosure. As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0017] It should be understood that when an element, such as a layer, region, or substrate, is referred to as being "on" or extending "onto" another element, it can be directly on or directly extending onto the other element, or there can be intervening elements. In contrast, when an element is referred to as being "directly on" or extending "directly" onto another element, there are no intervening elements. Similarly, it should be understood that when an element, such as a layer, region, or substrate, is referred to as being "above" or extending "above" another element, it can be directly above or extending directly above the other element, or there can be intervening elements. In contrast, when an element is referred to as being "directly above" or extending "directly over" another element, there are no intervening elements. It should also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0018] Relative terms, such as "below" or "above" or "up" or "lower" or "horizontally" or "vertical," may be used herein to describe one element, layer, or region's relationship to another element, layer, or region, as illustrated in the figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0019] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the term "comprising," when used herein, specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0020] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that the terms used herein should be interpreted as having a meaning consistent with that in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0021] Embodiments of the present disclosure relate to a low modulation bandwidth (LMB) envelope tracking (ET) circuit. In the examples discussed herein, the LMB ET circuit is configured to generate an ET modulation voltage at an output node based on a modulation target voltage for amplifying an LMB (e.g., <180 kHz) radio frequency (RF) signal. More specifically, the LMB ET circuit includes an amplifier configured to generate a modulation amplifier voltage based on the modulation target voltage; and an offset circuit configured to increase the modulation amplifier voltage by the modulation offset voltage at the output node. The offset circuit is configured to generate the modulation offset voltage based on a modulation target offset voltage that is proportional to the modulation target voltage. In this regard, both the ET modulation voltage and the modulation offset voltage can rise and fall depending on the modulation target voltage. As a result, it is possible to maintain the ET modulation voltage at a defined voltage level for a defined duration, allowing the LMB RF signal to be amplified to a defined power level for transmission, for example, in an Internet of Things (IoT) network.

[0022] Before discussing the LMB ET circuit of the present disclosure, a brief overview of the existing ET circuit is first discussed with reference to Figures 1A and 1B to help understand the challenges associated with generating ET modulation voltage for amplifying IoT communication signals with lower modulation bandwidth. Figure 2 Specific exemplary aspects of LMB ET circuits according to the present disclosure are discussed first.

[0023] In this regard, FIG. 1A is a schematic diagram of an exemplary prior art ET circuit 10 that may not be able to modulate the ET voltage V CC The desired peak level is maintained for a duration sufficient to continue amplifying the RF signal 12 modulated in the lower modulation bandwidth.

[0024] The amplifier 14 is configured to modulate the target voltage V 目标 and the supply voltage V BATAMP The modulated amplifier voltage V is generated at the amplifier output 18 PARAMP In a non-limiting example, the modulation target voltage V 目标 Can be provided in the form of a differential voltage, and the supply voltage V BATAMP The amplifier output 18 is coupled to the output node 20 of the existing ET circuit 10 via an offset capacitor 22. The offset capacitor 22 is configured to modulate the amplifier voltage V PARAMP Increase the offset voltage V 偏移 To generate the ET modulation voltage V at the output node 20 CC In this regard, the offset voltage V 偏移It can be expressed by the following equation (Equation 1).

[0025] V 偏移 =V CC -V PARAMP (Equation 1)

[0026] =V CC-峰值 -V PARAMP-峰值

[0027] In the above equation (Equation 1), V CC-峰值 and V PARAMP-峰值 Represents ET modulation voltage V CC The peak level and modulation amplifier voltage V PARAMP Peak level. Supply voltage V BATAMP It can be determined according to the following equations (Equation 2.1 and Equation 2.2).

[0028] V BATAMP =V PARAMP-峰值 +P 余量 (Equation 2.1)

[0029] =V CC-峰值 -V 偏移 +V HR (Equation 2.2)

[0030] In the equation (Equation 2), P 余量 Indicates a predefined voltage margin. In a non-limiting example, P 余量 and V 偏移 The offset capacitor 22 can be pre-configured to be approximately 0.2V and approximately 0.8V, respectively. PARAMP The voltage V is increased by about 1V to generate the ET modulation voltage V at the output node 20. CC From the above equations (Equation 2.1 and Equation 2.2), V CC-峰值 and P 余量 It can be further expressed as the following equations (Equation 3 and Equation 4).

[0031] V CC-峰值 =V BATAMP +V 偏移 -P 余量 (Equation 3)

[0032] P 余量 =V 偏移 +V BATAMP -V CC-峰值 (Equation 4)

[0033] The charge pump circuit 16 includes a charge pump 24, which may be, for example, a direct current (DC) to DC (DC-DC) buck-boost circuit. The charge pump 24 is configured to generate a voltage based on the battery voltage V BAT Generate DC voltage V DC In a non-limiting example, the battery voltage V BAT Less than 3.2 volts (<3.2V).

[0034] The conventional ET circuit 10 includes a control circuit 26, which may further include a bang-bang controller (BBC) (not shown) for controlling the charge pump circuit 16 and an ET controller (ETC) (not shown) for controlling the amplifier 14. The control circuit 26 may control the charge pump 24 to generate various levels of DC voltage V DC In a non-limiting example, the control circuit 26 may control the charge pump 24 to generate 0V, V BAT or 2×V BAT DC voltage V DC The charge pump circuit 16 includes an inductor 28 configured to be energized based on the DC voltage V DC The induced current I at the output node 20 CC .

[0035] The output node 20 is coupled to an amplifier circuit 30. The amplifier circuit 30 is configured to modulate the voltage V based on the ET. CC The RF signal 12 is converted from the input power P 输入 Amplify to output power P 输出 In one non-limiting example, the RF signal 12 may be an Internet of Things (IoT) RF signal corresponding to LMB (eg, <180 KHz).

[0036] Sometimes, the amplifier circuit 30 may need to amplify the RF signal 12 to a peak power level P 输出-峰值 In this regard, the existing ET circuit 10 is required to modulate the ET voltage V CC Maintain at peak level V CC-峰值 And the current I CC The desired current level is generated so that the amplifier circuit 30 can amplify the RF signal 12 to the peak power level P 输出-峰值 For example, the amplifier circuit 30 is required to amplify the RF signal 12 to a Class 2 output power exceeding 26 dBm. If the amplifier circuit 30 has a power amplifier efficiency (PAE) of 45% and the ET modulation voltage V CC The peak level is 5V, and the current I generated by the existing ET circuit 10 is CC About 314.6mA will be required.

[0037] Initially, the charge pump circuit 16 is configured to provide a current I based on the battery voltage V BAT However, assuming that the battery voltage V CC can be as low as 3.2V (or even lower than 3.0V), the DC voltage V BAT may not be sufficient to drive the inductor 28 to generate the current I at the desired current level DC . As a result, the amplifier 14 may be forced to provide a portion of the current I CC to make up the shortfall.

[0038] When the amplifier 14 starts to provide the current I CC , the offset capacitor 22 starts to discharge to reduce the offset voltage V 偏移 . Therefore, according to the above equation (Equation 3), the predetermined voltage margin P 余量 needs to be proportionally reduced to maintain the ET modulation voltage V CC at the peak level V CC-峰值 . However, when P 余量 drops to 0V, there will be no voltage margin left to compensate for a further reduction in the offset voltage V 偏移 . As a result, the existing ET circuit 10 can no longer maintain the ET modulation voltage V CC at the peak level V CC-峰值 . Therefore, the ET modulation voltage V CC may be clipped, resulting in the amplifier circuit 30 becoming unable to amplify the RF signal 12 to the peak power level P 输出-峰值 .

[0039] Figure 1B Graph 32 is an exemplary illustration of the ET modulation voltage V CC which decreases over time due to the discharge of the offset capacitor 22 in the existing ET circuit 10 of FIG. 1A. The elements of FIG. 1A are incorporated Figure 1B by reference and will not be described again herein.

[0040] Graph 32 includes an ideal voltage curve 34 and an actual voltage curve 36. As shown by the ideal voltage curve 34, the existing ET circuit 10 needs to maintain the ET modulation voltage V CC at approximately 5V between times T1 and T2. However, as shown by the actual voltage curve 36, the ET modulation voltage V CC starts to decrease at time T3 (T1 < T3 < T2) due to the discharge of the offset capacitor 22. In other words, the existing ET circuit 10 can only maintain the ET modulation voltage V CC at the 5V level between times T1 and T3. In a non-limiting example, the duration between times T1 and T3 can be approximately 15 microseconds (μs).​​

[0041] When the RF signal 12 is modulated with a higher modulation bandwidth (eg, ≥180 KHz), the conventional ET circuit 10 only needs to adjust the ET modulation voltage V CC Maintaining the 5V level for about 5μs. In this regard, it is assumed that the existing ET circuit 10 is capable of modulating the ET voltage V CC Maintaining the 5V level for a longer duration, the voltage drop as shown by the actual voltage curve 36 may not adversely affect the amplifier circuit 30 .

[0042] However, when the RF signal 12 is an IoT RF signal, the RF signal 12 is typically modulated at a modulation bandwidth much lower than 180 KHz (e.g., between 3.75 and 15 KHz). In this regard, the existing ET circuit 10 may need to modulate the ET modulation voltage V CC Maintaining the 5V level for 280μs is far beyond the capability of the existing ET circuit 10. Therefore, it may be necessary to enhance the existing ET circuit 10 so that the ET modulation voltage V CC The peak level can be maintained for a sufficient duration to amplify the lower modulation bandwidth RF signal to the desired peak power level.

[0043] in this regard, Figure 2 is configured to modulate the ET voltage V according to one embodiment of the present disclosure. CC The voltage level is maintained at a defined level sufficient to amplify the LMB RF signal 40 to a defined power level P 输出 Schematic diagram of an exemplary LMBET circuit 38 for a defined duration of time. In the examples discussed below, the defined power level corresponds to a peak power level P 输出-峰值 (For example, 26dBm). Therefore, the defined voltage level corresponds to the ET modulation voltage V CC The peak level (called "V CC-峰值 ”) (e.g., 5V). In addition, the defined duration may be 280 μs. It should be understood that this document refers to P 输出-峰值 and V CC-峰值 The operating principles discussed are also applicable to other power and voltage levels.

[0044] The LMB ET circuit 38 includes an input node 42 configured to receive a modulation target voltage V 目标 The LMB ET circuit 38 further includes an output node 44 configured to output an ET modulation voltage V CC and current I CC The LMB ET circuit 38 includes an amplifier 46 configured to generate a current based on a supply voltage V BATAMP and modulation target voltage V目标 A modulated amplifier voltage V is generated at the amplifier output 48. PARAMP In a non - limiting example, the supply voltage V is determined based on Equation (Equation 2.1) above. BATAMP .

[0045] The LMB ET circuit 38 includes an offset circuit 50 connected between the amplifier output 48 and the output node 44. In a non - limiting example, the offset circuit 50 includes an offset capacitor 52 and an offset control circuit 54 connected in parallel between the amplifier output 48 and the output node 44. The offset circuit 50 is configured to generate a modulated offset voltage V on the offset capacitor 52 based on a modulation target offset voltage V. 偏移-目标 The modulated offset voltage V is configured to raise the modulated amplifier voltage V to the ET modulation voltage V at the output node 44. 偏移 . The modulated offset voltage V 偏移 is configured to raise the modulated amplifier voltage V PARAMP to the ET modulation voltage V at the output node 44. CC In this regard, the modulated offset voltage V 偏移 can correspond to the voltage difference between the ET modulation voltage V CC and the modulated amplifier voltage V PARAMP .

[0046] As discussed in detail below, the offset circuit 50 receives a modulation target offset voltage V proportional to the modulation target voltage V. 目标 In this regard, the modulated offset voltage V can be generated based on the modulation target voltage V. 偏移-目标 and the ET modulation voltage V 目标 both. Thus, when the ET modulation voltage V 偏移 reaches a defined voltage level V CC , the modulated offset voltage V CC can also increase proportionally. As a result, when a portion of the amplifier 46 outputs current I CC-峰值 , it is possible to extend the discharge time of the offset capacitor 52, thereby allowing the LMB ET circuit 38 to maintain the ET modulation voltage V 偏移 at a peak level V CC for an extended duration (e.g., 280 μs) that may be sufficient to amplify the LMB RF signal 40 to a peak power level P CC for transmission in an IoT network, for example. CC-峰值 to a peak power level P 输出-峰值 for transmission in an IoT network, for example.

[0047] The LMB ET circuit 38 includes a voltage modulator 56 connected to the offset circuit 50. The voltage modulator 56 is configured to receive a copy of the modulation target voltage V from the input node 42 and scale the modulation target voltage V based on a predefined scaling factor k (0 < k < 1). 目标 and scale the modulation target voltage V based on a predefined scaling factor k (0 < k < 1). 目标To generate the scaled modulation target voltage k*V 目标 .

[0048] The voltage modulator 56 is also configured to utilize a predefined minimum offset voltage V 偏移0 Modulation scaling modulation voltage k*V 目标 , to generate the modulation target offset voltage V 偏移-目标 , and modulate the target offset voltage V 偏移-目标 Supplied to the offset circuit 50.

[0049] In a non-limiting example, the modulation target offset voltage V may be determined based on the following equation (Equation 5): 偏移-目标 .

[0050] V 偏移-目标 =k*(V 目标 -V 目标-MIN )+V 偏移0 (Equation 5)

[0051] ={V 偏移0 -k*V 目标-MIN}+{k*V 目标}

[0052] In the above equation (Equation 5), V 目标-MIN Indicates the modulation target voltage V 目标 Therefore, k*V 目标-MIN is considered to represent the minimum target voltage for scaling. It is worth noting that the term {V 偏移0 -k*V 目标-MIN} can be predetermined based on the specific design parameters of the LMBET circuit 38 and is therefore referred to as the modulation offset voltage V 偏移 In contrast, the term {k*V 目标} is considered as the modulation offset voltage V 偏移 "Dynamic items".

[0053] The offset capacitor 52 in the offset circuit 50 has a first terminal 58 and a second terminal 60 coupled to the amplifier output 48 and the output node 44, respectively. The offset control circuit 54 (which may be, for example, a field programmable gate array (FPGA)) is coupled in parallel to the offset capacitor 52 between the first terminal 58 and the second terminal 60. The offset control circuit 54 receives a modulated target offset voltage V from the voltage modulator 56. 偏移-目标 , and based on the modulation target offset voltage V 偏移-目标 Determine the modulation offset voltage V 偏移 Then, the offset control circuit 54 modulates the offset voltage V 偏移Applied to the offset capacitor 52. It is worth noting that the offset control circuit 54 can apply the modulated offset voltage V to the offset capacitor 52 directly or with the help of an auxiliary circuit (not shown) in the LMB ET circuit 38. 偏移 .

[0054] In response to the modulation offset voltage V generated and applied on the offset capacitor 52 偏移 , and can also prevent P 余量 becomes negative when the offset capacitor 52 is discharged. In a non-limiting example, P in the LMB ET circuit 38 余量 It can be determined by the following equation (Equation 6).

[0055] P 余量 ={V 偏移0 -k*V 目标-MIN}+(k-1)*V CC}+V BATAMP (Equation 6)

[0056] In this regard, when the ET modulation voltage V CC Maintained at the bottom (minimum) voltage level V CC-MIN When P 余量 Equal to approximately {V 偏移0 -V CC-MIN +V BATAMP}. On the contrary, when ET modulates the voltage V CC Maintaining the peak voltage level V CC-峰值 When P 余量 Approximately equal to {V 偏移0-VCC-峰值 +V BATAMP +k*(V CC-峰值 -V 目标-MIN In either case, the LMB ET circuit 38 can 余量 Maintain at a positive level.

[0057] The offset control circuit 54 can also receive the modulation amplifier voltage V by being coupled between the first terminal 58 and the second terminal 60. PARAMP and ET modulation voltage V CC In this regard, the offset control circuit 54 can determine the ET modulation voltage V CC and the modulation amplifier voltage V PARAMP Therefore, the offset control circuit 54 can generate an indication signal 62 indicating the voltage difference.

[0058] The LMB ET circuit 38 may include a control circuit 64 configured to receive the indication signal 62 from the offset control circuit 54. Thus, the control circuit 64 may control the amplifier 46 (eg, increase or decrease the modulation amplifier voltage V PARAMPIn a non-limiting example, the control circuit 64 includes an ETC (not shown) dedicated to controlling the amplifier 46 .

[0059] The LMB ET circuit 38 may further include a charge pump circuit 66 configured to generate a current I CC and provides it to the output node 44. In a non-limiting example, the charge pump circuit 66 includes a charge pump 68, which can be a DC-DC buck-boost circuit. The charge pump circuit 66 also includes an inductor 70 connected in series with the charge pump 68. The charge pump 68 is configured to generate a voltage based on the battery voltage V BAT Generate DC voltage V DC , which can be lower than 3.2V.

[0060] The control circuit 64 may further include a BBC (not shown) dedicated to controlling the charge pump circuit 66. The BBC may control the charge pump 68 to generate 0V, V BAT or 2×V BAT DC voltage V DC The inductor 70 is configured to be energized based on the DC voltage V DC The induced current I at the output node 20 CC .

[0061] The output node 44 may be coupled to an amplifier circuit 72. The amplifier circuit 72 is configured to modulate the voltage V based on the ET. CC and load current I 负载 The LMB RF signal 40 is increased from the output power level P 输入 Amplify to the limited power level P 输出 .

[0062] In a non-limiting example, the amplifier circuit 72 is required to increase the LMB RF signal 40 from an input power level P 输入 Amplify to peak power level P 输出-峰值 In this regard, by applying a modulated offset voltage V 偏移 , the LMB ET circuit 38 may modulate the ET voltage V CC Maintain at peak level V CC-峰值 The peak power level P 输出-峰值 For extended durations of transmission, such as in IoT networks.

[0063] Under certain operating conditions, the charge pump circuit 66 can be configured to 负载 The same amount generates current I CC Or, as follows Figure 3 As discussed in , it is also possible to configure the charge pump circuit 66 to convert the current ICC Generates load current I 负载 and uses a second charge pump circuit to generate a load current I 负载 the other half.

[0064] in this regard, Figure 3 Except Figure 2 Schematic diagram of an exemplary circuit 74 including a second ET circuit 76 in addition to the LMB ET circuit 38. Common element numbers are used to show Figure 2 and 3 , and they are not repeated in this article.

[0065] The second ET circuit 76 includes a second output node 78 coupled to the amplifier circuit 72. The second ET circuit 76 includes a second amplifier 80 coupled to the second output node 78 via a second offset capacitor 82. The second ET circuit 76 includes a second charge pump circuit 84 including a second charge pump 86 and a second inductor 88. The second ET circuit 76 may or may not be identical to the LMB ET circuit 38. In this regard, the second ET circuit 76 may or may not include the offset circuit 50 and the voltage modulator 56, as does the LMB ET circuit 38.

[0066] In a non-limiting example, the charge pump circuit 66 and the second charge pump circuit 84 may be configured to each generate a load current I required by the amplifier circuit 72 to amplify the LMB RF signal 40. 负载 The second amplifier 80 is not required to generate the ET modulation voltage V for the amplifier circuit 72. CC , and thus the second amplifier can be deactivated.

[0067] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered to be within the scope of the concepts disclosed herein and the claims that follow.

Claims

1. A low modulation bandwidth LMB envelope tracking ET circuit, the low modulation bandwidth LMB envelope tracking ET circuit comprising: an input node configured to receive a modulated target voltage; an output node configured to output an ET modulation voltage corresponding to the modulation target voltage; an amplifier configured to generate a modulated amplifier voltage at an amplifier output terminal based on the modulated target voltage; as well as an offset circuit, the offset circuit comprising an offset capacitor and an offset control circuit coupled in parallel to the offset capacitor between the amplifier output terminal and the output node, the offset circuit being configured to: receiving a modulation target offset voltage proportional to the modulation target voltage; as well as A modulation offset voltage is generated between the amplifier output terminal and the output node based on the modulation target offset voltage such that the ET modulation voltage is maintained at a defined voltage level for a defined duration.

2. The low modulation bandwidth LMB envelope tracking ET circuit of claim 1 , further comprising a voltage modulator coupled to the offset circuit and configured to: receiving the modulated target voltage from the input node; scaling the modulation target voltage based on a predefined scaling factor to generate a scaled modulation target voltage; modulating the scaled modulation target voltage with a predefined minimum offset voltage to generate the modulation target offset voltage proportional to the modulation target voltage; as well as The modulated target offset voltage is provided to the offset circuit.

3. The low modulation bandwidth (LMB) envelope tracking (ET) circuit of claim 2, wherein the predefined scaling factor is greater than zero and less than one.

4. The low modulation bandwidth LMB envelope tracking ET circuit according to claim 2, wherein: the offset capacitor having a first end coupled to the amplifier output and a second end coupled to the output node; as well as The offset control circuit is coupled in parallel to the offset capacitor between the first end and the second end, the offset control circuit being configured to: receiving the modulation target offset voltage from the voltage modulator; determining the modulation offset voltage based on the modulation target offset voltage; as well as The modulated offset voltage is applied across the offset capacitor.

5. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 4, wherein the offset control circuit is further configured to: receiving the modulation amplifier voltage and the ET modulation voltage from the first terminal and the second terminal respectively; determining a voltage difference between the ET modulation voltage and the modulation amplifier voltage; and An indication signal indicative of the voltage difference is generated.

6. The low modulation bandwidth LMB envelope tracking ET circuit according to claim 5, further comprising a control circuit, wherein the control circuit is configured to: receiving the indication signal from the offset control circuit; and The amplifier is controlled based on the voltage difference indicated by the indication signal. 7 . The low modulation bandwidth LMB envelope tracking ET circuit of claim 6 , further comprising a charge pump circuit configured to provide current to the output node.

8. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 7, wherein the charge pump circuit comprises: a charge pump configured to generate a direct current (DC) voltage based on a battery voltage; as well as An inductor is coupled between the charge pump and the output node, the inductor being configured to generate the current at the output node based on the DC voltage.

9. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 8, wherein the charge pump is further configured to generate the DC voltage at 0 volts, the battery voltage, or twice the battery voltage.

10. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 9, wherein the battery voltage is less than or equal to 3.2 volts.

11. The low modulation bandwidth LMB envelope tracking (ET) circuit according to claim 7, wherein the control circuit comprises: a relay controller configured to control the charge pump circuit; as well as An ET controller is configured to control the amplifier.

12. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 7, wherein: The output node is coupled to an amplifier circuit configured to amplify a LMB radio frequency (RF) signal based on the ET modulation voltage and a load current; and The offset circuit is further configured to generate the modulated offset voltage between the amplifier output and the output node such that the ET modulation voltage is maintained at a defined voltage level for a defined duration required to amplify the LMB radio frequency (RF) signal to a defined power level.

13. The low modulation bandwidth (LMB) envelope tracking (ET) circuit of claim 12, wherein the LMB radio frequency (RF) signal corresponds to a modulation bandwidth of less than 180 KHz.

14. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 12, wherein the charge pump circuit is further configured to generate the current equal to half of the load current.

15. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 14, wherein the amplifier circuit is further coupled to a second charge pump circuit configured to generate the other half of the load current.

16. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 2, wherein the modulation target offset voltage includes a static term and a dynamic term.

17. The low modulation bandwidth (LMB) envelope tracking (ET) circuit of claim 16, wherein the static term is determined based on the predefined minimum offset voltage and a scaled minimum target voltage.

18. The low modulation bandwidth (LMB) envelope tracking (ET) circuit of claim 16, wherein the dynamic term corresponds to the scaled modulation target voltage.

19. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 1, wherein the offset circuit is further configured to generate the modulation offset voltage between the amplifier output terminal and the output node so that the ET modulation voltage is maintained at a peak level within the defined duration.

20. The low modulation bandwidth LMB envelope tracking (ET) circuit of claim 19, wherein the offset circuit is further configured to generate the modulation offset voltage between the amplifier output terminal and the output node to maintain a positive voltage margin when the ET modulation voltage is maintained at the peak level.

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