BACKGROUND

Field

Embodiments of the invention relate to electronic systems, and in particular, to power amplifiers for radio frequency (RF) electronics.

Description of the Related Technology

Power amplifiers are used in RF communication systems to amplify RF signals for transmission via antennas. It is important to manage the power of RF signal transmissions to prolong battery life and/or provide a suitable transmit power level.

Examples of RF communication systems with one or more power amplifiers include, but are not limited to, mobile phones, tablets, base stations, network access points, customer-premises equipment (CPE), laptops, and wearable electronics. For example, in wireless devices that communicate using a cellular standard, a wireless local area network (WLAN) standard, and/or any other suitable communication standard, a power amplifier can be used for RF signal amplification. An RF signal can have a frequency in the range of about 30 kHz to 300 GHz, such as in the range of about 410 MHz to about 7.125 GHz for fifth generation (5G) communications in frequency range 1 (FR1).

SUMMARY

In certain embodiments, the present disclosure relates to an envelope tracking system. The envelope tracking system includes a power amplifier configured to amplify a radio frequency signal, and an envelope tracker configured to generate a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the radio frequency signal. The envelope tracker has a modulation bandwidth less than a full bandwidth of the radio frequency signal. The envelope tracking system further includes a bias modulation circuit configured to modulate a bias of the power amplifier based on a voltage level of the power amplifier supply voltage.

In various embodiments, the modulation bandwidth of the envelope tracker is less than 100 megahertz. According to a number of embodiments, the modulation bandwidth of the envelope tracker is less than 20 megahertz.

In several embodiments, the envelope signal is shaped.

In some embodiments, the envelope tracking system further includes a digital pre-distortion system configured to generate a digital transmit signal, and a modulator configured to generate the radio frequency signal based on the digital transmit signal. According to a number of embodiments, the envelope tracking system further includes a power amplifier supply voltage digital filter model configured to generate a supply voltage modeling signal estimating the voltage level of the power amplifier supply voltage at the power amplifier, the digital pre-distortion system operable to digitally pre-distort the digital transmit signal based on the supply voltage modeling signal.

In various embodiments, the bias modulation circuit is configured to modulate a bias of at least one cascode transistor of the power amplifier.

In several embodiments, the envelope tracker is implemented as a multi-level supply envelope tracker. According to a number of embodiments, the multi-level supply envelope tracker includes a multi-level supply DC-to-DC converter configured to generate a plurality of regulated voltages of different voltage levels, a modulator configured to receive the plurality of regulated voltages and having an output configured to control the voltage level of the power amplifier supply voltage, and a control circuit configured to control the modulator based on the envelope signal. In accordance with various embodiments, the multi-level supply envelope tracker further includes a passive filter interposed between the output of the modulator and a supply input to the power amplifier. According to some embodiments, the bias modulation circuit receives the power amplifier supply voltage from the output of the modulator prior to filtering by the passive filter, and the power amplifier receives the power amplifier supply voltage after filtering by the passive filter. In accordance with a number of embodiments, the envelope tracking system further includes a separate supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to various embodiments, the separate supply voltage filter is programmable. In accordance with some embodiments, the modulator further includes a plurality of switches each electrically connected between a corresponding one of the plurality of regulated voltages and the output.

In various embodiments, the envelope tracking system further includes a programmable supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to a number of embodiments, the programmable supply voltage filter is implemented as a low pass filter having a controllable corner frequency.

In several embodiments, the power amplifier includes a first power amplifier stage and a second power amplifier stage arranged in a cascade. According to a number of embodiments, the bias modulation circuit is configured to generate a bias signal for the second power amplifier stage and the second power amplifier stage is powered by the power amplifier supply voltage. In accordance with various embodiments, a bias of the first power amplifier stage is substantially fixed. According to some embodiments, both the first power amplifier stage and the second power amplifier stage are powered by the power amplifier supply voltage. In accordance with a number of embodiments, the bias modulation circuit is configured to generate a first bias signal that biases the first power amplifier stage and a second bias signal that biases the second power amplifier stage. According to various embodiments, the bias modulation circuit is operable to increase the first bias signal and decrease the second bias signal in response to the envelope tracker decreasing the voltage level of the power amplifier supply voltage. In accordance with some embodiments, the first power amplifier stage includes a first bipolar transistor having a base biased by the first bias signal and a collector that receives the power amplifier supply voltage, and a second bipolar transistor having a base biased by the second bias signal and a collector that receives the power amplifier supply voltage. According to a number of embodiments, at least one of the first power amplifier stage or the second power amplifier stage includes a cascode transistor. In accordance with various embodiments, the envelope tracking system further includes a cascode bias circuit configured to modulate a bias the cascode transistor. According to some embodiments, the cascode bias transistor is configured to modulate the bias of the cascode transistor based on the envelope signal.

In a number of embodiments, the envelope tracking system is implemented on a packaged module.

In certain embodiments, the present disclosure relates to a mobile device. The mobile device includes a transceiver configured to generate a radio frequency signal, a front end circuit including a power amplifier configured to amplify the radio frequency signal, and a power management circuit including an envelope tracker configured to generate a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the radio frequency signal. The envelope tracker has a modulation bandwidth less than a full bandwidth of the radio frequency signal, and the power management circuit further includes a bias modulation circuit configured to modulate a bias of the power amplifier based on a voltage level of the power amplifier supply voltage.

In various embodiments, the modulation bandwidth of the envelope tracker is less than 100 megahertz. According to a number of embodiments, the modulation bandwidth of the envelope tracker is less than 20 megahertz.

In several embodiments, the envelope signal is shaped.

In some embodiments, the mobile device further includes a digital processing circuit including a digital pre-distortion system configured to generate a digital transmit signal, the transceiver including a modulator configured to generate the radio frequency signal based on the digital transmit signal. According to a number of embodiments, the digital processing circuit further includes a power amplifier supply voltage digital filter model configured to generate a supply voltage modeling signal estimating the voltage level of the power amplifier supply voltage at the power amplifier, the digital pre-distortion system operable to digitally pre-distort the digital transmit signal based on the supply voltage modeling signal.

In various embodiments, the bias modulation circuit is configured to modulate a bias of at least one cascode transistor of the power amplifier.

In several embodiments, the envelope tracker is implemented as a multi-level supply envelope tracker. According to a number of embodiments, the multi-level supply envelope tracker includes a multi-level supply DC-to-DC converter configured to generate a plurality of regulated voltages of different voltage levels, a modulator configured to receive the plurality of regulated voltages and having an output configured to control the voltage level of the power amplifier supply voltage, and a control circuit configured to control the modulator based on the envelope signal. In accordance with some embodiments, the multi-level supply envelope tracker further includes a passive filter interposed between the output of the modulator and a supply input to the power amplifier. According to various embodiments, the bias modulation circuit receives the power amplifier supply voltage from the output of the modulator prior to filtering by the passive filter, and the power amplifier receives the power amplifier supply voltage after filtering by the passive filter. In accordance with a number of embodiments, the power management circuit further includes a separate supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to some embodiments, the separate supply voltage filter is programmable. In accordance with various embodiments, the modulator further includes a plurality of switches each electrically connected between a corresponding one of the plurality of regulated voltages and the output.

In some embodiments, the power management circuit further includes a programmable supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to a number of embodiments, the programmable supply voltage filter is implemented as a low pass filter having a controllable corner frequency.

In various embodiments, the power amplifier includes a first power amplifier stage and a second power amplifier stage arranged in a cascade. According to several embodiments, the bias modulation circuit is configured to generate a bias signal for the second power amplifier stage and the second power amplifier stage is powered by the power amplifier supply voltage. In accordance with a number of embodiments, a bias of the first power amplifier stage is substantially fixed. According some embodiments, both the first power amplifier stage and the second power amplifier stage are powered by the power amplifier supply voltage. In accordance with several embodiments, the bias modulation circuit is configured to generate a first bias signal that biases the first power amplifier stage and a second bias signal that biases the second power amplifier stage. According to a number of embodiments, the bias modulation circuit is operable to increase the first bias signal and decrease the second bias signal in response to the envelope tracker decreasing the voltage level of the power amplifier supply voltage. In accordance with some embodiments, the first power amplifier stage includes a first bipolar transistor having a base biased by the first bias signal and a collector that receives the power amplifier supply voltage, and a second bipolar transistor having a base biased by the second bias signal and a collector that receives the power amplifier supply voltage.

In various embodiments, at least one of the first power amplifier stage or the second power amplifier stage includes a cascode transistor. According to a number of embodiments, the power management circuit further includes a cascode bias circuit configured to modulate a bias the cascode transistor. In accordance with several embodiments, the cascode bias transistor is configured to modulate the bias of the cascode transistor based on the envelope signal.

In several embodiments, the mobile device further includes a battery operable to provide a battery voltage to the envelope tracker.

In some embodiments, the mobile device further includes an antenna configured to radiate a transmit wave in response to receiving an amplified radio frequency signal from the power amplifier.

In certain embodiments, the present disclosure relates to a method of envelope tracking. The method includes amplifying a radio frequency signal using a power amplifier, and generating a power amplifier supply voltage of the power amplifier based on an envelope signal using an envelope tracker, the envelope signal indicating an envelope of the radio frequency signal, and the envelope tracker having a modulation bandwidth less than a full bandwidth of the radio frequency signal. The method further includes modulating a bias of the power amplifier based on a voltage level of the power amplifier supply voltage using a bias modulation circuit.

In a number of embodiments, the modulation bandwidth of the envelope tracker is less than 100 megahertz.

In various embodiments, the modulation bandwidth of the envelope tracker is less than 20 megahertz.

In several embodiments, the envelope signal is shaped.

In some embodiments, the method further includes generating a digital transmit signal using a digital pre-distortion system, and processing the digital transmit signal to generate the radio frequency signal using a modulator. According to a number of embodiments, the method further includes generating a supply voltage modeling signal estimating the voltage level of the power amplifier supply voltage at the power amplifier, and digitally pre-distorting the digital transmit signal based on the supply voltage modeling signal. In accordance with several embodiments, modulating the bias of the power amplifier includes modulating a bias of at least one cascode transistor of the power amplifier.

In several embodiments, generating the power amplifier supply voltage includes generating a plurality of regulated voltages of different voltage levels using a multi-level supply DC-to-DC converter, and modulating the plurality of regulated voltages based on the envelope of the radio frequency signal to generate the power amplifier supply voltage using a modulator. According to a number of embodiments, the method further includes filtering the power amplifier supply voltage using a passive filter of the envelope tracker. In accordance with various embodiments, the method further includes providing the bias modulation circuit the power amplifier supply voltage from an output of the modulator prior to filtering by the passive filter, and providing the power amplifier supply voltage to the power amplifier after filtering by the passive filter.

In some embodiments, the method further includes filtering the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit using a programmable supply voltage filter.

In various embodiments, modulating the bias of the power amplifier includes generating a first bias signal for a first power amplifier stage of the power amplifier and a second bias signal for a second power amplifier stage of the power amplifier. According to a number of embodiments, the method further includes increasing the first bias signal and decreasing the second bias signal in response to the envelope tracker decreasing the voltage level of the power amplifier supply voltage.

In certain embodiments, the present disclosure relates to an envelope tracking system. The envelope tracking system includes a power amplifier configured to amplify a radio frequency signal, a multi-level supply envelope tracker configured to generate a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the radio frequency signal, and a bias modulation circuit configured to modulate a bias of the power amplifier based on a voltage level of the power amplifier supply voltage.

In various embodiments, the multi-level supply envelope tracker has a modulation bandwidth less than a full bandwidth of the radio frequency signal.

In some embodiments, the modulation bandwidth of the multi-level supply envelope tracker is less than 100 megahertz. According to a number of embodiments, the modulation bandwidth of the multi-level supply envelope tracker is less than 20 megahertz.

In several embodiments, the envelope signal is shaped.

In various embodiments, the envelope tracking system further includes a digital pre-distortion system configured to generate a digital transmit signal, and a modulator configured to generate the radio frequency signal based on the digital transmit signal. According to a number of embodiments, the envelope tracking system further includes a power amplifier supply voltage digital filter model configured to generate a supply voltage modeling signal estimating the voltage level of the power amplifier supply voltage at the power amplifier, the digital pre-distortion system operable to digitally pre-distort the digital transmit signal based on the supply voltage modeling signal.

In some embodiments, the bias modulation circuit is configured to modulate a bias of at least one cascode transistor of the power amplifier. According to a number of embodiments, the multi-level supply envelope tracker includes a multi-level supply DC-to-DC converter configured to generate a plurality of regulated voltages of different voltage levels, a modulator configured to receive the plurality of regulated voltages and having an output configured to control the voltage level of the power amplifier supply voltage, and a control circuit configured to control the modulator based on the envelope signal. In accordance with several embodiments, the multi-level supply envelope tracker further includes a passive filter interposed between the output of the modulator and a supply input to the power amplifier. According to various embodiments, the bias modulation circuit receives the power amplifier supply voltage from the output of the modulator prior to filtering by the passive filter, and the power amplifier receives the power amplifier supply voltage after filtering by the passive filter. In accordance with a number of embodiments, the envelope tracking system further includes a separate supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to several embodiments, the separate supply voltage filter is programmable. In accordance with various embodiments, the modulator further includes a plurality of switches each electrically connected between a corresponding one of the plurality of regulated voltages and the output.

In several embodiments, the envelope tracking system further includes a programmable supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to a number of embodiments, the programmable supply voltage filter is implemented as a low pass filter having a controllable corner frequency.

In various embodiments, the power amplifier includes a first power amplifier stage and a second power amplifier stage arranged in a cascade. According to a number of embodiments, the bias modulation circuit is configured to generate a bias signal for the second power amplifier stage and the second power amplifier stage is powered by the power amplifier supply voltage. In accordance with several embodiments, a bias of the first power amplifier stage is substantially fixed. According to some embodiments, both the first power amplifier stage and the second power amplifier stage are powered by the power amplifier supply voltage. In accordance with a number of embodiments, the bias modulation circuit is configured to generate a first bias signal that biases the first power amplifier stage and a second bias signal that biases the second power amplifier stage. According to several embodiments, the bias modulation circuit is operable to increase the first bias signal and decrease the second bias signal in response to the multi-level supply envelope tracker decreasing the voltage level of the power amplifier supply voltage. In accordance with some embodiments, the first power amplifier stage includes a first bipolar transistor having a base biased by the first bias signal and a collector that receives the power amplifier supply voltage, and a second bipolar transistor having a base biased by the second bias signal and a collector that receives the power amplifier supply voltage. According to a number of embodiments, at least one of the first power amplifier stage or the second power amplifier stage includes a cascode transistor. In accordance with several embodiments, the envelope tracking system further includes a cascode bias circuit configured to modulate a bias the cascode transistor. According to some embodiments, the cascode bias transistor is configured to modulate the bias of the cascode transistor based on the envelope signal.

In accordance with various embodiments, the envelope tracking system is implemented on a packaged module.

In certain embodiments, the present disclosure relates to a mobile device. The mobile device includes a transceiver configured to generate a radio frequency signal, a front end circuit including a power amplifier configured to amplify the radio frequency signal, and a power management circuit including a multi-level supply envelope tracker configured to generate a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the radio frequency signal, and a bias modulation circuit configured to modulate a bias of the power amplifier based on a voltage level of the power amplifier supply voltage.

In several embodiments, the multi-level supply envelope tracker has a modulation bandwidth less than a full bandwidth of the radio frequency signal.

In some embodiments, the modulation bandwidth of the multi-level supply envelope tracker is less than 100 megahertz. According to a number of embodiments, the modulation bandwidth of the multi-level supply envelope tracker is less than 20 megahertz.

In various embodiments, the envelope signal is shaped.

In several embodiments, the mobile device further includes a digital processing circuit including a digital pre-distortion system configured to generate a digital transmit signal, the transceiver including a modulator configured to generate the radio frequency signal based on the digital transmit signal. According to a number of embodiments, the digital processing circuit further includes a power amplifier supply voltage digital filter model configured to generate a supply voltage modeling signal estimating the voltage level of the power amplifier supply voltage at the power amplifier, the digital pre-distortion system operable to digitally pre-distort the digital transmit signal based on the supply voltage modeling signal.

In various embodiments, the bias modulation circuit is configured to modulate a bias of at least one cascode transistor of the power amplifier.

In some embodiments, the multi-level supply envelope tracker includes a multi-level supply DC-to-DC converter configured to generate a plurality of regulated voltages of different voltage levels, a modulator configured to receive the plurality of regulated voltages and having an output configured to control the voltage level of the power amplifier supply voltage, and a control circuit configured to control the modulator based on the envelope signal. According to a number of embodiments, the multi-level supply envelope tracker further includes a passive filter interposed between the output of the modulator and a supply input to the power amplifier. In accordance with several embodiments, the bias modulation circuit receives the power amplifier supply voltage from the output of the modulator prior to filtering by the passive filter, and the power amplifier receives the power amplifier supply voltage after filtering by the passive filter. According to various embodiments, the power management circuit further includes a separate supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. In accordance with a number of embodiments, the separate supply voltage filter is programmable. According to several embodiments, the modulator further includes a plurality of switches each electrically connected between a corresponding one of the plurality of regulated voltages and the output.

In various embodiments, the power management circuit further includes a programmable supply voltage filter operable to filter the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit. According to a number of embodiments, the programmable supply voltage filter is implemented as a low pass filter having a controllable corner frequency.

In several embodiments, the power amplifier includes a first power amplifier stage and a second power amplifier stage arranged in a cascade. According to a number of embodiments, the bias modulation circuit is configured to generate a bias signal for the second power amplifier stage and the second power amplifier stage is powered by the power amplifier supply voltage. In accordance with various embodiments, a bias of the first power amplifier stage is substantially fixed. According to some embodiments, both the first power amplifier stage and the second power amplifier stage are powered by the power amplifier supply voltage. In accordance with a number of embodiment, the bias modulation circuit is configured to generate a first bias signal that biases the first power amplifier stage and a second bias signal that biases the second power amplifier stage. According to various embodiments, the bias modulation circuit is operable to increase the first bias signal and decrease the second bias signal in response to the multi-level supply envelope tracker decreasing the voltage level of the power amplifier supply voltage. In accordance with several embodiments, the first power amplifier stage includes a first bipolar transistor having a base biased by the first bias signal and a collector that receives the power amplifier supply voltage, and a second bipolar transistor having a base biased by the second bias signal and a collector that receives the power amplifier supply voltage. According to a number of embodiments, at least one of the first power amplifier stage or the second power amplifier stage includes a cascode transistor. In accordance with various embodiments, the power management circuit further includes a cascode bias circuit configured to modulate a bias the cascode transistor. According to several embodiments, the cascode bias transistor is configured to modulate the bias of the cascode transistor based on the envelope signal.

In various embodiments, the mobile device further includes a battery operable to provide a battery voltage to the multi-level switching circuit.

In several embodiments, the mobile device further includes an antenna configured to radiate a transmit wave in response to receiving an amplified radio frequency signal from the power amplifier.

In certain embodiments, the present disclosure relates to a method of envelope tracking. The method includes amplifying a radio frequency signal using a power amplifier, generating a power amplifier supply voltage of the power amplifier based on an envelope signal using a multi-level supply envelope tracker, the envelope signal indicating an envelope of the radio frequency signal, and modulating a bias of the power amplifier based on a voltage level of the power amplifier supply voltage using a bias modulation circuit.

In various embodiments, the modulation bandwidth of the multi-level supply envelope tracker is less than 100 megahertz. According to a number of embodiments, the modulation bandwidth of the multi-level supply envelope tracker is less than 20 megahertz.

In several embodiments, the envelope signal is shaped.

In some embodiments, the method further includes generating a digital transmit signal using a digital pre-distortion system, and processing the digital transmit signal to generate the radio frequency signal using a modulator. According to a number of embodiments, the method further includes generating a supply voltage modeling signal estimating the voltage level of the power amplifier supply voltage at the power amplifier, and digitally pre-distorting the digital transmit signal based on the supply voltage modeling signal.

In various embodiments, modulating the bias of the power amplifier includes modulating a bias of at least one cascode transistor of the power amplifier.

In several embodiments, generating the power amplifier supply voltage includes generating a plurality of regulated voltages of different voltage levels using a multi-level supply DC-to-DC converter, and modulating the plurality of regulated voltages based on the envelope signal to generate the power amplifier supply voltage using a modulator. According to a number of embodiments, the method further includes filtering the power amplifier supply voltage using a passive filter of the multi-level supply envelope tracker. In accordance with various embodiments, the method further includes providing the bias modulation circuit the power amplifier supply voltage from an output of the modulator prior to filtering by the passive filter, and providing the power amplifier supply voltage to the power amplifier after filtering by the passive filter.

In some embodiments, the method further includes filtering the power amplifier supply voltage to generate a filtered power amplifier supply voltage that serves as an input to the bias modulation circuit using a programmable supply voltage filter.

In various embodiments, modulating the bias of the power amplifier includes generating a first bias signal for a first power amplifier stage of the power amplifier and a second bias signal for a second power amplifier stage of the power amplifier. According to several embodiments, the method further includes increasing the first bias signal and decreasing the second bias signal in response to the multi-level supply envelope tracker decreasing the voltage level of the power amplifier supply voltage.

