# US 9,520,845 B2 · Supply modulation for radio frequency power amplification > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,845 B2 - Document ID: US9520845B2 - Status: Granted - Kind: B2 - Application number: 14/543,021 - Filed: 2014-11-17 - Published: 2016-05-19 - Granted: 2016-12-13 - Earliest claimed: 2014-11-14 - Assignees: Microsoft Technology Licensing, LLC - Applicants: Microsoft Corporation - Inventors: Zhancang Wang - Web page: https://patentgrep.com/patent/US9520845B2 ## CPC - H03F 3/19: with semiconductor devices only - H03F 1/0222: {by using a signal derived from the input signal} - H03F 1/025: {by using a signal derived from the input signal} - H03F 1/32: Modifications of amplifiers to reduce non-linear distortion (by negative feedback H03F1/34) - H03F 3/195: in integrated circuits - H03F 3/245: {with semiconductor devices only} - H03F 2200/102: A non-specified detector of a signal envelope being used in an amplifying circuit - H03F 2200/451: the amplifier being a radio frequency amplifier - H03F 2200/504: the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier - H03F 2200/511: Many discrete supply voltages or currents or voltage levels can be chosen by a control signal in an IC-block amplifier circuit - H03F 2200/555: A voltage generating circuit being realised for biasing different circuit elements - H03F 2200/78: A comparator being used in a controlling circuit of an amplifier - H03F: AMPLIFIERS ## Abstract The subject matter described herein relates to supply modulation for power amplification. In one embodiment, the voltage level of the envelope with a tunable threshold voltage. The high level part of the envelope above the threshold voltage is maintained and amplified, for example, by the linear amplification process. On the other hand, the low level part of the envelope is replaced with the constant low voltage level. In amplification, the shaped low level part can be prompted to the predefined low supply voltage which may be directly output to the RFPA. By eliminating complicated amplification process on the lower level part of the envelope, the efficiency and bandwidth of the supply modulation can be improved and the circuitry can be simplified, without introducing any timing mismatch or delays. ## Claims ### Claim 1 A method comprising: comparing voltage of envelope of a radio frequency (RF) signal with threshold voltage; responsive to the voltage of the envelope being greater than or equal to the threshold voltage, shaping the envelope by keeping the envelope unchanged; responsive to the voltage of the envelope being below the threshold voltage, shaping the envelope by replacing the voltage of the envelope with predefined low voltage, the predefined low voltage being below the threshold voltage; and amplifying the shaped envelope, the amplified envelope provided to a radio frequency power amplifier (RFPA) for amplifying the RF signal. ### Claim 2 (depends on 1) The method of claim 1, wherein amplifying the shaped envelope comprises: responsive to the voltage of the envelope being greater than or equal to the threshold voltage, amplifying the shaped envelope by applying an envelope amplification process on the unchanged voltage of the envelope. ### Claim 3 (depends on 2) The method of claim 2, wherein applying the envelope amplification process comprises: applying a linear envelope amplification process on the unchanged voltage of the envelope with reference to high supply voltage, the high supply voltage being greater than the threshold voltage. ### Claim 4 (depends on 1) The method of claim 1, wherein amplifying the shaped envelope comprises: responsive to the voltage of the envelope being below the threshold voltage, amplifying the shaped envelope by increasing the predefined low voltage to low supply voltage, the low supply voltage being below the threshold voltage. ### Claim 5 (depends on 4) The method of claim 4, wherein the predefined low voltage is zero voltage, and wherein the low supply voltage is greater than knee voltage of the RFPA. ### Claim 6 (depends on 4) The method of claim 4, wherein amplifying the shaped envelope comprises: responsive to the voltage of the envelope being below the threshold voltage, providing the low supply voltage directly to the RFPA. ### Claim 7 (depends on 1) The method of claim 1, further comprising: detecting a peak-to-average-power-ratio (PAPR) of the RF signal; and updating the threshold voltage at least in part based on the detected PAPR. ### Claim 8 An apparatus comprising: an envelope shaping stage configured to: responsive to voltage of envelope of a radio frequency (RF) signal being greater than or equal to threshold voltage, shape the envelope by keeping the envelope unchanged, and responsive to the voltage of the envelope being below the threshold voltage, shape the envelope by replacing the voltage of the envelope with predefined low voltage, the predefined low voltage being below the threshold voltage; and an envelope amplification stage configured to amplify the shaped envelope, the amplified envelope provided to a radio frequency power amplifier (RFPA) for amplifying the RF signal. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the envelope amplification stage includes an envelope amplifier configured to, responsive to the voltage of the envelope being greater than or equal to the threshold voltage, apply an envelope amplification process on the unchanged voltage of the envelope. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the envelope amplifier includes a linear amplifier configured to apply a linear amplification process on the unchanged voltage of the envelope with reference to high supply voltage, the high supply voltage being greater than the threshold voltage. ### Claim 11 (depends on 8) The apparatus of claim 8, wherein the envelope amplification stage is configured to, responsive to the voltage of the envelope being below the threshold voltage, amplify the shaped envelope by increasing the predefined low voltage to low supply voltage, the low supply voltage being below the threshold voltage. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the predefined low voltage is zero voltage, and wherein the low supply voltage is greater than knee voltage of the RFPA. ### Claim 13 (depends on 11) The apparatus of claim 11, wherein the envelope amplification stage comprises a power switch configured to, responsive to the voltage of the envelope being below the threshold voltage, provide the low supply voltage directly to the RFPA. ### Claim 14 (depends on 8) The apparatus of claim 8, wherein the envelope shaping stage is further configured to update the threshold voltage based at least in part on a peak-to-average-power-ratio (PAPR) of the RF signal. ### Claim 15 A supply modulator comprising: an input node; an output node; a comparator coupled to the input node and having a voltage output, the comparator operable to: compare voltage of envelope of a radio frequency (RF) signal with threshold voltage, the envelope received from the input node, responsive to the voltage of the envelope being greater than or equal to the threshold voltage, provide the voltage of the envelope via the voltage output, and responsive to the voltage of the envelope being below the threshold voltage, provide constant low voltage via the voltage output; an amplifier coupled between the comparator and the output node, the amplifier, when enabled, operable to amplify the voltage of the envelope received from the voltage output of the comparator; a first switch coupled to the comparator and the amplifier, the first switch operable to enable or disable the amplifier based on the comparison by the comparator; and a second switch coupled to the comparator, the amplifier and the output node, the second switch operable to connect, based on the comparison by the comparator, the output node to an output of the amplifier or low supply voltage, the low supply voltage being below the threshold voltage. ### Claim 16 (depends on 15) The supply modulator of claim 15, wherein the comparator further has a control output and operable to: responsive to the voltage of the envelope being greater than or equal to the threshold voltage, provide a first control signal to the first switch and the second switch via the control output; and responsive to the voltage of the envelope being less than the threshold voltage, provide a second control signal to the first switch and the second switch via the control output. ### Claim 17 (depends on 16) The supply modulator of claim 16, wherein the amplifier has a reference voltage input coupled to the first switch, and wherein the first switch is operable to: responsive to the first control signal, connect the reference voltage input to high supply voltage, the high supply voltage being greater than the threshold voltage; and responsive to the second control signal, connect the reference voltage input to ground. ### Claim 18 (depends on 16) The supply modulator of claim 16, wherein the second switch is operable to: responsive to the first control signal, connect the output node to the output of the amplifier; and responsive to the second control signal, connect the output node to the low supply voltage. ### Claim 19 (depends on 15) The supply modulator of claim 15, further comprising: a first switch driving stage coupled between the comparator and the first switch and operable to drive the first switch based on the comparison by the comparator; and a second switch driving stage coupled between the comparator and the second switch and operable to control the second switch based on the comparison by the comparator. ### Claim 20 (depends on 15) The supply modulator of claim 15, wherein the constant low voltage is zero voltage, and wherein the low power supply is greater than knee voltage of a radio frequency power amplifier (RFPA) coupled to the output node.