ENVELOPE TRACKING SIGNAL GENERATOR INCORPORATING TRIM CELL

• US 20140085008A1
• Filed: 09/23/2013
• Published: 03/27/2014
• Est. Priority Date: 09/23/2012
• Status: Active Grant

• Current Assignee: DSP Group Ltd. (Synaptics Incorporated)
• Original Assignee: DSP Group Ltd. (Synaptics Incorporated)
• Inventors: Cohen, Avi, Gulko, Michael
• Granted Patent: US 9,105,395 B2
• Time in Patent Office: Days
• US Class Current: 330/297
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01F 19/04 Transformers or mutual inductances suitable for handling frequencies considerably beyond the audio range resonant circuits H03H
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 27/29 Terminals; Tapping arrangements for signal inductances
• CPC Class Codes: H01F 38/00 Adaptations of transformers or inductances for specific applications or functions
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H01L 2223/6611 Wire connections
• CPC Class Codes: H01L 2223/6655 Matching arrangements, e.g. arrangement of inductive and capacitive components
• CPC Class Codes: H01L 2223/6672 for integrated passive components, e.g. semiconductor device with passive components only
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 23/5227 Inductive arrangements or effects of, or between, wiring layers other inductive arrangements H01L23/645
• CPC Class Codes: H01L 23/645 Inductive arrangements H01L23/647, H01L23/66 take precedence
• CPC Class Codes: H01L 23/66 High-frequency adaptations
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 3/04 by static converters
• CPC Class Codes: H02M 3/1563 : without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H03F 1/02 : Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/0216 : Continuous control
• CPC Class Codes: H03F 1/0227 : using supply converters
• CPC Class Codes: H03F 1/0238 : using supply converters
• CPC Class Codes: H03F 1/0261 : with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 1/26 : Modifications of amplifiers to reduce influence of noise generated by amplifying elements
• CPC Class Codes: H03F 1/565 : using inductive elements
• CPC Class Codes: H03F 2200/102 : A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/105 : A non-specified detector of the power of a signal being used in an amplifying circuit
• CPC Class Codes: H03F 2200/18 : the bias of the gate of a FET being controlled by a control signal
• CPC Class Codes: H03F 2200/294 : the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/387 : A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/432 : Two or more amplifiers of different type are coupled in parallel at the input or output, e.g. a class D and a linear amplifier, a class B and a class A amplifier
• CPC Class Codes: H03F 2200/451 : the amplifier being a radio frequency amplifier
• CPC Class Codes: 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
• CPC Class Codes: H03F 2200/534 : Transformer coupled at the input of an amplifier
• CPC Class Codes: H03F 2200/537 : A transformer being used as coupling element between two amplifying stages
• CPC Class Codes: H03F 2200/541 : Transformer coupled at the output of an amplifier
• CPC Class Codes: H03F 2203/21106 : An input signal being distributed in parallel over the inputs of a plurality of power amplifiers
• CPC Class Codes: H03F 2203/21142 : Output signals of a plurality of power amplifiers are parallel combined to a common output
• CPC Class Codes: H03F 3/19 : with semiconductor devices only
• CPC Class Codes: H03F 3/193 : with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03F 3/195 : in integrated circuits
• CPC Class Codes: H03F 3/21 : with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/211 : using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/213 : in integrated circuits
• CPC Class Codes: H03F 3/24 : of transmitter output stages
• CPC Class Codes: H03F 3/245 : with semiconductor devices only
• CPC Class Codes: H03F 3/265 : with field-effect transistors only
• CPC Class Codes: H03F 3/45179 : using MOSFET transistors as the active amplifying circuit H03F3/45278 takes precedence
• CPC Class Codes: H03F 3/68 : Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H04B 1/0475 : with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/40 : Circuits
• CPC Class Codes: H04B 1/44 : Transmit/receive switching
• CPC Class Codes: H04B 2001/045 : with means for improving efficiency
• CPC Class Codes: H04L 27/0002 : analog front ends; means for connecting modulators, demodulators or transceivers to a transmission line duplex arrangements H04L5/143
• CPC Class Codes: Y02D 30/70 : in wireless communication networks

Abstract

A novel and useful radio frequency (RF) front end module (FEM) circuit that provides high linearity and power efficiency and meets the requirements of modern wireless communication standards such as 802.11 WLAN, 3G and 4G cellular standards, Bluetooth, ZigBee, etc. The configuration of the FEM circuit permits the use of common, relatively low cost semiconductor fabrication techniques such as standard CMOS processes. The FEM circuit includes a power amplifier made up of one or more sub-amplifiers having high and low power circuits and whose outputs are combined to yield the total desired power gain. An integrated multi-tap transformer having primary and secondary windings arranged in a novel configuration provide efficient power combining and transfer to the antenna of the power generated by the individual sub-amplifiers.

Claims

1. An envelope tracking system, comprising:

an envelope detector operative to extract an envelope from an input RF signal;

an analog to digital converter operative to generate a trim command based on said envelope; and

a DC-DC converter operative to generate a power amplifier (PA) supply voltage in response to said trim command, said DC-DC converter comprising;

a switching circuit coupled to a DC voltage source and operative to convert an input voltage into said PA supply voltage across an output capacitor in accordance with a reference voltage;

a feedback circuit coupled to said switching circuit and operative to generate a drive signal for said switching circuit; and

a plurality of trim cells, each trim cell incorporating a trim capacitor adapted to be charged to a predetermined trim voltage and connected in series with said output capacitor in accordance with a trim command thereby increasing said PA supply voltage substantially instantaneously.

2. The envelope tracking system according to claim 1, wherein said feedback circuit comprises:

an error amplifier configured to generate an error signal based on a difference between said reference signal and said PA supply voltage; and

a PWM comparator configured to generate a PWM signal in accordance with said error signal and an oscillator input signal.

3. The envelope tracking system according to claim 2, wherein said oscillator signal comprises a triangle or saw-tooth signal.

4. The envelope tracking system according to claim 1, wherein each said trim capacitor is normally charged to a different trim voltage which is added to said PA supply voltage in response to a trim command, said PA supply voltage transitioning substantially instantaneously due to there being no need to charge said output capacitor and said trim capacitors.

5. The DC-DC converter according to claim 1, wherein each trim capacitor is normally charged to a different trim voltage whereby one of said trim capacitors is adapted to be connected in series with said output capacitor in accordance with said trim command, said PA supply voltage transitioning substantially instantaneously due to there being no need to charge said output capacitor and said trim capacitors.

6. The envelope tracking system according to claim 1, wherein said reference voltage is adjusted by a predetermined amount in response to said trim command so as to maintain said feedback circuit in steady state condition.

7. The envelope tracking system according to claim 1, wherein each said trim capacitor is normally charged to a different trim voltage whereby the voltage on one of said trim capacitors is subtracted from said PA supply voltage in response to said trim command.

8. The envelope tracking system according to claim 1, wherein each said trim capacitor is normally charged to a different trim voltage whereby one of said trim capacitors is disconnected from said output capacitor in response to said trim command.

9. The envelope tracking system according to claim 1, wherein said DC-DC converter is adapted to provide a PA supply voltage to said power amplifier configured to transmit signals conforming to a wireless standard selected from the group consisting of 802.11 WLAN, LTE, WiMAX, HDTV, 3G cellular, 4G cellular and DECT.

10. An envelope tracking system, comprising:

an envelope detector operative to extract an envelope from an input RF signal;

an analog to digital converter operative to generate a trim command based on said envelope; and

a DC-DC converter operative to generate a power amplifier (PA) supply voltage in response to said trim command, said DC-DC converter comprising;

a switching circuit coupled to a DC voltage source and operative to convert an input voltage into said PA supply voltage across an output capacitor in accordance with a reference voltage;

a feedback circuit coupled to said switching circuit and operative to generate a drive signal for said switching circuit;

a first switch for connecting said output capacitor to ground;

a plurality of trim cells coupled to said output capacitor, each trim cell comprising;

a trim buffer operative to charge a trim capacitor to a trim voltage level;

a second switch connecting said trim capacitor to said output capacitor in series; and

trim control logic operative to control said first switch and said second switch in accordance with a trim control command.

11. The envelope tracking system according to claim 10, wherein said feedback circuit comprises:

an error amplifier configured to generate an error signal based on a difference between said reference signal and said output voltage; and

a PWM comparator configured to generate a PWM signal in accordance with said error signal and an oscillator input signal.

12. The envelope tracking system according to claim 11, wherein said oscillator signal comprises a triangle or saw-tooth signal.

13. The envelope tracking system according to claim 10, wherein said trim control logic is operative to open said first switch when any of said trim cells are active in response to a trim command.

14. The envelope tracking system according to claim 10, wherein said trim control logic is operative to close said first switch when none of said trim cells are active in response to a trim command.

15. The envelope tracking system according to claim 10, wherein said trim control logic is operative to close the second switch in the trim cell selected in response to a trim command while the second switches in all other trim cells are opened.

16. The envelope tracking system according to claim 10, wherein said reference voltage is adjusted up by a predetermined amount in response to a trim up control signal so as to maintain said feedback circuit in steady state condition.

17. The envelope tracking system according to claim 10, wherein said DC-DC converter is adapted to provide a PA supply voltage to a power amplifier configured to transmit signals conforming to a wireless standard selected from the group consisting of 802.11 WLAN, LTE, WiMAX, HDTV, 3G cellular, 4G cellular and DECT.

18. A method of envelope tracking, the method comprising:

extracting an envelope from an input RF signal;

generating a digital trim command based on said envelope;

generating a power amplifier (PA) supply voltage for an RF power amplifier in response to said trim command, by

providing a switching circuit coupled to a DC voltage source for converting an input voltage value into an output voltage value across an output capacitor in accordance with a reference voltage;

providing a feedback circuit coupled to said switching circuit for generating a drive signal for said switching circuit;

charging a plurality of trim capacitors to a trim voltage, each trim capacitor charged to a different trim voltage; and

connecting one of said trim capacitors in series with said output capacitor in response to a trim command thereby increasing said output voltage substantially instantaneously.

19. The method according to claim 18, further comprising disconnecting one of said trim capacitors from said output capacitor in response to a trim command thereby decreasing said output voltage substantially instantaneously.

20. The method according to claim 18, wherein only one of said trim capacitors is connected to said output capacitor at any one time, the trim capacitor selected corresponds to the trim cell whose trim voltage most closely matches that of said envelope.

21. The method according to claim 18, wherein none of said trim capacitors are connected to said output capacitor when the trim command corresponds to a minimal envelope.