# US 2014/0155002 A1 · Envelope Tracking Signal Bandwidth Control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0155002 A1 - Document ID: US20140155002A1 - Status: Published application - Kind: A1 - Application number: 13/930,433 - Filed: 2013-06-28 - Published: 2014-06-05 - Earliest claimed: 2012-12-03 - Assignees: Broadcom Corporation - Applicants: Broadcom Corporation - Inventors: Sriraman Dakshinamurthy; Robert Gustav Lorenz - Web page: https://patentgrep.com/patent/US20140155002A1 ## CPC - H04W 52/028: {switching on or off only a part of the equipment circuit blocks} - H03F 1/3223: {using feed-forward (H03F1/3211 takes precedence)} - H03F 3/24: of transmitter output stages - H04B 1/04: Circuits - H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)} - H04B 1/1615: {Switching on; Switching off, e.g. remotely (battery saving circuits associated with selective call operation H04W52/00; details of power consumption reduction in a PLL, H03L7/0802, H03L7/14, H03L2207/08, H03L2207/18; muting amplifiers by gain control see H03G3/34)} - H04B 2001/0441: {with linearisation using feed-forward} - Y02D 30/70: in wireless communication networks - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H03F: AMPLIFIERS - H04B: TRANSMISSION - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## Abstract An envelope tracking circuit for a transmit and receive path for a telecommunications device includes a filter to reduce the bandwidth of the transmit signal. The envelope of the filtered signal having the lower bandwidth is used to dynamically modulates the power amplifier voltage supply signal. The filter depends on current instantaneous values and also depends in a nonlinear way on instantaneous past and future values of the envelope tracking signal. The filter may be symmetric about peaks of the transmitted signal. ## Claims ### Claim 1 A system comprising: an envelope circuit configured to receive a transmit signal and produce an envelope signal representative of an envelope of the transmit signal; a power amplifier configured to amplify the transmit signal; a filter configured to receive the envelope signal and produce a filtered envelope signal, the filter implementing a nonlinear filter function that depends on a current instantaneous value of the envelope signal and depends nonlinearly on past instantaneous values of the envelope signal and future instantaneous values of the envelope signal; an envelope tracking circuit coupled to the filter and responsive to the filter envelope signal and coupled to the power amplifier to provide a power supply signal to power the power amplifier, the envelope tracking circuit producing the power supply signal according to the envelope of the filter output signal. ### Claim 2 (depends on 1) The system of claim 1 wherein the filter implements a filter function that depends symmetrically on the past instantaneous values of the envelope signal and the future instantaneous values of the envelope signal. ### Claim 3 (depends on 2) The system of claim 2 wherein the filter is operative to receive a set of filter coefficients and wherein the filter coefficients for the past instantaneous values of the envelope signal match the filter coefficients for the future instantaneous values of the envelope signal. ### Claim 4 (depends on 1) The system of claim 1 wherein the filter produces the filter output signal having a substantially lower bandwidth than bandwidth of the envelope signal. ### Claim 5 (depends on 1) The system of claim 1 wherein the filter combines respective filter coefficients with respective past instantaneous values of the envelope signal and respective future instantaneous values of the envelope signal and evaluates a maximum value for each instantaneous value of the envelope signal. ### Claim 6 (depends on 1) The system of claim 1 further comprising: a shaping table coupled between the filter and the envelope tracking circuit to map input values of the filter signal from the filter to output values; and a digital to analog converter coupled between the shaping table and the envelope tracking circuit to convert the output value from the shaping table to an input signal for the envelope tracking circuit. ### Claim 7 A method comprising: at a communication device, receiving a transmit signal for radio transmission; producing an envelope signal of the envelope of the transmit signal; amplifying the transmit signal in a power amplifier; filtering the envelope signal to reduce bandwidth of the envelope signal and produce a filtered envelope signal; and applying to the power amplifier a voltage supply signal having a voltage magnitude that tracks the envelope of the filtered envelope signal. ### Claim 8 (depends on 7) The method of claim 7 wherein filtering the transmit signal comprises reducing the bandwidth of the transmit signal from about 20 MHz to about 5 MHz. ### Claim 9 (depends on 7) The method of claim 7 wherein filtering the transmit signal comprises filtering the transmit signal in a symmetric peak filter. ### Claim 10 (depends on 7) The method of claim 7 wherein filtering the transmit signal comprises filtering the transmit signal in a non-linear filter that depends on a current instantaneous value and depends in a non-linear way on a future instantaneous value and a past instantaneous value. ### Claim 11 (depends on 10) The method of claim 10 wherein filtering the transmit signal comprises filtering the transmit signal in a non-linear filter that depends on a future instantaneous value and a past instantaneous value that are symmetrical about the current instantaneous value. ### Claim 12 (depends on 10) The method of claim 10 wherein filtering the transmit signal comprises combining respective filter coefficients with respective past instantaneous values of the transmit signal and respective future instantaneous values of the transmit signal and evaluating a maximum value for each instantaneous value of the transmit signal. ### Claim 13 (depends on 10) The method of claim 10 wherein filtering the transmit signal comprises: applying a finite impulse response filter to the transmit signal, the finite impulse response filter having filter coefficients chosen so that the filter coefficients for past instantaneous values of the transmit signal match filter coefficients for future instantaneous values of the transmit signal. ### Claim 14 (depends on 10) The method of claim 10 wherein filtering the transmit signal comprises: applying a finite impulse response filter to the transmit signal, the finite impulse response filter having filter coefficients ak chosen to have mirror symmetry such that αk=αN-k. ### Claim 15 (depends on 7) The method of claim 7 further comprising applying a de-troughing function to the transmit signal before filtering the transmit signal. ### Claim 16 (depends on 7) The method of claim 7 further comprising: applying the filtered signal to a shaping table to produce a shaped signal; and tracking the envelope of the shaped signal to produce the voltage supply signal. ### Claim 17 (depends on 16) The method of claim 16 further comprising: applying the shaped signal from the shaping table to a linear filter having a frequency response tailored to compensate for frequency selective effects introduced by generating the voltage supply signal having a voltage magnitude that tracks the envelope of the filtered envelope signal. ### Claim 18 (depends on 7) The method of claim 7 further comprising: applying a shaping function to the transmit signal to produce a shaped transmit signal; and filtering the shaped transmit signal in a symmetric peak filter. ### Claim 19 A communication device comprising: an antenna; system logic to control operation of the communication device; a transmit and receive path comprising: a baseband controller to produce a transmit signal; a power amplifier coupled to the baseband controller and the antenna to amplify the transmit signal and apply the amplified signal to the antenna for transmission from the communication device; an envelope tracking circuit coupled to the envelope circuit, the power amplifier and the baseband controller, the envelope tracking circuit comprising: an envelope circuit configured to produce an envelope signal representative of an envelope of the transmit signal; an envelope tracking power supply coupled to the envelope circuit and the power amplifier to provide a dynamically variable power supply signal to the power amplifier by tracking the envelope signal; and a filter coupled to the baseband controller to produce a filtered signal as the envelope signal by applying a non-linear filter function to the envelope signal using instantaneous current values, instantaneous past values and instantaneous future values with a non-linear dependency on the instantaneous past values and instantaneous future values. ### Claim 20 (depends on 19) The communication device of claim 19 wherein the filter comprises a symmetric filter. ### Claim 21 (depends on 20) The communication device of claim 20 wherein the filter comprises a filter producing a filtered signal which is symmetric about peaks of the envelope signal. ### Claim 22 (depends on 19) The communication device of claim 19 wherein the envelope tracking circuit further comprises a de-troughing module to limit negative excursions of the transmit signal before filtering the envelope signal in the filter. ### Claim 23 A method for reducing bandwidth of an envelope tracking power supply in a telecommunication device, the method comprising: receiving a transmit signal; generating an envelope signal of the transmit signal; filtering the envelope signal in a filter which depends non-linearly on future values of the envelope signal. ### Claim 24 A method for reducing bandwidth of an envelope tracking power supply in a telecommunication device, the method comprising: receiving a transmit signal; storing current and future values of the transmit signal; generating an envelope signal of the transmit signal; filtering the envelope signal in a filter so that the instantaneous value of the envelope amplitude is a function of both amplitude of the current transmit signal value as well as the amplitude of a stored future value of the transmit signal.