# US 2019/0318756 A1 · Devices for acoustic echo cancellation and methods thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0318756 A1 - Document ID: US20190318756A1 - Status: Published application - Kind: A1 - Application number: 15/954,813 - Filed: 2018-04-17 - Published: 2019-10-17 - Earliest claimed: 2018-04-17 - Assignees: Fortemedia, Inc. - Applicants: Fortemedia, Inc. - Inventors: Jianming LIU; Qing-Guang LIU - Web page: https://patentgrep.com/patent/US20190318756A1 ## CPC - G10L 21/0208: Noise filtering - G10L 21/0232: Processing in the frequency domain - H04R 3/04: for correcting frequency response - G10L 2021/02082: {the noise being echo, reverberation of the speech} - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) ## Abstract A device for acoustic echo cancellation includes a modulator, a speaker, a microphone, a demodulator, and an adaptive filter. The modulator duplicates a far-end signal to a frequency range that is higher than the far-end signal to be a first frequency-shifted signal and generates a modulated signal according to the far-end signal and the first frequency-shifted signal. The speaker generates a sound signal according to the modulated signal. The microphone generates a microphone signal according to a near-end signal and an echo signal. The echo signal is a convolution of the sound signal with a room impulse response. The demodulator extracts a demodulated signal and an echo-reference signal from the microphone signal. The adaptive filter generates a recovered signal to recover the near-end signal according to the demodulated signal and the echo-reference signal. ## Claims ### Claim 1 A device for acoustic echo cancellation, comprising: a modulator, duplicating a far-end signal to a frequency range that is higher than the far-end signal to be a first frequency-shifted signal and generating a modulated signal according to the far-end signal and the first frequency-shifted signal; a speaker, generating a sound signal according to the modulated signal; a microphone, generating a microphone signal according to a near-end signal and an echo signal, wherein the echo signal is a convolution of the sound signal with a room impulse response; a demodulator, extracting a demodulated signal and an echo-reference signal from the microphone signal; and an adaptive filter, generating a recovered signal to recover the near-end signal according to the demodulated signal and the echo-reference signal. ### Claim 2 (depends on 1) The device of claim 1, wherein the modulator comprises: an up-sampler, up-sampling the far-end signal to generate an up-sampled signal; a first frequency-shifter, up-converting the up-sampled signal with a carrier frequency to generate the first frequency-shifted signal, wherein the frequency range is determined by the carrier frequency; and a combiner, combining the up-sampled signal and the first frequency-shifted signal to generate the modulated signal. ### Claim 3 (depends on 2) The device of claim 2, wherein the first frequency-shifter up-converts the up-sampled signal to the first frequency-shifted signal by using amplitude modulation, ### Claim 4 (depends on 2) The device of claim 2, wherein the frequency range is an ultrasound frequency range. ### Claim 5 (depends on 2) The device of claim 2, wherein the sound signal comprises a high-frequency sound signal and a low-frequency sound signal, and the echo signal comprises a high-frequency echo signal and a low-frequency echo signal, wherein the high-frequency echo signal is a convolution of the high-frequency sound signal with the room impulse response, and the low-frequency echo signal is a convolution of the low-frequency sound signal with the room impulse response. ### Claim 6 (depends on 5) The device of claim 5, wherein the high-frequency sound signal corresponds to the first frequency-shifted signal and the low-frequency sound signal corresponds to the up-sampled signal. ### Claim 7 (depends on 5) The device of claim 5, wherein the demodulator comprises: a high-pass filter, extracting the high-frequency echo signal from the microphone signal; a second frequency-shifter, down-converting the high-frequency echo signal with the carrier frequency to generate a second frequency-shifted signal; and a first down-sampler, down-sampling the second frequency-shifted signal to generate the echo-reference signal. ### Claim 8 (depends on 7) The device of claim 7, wherein the demodulator further comprises: a low-pass filter, extracting a filtered signal from the microphone signal; and a second down-sampler, down-sampling the filtered signal to generate the demodulated signal. ### Claim 9 (depends on 8) The device of claim 8, wherein the demodulated signal comprises the low-frequency echo signal and the near-end signal. ### Claim 10 (depends on 9) The device of claim 9, wherein the adaptive filter subtracts the echo-reference signal from the demodulated signal to generate the recovered signal. ### Claim 11 A method for acoustic echo cancellation, comprising: duplicating a far-end signal to a frequency range that is higher than the far-end signal to be a first frequency-shifted signal; generating a modulated signal according to the far-end signal and the first frequency-shifted signal; using a speaker to generate a sound signal according to the modulated signal; using a microphone to generate a microphone signal according to a near-end signal and an echo signal, wherein the echo signal is a convolution of the sound signal with a room impulse response; extracting a demodulated signal and an echo-reference signal from the microphone signal; and using an adaptive filter to generate a recovered signal to recover the near-end signal according to the demodulated signal and the echo-reference signal. ### Claim 12 (depends on 11) The method of claim 11, wherein the step of duplicating the far-end signal to the frequency range that is higher than the far-end signal to be the first frequency-shifted signal comprises: up-sampling the far-end signal to generate an up-sampled signal; and up-converting the up-sampled signal with a carrier frequency to generate the first frequency-shifted signal, wherein the frequency range is determined by the carrier frequency. ### Claim 13 (depends on 12) The method of claim 12, wherein the up-sampled signal is up-converted with the carrier frequency by using amplitude modulation, frequency modulation, or pulse-width modulation. ### Claim 14 (depends on 12) The method of claim 12, wherein the step of generating the modulated signal according to the far-end signal and the first frequency-shifted signal comprises: combining the up-sampled signal and the first frequency-shifted signal to generate the modulated signal. ### Claim 15 (depends on 12) The method of claim 12, wherein the frequency range is the ultrasound frequency range. ### Claim 16 (depends on 12) The method of claim 12, wherein the sound signal comprises a high-frequency sound signal and a low-frequency sound signal, and the echo signal comprises a high-frequency echo signal and a low-frequency echo signal, wherein the high-frequency echo signal is a convolution of the high-frequency sound signal with the room impulse response, and the low-frequency echo signal is a convolution of the low-frequency sound signal with the room impulse response. ### Claim 17 (depends on 16) The method of claim 16, wherein the high-frequency sound signal corresponds to the first frequency-shifted signal and the low-frequency sound signal corresponds to the up-sampled signal. ### Claim 18 (depends on 16) The method of claim 16, wherein the step of extracting the demodulated signal and the echo-reference signal from the microphone signal comprises: extracting the high-frequency echo signal from the microphone signal; down-converting the high-frequency echo signal with the carrier frequency to generate a second frequency-shifted signal; and down-sampling the second frequency-shifted signal to generate the echo-reference signal. ### Claim 19 (depends on 18) The method of claim 18, wherein the step of extracting the demodulated signal and the echo-reference signal from the microphone signal further comprises: extracting a filtered signal from the microphone signal, wherein the filter signal comprises the low-frequency echo signal and the near-end signal; and down-sampling the filtered signal to generate the demodulated signal. ### Claim 20 (depends on 19) The method of claim 19, wherein the step of using the adaptive filter to recover the near-end signal from the demodulated signal according to the echo-reference signal further comprises: subtracting the echo-reference signal from the demodulated signal to generate the recovered signal.