# US 2021/0242947 A1 · Local oscillator leakage detecting and cancellation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0242947 A1 - Document ID: US20210242947A1 - Status: Published application - Kind: A1 - Application number: 17/238,775 - Filed: 2021-04-23 - Published: 2021-08-05 - Earliest claimed: 2020-06-16 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Joakim Hallin - Web page: https://patentgrep.com/patent/US20210242947A1 ## CPC - H04B 15/06: by local oscillators of receivers - H03D 7/161: {all the frequency changers being connected in cascade} - H03D 7/166: {using two or more quadrature frequency translation stages} - H04B 1/02: Transmitters - H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)} - H04B 1/1027: {assessing signal quality or detecting noise/interference for the received signal} - H04B: TRANSMISSION - H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66) ## Abstract A mixer circuitry comprises a mixer, a local oscillator (LO) leakage detector, a digital LO leakage cancellation controller and a DAC arrangement. The mixer is configured to mix a first LO signal having an LO frequency fLO with an intermediate frequency (IF) signal and generate an output signal, i.e. a wanted signal. The LO leakage detector measures the LO leakage at the output of the mixer in the presence of the wanted signal. Then in the digital LO leakage cancellation controller, a digital algorithm is run that automatically adjusts the LO leakage in the mixer by steering the digital-to-analog converter arrangement such that the intermediate frequency input signal level to the mixer is adjusted. ## Claims ### Claim 1 A mixer circuitry for detecting and cancelling Local Oscillator (LO) leakage, comprising: a first mixer configured to mix a first LO signal having an LO frequency with an Intermediate Frequency (IF) signal and generate a first output signal; a LO leakage detector configured to receive the first output signal from the first mixer and generate a digital word representing LO leakage detected from the first mixer; a digital processing unit is configured to process the digital word representing the LO leakage detected from the first mixer and generate a control word; and a Digital-to-Analog Converter (DAC) arrangement coupled to the IF signal of the first mixer and configured to receive the control word and adjust the IF signal of the first mixer. ### Claim 2 (depends on 1) The mixer circuitry according to claim 1, wherein the LO leakage detector comprises: a coupler coupled to an output of the first mixer; a second mixer configured to mix a second oscillator signal with the first output signal of the first mixer received from the coupler and generate a second output signal; a third quadrature mixer configured to mix the second output signal of the second mixer with an LO signal having a same frequency as the first LO signal, and generate quadrature output signals having a same frequency as a frequency of the second oscillator signal, via an output; an amplifier arrangement coupled to the third quadrature mixer for amplifying and filtering the quadrature output signals from the third quadrature mixer, and generating a third output signal; a fourth mixer arrangement configured to mix the third output signal from the amplifier arrangement with the second oscillator signal and generate a Direct Current (DC) signal; and an Analog-to-Digital Converter (ADC) arrangement for converting the DC signal from the fourth mixer arrangement and generating the digital word. ### Claim 3 (depends on 2) The mixer circuitry according to claim 2, wherein the frequency of the second oscillator signal is lower than a frequency of the IF signal. ### Claim 4 (depends on 2) The mixer circuitry according to claim 2, wherein the amplifier arrangement comprises two amplifiers for amplifying and filtering the quadrature output signals from the third quadrature mixer in parallel. ### Claim 5 (depends on 2) The mixer circuitry according to claim 2, wherein the fourth mixer arrangement comprises two mixers, and the ADC arrangement comprises two ADCs. ### Claim 6 (depends on 2) The mixer circuitry according to claim 2, wherein the fourth mixer arrangement comprises one single mixer, and the ADC arrangement comprises one single ADC. ### Claim 7 (depends on 2) The mixer circuitry according to claim 2 further comprising a selector coupled to the output of the third quadrature mixer for selecting one of the quadrature output signals from the third quadrature mixer at a time, and wherein the amplifier arrangement comprises one single amplifier coupled to the output of the third quadrature mixer via the selector for amplifying and filtering one of the quadrature output signals at a time. ### Claim 8 (depends on 1) The mixer circuitry according to claim 1, wherein the digital processing unit is configured to accumulate the LO leakage over a number of samples to generate the control word to adjust settings of the DAC arrangement such that an average of the LO leakage is minimized. ### Claim 9 (depends on 1) The mixer circuitry according to claim 1, wherein the first mixer is a quadrature mixer, and the DAC arrangement comprises two DACs configured to receive the control word and adjust the IF signal of the first mixer. ### Claim 10 (depends on 9) The mixer circuitry according to claim 9, wherein the digital processing unit is configured to accumulate I-phase and Q-phase LO leakage over a number of samples to generate the control word to adjust settings of the two DACs such that an average of the I-phase and Q-phase LO leakage (I2+Q2) is minimized. ### Claim 11 (depends on 10) The mixer circuitry according to claim 10, wherein the coupler is a capacitor. ### Claim 12 An electronic circuit comprising mixer circuitry, the mixer circuitry comprising: a first mixer configured to mix a first Local Oscillator (LO) signal having an LO frequency with an Intermediate Frequency (IF) signal and generate a first output signal; a LO leakage detector configured to receive the first output signal from the first mixer and generate a digital word representing the LO leakage detected from the first mixer; a digital processing unit configured to process the digital word representing LO leakage detected from the first mixer and generate a control word; and a Digital-to-Analog Converter (DAC) arrangement coupled to the IF signal of the first mixer and receive the control word and adjust the IF signal of the first mixer. ### Claim 13 (depends on 12) The electronic circuit according to claim 12, wherein the LO leakage detector comprises: a coupler coupled to an output of the first mixer; a second mixer configured to mix a second oscillator signal with the first output signal of the first mixer received from the coupler and generate a second output signal; a third quadrature mixer configured to mix the second output signal of the second mixer with an LO signal having a same frequency as the first LO signal, and generate quadrature output signals having a same frequency as a frequency of the second oscillator signal, via an output; an amplifier arrangement coupled to the third quadrature mixer for amplifying and filtering the quadrature output signals from the third quadrature mixer, and generating a third output; a fourth mixer arrangement configured to mix the third output signal from the amplifier arrangement with the second oscillator signal and generate a direct current (DC) signal; and an analog-to-digital converter (ADC) arrangement for converting the DC signal from the fourth mixer arrangement and generating the digital word. ### Claim 14 (depends on 12) The electronic circuit according to claim 12, wherein the frequency of the second oscillator signal is lower than a frequency of the IF signal. ### Claim 15 (depends on 13) The electronic circuit according to claim 13, wherein the amplifier arrangement comprises two amplifiers for amplifying and filtering the quadrature output signals from the third quadrature mixer in parallel. ### Claim 16 The electronic circuit according to 13, wherein the fourth mixer arrangement comprises two mixers, and the ADC arrangement comprises two ADCs. ### Claim 17 (depends on 13) The electronic circuit according to claim 13, wherein the fourth mixer arrangement comprises one single mixer, and the ADC arrangement comprises one single ADC. ### Claim 18 (depends on 13) The electronic circuit according to claim 13 further comprising a selector coupled to the output of the third quadrature mixer for selecting one of the quadrature output signals from the third quadrature mixer at a time, and wherein the amplifier arrangement comprises one single amplifier coupled to the output of the third quadrature mixer via the selector for amplifying and filtering one of the quadrature output signals at a time. ### Claim 19 (depends on 13) The electronic circuit according to claim 13 comprising any one of a frequency synthesiser, a transceiver, a transmitter, or a receiver. ### Claim 20 (depends on 13) The electronic circuit according to claim 13 comprising any one of a base station, beamforming base station, a mobile terminal, or a user equipment for a cellular communications system or in a wireless communication system.