# US 2014/0155013 A1 · Baseband harmonic rejection circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0155013 A1 - Document ID: US20140155013A1 - Status: Published application - Kind: A1 - Application number: 13/734,863 - Filed: 2013-01-04 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: Broadcom Corporation - Applicants: Broadcom Corporation - Inventors: David MURPHY; Hooman Darabi - Web page: https://patentgrep.com/patent/US20140155013A1 ## CPC - H04B 1/109: {by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input} - H03F 1/0277: {Selecting one or more amplifiers from a plurality of amplifiers} - H03F 3/195: in integrated circuits - H03F 3/211: {using a combination of several amplifiers (H03F3/60 takes precedence)} - H03F 3/45475: {using IC blocks as the active amplifying circuit} - H03F 3/72: Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal - H03F 2200/294: the amplifier being a low noise amplifier [LNA] - H03F 2203/45512: the FBC comprising one or more capacitors, not being switched capacitors, and being coupled between the LC and the IC - H03F 2203/45526: the FBC comprising a resistor-capacitor combination and being coupled between the LC and the IC - H03F 2203/45528: the FBC comprising one or more passive resistors and being coupled between the LC and the IC - H03F 2203/7215: the gated amplifier being switched on or off by a switch at the input of the amplifier - H03F 2203/7236: the gated amplifier being switched on or off by putting into parallel or not, by choosing between amplifiers by (a ) switch(es) - H04B: TRANSMISSION - H03F: AMPLIFIERS ## Abstract A circuit for baseband harmonic rejection includes multiple transconductance cells coupled to one another at outputs of the transconductance cells and configured to receive down-converted signals that vary from one another to produce a weighted current signal proportional to a voltage corresponding to a respective down-converted signal. The circuit also includes a feedback impedance coupled between an input of one of the transconductance cells and the outputs of the transconductance cells. Each of the transconductance cells has an effective transconductance of a first magnitude for frequency components of the down-converted signal arising from a first harmonic and an effective transconductance of a second magnitude less than the first magnitude for frequency components of the down-converted signal arising from harmonics at integer multiples of the first harmonic. ## Claims ### Claim 1 A transimpedance amplifier, comprising: a plurality of transconductance cells coupled to one another at outputs of the plurality of transconductance cells and configured to receive down-converted signals that vary from one another to produce a weighted current signal proportional to a voltage corresponding to a respective down-converted signal; and a feedback impedance coupled between an input of one of the plurality of transconductance cells and the outputs of the plurality of transconductance cells, wherein each of the plurality of transconductance cells has an effective transconductance of a first magnitude for frequency components of the down-converted signal arising from a first harmonic and an effective transconductance of a second magnitude less than the first magnitude for frequency components of the down-converted signal arising from harmonics at integer multiples of the first harmonic. ### Claim 2 (depends on 1) The transimpedance amplifier of claim 1, wherein each of the plurality of transconductance cells comprises differential inputs. ### Claim 3 (depends on 2) The transimpedance amplifier of claim 2, wherein each of the plurality of transconductance cells has a transconductance weighting of k  [ cos  ( 2  π   X M  ) ] , where X is an integer that represents one of the plurality of transconductance cells, where k is an arbitrary constant that determines the effective transconductance of the transconductance cell, where M is a number of local oscillator (LO) phases employed. ### Claim 4 (depends on 3) The transimpedance amplifier of claim 3, wherein the transconductance weighting is shifted to reject odd integer multiples of the wanted signal. ### Claim 5 (depends on 1) The transimpedance amplifier of claim 1, wherein each of the plurality of transconductance cells comprises a set of inputs, each of the set of inputs is configured to receive respective ones of the LO phases employed. ### Claim 6 (depends on 1) The transimpedance amplifier of claim 1, wherein each of the transconductance cells further comprises an input coupled to ground. ### Claim 7 (depends on 1) The transimpedance amplifier of claim 1, wherein the weighted current signals are each shifted in phase of one another by 360/M degrees, where M is a number of local oscillator phases employed. ### Claim 8 (depends on 1) The transimpedance amplifier of claim 1, wherein the down-converted signal is shifted in frequency according to a respective local oscillator signal. ### Claim 9 (depends on 1) The transimpedance amplifier of claim 1, wherein the voltage corresponding to the down-converted signal is equivalent to V IN  ∠  m * ( M - 1 ) M , where m is a LO harmonic from around which an input signal arises, and M represents a number of local oscillator phases employed. ### Claim 10 (depends on 1) The transimpedance amplifier of claim 1, wherein each of the plurality of transconductance cells comprises single-ended inputs. ### Claim 11 (depends on 10) The transimpedance amplifier of claim 10, wherein each of the plurality of transconductance cells has a transconductance weighting of k  [ 1 + cos  ( 2  π   X M  ) ] , where X is an integer that represents one of the plurality of transconductance cells, where k is an arbitrary constant that determines the effective transconductance of the transconductance cell, where M is a number of local oscillator (LO) phases employed. ### Claim 12 (depends on 10) The transimpedance amplifier of claim 10, wherein the transconductance weighting is shifted to reject integer multiples of a wanted signal arising from the first harmonic. ### Claim 13 (depends on 1) The transimpedance amplifier of claim 1, wherein the down-converted signals vary by being shifted in phase from one another. ### Claim 14 An apparatus in a receiver for baseband harmonic rejection, the apparatus comprising: a plurality of frequency conversion cells configured to mix an input signal with a plurality of non-overlapping local oscillator (LO) signals to produce down-converted signals; and a plurality of transimpedance amplifiers coupled to the plurality of frequency conversion cells and configured to produce output voltage signals proportional to respective ones of the down-converted signals, wherein each of the plurality of transimpedance amplifiers comprises: a plurality of transconductance cells coupled to one another at outputs of the plurality of transconductance cells and each configured to receive respective ones of the down-converted signals to produce a weighted current signal proportional to a voltage corresponding to the down-converted signal, wherein each of plurality of transconductance cells has an effective transconductance of a first magnitude for frequency components of the input signal arising from a first harmonic and an effective transconductance of a second magnitude less than the first magnitude for frequency components of the input signal arising from harmonics at integer multiples of the first harmonic. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the weighted current signals corresponding to the integer multiples of the first harmonic are configured with phases of opposing polarities such that their constructive sum is zero. ### Claim 16 (depends on 14) The apparatus of claim 14, wherein the output voltage signals are each proportional to a weighted current signal having frequency components corresponding to a wanted signal. ### Claim 17 (depends on 14) The apparatus of claim 14, wherein each of the plurality of transconductance cells is configured with a transconductance weighting that causes the effective transconductance of the transconductance cell to be non-zero when excited by a down-converted signal arising from a harmonic within a frequency band of interest but zero for a down-converted signal arising from harmonics outside the frequency band of interest. ### Claim 18 (depends on 14) The apparatus of claim 14, wherein the input signal comprises an input impedance profile that provides infinite resistance for frequency components arising from at least a portion of the harmonics at the integer multiples of the first harmonic. ### Claim 19 An apparatus for baseband amplification with harmonic rejection, the apparatus comprising: means for receiving a mixed signal down-converted from a radio frequency signal; means for converting the mixed signal into a weighted current signal proportional to a voltage corresponding to the mixed signal based on an effective transconductance; and means for outputting the mixed signal with amplification using a feedback impedance such that a wanted signal receives the amplification and unwanted signals are rejected without amplification, wherein the effective transconductance has a first magnitude for frequency components of the down-converted signal arising from a first harmonic and the effective transconductance has a second magnitude less than the first magnitude for frequency components of the down-converted signal arising from harmonics at integer multiples of the first harmonic. ### Claim 20 (depends on 19) The apparatus of claim 19, further comprising: means for receiving a local oscillator signal to produce the mixed signal by mixing the radio frequency signal with the local oscillator signal.