# US 2013/0157604 A1 · Harmonic cancellation for frequency conversion harmonic cancellation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0157604 A1 - Document ID: US20130157604A1 - Status: Published application - Kind: A1 - Application number: 13/327,836 - Filed: 2011-12-16 - Published: 2013-06-20 - Earliest claimed: 2011-12-16 - Assignees: Fresco Microchip Inc. - Inventors: Stephen A. Jantzi; Amr M. Fahim - Web page: https://patentgrep.com/patent/US20130157604A1 ## CPC - H04B 1/3805: with built-in auxiliary receivers - H04B 1/525: with means for reducing leakage of transmitter signal into the receiver - H04B: TRANSMISSION ## Abstract A radio frequency (RF) receiver, such as a television tuner, includes a harmonic cancellation circuit. The harmonic cancellation circuit includes a primary signal path to generate a first intermediate frequency (IF) signal by mixing an RF signal with a reference signal and a harmonic feedforward signal path to generate a second IF signal representing signal content of the RF signal near an nth-order harmonic of a frequency fLO of the first reference signal, n comprising a positive integer. The harmonic cancellation circuit further includes a summation stage to generate a third IF signal based on a difference between the first IF signal and the second IF signal. ## Claims ### Claim 1 In a radio frequency (RF) receiver, a method for harmonic rejection comprising: generating a first intermediate frequency (IF) signal by mixing an RF signal with a first reference signal; generating a second IF signal representing signal content of the RF signal near an nth-order harmonic of a frequency fLO of the first reference signal, n comprising a positive integer; and generating a third IF signal based on a difference between the first IF signal and the second IF signal. ### Claim 2 (depends on 1) The method of claim 1, wherein generating the second IF signal comprises: downscaling the RF signal by a first gain weight that is inversely proportional to n to generate a downscaled RF signal; and mixing the downscaled RF signal with a second reference signal having a frequency of n*fLO. ### Claim 3 (depends on 2) The method of claim 2, wherein: generating the first IF signal comprises scaling the RF signal by a second gain weight to generate a scaled RF signal and mixing the scaled RF signal with the first reference signal; and the first gain weight is proportional to the second gain weight and inversely proportional to n. ### Claim 4 (depends on 3) The method of claim 3, further comprising: monitoring an amplitude relationship between the first IF signal and the second IF signal; and adjusting at least one of the first gain weight or the second gain weight based on the amplitude relationship. ### Claim 5 (depends on 1) The method of claim 1, further comprising: generating a fourth IF signal representing signal content of the RF signal near a kth-order harmonic of the frequency fLO of the first reference signal, k comprising a positive integer greater than n; and wherein generating the third IF signal comprises generating the third IF signal further based on a difference between the first IF signal and the fourth IF signal. ### Claim 6 (depends on 5) The method of claim 5, wherein n equals 3 and k equals 5. ### Claim 7 (depends on 1) The method of claim 1, wherein n equals 3. ### Claim 8 (depends on 1) The method of claim 1, further comprising: monitoring a phase relationship between the first IF signal and the second IF signal; and adjusting a phase of at least one of the first reference signal or the second reference signal based on the phase relationship. ### Claim 9 A system comprising: a harmonic cancellation circuit comprising: a primary signal path to generate a first intermediate frequency (IF) signal by mixing an RF signal with a first reference signal; a first harmonic feedforward signal path to generate a second IF signal representing signal content of the RF signal near an nth-order harmonic of a frequency fLO of the first reference signal, n comprising a positive integer; and a summation stage to generate a third IF signal based on a difference between the first IF signal and the second IF signal. ### Claim 10 (depends on 9) The system of claim 9, wherein the first harmonic feedforward signal path comprises: a first gain stage to downscale the RF signal by a first gain weight that is inversely proportional to n to generate a downscaled RF signal; and a first mixer to mix the downscaled RF signal with a second reference signal having a frequency of n*fLO. ### Claim 11 (depends on 10) The system of claim 10, wherein the primary signal path comprises: a second gain stage to scale the RF signal by a second gain weight to generate a scaled RF signal; and a second mixer to mix the scaled RF signal with the first reference signal; wherein the first gain weight is proportional to the second gain weight and inversely proportional to n. ### Claim 12 (depends on 11) The system of claim 11, wherein harmonic cancellation circuit further comprises: a calibration circuit to monitor an amplitude relationship between the first IF signal and the second IF signal and to adjust at least one of the first gain weight or the second gain weight based on the amplitude relationship. ### Claim 13 (depends on 9) The system of claim 9, wherein the harmonic cancellation circuit further comprises: a second harmonic feedforward signal path to generate a fourth IF signal representing signal content of the RF signal near a kth-order harmonic of the frequency fLO of the first reference signal, k comprising a positive integer greater than n; and wherein the summation stage is to generate the third IF signal further based on a difference between the first IF signal and the fourth IF signal. ### Claim 14 (depends on 13) The system of claim 13, wherein n equals 3 and k equals 5. ### Claim 15 (depends on 9) The system of claim 9, wherein n equals 3. ### Claim 16 (depends on 11) The system of claim 11, further wherein the harmonic cancellation circuit further comprises: a calibration circuit to monitor a phase and amplitude relationship between the first IF signal and the second IF signal and to adjust a phase of at least one of the first reference signal or the second reference signal based on the phase relationship. ### Claim 17 (depends on 9) The system of claim 9, further comprising: a RF receiver comprising the harmonic cancellation circuit. ### Claim 18 (depends on 17) The system of claim 17, wherein the RF receiver comprises a television tuner. ### Claim 19 In a radio frequency (RF) receiver, a method comprising: mixing an RF signal with a first reference signal having a frequency fLO to generate a primary IF signal; for each harmonic of a plurality of harmonics of the frequency fLO: generating a corresponding harmonic feedforward signal representative of signal content of the RF signal near the harmonic and downscaled based on a Fourier series coefficient associated with the harmonic; and modifying the primary IF signal based on the harmonic feedforward signal. ### Claim 20 (depends on 19) The method of claim 19, wherein generating a corresponding harmonic feedforward signal comprises: downscaling the RF signal based on a gain weight that is proportional to a product of the Fourier series coefficient associated with the harmonic and a gain weight of a gain stage used to scale the RF signal for generation of the primary IF signal. ### Claim 21 (depends on 20) The method of claim 20, wherein the plurality of harmonics includes the third-order harmonic. ### Claim 22 (depends on 20) The method of claim 20, wherein modifying the primary IF signal based on the harmonic feedforward signal comprises removing signal content of the harmonic feedforward signal from the primary IF signal.