# US 7,746,187 B2 · Self-calibrating modulator apparatuses and methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,187 B2 - Document ID: US7746187B2 - Status: Granted - Kind: B2 - Application number: 12/131,417 - Filed: 2008-06-02 - Published: 2009-12-03 - Granted: 2010-06-29 - Earliest claimed: 2008-06-02 - Assignees: Panasonic Corporation - Inventors: Wayne S. Lee; Akira Kato; Toru Matsuura - Web page: https://patentgrep.com/patent/US7746187B2 ## CPC - H03C 3/0941: {applying frequency modulation at more than one point in the loop} - H03C 3/08: Modifications of modulator to linearise modulation, e.g. by feedback, and clearly applicable to more than one type of modulator - H03C 3/095: {applying frequency modulation to the loop in front of the voltage controlled oscillator} - H03C 3/0975: {applying frequency modulation in the phase locked loop at components other than the divider, the voltage controlled oscillator or the reference clock} - H03C 3/0991: {including calibration means or calibration methods} - H03C 5/00: Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal (H03C7/00 takes precedence) - H03C: MODULATION (masers or lasers H01S; coding, decoding or code conversion H03M) ## Abstract A self-calibrating modulator apparatus includes a modulator having a controlled oscillator and an oscillator gain calibration circuit. The oscillator gain calibration circuit includes an oscillator gain coefficient calculator configured to calculate a plurality of frequency dependent oscillator gain coefficients from results of measurements taken at the output of the controlled oscillator in response to a test pattern signal representing a plurality of different reference frequencies. The plurality of frequency dependent gain coefficients determined from the calibration process are stored in a look up table (LUT), where they are made available after the calibration process ends to scale a modulation signal applied to the modulator. By scaling the modulation signal prior to it being applied to the control input of the controlled oscillator, the nonlinear response of the controlled oscillator is countered and the modulation accuracy of the modulator is thereby improved. ## Claims ### Claim 1 A self-calibrating modulator apparatus, comprising: a modulator having a direct modulation path, a feed-forward path, and a controlled oscillator having a control input configured to receive signals from the direct modulation path and the feed-forward path; and an oscillator gain calibration circuit coupled to the feed-forward path of said modulator operable to determine a plurality of frequency dependent oscillator gain coefficients used to counter nonlinear effects of said controlled oscillator, wherein said direct modulation path and said feed-forward path receive a modulation signal. ### Claim 2 (depends on 1) The self-calibrating modulator apparatus of claim 1, further comprising a test pattern generator configured to generate a test pattern signal for the feed-forward path of said modulator, said test pattern signal representing a plurality of different reference frequencies. ### Claim 3 (depends on 2) The self-calibrating modulator apparatus of claim 2, further comprising circuitry configured to measure a plurality of output frequencies of the controlled oscillator for each of the different reference frequencies represented in said test pattern signal. ### Claim 4 (depends on 3) The self-calibrating modulator apparatus of claim 3 wherein said oscillator gain calibration circuit includes an oscillator gain coefficient calculator configured to calculate a plurality of frequency dependent oscillator gain coefficients from said plurality of measured output frequencies. ### Claim 5 (depends on 4) The self-calibration modulator apparatus of claim 4, further comprising a look up table (LUT) configured to store said plurality of frequency dependent oscillator gain coefficients. ### Claim 6 (depends on 5) The self-calibration modulator apparatus of claim 5 wherein said feed-forward path includes a multiplier operable to scale said modulation signal received in said feed-forward path by the frequency dependent oscillator gain coefficients stored in said LUT to counter frequency dependent nonlinearities of said controlled oscillator. ### Claim 7 (depends on 6) The self-calibration modulator apparatus of claim 6, further comprising an interpolation filter configured to interpolate additional oscillator gain coefficients from two or more of the plurality of frequency dependent oscillator gain coefficients stored in said LUT. ### Claim 8 (depends on 2) The self-calibration modulator apparatus of claim 2 wherein the plurality of different reference frequencies represented in said test pattern signal includes frequencies that cause the output frequency of said controlled oscillator to symmetrically deviate above and below a center frequency. ### Claim 9 (depends on 2) The self-calibration modulator apparatus of claim 2 wherein the reference frequencies represented in said test pattern signal are configured so that the output frequency of the controlled oscillator increases from a low frequency deviation from the center frequency to progressively larger frequency deviations from a center frequency. ### Claim 10 (depends on 4) The self-calibrating modulator apparatus of claim 4 wherein said oscillator gain calibration circuit is further configured to factor out effects of frequency drift of the controlled oscillator in calculating the plurality of frequency dependent oscillator gain coefficients. ### Claim 11 A method of countering nonlinearities of a controlled oscillator, comprising: configuring a controlled oscillator in a closed-loop frequency control circuit of a modulator apparatus; tuning and locking said frequency control circuit to cause an output frequency of said controlled oscillator to be centered at a center frequency; opening a loop of the frequency control circuit; applying a test pattern signal to a control input of said controlled oscillator, said test pattern signal representing a plurality of reference frequencies that cause the output frequency of the controlled oscillator to deviate from said center frequency; measuring a plurality of output frequencies of the controlled oscillator for each reference frequency represented in the test pattern signal; and calculating a plurality of oscillator gain coefficients from said plurality of measured output frequencies. ### Claim 12 (depends on 11) The method of claim 11, further comprising storing said plurality of oscillator gain coefficients in a look up table (LUT). ### Claim 13 (depends on 11) The method of claim 11, further comprising scaling a modulation signal applied to the modulator apparatus by one or more oscillator gain coefficients of said plurality of oscillator gain coefficients, and applying the resulting scaled modulation signal to the control input of the controlled oscillator. ### Claim 14 (depends on 12) The method of claim 12, further comprising interpolating additional oscillator gain coefficients from two or more oscillator gain coefficients of said plurality of oscillator gain coefficients. ### Claim 15 (depends on 11) The method of claim 11 wherein calculating the plurality of oscillator gain coefficients from said plurality of measured output frequencies includes factoring out effects of frequency drift caused by measuring the plurality of measured output frequencies open-loop. ### Claim 16 (depends on 11) The method of claim 11 wherein the plurality of reference frequencies comprise one or more pairs of reference frequencies that are symmetrical about the center frequency and which cause the controlled oscillator output frequency to deviate above and below the center frequency. ### Claim 17 (depends on 16) The method of claim 16 wherein each consecutive pair of reference frequencies results in a greater frequency deviation of the controlled oscillator output frequency from the center frequency fc. ### Claim 18 A polar modulation transmitter, comprising: an amplitude modulation path having an amplitude modulator configured to amplitude modulate a direct current power supply signal according to amplitude variations in an amplitude modulation signal received in the amplitude modulation path; a phase modulation path including a self-calibrating modulator apparatus having a phase modulator having a direct modulation path, a feed-forward path, and a controlled oscillator having a control input configured to receive signals from the direct modulation path and the feed-forward path and an oscillator gain calibration circuit coupled to the feed-forward path of said phase modulator, said self-calibrating modulator apparatus operable to calculate frequency dependent oscillator gain coefficients for use by said phase modulator to counter nonlinear frequency responses of said controlled oscillator; and a power amplifier configured to amplify a phase modulated carrier signal generated by said phase modulator according to an amplitude modulated power supply signal applied to a power setting input of said power amplifier from said amplitude modulator, wherein said direct modulation path and said feed-forward path receive a modulation signal. ### Claim 19 (depends on 18) The polar modulation transmitter of claim 18 wherein said phase modulator is configurable to receive said modulation signal or a test pattern signal, depending on whether said self-calibrating modulator apparatus is performing a calibration process. ### Claim 20 (depends on 19) The polar modulation transmitter of claim 19 wherein said feed-forward path serves as a means for introducing the test pattern signal to a control input of the VCO when the self-calibrating modulator apparatus is performing said calibration process. ### Claim 21 (depends on 20) The polar modulation transmitter of claim 20 wherein after the calibration process has completed the feed-forward path serves as path for scaling the modulation signal by the frequency dependent oscillator gain coefficients and as an auxiliary modulation path for coupling the resulting scaled modulation signal to the control input of the controlled oscillator. ### Claim 22 (depends on 18) The polar modulation transmitter of claim 18 wherein said self-calibrating modulator apparatus includes circuitry configured to measure a plurality of output frequencies of said controlled oscillator in response to a test signal pattern representing a plurality of different reference frequencies. ### Claim 23 (depends on 22) The polar modulation transmitter of claim 22 wherein said self-calibrating modulator apparatus includes an oscillator gain coefficient calculator configured to calculate said frequency dependent oscillator gain coefficients based on said plurality of measured output frequencies. ### Claim 24 (depends on 23) The polar modulation transmitter of claim 23 wherein said self-calibrating modulator apparatus includes a look up table (LUT) configured to store said frequency dependent oscillator gain coefficients. ### Claim 25 (depends on 24) The polar modulation transmitter of claim 24 wherein said self-calibrating modulator apparatus includes an interpolation filter operable to determine additional oscillator gain coefficients from the oscillator gain coefficients stored in said LUT.