# US 7,609,123 B2 · Direct modulation type voltage-controlled oscillator using MOS varicap > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,123 B2 - Document ID: US7609123B2 - Status: Granted - Kind: B2 - Application number: 11/953,345 - Filed: 2007-12-10 - Published: 2008-06-26 - Granted: 2009-10-27 - Earliest claimed: 2006-12-12 - Assignees: Panasonic Corporation - Inventors: Masakatsu Maeda - Web page: https://patentgrep.com/patent/US7609123B2 ## CPC - H03C 3/225: {using field effect transistors (H03C3/227 takes precedence)} - H03B 5/1215: {the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair} - H03B 5/1228: {the amplifier comprising one or more field effect transistors} - H03B 5/1253: {the transistors being field-effect transistors} - H03C: MODULATION (masers or lasers H01S; coding, decoding or code conversion H03M) - H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H) ## Abstract Transistors M11 and M12 are cross-coupled to each other so as to form a negative resistance circuit. First and second variable capacitor sections 10 and 20 are connected in parallel with an inductor circuit so as to form a parallel resonant circuit. A first reference voltage Vref1 and a control voltage VT1 corresponding to a carrier wave component are fed to both terminals, respectively, of each of variable capacitors VC11 and VC12 included in the first variable capacitor section 10. A second reference voltage Vref2 and a control voltage VT2 corresponding to a modulated wave component are fed to both terminals, respectively, of each of variable capacitors VC21 and VC22 included in the second variable capacitor section 20. A DC control section 30 includes a resistance R31 interposed between the second reference voltage Vref2 and a common connection point of resistances R21 and R22, and a capacitor C31 for feeding only an AC component included in the modulated wave component to the common connection point of the resistances R21 and R22. Thus, a DC voltage, on which the AC component included in the modulated wave component is superimposed, is changed from a certain DC bias to a DC bias of the second reference voltage Vref2. ## Claims ### Claim 1 A direct modulation type voltage-controlled oscillator for oscillating a signal in which a carrier wave component is modulated by a modulated wave component, the direct modulation type voltage-controlled oscillator comprising: a first variable capacitor section having a first terminal and a second terminal, the first variable capacitor section including a variable capacitor whose capacitance value varies in accordance with a potential difference between a control voltage, corresponding to the carrier wave component, which is fed to the first terminal and a first reference voltage applied to the second terminal; a second variable capacitor section having a first terminal and a second terminal, the second variable capacitor section including a variable capacitor whose capacitance value varies in accordance with a potential difference between a control voltage, corresponding to the modulated wave component, which is fed to the first terminal and a second reference voltage applied to the second terminal; and a voltage setting section operable to set the control voltage corresponding to the modulated wave component based on the second reference voltage, wherein the voltage setting section includes: an offset circuit operable to detect an intermediate capacitance value in the second variable capacitor section and to generate, based on the second reference voltage, a third reference voltage corresponding to the intermediate capacitance value; a resistance located between the offset circuit and the first terminal of the second variable capacitor section, the third reference voltage passing through the resistance prior to being received at the first terminal of the second variable capacitor section; and a capacitor located before the first terminal of the second variable capacitor section, the capacitor being operable to pass only an AC component included in the modulated wave component to the first terminal of the second variable capacitor section. ### Claim 2 (depends on 1) The direct modulation type voltage-controlled oscillator according to claim 1, wherein the variable capacitors included in the first and second variable capacitor sections are MOS varicaps. ### Claim 3 A direct modulation type voltage-controlled oscillator for oscillating a signal in which a carrier wave component is modulated by a modulated wave component, the direct modulation type voltage-controlled oscillator comprising: a first variable capacitor section having a first terminal and a second terminal, the first variable capacitor section including a variable capacitor whose capacitance value varies in accordance with a potential difference between a control voltage, corresponding to the carrier wave component, which is fed to the first terminal and a first reference voltage applied to the second terminal; a second variable capacitor section having a first terminal and a second terminal, the second variable capacitor section including a variable capacitor whose capacitance value varies in accordance with a potential difference between a control voltage, corresponding to the modulated wave component, which is fed to the first terminal and a second reference voltage applied to the second terminal; and a voltage setting section operable to set the control voltage corresponding to the modulated wave component which is differentially inputted, based on the second reference voltage. ### Claim 4 (depends on 3) The direct modulation type voltage-controlled oscillator according to claim 3, wherein the voltage setting section includes: an offset circuit operable to detect an intermediate capacitance value in the second variable capacitor section and to generate, based on the second reference voltage, a third reference voltage corresponding to the intermediate capacitance value; and an operational amplifier circuit having a positive terminal and a negative terminal, the positive terminal receiving the third reference voltage and the positive terminal and the negative terminal differentially receiving the modulated wave component, the operational amplifier circuit being operable to feed the third reference voltage, on which an AC component included in the modulated wave component is superimposed, to the first terminal of the second variable capacitor section. ### Claim 5 (depends on 4) The direct modulation type voltage-controlled oscillator according to claim 4, wherein the voltage setting section further includes a gain correction section operable to calculate a correction coefficient for canceling a gain fluctuation amount and to correct a value of the modulated wave component by using the correction coefficient. ### Claim 6 (depends on 3) The direct modulation type voltage-controlled oscillator according to claim 3, wherein the variable capacitors included in the first and second variable capacitor sections are MOS varicaps.