Linearized wide tuning range oscillator using magnetic balun/transformer
First Claim
1. A voltage controlled oscillator (VCO), comprising:
- an active negative transconductance circuit comprising;
cross-coupled transistors having drains connected with a resonant tank circuit;
the resonant tank circuit comprising;
a first variable capacitor element having first and second ends connected to respective first ends of respective first coils of a respective first and second magnetic balun, and respective second ends of respective first coils of respective first and second magnetic baluns being connected to a first reference supply voltage; and
a second variable capacitor element having a first end and a second end connected to a respective first end of a respective second coil of each said respective first and second magnetic baluns, and respective second ends of respective second coils of respective first and second magnetic baluns being connected to a second reference supply voltage, anda bias current circuit for sourcing or sinking a bias current through the resonant tank circuit and the active negative transconductance circuit to generate an oscillating signal, said tank circuit providing a low parasitic capacitance coupling structure and said first and second reference supply voltages each providing a voltage offset for extending a linear characteristic of a frequency tuning range of said oscillator.
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Accused Products
Abstract
A voltage controlled oscillator (VCO) circuit and method achieves linearized frequency tuning over an extended range of analog tuning voltage by implementing a magnetic balun/transformer for biasing and coupling varactor elements. An active negative transconductance circuit of cross-coupled transistors have drains connected with a resonant tank circuit and at least a first varactor element having ends connected to respective first ends of respective first coils of a respective first and second magnetic balun. Respective second ends of respective first coils of respective first and second baluns are connected to a first reference supply voltage. A second varactor element has ends connecting respective first ends of respective second coils of said first and second baluns. A sinking of a bias current through the resonant tank circuit and the transconductance circuit generates an oscillating signal. A calibration method achieves precise VCO gain over wide tuning voltage range, thereby enhancing VCO linearity.
12 Citations
20 Claims
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1. A voltage controlled oscillator (VCO), comprising:
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an active negative transconductance circuit comprising;
cross-coupled transistors having drains connected with a resonant tank circuit;
the resonant tank circuit comprising;a first variable capacitor element having first and second ends connected to respective first ends of respective first coils of a respective first and second magnetic balun, and respective second ends of respective first coils of respective first and second magnetic baluns being connected to a first reference supply voltage; and a second variable capacitor element having a first end and a second end connected to a respective first end of a respective second coil of each said respective first and second magnetic baluns, and respective second ends of respective second coils of respective first and second magnetic baluns being connected to a second reference supply voltage, and a bias current circuit for sourcing or sinking a bias current through the resonant tank circuit and the active negative transconductance circuit to generate an oscillating signal, said tank circuit providing a low parasitic capacitance coupling structure and said first and second reference supply voltages each providing a voltage offset for extending a linear characteristic of a frequency tuning range of said oscillator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A voltage controlled oscillator (VCO), comprising:
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a first active negative transconductance circuit comprising;
cross-coupled transistors having drains connected with a resonant tank circuit;a second active negative transconductance circuit comprising;
cross-coupled transistors having drains connected with the resonant tank circuit;the resonant tank circuit comprising; a first variable capacitor element having first and second ends connected to respective first ends of respective first coils of a respective first and second magnetic balun, and respective second ends of respective first coils of respective first and second magnetic baluns being connected to a reference supply voltage; and a second variable capacitor element having at least one first end connected to a respective first end of a respective second coil of said respective first and second magnetic baluns, and respective second ends of respective second coils of respective first and second magnetic baluns being connected to a virtual signal ground, wherein said second active negative transconductance circuit drains connect to said respective first ends of respective second coils of said respective first and second magnetic baluns; and a bias current circuit for sourcing or sinking a bias current through the resonant tank circuit, the first active negative transconductance circuit and the second active negative transconductance circuit to generate an oscillating signal, said tank circuit providing a low parasitic capacitance coupling structure and said reference supply voltage providing a voltage offset for extending a linear characteristic of a frequency tuning range of said oscillator. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of operating a voltage controlled oscillator (VCO), the method comprising:
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receiving a bias current at an active circuit comprising cross-coupled transistors having drains connected with a resonant tank circuit, said active circuit presenting a negative transconductance condition for generating an oscillating signal responsive to the bias current, said tank circuit comprising; a first variable capacitor element having first and second ends connected to respective first ends of respective first coils of a respective first and second magnetic balun, and a second variable capacitor element having at least one first end connected to a respective first end of respective second coil of said respective first and second magnetic baluns, applying a first bias voltage to said first variable capacitor element via respective second ends of respective first coils of the respective first and second magnetic balun; and applying a second bias voltage to said second variable capacitor element via respective second ends of respective second coils of the respective first and second magnetic balun, said first and second bias voltages each providing a voltage offset for extending a linear characteristic of a frequency tuning range of said oscillator. - View Dependent Claims (18, 19, 20)
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Specification