Linearized wide tuning range oscillator using magnetic balun/transformer

A voltage controlled oscillator (VCO), comprising:

• 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.

A method of operating a voltage controlled oscillator (VCO), the method comprising:

• 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.