Frequency control in a multi-mode VCO

A method of operating a Voltage-Controlled Oscillator (VCO) having a mode select switch, a primary varactor, and one or more secondary varactors, the method comprising:

• setting a condition of the mode select switch based on a desired operating frequency;
• controlling one or more settings of the primary varactor to oscillate the VCO at a particular center frequency when the mode select switch condition is ON;
• and
• applying voltages with a same polarity to the primary varactor and one or more secondary varactors to generate oscillation at the particular center frequency when the mode select switch condition is OFF, wherein the mode switch provides a ground voltage at an end of a secondary coil, when the mode switch is ON.

A method of manufacturing a Voltage-Controlled Oscillator (VCO), the method comprising:

• providing a cross-coupled transconductance cell;
• providing a transformer comprising a primary coil and at least one secondary coil, wherein the primary coil is connected to the cross-coupled transconductance cell;
• connecting a primary coil varactor to the cross-coupled transconductance cell in parallel to the primary coil;
• connecting a variable inductive tuning component to the at least one secondary coil;
• and
• providing a mode switch connected to the at least one secondary coil, selecting a frequency mode of operation of the VCO by engaging or disengaging the variable inductive tuning component from operation with the primary coil varactor;
• and
• generating oscillation at a center frequency of the VCO, wherein the mode switch provides a ground voltage at an end of the at least one secondary coil, when the mode switch is ON.