Voltage-controlled oscillator (lc vco) and method of operation thereof

A method for operating a dual-tank LC-tuned voltage-controlled oscillator (LC VCO), comprising the steps of:

• a. providing a negative impedance circuit comprising:
• i. a lower pair of transistors comprising a first (M1) and second (M2) transistors;
• ii. an upper pair of transistors comprising a third (M3) and fourth (M4) transistors;
• iii. connecting a drain terminal of the third transistor (M3) to a drain terminal of the first transistor (M1), and connecting a drain terminal of the fourth transistor (M4) to a drain terminal of the second transistor (M2);
• iv. coupling a gate terminal of the first transistor (M1) to a gate terminal of the second transistor (M2) through a pair of serially connected inductors (L1, L2), and coupling a gate terminal of the third transistor (M3) to a gate terminal of the fourth transistor (M4) through another pair of serially connected inductors (L1, L2);
• b. providing a swing extension circuit comprising:
• i. AC coupling of each transistor pair through individual capacitors (C1, C2, C3, C4);
• c. providing a Voltage Controlled Oscillator (VCO) tank circuit (101) comprising:
• i. an inductive element (LT) and a pair of capacitive elements (C5T, C6T) coupled across the drains of the lower pair of transistors and the drain terminals of the upper pair of transistors;
• d. providing a biasing circuit comprising:
• i. applying a first Digital-to-Analog Converter (DAC) (D1) to a center tap of the serially connected inductors (L1, L2) positioned between the gate terminal of the first transistor (M1) and the gate terminal of the second transistor (M2);
• ii. applying a second Digital-to-Analog Converter (DAC) (D2) to a center tap of the serially connected inductors (L1, L2) positioned between the gate terminal of the third transistor (M3) and the gate terminal of the fourth transistor (M4);
• e. maintaining the negative impedance circuit in the saturation region using the swing extension circuit and the biasing circuit;
• f. generating two outputs, VOP and VON, from the VCO tank circuit with a 180-degree phase shift, wherein VOP and VON are directly connected to the drain terminals of the transistors (M1, M2) and (M3, M4), respectively.