Infrastructure-grade integrated voltage controlled oscillator (VCO) with linear tuning characteristics and low phase noise
View Patent ↗The described devices, systems and methods include a voltage controlled oscillator. The voltage controlled oscillator includes a fine-tuning varactor network, a switch capacitor array having a first plurality of binary capacitor array elements and a second plurality of thermometer code capacitor array elements, and a tank inductor network including a first inductor in parallel with a second inductor.
1. A capacitor array comprising:
a capacitor array element including an NFET switch coupled to a capacitor to form a first node;
a DC pedestal and a voltage swing reduction circuit comprising:
a first filter having a first filter input and a first filter output, the first filter input coupled to the first node;
a second filter having a second filter input and a second filter output;
a transmission gate coupled to the first filter output and the second filter input;
a pedestal switch coupled to the second filter output; and
wherein the transmission gate and the pedestal switch are configured to be on when the NFET switch is off.
2. The capacitor array of claim 1 wherein the pedestal switch further includes a FET transistor, a first resistor coupled between a drain of the transistor and a supply voltage, and a second resistor coupled between a source of the transistor and ground.
3. The capacitor array of claim 1 wherein the first filter is a single pole resistor-capacitor filter, and the second filter is a single pole resistor-capacitor filter.
4. The capacitor array of claim 1 wherein the transmission gate comprises a first PFET transistor coupled in parallel with a first NFET transistor.
5. The capacitor array of claim 1 wherein the capacitor in the capacitor array element is coupled between a supply voltage and the first node.
6. The capacitor array of claim 1 wherein a drain of the NFET switch is coupled to the first node and a source of the NFET switch is coupled to ground.
7. The capacitor array of claim 6 wherein the transmission gate comprises a first PFET transistor coupled in parallel with a first NFET transistor.
8. The capacitor array of claim 7 wherein a gate of the NFET switch is coupled to a gate of the first PFET transistor and coupled to a gate of the first NFET transistor via an inverter.
9. A capacitor array comprising:
a capacitor coupled between a supply voltage and a first node;
a capacitor switching element coupled between the first node and ground;
a first filter coupled between the first node and a second node;
a transmission gate coupled between the second node and a third node;
a second filter coupled between the third node and a fourth node; and
a pedestal switching element coupled between the fourth node and ground.
10. The capacitor array of claim 9 wherein the transmission gate and the pedestal switching element are operated complementary to the capacitor switching element.