Voltage-follower based cross-coupling oscillators with embedded phase-interpolation function

1. A circuit comprising:

a first ring oscillator comprising a plurality of stages; and

each output of the stages of the first ring oscillator coupled via a voltage follower cross-coupling to a plurality of stages of a second ring oscillator.

2. The circuit of claim 1 , wherein the plurality of stages of the first ring oscillator comprise A 1 , A 2 , and A 3 , and the plurality of stages of the second ring oscillator comprise B 1 , B 2 , and B 3 , and cross-coupling between the first ring oscillator and the second ring oscillator comprises <A 1 :B 2 , B 3 >, <A 2 :B 3 , B 1 > and <A 3 :B 1 , B 2 >.

3. The circuit of claim 1 , wherein the plurality of stages of the first ring oscillator comprise A 1 , A 2 , and A 3 , and the plurality of stages of the second ring oscillator comprise B 1 , B 2 , and B 3 , and cross-coupling between the first ring oscillator and the second ring oscillator comprises <A 1 :B 1 , B 2 >, <A 2 :B 2 , B 3 > and <A 3 :B 3 , B 1 >.

4. The circuit of claim 1 , wherein the voltage follower cross-coupling for each of the stages comprises one or more first voltage follower having a first strength, and one or more second voltage follower having a second strength different than the first strength.

5. The circuit of claim 1 , further comprising:

a third ring oscillator comprising a plurality of stages; and

each of the stages of the third ring oscillator coupled via a voltage follower cross-coupling to a plurality of stages of a fourth ring oscillator.

6. A circuit comprising:

a first ring oscillator comprising a plurality of stages; and

each output of the stages of the first ring oscillator coupled via a voltage follower cross-coupling to a corresponding adjacent stage of a second ring oscillator.

7. The circuit of claim 6 , wherein the plurality of stages of the first ring oscillator comprise A 1 , A 2 , and A 3 , and the plurality of stages of the second ring oscillator comprise B 1 , B 2 , and B 3 , and cross-coupling between the first ring oscillator and the second ring oscillator comprises <A 1 :B 2 >, <A 2 :B 3 > and <A 3 :B 1 >.

8. The circuit of claim 6 , further comprising:

a third ring oscillator comprising a plurality of stages; and

each of the stages of the second ring oscillator coupled via a voltage follower cross-coupling to a corresponding adjacent stage of the third ring oscillator.

9. The circuit of claim 8 , wherein the plurality of stages of the first ring oscillator comprise B 1 , B 2 , and B 3 , and the plurality of stages of the second ring oscillator comprise C 1 , C 2 , and C 3 , and cross-coupling between the first ring oscillator and the second ring oscillator comprises <B 1 :C 2 >, <B 2 :C 3 > and <B 3 :C 1 >.

10. The circuit of claim 8 , wherein each voltage follower cross-coupling of each stage of the first ring oscillator to a corresponding adjacent stage of a second ring oscillator has a first strength, and each voltage follower cross-coupling of each stage of the second ring oscillator to a corresponding adjacent stage of the third ring oscillator has a second strength.

11. A circuit comprising:

a plurality of multi-stage ring oscillators; and

a plurality of voltage follower cross-couplings between outputs of different stages of different ones of the ring oscillators.

12. The circuit of claim 11 , wherein stages of a first ring oscillator of the ring oscillators comprise A 1 , A 2 , and A 3 , and stages of a second ring oscillator of the ring oscillators comprise B 1 , B 2 , and B 3 , and the voltage follower cross-couplings between the first ring oscillator and the second ring oscillator comprise <A 1 :B 2 , B 3 >, <A 2 :B 3 , B 1 > and <A 3 :B 1 , B 2 >.

13. The circuit of claim 11 , wherein stages of a first ring oscillator of the ring oscillators comprise A 1 , A 2 , and A 3 , and stages of a second ring oscillator of the ring oscillators comprise B 1 , B 2 , and B 3 , and voltage follower cross-couplings between the first ring oscillator and the second ring oscillator comprise <A 1 :B 1 , B 2 >, <A 2 :B 2 , B 3 > and <A 3 :B 3 , B 1 >.

14. The circuit of claim 11 , wherein the voltage follower cross-couplings comprise one or more first voltage follower having a first strength, and one or more second voltage follower having a second strength different than the first strength.

15. The circuit of claim 11 , wherein the ring oscillators comprise a quadrature oscillator wherein each of the stages of each ring oscillator are coupled via a voltage follower cross-coupling to a plurality of stages of a different ring oscillator.