Apparatus and method for interpolating between a first signal and a second signal

1. An apparatus for interpolating between a first signal and a second signal, comprising:

a first plurality of interpolation cells configured to generate a first interpolation signal at a first node, wherein at least one of the first plurality of interpolation cells is configured to supply, based on a first number of bits of a control word, at least one of the first signal and the second signal to the first node;

a second plurality of interpolation cells configured to generate a second interpolation signal at a second node, wherein at least one of the second plurality of interpolation cells is configured to supply, based on a second number of bits of the control word, at least one of the first signal and the second signal to the second node; and

an interpolation circuit configured to weight the second interpolation signal based on a weighting factor, and to combine the first interpolation signal and the weighted second interpolation signal to generate a third interpolation signal.

2. The apparatus of claim 1 , wherein the second plurality of interpolation cells comprises 2 M 2 −1 interpolation cells with M 2 denoting the second number of bits of the control word.

3. The apparatus of claim 1 , wherein the weighting factor is based on the number of interpolation cells in the second plurality of interpolation cells.

4. The apparatus of claim 3 , wherein the weighting factor is 2 M 2 −1 with M 2 denoting the second number of bits of the control word.

5. The apparatus of claim 1 , further comprising:

a third plurality of interpolation cells configured to generate a fourth interpolation signal at a third node, wherein at least one of the third plurality of interpolation cells is configured to supply, based on a third number of bits of the control word, at least one of the first signal and the second signal to the third node,

wherein the interpolation circuit is configured to weight the fourth interpolation signal based on a second weighting factor, and to combine the third interpolation signal and the weighted fourth interpolation signal to generate a fifth interpolation signal.

6. The apparatus of claim 5 , wherein the third plurality of interpolation cells comprises 2 M 3 −1 interpolation cells with M 3 denoting the third number of bits of the control word.

7. The apparatus of claim 5 , wherein the second weighting factor is based on the number of interpolation cells in the third plurality of interpolation cells.

8. The apparatus of claim 5 , wherein the second weighting factor is 2 M 3 −1 with M 3 denoting the third number of bits of the control word.

9. The apparatus of claim 5 , wherein the interpolation circuit comprises:

one first inverter configured to receive the first interpolation signal;

a plurality of second inverters each configured to receive the second interpolation signal;

a first signal combiner configured to combine outputs of the first inverter and the second inverters to the third interpolation signal;

one third inverter configured to receive the third interpolation signal;

a plurality of fourth inverters each configured to receive the fourth interpolation signal, wherein the number of the fourth inverters is equal to the second weighting factor; and

a second signal combiner configured to combine outputs of the third inverter and the fourth inverters to the fifth interpolation signal.

10. The apparatus of claim 1 , further comprising:

a third plurality of interpolation cells configured to generate a fourth interpolation signal at a third node, wherein at least one of the third plurality of interpolation cells is configured to supply, based on a third number of bits of the control word, at least one the first signal and the second signal to the third node,

wherein the interpolation circuit is configured to weight the fourth interpolation signal based on a second weighting factor, and to combine the first interpolation signal, the weighted second interpolation signal and the weighted fourth interpolation signal to generate the third interpolation signal.

11. The apparatus of claim 9 , wherein the interpolation circuit comprises:

one first inverter configured to receive the first interpolation signal;

a plurality of second inverters each configured to receive the second interpolation signal;

a plurality of third inverters each configured to receive the fourth interpolation signal, wherein the number of the fourth inverters is equal to the second weighting factor; and

a signal combiner configured to combine outputs of the of the first inverter, the second inverters and the third inverters to the third interpolation signal.

12. The apparatus of claim 10 , wherein the third plurality of interpolation cells comprises 2 M 3 −1 interpolation cells with M 3 denoting the third number of bits of the control word.

13. The apparatus of claim 12 , wherein the second weighting factor is based on the number of interpolation cells in the third plurality of interpolation cells and the number of interpolation cells in the second plurality of interpolation cells.

14. The apparatus of claim 13 , wherein the second weighting factor is 2 M 2 +M 3 −1 with M 2 denoting the second number of bits of the control word and M 3 denoting the third number of bits of the control word.

15. The apparatus of claim 1 , wherein the interpolation circuit comprises:

one first inverter configured to receive the first interpolation signal;

a plurality of second inverters each configured to receive the second interpolation signal; and

a signal combiner configured to combine outputs of the first inverter and the second inverters to the third interpolation signal.

16. The apparatus of claim 15 , wherein the number of the second inverters is equal to the weighting factor.

17. The apparatus of claim 1 , wherein the first plurality of interpolation cells comprises 2 M 1 interpolation cells with M 1 denoting the first number of bits of the control word.

18. The apparatus of claim 1 , wherein the second signal is a phase shifted replica of the first signal.

19. The apparatus of claim 1 , wherein the first plurality of interpolation cells is further configured to generate a fourth interpolation signal at a fourth node, the fourth interpolation signal being inverted with respect to the first interpolation signal, wherein the second plurality of interpolation cells is further configured to generate a fifth interpolation signal at a fifth node, the fifth interpolation signal being inverted with respect to the second interpolation signal, and wherein the interpolation circuit is further configured to weight the fifth interpolation signal based on the weighting factor, and to combine the fourth interpolation signal and the weighted fifth interpolation signal to generate a sixth interpolation signal.

20. A digital-to-time converter comprising an apparatus for interpolating between a first signal and a second signal according to claim 1 .

21. A mobile device comprising a digital-to-time converter according to claim 20 .

22. The mobile device of claim 21 , wherein the digital-to-time converter is part of a radio frequency transceiver.

23. A method for interpolating between a first signal and a second signal, comprising:

generating a first interpolation signal at a first node using a first plurality of interpolation cells, wherein at least one of the first plurality of interpolation cells is configured to supply, based on a first number of bits of a control word, at least one of the first signal and the second signal to the first node;

generating a second interpolation signal at a second node using a second plurality of interpolation cells, wherein at least one of the second plurality of interpolation cells is configured to supply, based on a second number of bits of the control word, at least one of the first signal and the second signal to the second node;

weighting the second interpolation signal based on a weighting factor; and

combining the first interpolation signal and the weighted second interpolation signal to generate a third interpolation signal.

24. The method of claim 23 , further comprising:

generating a fourth interpolation signal at a third node using a third plurality of interpolation cells, wherein at least one of the third plurality of interpolation cells is configured to supply, based on a third number of bits of the control word, at least one of the first signal and the second signal to the third node;

weighting the fourth interpolation signal based on a second weighting factor; and

combining the third interpolation signal and the weighted fourth interpolation signal to generate a fifth interpolation signal.

25. The method of claim 23 , further comprising:

generating a fourth interpolation signal at a third node using a third plurality of interpolation cells, wherein at least one of the third plurality of interpolation cells is configured to supply, based on a third number of bits of the control word, at least one of the first signal and the second signal to the third node;

weighting the fourth interpolation signal based on a second weighting factor; and

combining the first interpolation signal, the weighted second interpolation signal and the weighted fourth interpolation signal to generate the third interpolation signal.