Demodulation mixing for a near field communications (NFC) device

1. An in-phase, quadrature-phase (IQ) mixer, comprising:

a signal provider configured to provide an in-phase (I) mixing signal and a quadrature-phase (Q) mixing signal, wherein a period for the I mixing signal is equal to a period for the Q mixing signal;

a controller configured to control the signal provider so that:

the I mixing signal is at a first level for an equal number of clock cycles during the period as is the Q mixing signal,

the I mixing signal is at a second level for an equal number of clock cycles during the period as is the Q mixing signal, and

the I mixing signal is at a null for an equal number of clock cycles during the period as is the Q mixing signal, wherein the null is equal to a remainder of the period that the I mixing signal and the Q mixing signal are not at the first level or the second level; and

a clock signal provider configured to provide a clock signal to the signal provider and the controller, wherein the clock cycles are derived from the clock signal.

2. The IQ mixer of claim 1 , further comprising:

a first signal mixer configured to multiply a received signal with the I mixing signal; and

a second signal mixer configured to multiply the received signal with the Q mixing signal.

3. The IQ mixer of claim 2 , wherein the first signal mixer is further configured to:

provide the received signal unaltered when the I mixing signal is at the first level; and

invert the received signal when the I mixing signal is at the second level.

4. The IQ mixer of claim 2 , wherein the second signal mixer is further configured to:

provide the received signal unaltered when the Q mixing signal is at the first level; and

invert the received signal when the Q mixing signal is at the second level.

5. The IQ mixer of claim 1 , wherein the controller is further configured to:

determine whether a duration of one-quarter of the period for the I mixing signal and the Q mixing signal is equivalent to an integer number of clock cycles derived from the clock signal.

6. The IQ mixer of claim 5 , wherein the controller is further configured to:

multiply the duration of one-quarter of the period for the I mixing signal and the Q mixing signal by two to generate a duration of one-half of the period for the I mixing signal and the Q mixing signal; and

round down the duration of one-half of the period to a nearest integer to generate a half cycle time for the I mixing signal and the Q mixing signal when the duration of one-quarter of the period for the I mixing signal and the Q mixing signal is not equivalent to the integer number of clock cycles.

7. The IQ mixer of claim 6 , wherein the controller is further configured to control the signal provider so that:

the I mixing signal is at the first level for the half cycle time and at the second level for the half cycle time;

the Q mixing signal is at the first level for the half cycle time and at the second level for the half cycle time; and

the I mixing signal and the Q mixing signal are at the null for a difference between the period of the I mixing signal and the Q mixing signal and a clock signal period.

8. An in-phase, quadrature-phase (IQ) mixer, comprising:

a signal provider configured to provide an in-phase (I) mixing signal and a quadrature-phase (Q) mixing signal, wherein a period for the I mixing signal is equal to a period for the Q mixing signal;

a controller configured to control the signal provider so that:

an average of the I mixing signal, at a first level for a first quantity of clock cycles and at a second level for a second quantity of clock cycles, over a first I mixing signal period and a second I mixing signal period is minimized,

an average propagation delay for the I mixing signal over the first I mixing signal period and the second I mixing signal period is minimized,

an average of the Q mixing signal, at the first level for the first quantity of clock cycles and at the second level for the second quantity of clock cycles, over a first Q mixing signal period and a second Q mixing signal period is minimized, and

an average propagation delay for the Q mixing signal over the first Q mixing signal period and the second Q mixing signal period is minimized; and

a clock signal provider configured to provide a clock signal to the signal provider and the controller, wherein the clock cycles are derived from the clock signal.

9. The IQ mixer of claim 8 , wherein the average of the I mixing signal, at the first level for the first quantity of clock cycles and at the second level for the second quantity of clock cycles, over the first I mixing signal period and the second I mixing signal period is zero.

10. The IQ mixer of claim 8 , wherein the average of the Q mixing signal, at the first level for the first quantity of clock cycles and at the second level for the second quantity of clock cycles, over the first Q mixing signal period and the second Q mixing signal period is zero.

11. The IQ mixer of claim 8 , wherein the average propagation delay for the I mixing signal is determined from an average of a first propagation delay for the I mixing signal over the first I mixing signal period and a second propagation delay for the I mixing signal over the second I mixing signal period.

12. The IQ mixer of claim 8 , wherein the average propagation delay for the Q mixing signal is determined from an average of a first propagation delay for the Q mixing signal over the first Q mixing signal period and a second propagation delay for the Q mixing signal over the second Q mixing signal period.

13. The IQ mixer of claim 12 , wherein an average propagation delay for the I mixing signal and the average propagation delay for the Q mixing signal is one-quarter of a clock cycle.

14. An in-phase, quadrature-phase (IQ) mixer, comprising:

a signal provider configured to provide an in-phase (I) mixing signal and a quadrature-phase (Q) mixing signal, wherein a period for the I mixing signal is equal to a period for the Q mixing signal;

a controller configured to control the signal provider so that:

an average of the I mixing signal at a first level for a first quantity of clock cycles and at a second level for a second quantity of clock cycles over a first I mixing signal period and a second I mixing signal period is minimized,

an average propagation delay for the I mixing signal over the first I mixing signal period and the second I mixing signal period is minimized based on the I mixing signal being at a I mixing signal null,

an average of the Q mixing signal at a first level for a first quantity of clock cycles and at a second level for a second quantity of clock cycles over a first Q mixing signal period and a second Q mixing signal period is minimized, and

an average propagation delay for the Q mixing signal over the first Q mixing signal period and the second Q mixing signal period is minimized based on the Q mixing signal being at a Q mixing signal null; and

a clock signal provider configured to provide a clock signal to the signal provider and the controller, wherein the clock cycles are derived from the clock signal.

15. The IQ mixer of claim 14 , wherein the I mixing signal null is equal to a remainder of the first I mixing signal period and the second I mixing signal period that the I mixing signal is not at the first level or the second level.

16. The IQ mixer of claim 14 , wherein the Q mixing signal null is equal to a remainder of the first Q mixing signal period and the second Q mixing signal period that the Q mixing signal is not at the first level or the second level.

17. The IQ mixer of claim 15 , wherein the average propagation delay of the I mixing signal is based on an average of when the I mixing signal is at the I mixing signal null.

18. The IQ mixer of claim 16 , wherein the average propagation delay for the Q mixing signal average is based on an average of when the Q mixing signal is at the Q mixing signal null.

19. The IQ mixer of claim 14 , wherein the average of the I mixing signal at the first level for the first quantity of clock cycles and at the second level for the second quantity of clock cycles over the first I mixing signal period and the second I mixing signal period is zero.

20. The IQ mixer of claim 14 , Wherein the average of the Q mixing signal at the first level for the first quantity of clock cycles and at the second level for the second quantity of clock cycles over the first Q mixing signal period and the second Q mixing signal period is zero.