Electrical signal conversion with reduced-distance element rotation

1. An electrical signal converter, comprising:

an input for receiving a first species of signal;

at least four discrete converter elements for converting the first species of signal into a second species of signal, wherein the converter elements are arranged in an array;

a switch for mapping the input to the converter elements; and

logic configured to cause the switch to:

on a first cycle, use a first converter element at a first position to convert the input; and

on a second cycle, use a second converter element at a second position to convert the input, wherein the second position is no more than two positions away from the first position.

2. The electrical signal converter of claim 1 , wherein the converter elements are digital-to-analog converter elements.

3. The electrical signal converter of claim 2 , comprising a plurality of inputs, and wherein the plurality of inputs form a thermometer code.

4. The electrical signal converter of claim 1 , wherein the converter elements are analog-to-digital converters.

5. The electrical signal converter of claim 4 , wherein the second species of signal comprises a thermometer code.

6. The electrical signal converter of claim 1 , wherein the logic is configured to select the second position according to a pseudorandom input.

7. The electrical signal converter of claim 1 , wherein the logic is configured to select the second position according to a pseudorandom input plus a constant.

8. The electrical signal converter of claim 1 , wherein the first position is k, the second position is k t+1 , and wherein selecting k t+1 comprises:

if k is even, k t+1 =2; and if k is odd, k t+1 =k−2.

9. The electrical signal converter of claim 8 , wherein selecting k t+1 further comprises:

if k==1, k t+1 =2; and if k is even and k==n, k t+1 =k−1.

10. The electrical signal converter of claim 1 , wherein the first position is k, the second position is k t+1 , and wherein selecting k t+1 comprises swapping k and k+1.

11. The electrical signal converter of claim 1 comprising exactly n converter elements, wherein the first position is k, the second position is k t+1 , and wherein selecting k t+1 comprises:

on even cycles, if k is odd and k≠n, swap k and k+1;

on odd cycles, if k is even and k≠n, swap k and k+1.

12. A delta-sigma modulator comprising:

an analog-to-digital converter configured to receive an analog input and provide a digital output, the analog-to-digital converter comprising a plurality of n ordered converter elements, wherein n>3, and logic to rotate converter elements according to a first stepwise pattern wherein at a step, each converter element is switched to a position not more than two positions from its previous position;

a digital-to-analog converter configured to receive the digital output of the analog-to-digital converter and provide an analog output, the digital-to-analog converter comprising a plurality of ordered converter elements and logic to rotate converter elements according to a second stepwise pattern wherein at a step, each converter element is switched to a position not more than two positions from its previous position;

a loop filter configured to receive the analog input and the analog output of the digital-to-analog converter, and to provide a filtered analog signal the analog-to-digital converter; and

element selection logic configured to select a number of steps;

wherein the first stepwise pattern and second stepwise pattern each ensure that a converter element used at a position k on a first conversion cycle is used at k t+1 on a second conversion cycle, wherein |k−k t+1 |≦2.

13. The delta-sigma modulator of claim 12 , wherein:

at least one of the stepwise patterns comprises, for element k, if k is of a first species, k t+1 =k+2; if k is of a second species, k t+1 =k−2.

14. The delta-sigma modulator of claim 12 , wherein:

the digital-to-analog converter comprises n converter elements;

the second pattern comprises two cycles, wherein, for element k:

on the first cycle, if k is odd, swap k and k+1;

on the second cycle, if k is even, swap k and k+1.

15. The delta-sigma modulator of claim 12 , wherein the element selection logic selects the number of steps by calculating a pseudorandom number plus a constant.

16. A method performed by an electrical signal converter, comprising:

during a first time period, selecting a first converter element from among a plurality of n available ordered converter elements in an electrical signal converter, wherein n>3;

during a second time period:

calculating a pseudorandom number;

selecting a second converter element by stepping through available converter elements according to a stepwise pattern, wherein the number of steps is a function of the pseudorandom number and is less than two.

17. The method of claim 16 , wherein the function of the pseudorandom number includes addition of a constant.

18. The method of claim 17 , wherein the constant is one.

19. The method of claim 16 , wherein stepwise pattern includes the steps 1-2-4-6-8 and 7-5-3-1.

20. The method of claim 16 , wherein the stepwise pattern comprises shifting converter elements up or down two elements.

21. The method of claim 16 , wherein the stepwise pattern comprises swapping adjacent converter elements.

22. The method of claim 16 , wherein the stepwise pattern comprises:

for element k, if k is of a first species, k t+1 −k+2; if k is of a second species, select k t+1 =k−2.

23. The method of claim 16 , wherein:

the stepwise pattern comprises two cycles, wherein, for element k:

on the first cycle, for a first species of k, swap k and k+1;

on the second cycle, for a second species of k, swap k and k+1.