Low EMI signaling for parallel conductor interfaces

• US 9,369,312 B1
• Filed: 02/02/2015
• Issued: 06/14/2016
• Est. Priority Date: 02/02/2014
• Status: Active Grant

• Current Assignee: Kandou Labs, SA
• Original Assignee: Kandou Labs, SA
• Inventors: Chiurtu, Nicolae, Shokrollahi, Amin
• Primary Examiner(s): Tran, Khanh C
• Application Number:
  US14/612,245
• Time in Patent Office: 498 Days
• Field of Search: 375259-260, 375/265, 375/285, 375/257, 375295-296, 455/63.1, 455/114.2
• US Class Current: 1/1
• CPC Class Codes: H04L 1/0042 Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 2001/0094 Bus
• CPC Class Codes: H04L 2001/0096 Channel splitting in point-to-point links
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/028 Arrangements specific to the transmitter end
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
• CPC Class Codes: H04L 25/4917 using multilevel codes

Abstract

Methods are disclosed for creation of vector signaling codes having reduced or minimized electromagnetic emissions when transmitted over multiple conductor communications media such as microstrip channels. Particular code formulation constraints are shown to correlate with physical propagation characteristics leading to beneficial cancellation of far fields from adjacent signal conductors, and the number of such constraints may be chosen to balance EMI characteristics with information encoding capacity in the resulting code.

Claims

1. A method comprising:

receiving a set of data bits representing information;

mapping the data bits to low electromagnetic interference (EMI) codewords in a set of low EMI codewords, wherein the set of low EMI codewords when represented as a polynomial are divisible by the polynomial (X−

1)^M where M is at least 1; and

transmitting the set of low EMI codewords on a multiwire system.

2. The method of claim 1, wherein the set of low EMI codewords is generated from modulating an initial set of codewords represented as a polynomial of maximum degree N−

M−

1 and a polynomial (X−

1)^M where N is a number of wires in the multiwire system and M is an order of electromagnetic interference reduction, and wherein N>

M.

3. The method of claim 2, wherein M is at least 2, representing a plurality of orders of electromagnetic interference reduction.

4. The method of claim 2, wherein the initial set of codewords are formed using a Hadamard matrix with a size of at least 3.

5. The method of claim 4, wherein the Hadamard matrix has a size of 4, and the initial set of codewords belong to an Ensemble Non-Return to Zero (ENRZ) code.

6. The method of claim 4, wherein the Hadamard matrix has a size of 8 (H8), and the initial codewords belong to an H8 code.

7. The method of claim 4, wherein the Hadamard matrix has a size of 16 (H16), and the initial codewords belong to an H16 code.

8. The method of claim 2, wherein N is at least 3.

9. The method of claim 2, wherein the low EMI codewords C={c₁ . . . c_N} transmitted on N wires of the multiwire system satisfies at least a first and second relationship given by Σ

_l=0<sup>N−

1</sup> l^Kc_il, the at least first and second relationships determined by consecutive integer values of K starting at zero, where c_il represents an ith low EMI codeword component transmitted on wire l of the multiwire system.

10. The method of claim 2, wherein the low EMI codewords represent a portion of the initial set of codewords.

11. An apparatus comprising:

an encoder configured to receive a set of bits representing information, and responsively generate a set of low electromagnetic interference (EMI) codewords, wherein the set of low EMI codewords when represented as a polynomial are divisible by the polynomial (X−

1)^M where M is at least 1; and

a multiwire bus configured to transmit the set of low EMI codewords.

12. The apparatus of claim 11, wherein generating the set of low EMI codewords comprises modulating an initial set of codewords represented as a polynomial of maximum degree N−

M−

1 and a polynomial (X−

1)^M where N is a number of wires in the multiwire bus and M is an order of electromagnetic interference reduction, wherein N>

M.

13. The apparatus of claim 12, wherein M is at least 2, representing a plurality of orders of electromagnetic interference reduction.

14. The apparatus of claim 12, wherein the low EMI codewords represent a portion of the initial set of codewords.

15. The apparatus of claim 12, wherein N is at least 3.

16. The apparatus of claim 12, wherein the initial set of codewords are formed using a Hadamard matrix with a size of at least 3.

17. The apparatus of claim 16, wherein the Hadamard matrix has a size of 4, and the initial codewords belong to an Ensemble Non-Return to Zero (ENRZ) code.

18. The apparatus of claim 16, wherein the Hadamard matrix has a size of 8 (H8), and the initial codewords belong to an H8 code.

19. The apparatus of claim 16, wherein the Hadamard matrix has a size of 16 (H16), and the initial codewords belong to an H16 code.

20. The apparatus of claim 11, wherein the low EMI codewords C={c₁ . . . c_N} transmitted on N wires of the multiwire system satisfies at least a first and second relationship given by Σ

_l=0<sup>N−

1</sup> l^Kc_il, the at least first and second relationships determined by consecutive integer values of K starting at zero, where c_il represents an ith low EMI codeword component tranmsitted on wire l of the multiwire bus.