EMI rejection for near field links

• US 10,763,037 B2
• Filed: 03/11/2019
• Issued: 09/01/2020
• Est. Priority Date: 03/23/2018
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Richardson, Kenneth G.
• Primary Examiner(s): Hernandez, William
• Application Number:
  US16/298,913
• Publication Number:
  US 20190295770A1
• Time in Patent Office: 540 Days
• Field of Search: 307104
• CPC Class Codes: G01V 3/107 using compensating coil or loop arrangements
• CPC Class Codes: H01F 27/33 Arrangements for noise damping
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H01L 2223/6677 for antenna, e.g. antenna included within housing of semiconductor device antennas per se H01Q
• CPC Class Codes: H01L 23/66 High-frequency adaptations
• CPC Class Codes: H04B 1/12 Neutralising, balancing, or compensation arrangements
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 15/005 Reducing noise, e.g. humm, from the supply
• CPC Class Codes: H04B 5/263 Multiple coils at either side
• CPC Class Codes: H04B 5/72 for local intradevice communication

Abstract

For near field communications, inductive coils coupled to each communicating circuit are brought close together so that there is inductive coupling between the two coils. Data signals can then be relayed between the two circuits without any direct connection between them. However, the system is susceptible to common mode noise, such as ambient EMI. In addition to the “active” coil pairs used for transmitting and receiving data, a pair of “passive” coils is provided, proximate to the active coil pairs, that is only used for detecting the ambient EMI. The EMI signals detected by the passive coils are processed by a noise detector/processor, and the noise detector processor then controls the transmitters and/or receivers to at least partially compensate for the detected EMI signals. Transmit power or receiver thresholds may be controlled by the noise detector/processor to improve the signal-to-noise ratio, or other compensation techniques can be used.

Claims

1. A system comprising:

a first circuit for transmitting data;

a second circuit for receiving the transmitted data;

a first electromagnetic interference (EMI) detection circuit;

a first inductive coil coupled to the first circuit for transmitting the data using near field communications;

a second inductive coil coupled to the second circuit for receiving the data using near field communications, the second inductive coil being proximate to the first inductive coil for magnetic coupling between the second inductive coil and the first inductive coil; and

a third inductive coil coupled to the first EMI detection circuit for detecting EMI signals that are also substantially received by the first inductive coil or the second inductive coil,

wherein the first EMI detection circuit is configured to control at least one of the first circuit or the second circuit to improve a signal-to-noise ratio of a data signal based on the EMI signals detected by the third inductive coil.

2. The system of claim 1 wherein the first inductive coil comprises a flat first spiral and the second inductive coil comprises a flat second spiral, wherein the first spiral and the second spiral overlap and are separated by a dielectric layer.

3. The system of claim 1 further comprising:

a fourth inductive coil, the third inductive coil being proximate to the fourth inductive coil for magnetic coupling between the third inductive coil and the fourth inductive coil; and

a second EMI detection circuit coupled to the fourth inductive coil, wherein the second EMI detection circuit is configured to control at least one of the first circuit or the second circuit to improve the signal-to-noise ratio of the data signal based on EMI signals detected by the fourth inductive coil.

4. The system of claim 3 wherein physical and electrical properties of the first inductive coil and the second inductive coil, when proximate to each other, are substantially identical to the physical and electrical properties of the third inductive coil and the fourth inductive coil when proximate to each other.

5. The system of claim 4 wherein the first inductive coil and the second inductive coil are both in a first die within a package, and the third inductive coil and the fourth inductive coil are both in a second die within the package.

6. The system of claim 3 wherein the first EMI detection circuit is located on a first die along with the first circuit, and the second EMI detection circuit is located on a second die along with the second circuit.

7. The system of claim 1 wherein the first circuit comprises a transmitter, and the first EMI detection circuit controls an output power of the transmitter based on detected EMI signals.

8. The system of claim 1 wherein the second circuit comprises a receiver, and the first EMI detection circuit controls a threshold of the receiver for determining a binary level of the transmitted data.

9. The system of claim 1 wherein the first circuit comprises a transmitter, and the first EMI detection circuit compensates a data signal to be transmitted by the transmitter based on detected EMI signals.

10. The system of claim 1 wherein the second circuit comprises a receiver, and the first EMI detection circuit compensates a received data signal based on detected EMI signals.

11. The system of claim 1 wherein the second circuit comprises a summer for receiving signals from the second inductive coil and receiving signals obtained from the third inductive coil, where an output of the summer is a difference between the signals from the second inductive coil and the signals obtained from the third inductive coil, wherein the output of the summer comprises a data signal that has been at least partially compensated for the EMI signals.

12. The system of claim 1 wherein the first circuit comprises a summer for receiving signals to be transmitted and receiving signals obtained from the third inductive coil, where an output of the summer is a difference between the signals to be transmitted and the signals obtained from the third inductive coil, wherein the output of the summer comprises an output power control signal for the first circuit.

13. The system of claim 1 wherein the first circuit transmits single-ended data signals, and the second circuit receives the single-ended data signals.

14. The system of claim 1 wherein the first circuit transmits differential data signals, and the second circuit receives the differential data signals.

15. The system of claim 14 further comprising:

a fourth inductive coil coupled to the first circuit for transmitting, in conjunction with the first inductive coil, the differential data signals using near field communications; and

a fifth inductive coil coupled to the second circuit for receiving, in conjunction with the second inductive coil, the differential data signals using near field communications, the fourth inductive coil being proximate to the fifth inductive coil for magnetic coupling between the fourth inductive coil and the fifth inductive coil.

16. A method performed by a system comprising:

transmitting data by a first circuit;

receiving the transmitted data by a second circuit;

detecting electromagnetic interference (EMI) by a first EMI detection circuit;

transmitting the data using near field communications via a first inductive coil coupled to the first circuit;

receiving the data using near field communications via a second inductive coil coupled to the second circuit, the second inductive coil being proximate to the first inductive coil for magnetic coupling between the second inductive coil and the first inductive coil; and

detecting EMI signals by a third inductive coil coupled to the first EMI detection circuit, wherein the EMI signals are also substantially received by the first inductive coil or the second inductive coil,

controlling, by the first EMI detection circuit, at least one of the first circuit or the second circuit to improve a signal-to-noise ratio of a data signal based on the EMI signals detected by the third inductive coil.

17. The method of claim 16 further comprising:

detecting the EMI signals by a fourth inductive coil coupled to a second EMI detection circuit, wherein the third inductive coil is proximate to the fourth inductive coil for magnetic coupling between the third inductive coil and the fourth inductive coil; and

controlling, by the second EMI detection circuit, at least one of the first circuit or the second circuit to improve the signal-to-noise ratio of the data signal based on EMI signals detected by the fourth inductive coil.

18. The method of claim 17 wherein the first EMI detection circuit is located in a first die along with the first circuit, and the second EMI detection circuit is located in a second die along with the second circuit.

19. The method of claim 17 wherein physical and electrical properties of the first inductive coil and the second inductive coil, when proximate to each other, are substantially identical to the physical and electrical properties of the third inductive coil and the fourth inductive coil when proximate to each other.

20. A system comprising:

a first means for transmitting data;

a second means for receiving the transmitted data;

a third means for detecting electromagnetic interference (EMI);

a first inductive coil coupled to the first means for transmitting the data using near field communications;

a second inductive coil coupled to the second means for receiving the data using near field communications, the second inductive coil being proximate to the first inductive coil for magnetic coupling between the second inductive coil and the first inductive coil; and

a third inductive coil coupled to the third means for detecting EMI signals that are also substantially received by the first inductive coil or the second inductive coil,

wherein the third means is configured to control at least one of the first means or the second means to improve a signal-to-noise ratio of a data signal based on the EMI signals detected by the third inductive coil.