# US 2019/0356049 A1 · Superposition of electromagnetic fields by antenna current phase alignment

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- Number: US 2019/0356049 A1
- Document ID: US20190356049A1
- Status: Published application
- Kind: A1
- Application number: 15/983,364
- Filed: 2018-05-18
- Published: 2019-11-21
- Earliest claimed: 2018-05-18
- Assignees: NXP B.V.
- Applicants: NXP B.V.
- Inventors: Jens Fleischhacker
- Web page: https://patentgrep.com/patent/US20190356049A1

## CPC

- H01Q 3/2694: {using also variable phase-shifters (H01Q3/2688 takes precedence)}
- H04B 7/0617: {for beam forming}
- H01Q 1/3241: {particular used in keyless entry systems}
- H01Q 1/3283: {side-mounted antennas, e.g. bumper-mounted, door-mounted (mounted on windscreens H01Q1/1271)}
- H01Q 3/38: the phase-shifters being digital
- H04B 7/086: {using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming}
- H04W 52/0261: {managing power supply demand, e.g. depending on battery level}
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

A system for simultaneously driving a plurality of antennas for transmission of an electromagnetic wave includes a first terminal, a second terminal, a first driver coupled to the first terminal, and a second driver coupled to the second terminal. The system includes a circuit configured to generate an indication of a phase difference between a first current through the first terminal and a second current through the second terminal. The system includes a control circuit configured to enable the first driver and the second driver to concurrently drive a first signal through the first terminal and a second signal through the second terminal, respectively, and configured to adjust a delay between the first signal and the second signal based on the indication of the phase difference and a predetermined target phase difference.

## Claims

### Claim 1

A system for simultaneously driving a plurality of antennas for generation of an electromagnetic field, the system comprising:
a first terminal;
a second terminal;
a first driver coupled to the first terminal;
a second driver coupled to the second terminal;
a circuit configured to generate an indication of a phase difference between a first current through the first terminal and a second current through the second terminal; and
a control circuit configured to enable the first driver and the second driver to concurrently drive a first signal through the first terminal and a second signal through the second terminal, respectively, and configured to adjust a delay between the first signal and the second signal based on the indication of the phase difference and a predetermined target phase difference.

### Claim 2 (depends on 1)

The system, as recited in claim 1, further comprising:
a first antenna coupled to the first terminal, the first antenna being configured to transmit a first Low Frequency (LF) signal in response to the first signal; and
a second antenna coupled to the second terminal, the second antenna being configured to transmit a second LF signal in response to the second signal.

### Claim 3 (depends on 1)

The system, as recited in claim 1, wherein the circuit comprises:
a discrete-Fourier transform circuit configured to compute a first digital frequency domain representation of the first signal and a second digital frequency domain representation of the second signal based on a digital version of the first signal and a digital version of the second signal; and
a digital circuit configured to generate the indication of the phase difference based on the first digital frequency domain representation and the second digital frequency domain representation.

### Claim 4 (depends on 1)

The system, as recited in claim 1, wherein the circuit comprises:
a storage circuit; and
a processor configured to execute instructions stored in the storage circuit, the instructions being executable by the processor to cause the processor to compute the indication of the phase difference based on a digital version of the first signal and a digital version of the second signal.

### Claim 5 (depends on 1)

The system, as recited in claim 1, further comprising:
a selectable delay element configured to provide a delayed data signal based on a digital data signal; and
a digital-to-analog converter circuit configured to convert the delayed data signal to an analog delayed data signal and to provide the analog delayed data signal as one of the first signal and the second signal,
wherein the first driver and the second driver each comprise a class AB amplifier circuit.

### Claim 6 (depends on 1)

The system, as recited in claim 1, further comprising:
a selectable delay element configured to provide a delayed data signal as one of the first signal and the second signal based on a digital delay code and a data signal; and
wherein the first driver and the second driver each comprise a class D amplifier circuit.

### Claim 7 (depends on 1)

The system, as recited in claim 1, wherein the predetermined target phase difference is zero degrees and after the control circuit adjusts the delay, the phase difference between the first current and the second current is within +/−10%.

### Claim 8 (depends on 1)

The system, as recited in claim 1, further comprising:
a plurality of terminals,
wherein the control circuit is configured to select for operation the first terminal and the second terminal from the plurality of terminals; and,
wherein other terminals of the plurality of terminals are disabled while the first terminal and the second terminal are selected for operation.

### Claim 9 (depends on 8)

The system, as recited in claim 8, further comprising:
a vehicle; and
a plurality of antennas positioned at locations around the vehicle to transmit a signal to a remote transceiver, the signal being a superposition of a first Low Frequency (LF) signal based on the first signal and a second LF signal based on the second signal, the predetermined target phase difference being zero degrees, and the first LF signal and the second LF signal having the same phase.

### Claim 10 (depends on 9)

The system, as recited in claim 9, further comprising:
a remote transceiver configured to receive a superposition of the first LF signal and the second LF signal.

### Claim 11

A method for increasing a range of an electromagnetic field generated using multiple antennas, the method comprising:
driving a first antenna by a first driver using a first signal;
driving a second antenna by a second driver using a second signal, the second signal being driven concurrently with the first signal;
determining a phase difference between a first current through the first driver and a second current through the second driver; and
adjusting at least one of the first signal and the second signal based on the phase difference and a predetermined target phase difference.

### Claim 12 (depends on 11)

The method, as recited in claim 11, wherein the adjusting comprises:
generating a phase compensation signal based on the phase difference and the predetermined target phase difference; and
delaying at least one of the first signal and the second signal using the phase compensation signal.

### Claim 13 (depends on 12)

The method, as recited in claim 12, wherein the phase compensation signal is a digital signal indicating an amount of delay selected to be inserted into a first pulse train of the first signal or a second pulse train of the second signal.

### Claim 14 (depends on 11)

The method, as recited in claim 11, wherein the phase difference is determined based on a time difference between a first maxima of a first magnitude of the first current and a second maxima of a second magnitude of the second current.

### Claim 15 (depends on 11)

The method, as recited in claim 11, wherein determining the phase difference comprises:
sensing the first current through the first driver;
sensing the second current through the second driver;
generating a first digital frequency domain representation of the first current; and
generating a second digital frequency domain representation of the second current,
wherein the phase difference is determined based on the first digital frequency domain representation and the second digital frequency domain representation.

### Claim 16 (depends on 11)

The method, as recited in claim 11, wherein the predetermined target phase difference is zero degrees, and after the adjusting, the phase difference between the first current and the second current is within +/−10%.

### Claim 17 (depends on 11)

The method, as recited in claim 11, wherein the predetermined target phase difference is zero degrees and after the adjusting, the phase difference between the first current and the second current is negligible.

### Claim 18 (depends on 11)

The method, as recited in claim 11, wherein the first antenna and the second antenna transmit a first LF signal and a second LF signal, respectively, the predetermined target phase difference being zero degrees and the first LF signal and the second LF signal having the same phase.

### Claim 19 (depends on 11)

The method, as recited in claim 11, further comprising:
selecting the first antenna and the second antenna from a plurality of antennas positioned at locations around a vehicle,
wherein the predetermined target phase difference is zero degrees and driving the first antenna and driving the second antenna cause transmission of a signal to a remote transceiver, the signal being a superposition of a first Low Frequency (LF) signal based on the first signal and a second LF signal based on the second signal, the first LF signal and the second LF signal having the same phase.

### Claim 20

A method for increasing a range of an electromagnetic field generated using multiple antennas, the method comprising:
concurrently driving a first antenna by a first driver and a second antenna by a second driver using a first signal and a second signal, respectively; and
delaying at least one of the first signal and the second signal based on a predetermined target phase difference and a phase difference between a first current through the first driver and a second current through the second driver.