Near field communications apparatus
First Claim
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1. A near field communications (NFC) apparatus comprising:
- a transmit antenna;
a signal source configured to generate a chirp signal which is transmitted using the transmit antenna, the chirp signal having a frequency that increases from an initial frequency to a final frequency over a period of time;
a receive section coupled to the transmit antenna and configured to detect changes in an input impedance of the transmit antenna as the frequency of the chirp signal changes; and
a processor configured to determine, based on the detected changes in the input impedance of the transmit antenna, whether a compatible NFC device is within an operating range of the NFC apparatus and whether the compatible NFC device is either a passive NFC device or an active NFC device;
wherein the receive section is configured to detect a change in a real part or an imaginary part of the input impedance of the transmit antenna, andwherein the processor is configured to;
identify the passive NFC device based on the detected change in the real part of the input impedance of the transmit antenna;
oridentify the active NFC device based on the detected change in the imaginary part of the input impedance of the transmit antenna.
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Abstract
A near field communications apparatus comprising a signal source, a transmit antenna and means for detecting a change in the input impedance of the transmit antenna to detect the presence of a device which is compatible with the apparatus.
48 Citations
16 Claims
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1. A near field communications (NFC) apparatus comprising:
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a transmit antenna; a signal source configured to generate a chirp signal which is transmitted using the transmit antenna, the chirp signal having a frequency that increases from an initial frequency to a final frequency over a period of time; a receive section coupled to the transmit antenna and configured to detect changes in an input impedance of the transmit antenna as the frequency of the chirp signal changes; and a processor configured to determine, based on the detected changes in the input impedance of the transmit antenna, whether a compatible NFC device is within an operating range of the NFC apparatus and whether the compatible NFC device is either a passive NFC device or an active NFC device; wherein the receive section is configured to detect a change in a real part or an imaginary part of the input impedance of the transmit antenna, and wherein the processor is configured to; identify the passive NFC device based on the detected change in the real part of the input impedance of the transmit antenna;
oridentify the active NFC device based on the detected change in the imaginary part of the input impedance of the transmit antenna. - View Dependent Claims (2, 3, 4, 5, 11, 12, 13)
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6. A method of operating a near field communications (NFC) apparatus, the method comprising:
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transmitting a chirp signal generated by a signal source using a transmit antenna, the chirp signal having a frequency that increases from an initial frequency to a final frequency over a period of time; receiving, at a receive section of the NFC apparatus, a current that is proportional to a current in the transmit antenna; detecting changes in an input impedance of the transmit antenna as the frequency of the transmitted chirp signal changes, wherein the detecting comprises detecting a change in a real part or an imaginary part of the input impedance of the transmit antenna; determining, based on the detected changes in the input impedance of the transmit antenna, whether a compatible NFC device is within an operating range of the NFC apparatus and whether the compatible NFC device is a passive NFC device or an active NFC device; and identifying the passive NFC device based on the detected change in the real part of the input impedance of the transmit antenna, or identifying the active NFC device based on the detected change in the imaginary part of the input impedance of the transmit antenna. - View Dependent Claims (7, 8, 9, 10, 14, 15, 16)
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Specification