Transceiver supporting multiple modulation schemes

• US 9,071,289 B2
• Filed: 04/23/2012
• Issued: 06/30/2015
• Est. Priority Date: 04/23/2012
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: McFarthing, Anthony
• Primary Examiner(s): Kim, Wesley
• Assistant Examiner(s): SANDIFORD, DEVAN A
• Application Number:
  US13/453,997
• Publication Number:
  US 20130281016A1
• Time in Patent Office: 1,163 Days
• Field of Search: 455/41.1, 455/41.2
• US Class Current: 1/1
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

The present application relates to a transceiver for use in a communications system that uses magnetic field induction to transmit data, the transceiver having an amplifier for driving an antenna, the amplifier forming, with a capacitance and a resistance connected in parallel with the antenna, a parallel resonant circuit. The resistance value of the resistance is adjustable, to permit adjustment of the loaded quality factor of the parallel resonant circuit. The transceiver includes a processing unit configured to determine the signal to noise ratio (SNR) of a signal received by the transceiver, and based on this SNR select a modulation scheme to apply to a data signal to be transmitted by the transceiver. The value of the resistance is adjusted to a level at which the loaded quality factor of the parallel resonant circuit is able to support the bandwidth and data rate required by the selected modulation scheme.

Claims

1. A transceiver for use in a communications system that uses magnetic field induction to transmit data, the transceiver comprising:

an antenna;

a transmit section including;

an amplifier for driving an antenna;

a capacitance connected in parallel with the antenna;

a resistance connected in parallel with the capacitance and the antenna, such that the antenna, capacitance and resistance form a parallel resonant circuit, wherein the value of the resistance is variable to permit adjustment of the loaded quality factor of the resonant circuit; and

a processing unit configured to determine a signal to noise ratio (SNR) of a signal received by the transceiver and to select, based on the determined SNR of the signal received by the transceiver, a modulation scheme for modulating a signal to be transmitted subsequently by the transceiver; and

a receive section, separate from the transmit section, the receive section including;

a resonant circuit comprising a variable resistance, a capacitance and a self-impedance of the antenna, the variable resistance of the receive section being implemented by inductive or capacitive degeneration.

2. A transceiver according to claim 1 wherein the value of the capacitance is variable, to permit tuning of a resonant frequency of the resonant circuit.

3. A transceiver according to claim 1 wherein the processing unit is configured to control the value of the resistance.

4. A transceiver according to claim 1 wherein the processing unit is configured to adjust the value of the resistance to adjust the loaded quality factor of the parallel resonant circuit to support the signal bandwidth required by the selected modulation scheme.

5. A transceiver according to claim 1 wherein the value of the capacitance is variable to permit tuning of a resonant frequency of the parallel resonant circuit, the processing unit being configured to control the value of the capacitance.

6. A transceiver according to claim 1 wherein the power amplifier is implemented by one or more transistors.

7. A transceiver according to claim 6 wherein the transistors are PMOS or NMOS transistors.

8. A transceiver according to claim 1 wherein the resistance is implemented by one or more variable cascodes.

9. A transceiver according to claim 1 wherein the capacitance is implemented by one or more digitally variable capacitors.