Apparatus and method for compensation of AM noise in RFID devices through modulation of a received signal
A method and apparatus for compensation of noise in a Radio Frequency Identification (RFID) device through modulation of a received signal is described. The method includes determining an amplitude signal proportional to an amplitude of a transmitter signal and associated noise; processing the amplitude signal to derive a correction signal; and modulating a received signal during a receive period with the correction signal to substantially remove the associated noise from the received signal. An RFID device and an RFID transceiver integrated circuit (IC) are also described.
1. A method for compensation of noise in a Radio Frequency Identification (RFID) device through modulation of a received signal, the method comprising:
determining an amplitude signal proportional to an amplitude of a transmitter signal and associated noise;
processing the amplitude signal to derive a correction signal through a programmable stage that amplifies the amplitude signal and creates the correction signal; and
modulating a received signal during a receive period with the correction signal to substantially remove the associated noise from the received signal.
2. The method of claim 1 , further comprising:
processing the amplitude signal to derive the correction signal inversely proportional to an amplitude of the amplitude signal; and
modulating the received signal by multiplying the received signal by the correction signal to reduce the associated noise on the received signal.
3. The method of claim 1 , wherein a percentage of modulation required is independent of a level and phasing of the received signal, and further comprising:
continuing the modulating regardless of changes in the level and the phasing of the received signal.
4. The method of claim 1 , further comprising:
performing the modulating at a receiver section; and preventing changes or transitions in a transmitter between modulated and un-modulated modes that cause off-channel emissions.
5. The method of claim 1 , further comprising:
modulating the received signal by dividing the received signal by the correction signal to reduce the associated noise on the received signal.
6. The method of claim 1 , further comprising:
determining the amplitude signal either by processing a baseband signal or detecting the amplitude signal at RF.
7. The method of claim 1 , further comprising:
adjusting the programmable stage during a calibration such that modulation applied to the transmitter is removed from the received signal.
8. The method of claim 1 , further comprising:
modulating the received signal through continuously variable gain in a receiver RF path which is controlled by the correction signal to apply a compensating amplitude modulation to the received signal.
9. The method of claim 1 , further comprising:
performing the modulating utilizing a parasitic LO multiplier Gilbert cell.
10. The method of claim 1 , further comprising:
performing the modulating utilizing a parasitic RF multiplier Gilbert cell.
11. The method of claim 1 , further comprising:
performing the modulating utilizing a parasitic Tayloe multiplier.
12. A Radio Frequency Identification (RFID) device, the RFID device comprising:
a transmitter;
a receiver;
a coupling device coupling the transmitter and the receiver to an antenna;
a noise compensation function comprising circuitry configured to:
determine an amplitude signal proportional to an amplitude of a transmitter signal and associated noise from the transmitter;
process the amplitude signal to derive a correction signal through a programmable stage that amplifies the amplitude signal and creates the correction signal; and
modulate a received signal during a receive period from the receiver with the correction signal to substantially remove the associated noise from the received signal.
13. The RFID device of claim 12 , wherein the circuitry is further configured to:
process the amplitude signal to derive the correction signal inversely proportional to an amplitude of the amplitude signal; and modulate the received signal by multiplying the received signal by the correction signal to reduce the associated noise on the received signal.
14. The RFID device of claim 12 , wherein the circuitry is further configured to:
modulate the received signal by dividing the received signal by the correction signal to reduce the associated noise on the received signal.
15. The RFID device of claim 12 , wherein the circuitry is further configured to:
determine the amplitude signal either by processing a baseband signal or detecting the amplitude signal at RF.
16. The RFID device of claim 12 , wherein the circuitry is further configured to:
adjust the programmable stage during a calibration such that modulation applied to the transmitter is removed from the received signal.
17. The RFID device of claim 12 , wherein the circuitry is further configured to:
modulate the received signal through continuously variable gain in a receiver RF path which is controlled by the correction signal to apply a compensating amplitude modulation to the received signal.
18. A Radio Frequency Identification (RFID) transceiver integrated circuit, the RFID transceiver integrated circuit comprising:
a transmitter;
a receiver, wherein each of the transmitter and the receiver are configured to utilize a same antenna;
a noise compensation function comprising circuitry configured to:
determine an amplitude signal proportional to an amplitude of a transmitter signal and associated noise from the transmitter;
process the amplitude signal to derive a correction signal through a programmable stage that amplifies the amplitude signal and creates the correction signal; and
modulate a received signal during a receive period from the receiver with the correction signal to substantially remove the associated noise from the received signal.