Tag reader transmitter with high-Q antenna

1. A radio-frequency (RF) transmitter circuit comprising:

a controller circuit to generate transmission control signaling;

a modulator circuit to modulate a RF carrier wave having a fixed frequency with a baseband signal;

a RF driver circuit to be coupled to an antenna, the RF driver circuit to amplify the modulated carrier wave for transmission via the antenna;

a power control circuit to dynamically adjust supply power to the RF driver circuit in response to the transmission control signaling, wherein the supply power controls a degree of amplification applied by the RF driver circuit to control a strength of the transmission;

a field sensor to be coupled to the antenna and configured to measure a resonance condition of the transmission;

a resonance control circuit to dynamically adjust a resonance frequency of the antenna, in response to the transmission control signaling, to maintain resonance of the transmission at the fixed frequency of the carrierwave;

wherein in operation the controller circuit generates the transmission control signaling in response to a measured strength and the resonance condition of the transmission.

2. The RF transmitter circuit of claim 1 , further comprising the antenna, wherein the antenna has a quality factor Q of at least 100.

3. The RF transmitter circuit of claim 1 , further comprising the antenna, wherein the resonance control circuit is magnetically coupled to the antenna.

4. The RF transmitter circuit of claim 1 , wherein the field sensor outputs a phase error signal for use by the controller, the phase error signal representing an extent of deviation from resonance of the transmission.

5. The RF transmitter circuit of claim 4 , wherein the field sensor further outputs an amplitude error signal for use by the controller, the amplitude error signal representing an extent of deviation from a target amplitude of the transmission.

6. The RF transmitter circuit of claim 1 , wherein the transmission control signaling includes resonance control signaling supplied to the resonance control circuit, and power control signaling supplied to the power control circuit.

7. The RF transmitter circuit of claim 1 , wherein the controller circuit is to supply the baseband signal to the modulator circuit.

8. The RF transmitter circuit of claim 1 , wherein the RF transmitter circuit is part of a radio-frequency identification (RFID) reader device, and wherein the transmission is a RFID driving signal to activate a RFID tag.

9. The RF transmitter circuit of claim 1 , wherein the transmission control signaling includes first indicia corresponding to relatively shorter-distance transmission, and second indicia corresponding to relatively longer-distance transmission, wherein the second indicia calls for a higher supply power than supply power called for by the first indicia.

10. The RF transmitter circuit of claim 9 , wherein the RF driver circuit is constructed to generate:

at a first time, a first modulated carrier wave corresponding to the relatively shorter-distance transmission at the supply power called for by the first indicia; and

at a second time, a second modulated carrier wave corresponding to the relatively longer-distance transmission at the supply power called for by the second indicia.

11. The RF transmitter circuit of claim 9 , wherein the relatively shorter-distance transmission comprises a radio-frequency identification (RFID) tag driving signal to

activate a RFID tag, and wherein the relatively longer-distance transmission comprises a data-communication signal to be received by a remote receiver.

12. The RF transmitter circuit of claim 9 , wherein the higher supply power called for by the second indicia is at least 100 times greater than the supply power called for by the first indicia.

13. The RF transmitter circuit of claim 1 , wherein the power control circuit to is to dynamically adjust supply power to the RF driver circuit over a range of less than 10 V to greater than 100 V.

14. A radio-frequency (RF) transmitter circuit comprising:

a controller circuit to generate transmission control signaling that includes first indicia corresponding to relatively shorter-distance transmission, and second indicia corresponding to relatively longer-distance transmission;

a modulator circuit to modulate a RF carrier wave having a fixed frequency with a baseband signal;

a RF driver circuit to be coupled to an antenna, the RF driver circuit to amplify the modulated carrier wave for transmission via the antenna;

a power control circuit to dynamically adjust supply power to the RF driver circuit in response to the transmission control signaling, wherein the supply power controls a degree of amplification applied by the RF driver circuit to control a strength of the transmission, wherein a relatively lower strength of transmission corresponds to the first indicia, and a relatively higher strength of transmission corresponds to the second indicia;

wherein the RF driver circuit is constructed to generate:

at a first time, a first modulated carrier wave corresponding to the relatively shorter-distance transmission at the supply power called for by the first indicia; and

at a second time, a second modulated carrier wave corresponding to the relatively longer-distance transmission at the supply power called for by the second indicia.

15. The RF transmitter circuit of claim 14 , wherein the relatively shorter-distance transmission comprises a radio-frequency identification (RFID) tag driving signal to activate a RFID tag, and wherein the relatively longer-distance transmission comprises a data-communication signal to be received by a remote receiver.

16. The RF transmitter circuit of claim 14 , wherein the higher supply power called for by the second indicia is at least 100 times greater than the supply power called for by the first indicia.

17. The RF transmitter circuit of claim 14 , wherein the power control circuit to is to dynamically adjust supply power to the RF driver circuit over a range of less than 10 V to greater than 100 V.

18. The RF transmitter circuit of claim 14 , wherein the power control circuit to is to dynamically adjust supply power to the RF driver circuit over a range of less than 10 V to greater than 200 V.

19. The RF transmitter circuit of claim 14 , further comprising the antenna, wherein the antenna has a quality factor Q of at least 100.

20. The RF transmitter circuit of claim 14 , wherein the modulator circuit is to apply a dynamically-variable depth of modulation of the RF carrier wave based on a modulation control signal.