Systems and methods for providing modulation of switchmode RF power amplifiers
View Patent ↗Systems and methods are provided for generating an amplitude modulation signal to a switchmode power amplifier. A DC to DC switch is configured to receive a DC input voltage and to provide a DC output voltage. A low dropout regulator is configured to provide the amplitude modulation signal according to a modulation control signal received by the low dropout regulator. A control circuit is configured to establish a nominal operating power level for the power amplifier via the amplitude modulation signal and to maintain a minimum voltage difference between the DC output voltage and the low dropout regulator output. A modulator control circuit is configured to provide the modulation control signal to the low dropout regulator. The modulator control circuit provides the transition from a high amplitude to a low amplitude and a transition from the low amplitude to the high amplitude at configurable first and second slopes, respectively.
1. An apparatus for generating an amplitude modulation signal, comprising:
a modulator control circuit configured to generate a modulation control signal including transitions from a high amplitude to a low amplitude back to a high amplitude, the modulator control circuit is configured to provide the transition from the high amplitude to the low amplitude at a first slope, the modulator control circuit is configured to provide the transition from the low amplitude to the high amplitude at a second slope, wherein the modulator control circuit is adapted to selectively configure at least one of the first and second slopes to comply with a spectral mask; and
a low dropout regulator configured to receive the modulation control signal from the modulator control circuit and provide the amplitude modulation signal according to the modulation control signal.
2. The apparatus of claim 1 , further comprising a switchmode power amplifier responsive to the amplitude modulation signal, the switchmode power amplifier configured to provide an AC output signal proportional to the amplitude modulation signal.
3. The apparatus of claim 2 , wherein the modulator control circuit is adapted to selectively configure at least one of the first and second slopes to reduce the spectral density of the AC output signal.
4. The apparatus of claim 3 , wherein the spectral density is reduced to comply with the spectral mask.
5. The apparatus of claim 1 , wherein the modulation control signal is configured to remain at the low amplitude for a dwell time, wherein the modulator control circuit controls the length of the dwell time.
6. The apparatus of claim 1 , wherein the modulator control circuit is configured to receive a first slope input, a second slope input, and a data input, wherein the modulation control signal is a representation of the data input, wherein the first slope is controlled by the first slope input, wherein the second slope is controlled by the second slope input.
7. The apparatus of claim 1 , wherein the modulator control circuit is configured to receive a modulation depth input, wherein a difference between the high amplitude and the low amplitude is controlled by the modulator control circuit according to the modulation depth input.
8. The apparatus of claim 2 , wherein the AC output signal is connected to an antenna.
9. The apparatus of claim 8 , wherein the antenna is configured to output an interrogation signal to an RFID circuit that responds to the interrogation signal.
10. The apparatus of claim 9 , wherein the interrogation signal is proportional to the AC output signal.
11. The apparatus of claim 9 , wherein the RFID circuit is attached to one of a medical sponge and a medical instrument.
12. The apparatus of claim 9 , wherein the antenna is configured for use in a medical environment, wherein the modulator control circuit is adapted to selectively configure at least one of the first and second slopes to reduce interference with electronic medical devices.
13. The apparatus of claim 12 , wherein the modulator control circuit is adapted to selectively configure at least one of the first and second slopes to reduce interference with a heart pacemaker.
14. The apparatus of claim 1 , further comprising a DC to DC switch configured to receive a DC input voltage and to provide a DC output voltage, wherein the low dropout regulator is powered by the DC output voltage.
15. The apparatus of claim 14 , further comprising a control circuit connected the DC to DC switch and the low dropout regulator.
16. The apparatus of claim 15 , wherein the control circuit is configured to establish a nominal operating power level for the power amplifier via the amplitude modulation signal.
17. The apparatus of claim 15 , wherein the control circuit is configured to maintain a minimum voltage difference between the DC output voltage and an output of the low dropout regulator.
18. The apparatus of claim 17 , wherein the minimum voltage difference is set at a particular level.
19. An apparatus for generating an amplitude modulation signal for an antenna configured for use in a medical environment, the apparatus comprising:
a modulator control circuit configured to generate a modulation control signal including transitions from a high amplitude to a low amplitude back to a high amplitude, the modulator control circuit configured to provide the transition from the high amplitude to the low amplitude at a first slope, the modulator control circuit configured to provide the transition from the low amplitude to the high amplitude at a second slope, wherein the modulator control circuit is adapted to selectively configure at least one of the first and second slopes to reduce interference with electronic devices in the medical environment; and
a low dropout regulator configured to receive the modulation control signal from the modulator control circuit and provide the amplitude modulation signal according to the modulation control signal.