RF precision heating apparatuses and methods
Apparatuses and methods for rapid heating a load having magnetic material(s). In some embodiments, the apparatus includes a source of radio frequency (RF) signals and a power management assembly that receives the RF signals and that increases or decreases power of the RF signals. The apparatus additionally includes directional coupler(s) that measure power of the RF signals received from the power management assembly and power of the RF signals reflected from the load to the at least one directional coupler. The apparatus further includes a control assembly operable to receive the measured powers, determine a temperature of the load based on the measured powers, and send one or more control signals to the power management assembly instructing the power management assembly to increase or decrease power of the RF signals received from the source of RF signals to maintain the determined temperature of the load at a predetermined temperature.
1. A heating apparatus for heating a load having at least one magnetic material, comprising:
a source of radio frequency (RF) signals;
a power management assembly that receives the RF signals and that increases or decreases power of the RF signals;
at least one directional coupler that measures power of the RF signals received from the power management assembly and power of the RF signals reflected from the load to the at least one directional coupler; and
a control assembly operable to:
receive the measured power of the RF signals received from the power management assembly and the measured power of the RF signals reflected from the load,
determine a temperature of the load based on the measured power of the RF signals received from the power management assembly and the measured power of the RF signals reflected from the load, and
send one or more control signals to the power management assembly instructing the power management assembly to increase or decrease power of the RF signals received from the source of RF signals to maintain the determined temperature of the load at a predetermined temperature,
wherein the control assembly includes:
a first power detector that converts a portion of the RF signals from the power management assembly into a first voltage;
a second power detector that converts a portion of the RF signals reflected from the load to the at least one directional coupler into a second voltage;
a comparator that compares the first and second voltages and generates an output voltage based on comparing the first and second voltages;
a low pass RC filter that receives the output voltage from the comparator; and
an amplifier that amplifies the output voltage from the low pass RC filter, the output voltage from the amplifier being the one or more control signals.
2. The heating apparatus of claim 1 , wherein the control assembly is further operable to:
calculate a reflection coefficient from the received measured power of the RF signals received from the power management assembly and the received measured power of the RF signals reflected from the load; and
send one or more control signals to the power management assembly instructing the power management assembly to increase or decrease power of the RF signals received from the source of RF signals to maintain a reflection coefficient that corresponds to the predetermined temperature.
3. The heating apparatus of claim 1 , wherein the power management assembly includes at least one of an attenuator or an amplifier.
4. The heating apparatus of claim 1 , further comprising at least one load capacitor that at least substantially reduces positive reactance of the load.
5. The heating apparatus of claim 1 , further comprising an attenuator that absorbs at least a substantial portion of the RF signals reflected from the load, wherein the at least one directional coupler is disposed between the attenuator and the load.
6. The heating apparatus of claim 1 , wherein the at least one directional coupler includes two single directional couplers.
7. The heating apparatus of claim 1 , wherein the at least one directional coupler includes a forward directional coupler and a reverse directional coupler, the forward directional coupler measures power of the RF signals received from the power management assembly, and the reverse directional coupler measures power of the RF signals reflected from the load.
8. The heating apparatus of claim 1 , wherein the at least one directional coupler includes a transformer coupler.
9. A method of heating a load having at least one magnetic material via radio frequency (RF) signals, comprising:
transmitting RF signals to heat the load;
measuring power of the RF signals transmitted to the load;
measuring power of RF signals reflected from the load;
determining a temperature of the load based on the measured power of the RF signals transmitted to the load and the measured power of RF signals reflected from the load; and
adjusting power of the RF signals transmitted to the load to maintain the determined temperature at a predetermined temperature, wherein adjusting power of the RF signals includes:
converting a portion of the transmitted RF signals into a first voltage,
converting a portion of the reflected RF signals into a second voltage,
comparing the first and second voltages,
generating an output voltage based on comparing the first and second voltages,
receiving the generated output voltage, and
adjusting the power of the RF signals transmitted to the load to maintain the determined temperature at the predetermined temperature via the received output voltage.
10. The method of claim 9 , further comprising calculating a reflection coefficient from the measured power of the RF signals transmitted to the load and the measured power of RF signals reflected from the load, wherein adjusting power of the RF signals transmitted to the load to maintain the determined temperature at a predetermined temperature includes adjusting power of the RF signals transmitted to the load to maintain a reflection coefficient that corresponds to the predetermined temperature.
11. The method of claim 9 , wherein the predetermined temperature is within a Curie point transition range in which the at least one magnetic material transitions between ferromagnetic and paramagnetic phases.
12. The method of claim 9 , further comprising at least substantially reducing positive reactance of the load.
13. The method of claim 9 , absorbing at least a substantial portion of the RF signals reflected from the load.
14. The method of claim 9 , wherein adjusting power of the RF signals transmitted to the load further includes amplifying the received output voltage and adjusting the power of the RF signals transmitted to the load to maintain the determined temperature at the predetermined temperature via the amplified output voltage.