Dynamic impedance matching in RF resonator cavity

• US 20090057302A1
• Filed: 08/28/2008
• Published: 03/05/2009
• Est. Priority Date: 08/30/2007
• Status: Active Grant

• Current Assignee: Joliet 2010 Limited
• Original Assignee: RF Dynamics Ltd.
• Inventors: Bilchinsky, Alexander, Ben-Shmuel, Eran
• Granted Patent: US 9,131,543 B2
• Time in Patent Office: Days
• US Class Current: 219/748
• CPC Class Codes: A23L 5/15 using wave energy, irradiation, electrical means or magnetic fields, e.g. oven cooking or roasting using radiant dry heat
• CPC Class Codes: A23V 2002/00 Food compositions, function of food ingredients or processes for food or foodstuffs
• CPC Class Codes: H05B 6/6402 Aspects relating to the microwave cavity
• CPC Class Codes: H05B 6/6447 Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors
• CPC Class Codes: H05B 6/705 using microwave tuning
• CPC Class Codes: H05B 6/72 Radiators or antennas
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

A method for matching an impedance of a system comprising a cavity and one or more feeds to an impedance of one or more sources of electromagnetic radiation irradiating a plurality of frequencies into the cavity via the feeds, comprising: determining a plurality of s-parameter of the system for a frequency band; determining the system impedance based on the s-parameters; and modifying the system impedance according to the difference between the impedance of the system and the impedance of the source.

Claims

1. A method for matching an impedance of a system comprising a cavity and one or more feeds to an impedance of one or more sources of electromagnetic radiation irradiating a plurality of frequencies into the cavity via the feeds, comprising:

(a) determining the system impedance of the system for a frequency band; and

(b) modifying the system impedance to obtain a better match between the impedance of the system and the impedance of the one or more sources.

2. A method according to claim 1, wherein said system impedance is determined by a plurality of s-parameters of the system.

3. A method according to claim 1, wherein the plurality of frequencies comprises RF radiation in a microwave region.

4. A method according to claim 1, wherein a frequency band comprises a smaller bandwidth relative to the source'"'"'s plurality of frequencies.

5. A method according to claim 2, wherein determining a plurality of s-parameter comprises:

(a) irradiating one or more frequency bands into the cavity by one or more antennas;

(a) measuring reflected energy by one or more antennas; and

(b) determining one or more relations between the reflected energy and the irradiated energy at one or more bands.

6. A method according to claim 1, wherein the impedance of at least one source is a resistance.

7. A method according to claim 6, wherein the resistance of at least one source is 50Ω

.

8. A method according to claim 1, wherein the system impedance comprises a combination of the impedance of the feed and the cavity.

9. A method according to claim 1, wherein varying the impedance of the feed comprises varying at least one of the capacitance or induction or resistance or transformer'"'"'s impedance ratio in the feed.

10. A method according to claim 1, wherein varying the impedance of the cavity comprises moving a one or more elements inwards or outwards in the cavity.

11. A method according to claim 1, wherein varying the impedance of the cavity comprises moving an element in the cavity.

12. A method according to claim 1, wherein varying the impedance of the cavity comprises varying the shape of an element in the cavity.

13. A method according to claim 1, wherein the cavity is a resonant cavity.

14. A method according to claim 1, wherein the cavity contains a removable added object.

15. A method according to claim 14, wherein the object is heated by the irradiated energy.

16. A method according to claim 15, wherein the object comprises food.

17. A method according to claim 14, wherein the system impedance comprises a combination of the impedances of the feed, of the cavity and of the object.

18. A method according to claim 1, wherein varying the impedance of the cavity comprises moving said object in the cavity.

19. A method according to claim 1, wherein the impedance matching is repeated a plurality of times during the irradiation.

28. An electromagnetic radiation heater which performs the method of claim 1.

20. A method for determining a match of an impedance of a system comprising a cavity and one or more feeds to an impedance of one or more sources of electromagnetic radiation irradiating a plurality of frequencies into the cavity via the feeds, comprising:

(a) determining a plurality of s-parameter of the system for a frequency band;

(b) calculating an absorption intensity in the cavity at the band; and

(c) enlarging the calculated absorption at the band by varying an impedance of at least the feed or the cavity.

21. A method according to claim 20, wherein enlarging the calculated absorption comprises maximizing the calculated absorption.

22. A method according to claim 21, wherein maximizing comprises maximizing within a threshold.

29. An electromagnetic radiation heater which performs the method of claim 20.

23. A method for improving an absorption of electromagnetic energy from a source irradiating at a plurality of frequencies into a cavity via one or more feeds in a system comprising the cavity and the feeds, comprising:

(a) determining a plurality of s-parameter of the system for a frequency band;

(b) determining an absorption intensity in the cavity at the band; and

(c) enlarging the absorption at the band by varying the impedance of at least one of the feed, the feed matching circuitry and the cavity.

24. A method according to claim 23, wherein enlarging the absorption comprises maximizing the absorption.

25. A method according to claim 24, wherein maximizing comprises maximizing within a threshold.

26. A method according to claim 23, wherein improving the absorption is repeated a plurality of times during the irradiation.

27. A method according to claim 23, wherein varying the impedance of at least the feed or the cavity is performed responsive to a predefined change in the energy absorption at one or more frequencies.

30. An electromagnetic radiation heater which performs the method of claim 23.