Heating of objects by microwave energy

Patent metadata

Field	Value
Publication number	US-10893581-B2
Application number	US-201515322329-A
Country	US
Kind code	B2
Filing date	Jun 30, 2015
Priority date	Jun 30, 2014
Publication date	Jan 12, 2021
Grant date	Jan 12, 2021

Abstract

An apparatus for heating a load with microwave energy is provided. The microwave energy is applied by the apparatus at frequencies wherein the load's dielectric constant is within a predetermined range. The apparatus may include a microwave power source configured to supply microwave energy at the applied frequencies; and a radiating plate. The radiating plate may include an electrically conductive structure that includes a plurality of radiating elements; and a feeding port, connecting the electrically conductive structure to the microwave power source. The radiating plate is configured so that most of the power fed from the microwave source through the feeding port returns towards the power source when no load is contacting the radiating plate, and most of the power fed from the microwave source through the feeding port is absorbed by the load to be heated by the apparatus when the load is contacting the radiating plate, even in absence of a microwave cavity that encloses the radiating plate and the load.

First claim

The invention claimed is:

1. A heating apparatus for heating an object, the apparatus comprising an enclosure for accepting the object adjacent to a radiating plate for heating and a microwave power source coupled to the radiating plate and configured to feed the radiating plate at one or more microwave frequencies, wherein:
the radiating plate is an object heating radiating plate configured to heat the object with feed signals having a range of microwave working frequencies of between 300 MHz and 3 GHz, and the radiating plate comprises:
a ground plate; and
at least one or more radiating elements spaced from the ground plate by a dielectric layer,
wherein at least a size and a shape of the one or more radiating elements and at least a thickness of the dielectric layer satisfy the following conditions:
a free space efficiency of the radiating plate is less than −6 dB and a contact efficiency of the radiating plate is greater than 50%,
the free space efficiency is a ratio of power not returned from the radiating plate to power fed to the radiating plate at a test frequency in the range of working frequencies in a free space condition in which there is a volume of free space covering the radiating plate,
the contact efficiency is a ratio of power not returned from the radiating plate when a test load rests on top of the radiating plate to power fed to the radiating plate at the test frequency, and
the test load has a dielectric constant in the range of 20 to 60 and a loss tangent in the range of 0.1 to 0.5 at the test frequency,
wherein said conditions are configured to provide a first amount of energy transfer from the radiating plate to the test load with the radiating plate being in contact with the test load while providing a second amount of energy transfer, smaller than the first amount, with the radiating plate not being in contact with the test load.

2. The heating apparatus according to claim 1 , wherein the free space efficiency of the radiating plate is less than −6 dB and the contact efficiency of the radiating plate is greater than 0.5 for test loads having respective dielectric constants of 20, 40 and 60.

3. The heating apparatus according to claim 1 , wherein the free space efficiency of the radiating plate is less than −6 dB and the contact efficiency of the radiating plate is greater than 0.5 for test loads having respective loss tangents of 0.1, 0.3 and 0.5.

4. The heating apparatus according to claim 1 , wherein the dielectric layer comprises an air layer.

5. The heating apparatus according to claim 1 , further comprising a dielectric cover layer covering the one or more radiating elements on a side of the one or more radiating elements not facing the dielectric layer, wherein the dielectric cover layer is made from food grade material.

6. The heating apparatus according to claim 1 , wherein the radiating plate is structured and arranged to act as a load bearing plate capable of supporting a weight of 1 kg.

7. The heating apparatus according to claim 1 , further comprising a plurality of decoupled radiating elements decoupled from each other at the microwave working frequencies, each fed by a respective feed.

8. The heating apparatus according to claim 7 , wherein pairs of the plurality of decoupled radiating elements are decoupled by a respective choke.

9. The heating apparatus according to claim 1 , wherein the one or more radiating elements are printed on the dielectric layer.

10. The heating apparatus as claimed in claim 1 , wherein the radiating plate is disposed in a tray configuration, enabling the object to rest on top of the radiating plate when the object is disposed adjacent to the radiating plate.

11. The heating apparatus as claimed in claim 1 , wherein the radiating plate is disposed so that the object disposed in the enclosure for heating rests below the radiating plate.

12. The heating apparatus as claimed in claim 10 , wherein a plurality of radiating plates are mutually spaced in a vertical direction to accommodate the object between each pair of the plurality of radiating plates.

13. The heating apparatus as claimed in claim 1 , the apparatus further comprising:
a controller coupled to the microwave power source and configured to control the microwave power source based on feedback received from the radiating plate.

14. The heating apparatus as claimed in claim 13 , wherein the controller is configured to change one of:
frequency;
phase between a pair of feeding ports;
amplitude of one feeding port relative to another feeding port;
frequency, and phase between a pair of feeding ports;
frequency, and amplitude of one feeding port relative to another feeding port;
frequency, phase between a pair of feeding ports, and amplitude of one feeding port relative to another feeding port; and
phase between a pair of feeding ports, and amplitude of one feeding port relative to another feeding port,
according to which energy is supplied to increase the contact efficiency in response to the feedback.

15. The heating apparatus as claimed in claim 13 , wherein the microwave power source is configured to selectively couple one or more feeds of the radiating plate to the microwave power source and the controller is configured to increase the contact efficiency, in response to the feedback.

16. The heating apparatus as claimed in claim 1 , further comprising: a secondary heating arrangement, wherein a controller is arranged to cause heating of the test load using the secondary heating arrangement until the contact efficiency is estimated to have risen above a threshold value and cause heating of the test load using the radiating plate once the contact efficiency is estimated to have risen above the threshold value.

17. The heating apparatus as claimed in claim 16 , wherein the secondary heating arrangement comprises a microwave heating arrangement.

18. The heating apparatus as claimed in claim 16 , wherein the secondary heating arrangement comprises a convection heater for causing circulation of heated air around the object.

19. The heating apparatus as claimed in claim 16 , wherein the secondary heating arrangement is a resistive or inductive heating arrangement comprising a resistive or inductive heating element.

20. The heating apparatus as claimed in claim 19 , wherein the resistive or inductive heating element is embedded in the radiating plate.

21. A heating apparatus for heating an object, the apparatus comprising an enclosure for accepting the object adjacent to a radiating plate for heating and a microwave power source coupled to the radiating plate and configured to feed the radiating plate at one or more microwave frequencies, wherein:
the radiating plate is an object heating radiating plate, configured to heat the object with feed signals having a range of microwave working frequencies of between 300 MHz and 3 GHz, and the radiating plate comprises:
a ground plate; and
at least one or more radiating elements spaced from the ground plate by a dielectric layer,
wherein at least a size and a shape of the one or more radiating elements and at least a thickness of the dielectric layer satisfy the following conditions:
the one or more radiating elements are configured to resonate at a wavelength corresponding to a test frequency within the range of microwave working frequencies in a medium having a dielectric constant in the range of 20 to 60 and a loss tangent in the range of 0.1 to 0.5,
wherein said conditions are configured to provide a first amount

Assignees

• Goji Ltd

Inventors

• Ibragimov Zalman

Classifications

• H05B6/6494 Primary

  for cooking · CPC title

• H05B6/6488

  combined with induction heating · CPC title

• H05B6/6473 Primary

  combined with convection heating (H05B6/6485 takes precedence) · CPC title

• H05B6/682

  wherein the switching control is based on measurements of electrical values of the circuit · CPC title

• H05B6/72

  Radiators or antennas · CPC title