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.