Patent ID: 9161394
Filing Date: 2015-10-13
Classification: H05B

Abstract:
1. A microwave heating apparatus comprising: a cavity arranged to receive a load; a microwave generator arranged to generate microwaves to heat the load; a transmission line arranged to transmit the generated microwaves to the cavity; a sensing device arranged to measure electromagnetic field strengths at four different positions along the transmission line, wherein the spacing between two adjacent position is approximately equal to λ/8+n×λ/2, wherein λ is a wavelength corresponding to the operating frequency of the microwave generator or a mid-value of wavelengths available in a operating frequency band of said microwave generator and n is an integer, and wherein the measured field strengths at all four positions provide information about the phase of a reflection coefficient being representative of the ratio between the amount of microwaves reflected back towards the microwave generator and the amount of microwaves transmitted in the transmission line from the microwave generator and measured field strengths at the two adjacent positions provide information on complex impedance experienced at the microwave generator; and a control unit configured to control the frequencies of the microwaves to the cavity based on the reflection coefficient and the complex impedance.