Search

A new multimode microwave applicator has been designed and constructed to provide efficient energy coupling and uniform heating of specimens at 2.45 GHz. The applicator is circular cylindrical with a diameter of 12.9 inches (32.8 cm) and a motorized endwall producing periodic variation of the cavity length between 7 inches (17.8 cm) and 13 inches (33.0 cm). The positions of the endwall cause 19 distinct and identified modes to be scanned. The close proximity of the resonant modes in this applicator as a function of the length of the applicator provides significant mode overlap in the presence of a load. The mode overlap results in a constant input impedance as the length of the cavity changes. The input impedance of the applicator can therefore be matched over a range of different loads.

An idealized transmission moisture sensor is described incorporating means for controlling the temperature and moisture content of the sample. A theory is developed based upon the constitutive parameters of the material. An independent measurement of these parameters by means of the short circuited line method leads to an evaluation of the theory, It is found thai a zero order theory is adequate for most applications.