A dielectrically loaded rectangular cavity is studied for its multimode behavior. A graphical method in calculating numbers of resonant modes for a given frequency band width is suggested and is shown to be very effective in understanding the mode structure. One may show from this analysis that surface wave modes exist in the dielectrically loaded cavity. An expression for the input imepedance and quality factor Q of the cavity for this surface wave mode has been derived for the case when a probe is used for the excitation of the cavity.
The number of resonant modes are measured for a cavity loaded with paraffin wax. For a surface wave mode, in particular, Q and the input impedance of the loaded cavity are measured and compared with the theory, which shows a close agreement.