High Q RF Resonant Cavity for Detecting Biological Tissue Nonlinearities

To investigate whether biological cells exhibit nonlinearity in the radiofrequency (RF) region, a high quality factor resonant cavity has been built. The cavity is fitted with two loop antennas, one transmitting at 880-890 MHz and a second one receiving at 1760-1790 MHz. The antenna operating at the low frequency (LF) band actively excites the TE$_{111}$ cavity mode; the high frequency antenna must receive the energy of the TE$_{113}$ mode at twice the frequency of the LF antenna. The cavity and the two antennas have been built. The Q of the cavity is over 6000 for both the frequencies of operation. Experiments to detect nonlinear RF frequency conversion by biological tissue can be performed using this high quality factor device.