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Abstract
Potential demodulating ability in biological tissue exposed to radio-frequency (RF) signals intrinsically requires an unsymmetrical diode-like non-linear response in tissue samples. This may be investigated by observing possible generation of the second harmonic in a cavity resonator designed to have fundamental and second harmonic resonant frequencies with collocated antinodes. Such a response would be of interest as being a mechanism that could enable demodulation of information-carrying waveforms having modulating frequencies in ranges that could interfere with cellular processes. Previous studies have developed an experimental system to test for such responses: the present study reports a circuit model to facilitate calibration of any non-linear RF energy conversion occurring within a test-piece inside the cavity. The method is validated computationally and experimentally using a well-characterised non-linear device. The proposed model demonstrates that the sensitivity of the measurement equipment plays a vital role in deciding the required input power to detect any second harmonic signal, which is expected to be very weak. The model developed here provides a lookup table giving the level of the second harmonic signal in the detector as a function of the input power applied in a measurement. Experimental results are in good agreement with the simulated results.
Highlights
With the rapid growth of mobile communication usage over recent decades, public concerns have been raised about the possible biological effects of nonionising radiation with specific regard to radio-frequency (RF) radiation from mobile phones [1,2]
The purpose of the loaded test was to examine whether additional dielectric material introduced into the cavity, e.g. cells, tissue and/or medium, would result in any changes in resonant frequencies. In both test result graphs, the frequency fed to the transmitting antenna has been multiplied by a factor of two to enable direct comparison with second harmonic responses in the desired operating band
By using a simulated diode connected to very short dipole arms, the nonlinear response of the proposed model was established. For this rectifying element model, a nonlinear relationship was demonstrated between fundamental input power and second harmonic output power
Summary
With the rapid growth of mobile communication usage over recent decades, public concerns have been raised about the possible biological effects of nonionising radiation with specific regard to radio-frequency (RF) radiation from mobile phones [1,2]. Balzano, with co-workers, [8,9,10,11] has proposed novel experiments to detect the presence of asymmetrical (rectifying) nonlinear interactions at cellular or tissue-sample level, under exposure by low-amplitude RF carrier signals. These build on the observation that demodulation of a modulated carrier inherently requires such asymmetrical behaviour and this would necessarily cause the production of second harmonics. Such demodulation has been postulated as a plausible mode for putative non-thermal effects of RF radiation on any contiguous living system
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