Radio Frequency (RF) Tomography is proposed to detect underground voids, such as tunnels or caches, over relatively wide areas of interest.The RF tomography approach requires a set of low-cost transmitters and receivers deployed randomly on the surface of the ground, or slightly buried. Using the principles of inverse scattering and diffraction tomography, it is possible to develop a simplified theory for below-ground imaging, thus revealing and locating buried objects and hidden targets.In this work, we introduce the principles and our motivations in support of RF tomography. Furthermore, we derive simple inversion schemes for sensors randomly deployed in a 3D region. Then, we assess limitations to performance, and discuss some system considerations. Finally, we demonstrate the effectiveness of RF Tomography by presenting images reconstructed via the processing of synthetic data.

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We propose a new analog self-interference cancellation (SIC) technique for in-band full-duplex transmission (IBFD) in single-antenna systems. We use an RF circulator to separate transmitted (Tx) and received (Rx) signals. Instead of estimating the self-interference (SI) signals and subtracting them from the Rx signals, we use the inherent secondary SI signals at the circulator, reflected by the antenna, to cancel the primary SI signals leaked from the Tx port to the Rx port. We modified the frequency response of the secondary SI signals using a reconfigurable impedance mismatched terminal (IMT) circuit, which consists of two varactor diodes at the antenna port. We can also adjust the frequency band and bandwidth by controlling the varactor diodes bias voltages. The IMT adjustability makes it robust to antenna input impedance variations and fabrication errors. We analyze and fabricate a prototype of the proposed technique at 2.45 GHz. We achieved more than 40 dB cancellation over 65 MHz of bandwidth. Our technique is independent of the RF circulator and antenna type and it can be applied to any frequency band. It is also very relevant to small mobile devices because it provides a simple, low-power and low-cost adjustable analog SIC technique.

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We present an approach to performing rapid calculations of temperature within tissue by interleaving, at regular time intervals, 1) an analytical solution to the Pennes (or other desired) bioheat equation excluding the term for thermal conduction and 2) application of a spatial filter to approximate the effects of thermal conduction. Here, the basic approach is presented with attention to filter design. The method is applied to a few different cases relevant to magnetic resonance imaging, and results are compared to those from a full finite-difference (FD) implementation of the Pennes bio-heat equation. It is seen that results of the proposed method are in reasonable agreement with those of the FD approach, with about 15% difference in the calculated maximum temperature increase, but are calculated in a fraction of the time, requiring less than 2% of the calculation time for the FD approach in the cases evaluated.