Jamming Effects on Hybrid Multistatic Radar Network Range and Velocity Estimation Errors

This research studies the effects of three noise jamming techniques on the performance of a hybrid multistatic radar network in a selection of different electronic warfare (EW) situations. The performance metrics investigated are the range and velocity estimation errors found using the Cramér-Rao lower bounds (CRLBs). The hybrid multistatic network simulated is comprised of a single active radar transmitter, three illuminators of opportunity (IO), a receiver co-located at the active transmitter site, and two separately located silent receivers. Each IO transmits at a unique frequency band commonly used for civilian applications, including Digital Video Broadcasting-Terrestrial (DVB-T), Digital Audio Broadcasting (DAB), and FM radio. Each receiver is capable of receiving signals at all three IO frequency bands as well as the operating frequency band of the active radar transmitter. The investigations included compare the performance of the network at detecting a single flying target under conditions where different combinations of jammer type, operating mode, directivity, and number of jammers operating are used. The performance degradation of the system compared to operation in a non-contested environment is determined and a comparison between the performance of the hybrid multistatic radar with that achievable by a monostatic radar and an active-only multistatic radar network within a selection of contested scenarios is made. Results show that the use of spatially distributed nodes and frequency diversity within the system enable greater theoretical functionality in the presence of jamming over conventional radar systems

Decoding the protein-DNA recognition rules

The C2H2 zinc finger (ZF) transcription factors (TF) form the largest family of DNA binding proteins in eukaryotes. TFs are key proteins involved in gene regulation that bind to specific DNA sites. A major obstacle towards understanding the molecular basis of transcriptional regulation is the lack of a recognition code for protein-DNA interactions. We aim to understand molecular mechanisms of DNA recognition and to quantitatively estimate recognition rules for TF-DNA interactions. We identified key residues playing an important role in ZF-DNA interactions and found that they are prealigned to conformations observed in the bound state prior to binding. A binding site for Cl- ions corresponding to the pocket where DNA phosphates are found most buried in the complex of ZFs is identified. Bound ions constrain conformations of important residues consistent with observations of increased binding affinity with increased ionic strength in protein-DNA interactions. These results suggest a general mechanism where ZFs, through their key residues, rapidly form encounter complexes amenable for a fast readout of the DNA. We developed a novel experimentally-based approach using crystal structures and binding data on the C2H2 ZFs and decoded ten fundamental specific interactions for protein-DNA recognition. These are: Five hydrogen bonds, three desolvation penalties, a non-polar energy, and a novel water accessibility factor. The code is applied to three data sets with a total of 89 ZF mutants on three ZFs of EGR. Guided by simulations of individual ZFs, we mapped the interactions into homology models with all feasible intra- and inter- molecular bonds and selected the structure with the lowest free energy for each ZF. The interactions reproduce changes in affinity of 35 mutants of finger I (FI) (R2 = 0.99), 23 mutants of FII (R2 = 0.97) and 31 human ZFs on FIIII (R2 = 0.95). The method predicts bound ZF-DNA complexes for all mutants, decoding molecular basis of ZF-DNA specificity. These findings reveal recognition rules that depend on DNA sequence/structure, molecular water at the interface and induced fit of the C2H2 TFs. In summary, our method provides the first robust framework to decode the molecular basis of TFs binding to DNA

Examining Food Quality via RFID Tag Array

Radio-frequency identification (RFID) tags are widely used in the food supply chain where they can be used to hold identification data of tagged objects. They can also be used to provide information related to the quality and safety of the tagged object. This can be achieved by analyzing the RF signals emitted by the tag which couples with the tagged objects, and hence can be used to acquire useful information related to the safety and quality of that object. This paper investigates the correlation between the radiated signals from the tags and the quality characteristics of the tagged objects. It focuses on analyzing the mutual coupling between the tags in an array, in particular, of orthogonal polarization configuration, which shows that more information can be extracted by an array of tags compared to the use of a single RFID tag emitter

An Experimental Study of Radar-Centric Transmission for Integrated Sensing and Communications

This study proposes a dual-function radar and communication (DFRC) system that utilizes radar transmission parameters as modulation indexes to transmit data to the users while performing radar sensing as its primary function. The proposed technique exploits index modulation (IM) using the center frequency of radar chirps, their bandwidths, and polarization states as indexes to modulate the communication data within each radar chirp. By utilizing the combination of these indexes, the proposed DFRC system can reach up to 17 Mb/s throughput, while observing a robust radar performance. Through our experimental study, we also reveal the trade-off between the radar sensing performance and communication data rate, depending on the radar waveform parameters selected in the DFRC system. This study also demonstrates the implementation of the proposed DFRC system and presents its real-time over-the-air experimental measurements. Consequently, the simulation results are verified by real-time over-the-air experiments, where ARESTOR, a high-speed signal processing and experimental radar platform, has been employed

Erythema Multiforme After Third Covid-19 Vaccination (Pfizer-biontech)

We present a case of erythema multiforme (EM) associated with a third (booster) dose of COVID-19 vaccination in a patient who had no cutaneous reactions to previous doses. To our knowledge, this is the first documented case of vaccine-associated EM occurring after a third/booster vaccination. Furthermore, our case emphasizes the need to remain vigilant for vaccine-associated EM in any patient recently vaccinated, regardless of whether previous vaccinations were administered without cutaneous reactions

Multibeam Cylindrical Conformal Array in the Presence of Enhanced Mutual Coupling

The limitations of conventional sensors have made array antennas increasingly crucial for gathering information and communication applications in intelligent transportation and communication systems. Compact cylindrical arrays are particularly favored for their ability to achieve azimuth angle scanning. However, the substantial mutual coupling effect between the elements on curved surfaces and its implication for these arrays remain unclear, which is a key factor to consider when such arrays are used for multibeam applications. This study investigates the effect of mutual coupling in a dual-slant-polarized cylindrical array. The results showed that mutual coupling is predominantly observed among the closely located elements, and it is essential for achieving an ultra-wide bandwidth. The study also analyzes the impact of mutual coupling on the scan impedance and radiation characteristics for multibeam applications and reveals that these arrays exhibit robust multibeam capability, hence having great potential for use in sensing and communication applications

Calibration of Aperture Arrays in Time Domain Using the Simultaneous Perturbation Algorithm

Online calibration is desired in antenna arrays of ultrawide bandwidth. This study proposes a time domain calibration method based on the simultaneous perturbation algorithm. Two objective functions were established: power of the received signal at array output; or combination of power and correlation coefficient between the signal at array output and a target signal. For both criteria, the convergence settings require only two measurements at each iteration. One advantage of the method is that the entire signal operation for calibration is performed in the time domain. This is achieved by resolving the effects of distortion on time delay of each channel, which accounts for both amplitude and phase distortions at different frequencies. Therefore, the proposed method significantly increased the calibration efficiency for ultra-wideband antenna arrays. Since time delay coefficients for calibration associated with array elements were determined independently due to characteristic of the simultaneous perturbation, estimation accuracy of the method is tangential to the number of elements in the array, and is mainly dependent on the convergence conditions. This gives the method an additional distinct advantage for calibrating large-scale antenna arrays with ultrawide bandwidth. An estimation accuracy of 99% on time delay adjustments has been achieved and demonstrated

Equivalent Circuit of Metamaterial Formed by Array of Conductive Disks

The use of metamaterials to obtain a wideband wide angle impedance matching (WAIM) for compact phased array of interconnected crossed rings is investigated. The metamaterial layer above the planar array is formed by array of conductive disks in contrast to the conventional multilayer homogeneous dielectric structure. The equivalent circuit of the metamaterial layer to enhance wideband array antenna design is derived based on a hybrid technique. The values of the components in the equivalent circuit to represent metamaterial layer is given. The response from the equivalent circuit is verified by using the full-wave numerical simulations on the metamaterial structure. The results show the effectiveness of the method in analyzing the electromagnetic characteristics of the structure and improving the performance of the whole array system