The design of a new miniature broadband implantable antenna and a dual-band on-body antenna are presented along with the transmission performance between the two. The former and latter antennas are ...intended for integration into implantable medical devices (IMDs) and on-body repeaters, respectively. The on-body repeater antenna favors the use of very low power IMDs. The on-body repeater receives low power data from an IMD (MedRadio band, 401-406 MHz) and retransmits it to remote devices placed further apart (ISM band, 2400-2480 MHz ). The MedRadio implantable antenna maintains miniature size (399 mm 3 ), and exhibits two close resonances which increase the -10 dB bandwidth inside muscle tissue (87 MHz). The on-body antenna is relatively small (6720 mm 3 ), and exhibits dual resonances in the MedRadio and ISM bands. Assuming a typical arm implantation scenario and an on-body receiver sensitivity of -75 dBm, the proposed configuration is found to enable reduction of the IMD power by a factor of 100. Patient safety and tolerance to electromagnetic interference are, thus, preserved, and lifetime of the IMD is increased. The setup is, finally, shown to be robust to antenna misalignment and polarization rotation.
Large quantum networks Sukachev, D D
Physics Uspekhi,
10/2021, Letnik:
64, Številka:
10
Journal Article
Recenzirano
Abstract
Quantum networks that allow generating entangled states between distant qubits have enormous scientific and applied potential. They can be used for secure quantum cryptography and the ...teleportation of quantum states between cities and countries, in high-resolution astronomy, and in distributed quantum computing. The scattering of photons in an optical fiber and the difficulties in creating full-fledged quantum nodes impede the construction of large quantum networks. We review current approaches to the creation of such networks, with the emphasis on quantum repeaters intended for 'compensating' losses in optical fibers. We also discuss methods for increasing the range of quantum cryptography systems without using quantum repeaters.
By partial interception and multiple forwarding of a radar transmitting signal, digital radio frequency memory-based interrupted sampling repeater jamming can yield a partial processing gain and form ...multiple false target groups in the range direction, achieving jamming effects of both suppression and deception. Various improved jamming strategies have been proposed, while jamming suppression problems have not been fully addressed. In this study, a jamming suppression method based on the idea of ‘reconstruction and cancellation’ is proposed by analysing the jamming principle. The method firstly analyses the pulse compression results with time-frequency analysis to obtain the intercepted slice number and forwarding times; then, the slice width is estimated by deconvolution processing; finally, iterative cancellation is used to suppress the jamming. Performance of the method was verified by Monte Carlo simulation. The results show that the normalised error of the slice width estimation is <5% when the jamming-to-noise ratio reaches 15 dB (after pulse compress); the cancellation method can effectively restrain the jamming by bringing an improvement of signal-to-jamming ratio >16 dB.
Main-lobe interrupted sampling repeater jamming (ISRJ) poses a serious threat to the normal use of radar. The existing anti-ISRJ target detection methods based on deep learning have problems, such as ...a large number of training samples required, complex use steps, inability to achieve ranging and speed measurement at the same time, and poor detection probability under a very low signal-to-noise ratio (SNR) environment. To solve these problems, this article proposes an end-to-end anti-ISRJ target detection method based on the range-Doppler spectrum. First, a visual object detection network based on convolutional neural networks (CNNs) is designed and trained with fewer than 9000 samples. Focal loss is introduced to train the network. It can adaptively improve the loss weight of hard samples and, therefore, improve the performance of the network under a low SNR environment. After that, the range-Doppler spectrum corresponding to the radar echo signal is input into the trained network, and then, the detection, ranging, and speed measurement of the targets under ISRJ conditions can be realized. The simulation results show that the detection probability of the proposed method under various SNRs, signal-to-jamming ratios (SJRs), and false alarm rates is better than that of the compared method. The proposed method can achieve a detection probability of more than 80% under the condition of a false alarm rate of <inline-formula> <tex-math notation="LaTeX">1e-4 </tex-math></inline-formula>, an SNR of −20 dB, and an SJR of not less than −20 dB.
As a new type of coherent jamming pattern in modern electronic warfare, Interrupted Sampling Repeater Jamming (ISRJ) has attracted increasing attention in past decades. In this paper, the joint ...optimization of transmit waveform and receive filter for wideband polarimetric radars is introduced to increase the freedom degrees of radar anti-ISRJ design. The figure of merit is formulated on the basis of the penalty function and Pareto balance framework. Different from off-the-shelf anti-jamming methods employing waveform design, the modulation of Target Impulse Response Matrix (TIRM) to the target echo is considered in the system model, for the sake of matching with a wideband illumination scenario. To solve the non-convex problem, a Majorization-Minimization (MM) based alternate iteration method is proposed. Numerical results validate the effectiveness of the proposed method, and highlight that compared to conventional single-polarization radars, a better anti-ISRJ performance can be achieved by waveform design of polarimetric radars.
High‐throughput satellite (HTS) is an ideal way to realize cross‐regional massive, multifaceted digital exchange services, and it requires a signal processing module that can be massively multiplexed ...and has high flexibility. Due to the limitations of the frequency characteristics, microwave integrated circuits are difficult to meet this requirement. One solution to this problem is photonic integrated circuits (PICs). However, full‐size PIC satellite payloads containing main optoelectronic components are extremely challenging to implement on monolithic or hybrid integrated platforms. Here, the study demonstrates a hybrid integrated on‐chip microwave‐photonic satellite repeater with large‐scale multiplexing potential and high flexibility. This is a demonstration of a hybrid integration of a InP/Si3N4 external cavity laser, arrayed InP modulators, and semiconductor optical amplifiers (SOAs), as well as multifunctional Si3N4 signal processors, to fulfill a 1 × 4 Ka‐band repeater module with on‐chip arrayed frequency down‐conversion and outstanding narrowband photonic channelization. When combined with the full‐chip photonic RF repeater, broadband, highly integrated, and cost‐effective communications satellite payloads will become realizable more quickly in the near future.
A hybrid integrated on‐chip microwave‐photonic repeater is demonstrated. An InP/Si3N4 external cavity laser, arrayed InP modulators, and amplifier, as well as multifunctional Si3N4 signal processors are combined to fulfill a photonic repeater with on‐chip frequency down‐conversion and narrowband photonic channelization. When combined with the full‐chip photonic repeater, highly integrated communication payloads will become realizable more quickly in the near future.
The interrupted sampling repeater jamming (ISRJ) can effectively degrade the image quality and affect the subsequent target recognition by creating deceptive multiple false targets on synthetic ...aperture radar (SAR) images. A time-domain filtering method based on pulse coding to counter ISRJ is proposed in this article. First, this coding method requires the radar to transmit a full pulse signal consisting of multiple subpulse signals several times in the original pulse repetition interval (PRI), and there is a difference in the time distribution of the subpulses transmitted at different moments. Then, use the observation matrix determined by the echo conditions contained in each receiving window to filter the echo in the time domain to obtain the echo corresponding to each subpulse. Finally, the subpulse echo of the jammer sampling section is discarded and the remaining uninterfered subpulse echoes are segmented for pulse compression and subsequent imaging processing to obtain SAR images with a low jamming-to-signal ratio (JSR). Several groups of simulations show that the proposed method is effective against different kinds of ISRJ, and this time-domain filtering method can improve the effect of radar anti-ISRJ and has a high freedom of waveform design.
Abstract
Long-distance quantum communication via entanglement distribution is of great importance for the quantum internet. However, scaling up to such long distances has proved challenging due to ...the loss of photons, which grows exponentially with the distance covered. Quantum repeaters could in theory be used to extend the distances over which entanglement can be distributed, but in practice hardware quality is still lacking. Furthermore, it is generally not clear how an improvement in a certain repeater parameter, such as memory quality or attempt rate, impacts the overall network performance, rendering the path toward scalable quantum repeaters unclear. In this work we propose a methodology based on genetic algorithms and simulations of quantum repeater chains for optimization of entanglement generation and distribution. By applying it to simulations of several different repeater chains, including real-world fiber topology, we demonstrate that it can be used to answer questions such as what are the minimum viable quantum repeaters satisfying given network performance benchmarks. This methodology constitutes an invaluable tool for the development of a blueprint for a pan-European quantum internet. We have made our code, in the form of NetSquid simulations and the
smart-stopos
optimization tool, freely available for use either locally or on high-performance computing centers.
Repeater F-waves (Freps) were seen in patients with amyotrophic lateral sclerosis (ALS). The factors implicated for the presence and frequency of Freps were loss of the motor neurons and the changes ...in their excitability. The aim of this study was to assess the Freps in ALS patients and to compare their frequencies in thenar and hypothenar muscles.
Sixteen ALS patients and 11 healthy controls were recruited to the study. All patients had ⩾2mV CMAPs recorded from the hand muscles. Ninety F-waves were recorded from abductor digiti minimi (ADM) and abductor pollicis brevis (APB). The index of repeater neurons (RN) and Freps were calculated.
Mean index RN and index Freps values of ADM and APB muscles in ALS group (17.1 and 42.6 for ADM and 16.3 and 41.9 for APB) were significantly higher than those of healthy controls (4.7 and 13.9 for APB and 1.5 and 3.6 for ADM). ALS group had a lower persistence of F-waves for both muscles than healthy controls (56.4 and 94.6 for APB and 83.4 and 97.0 for ADM). Freps parameters were not different between thenar and hypothenar muscles, whereas persistence of F-waves was lower in the thenar (56.4%) as compared to the hypothenar (83.4%) muscles.
Similar Freps parameters in the thenar and hypothenar muscles might be caused by the inclusion criteria. Lower F-persistence in the thenar muscles was in accordance with the split-hand phenomenon.
The assessment of Freps and F persistence may be useful in understanding of the electrophysiological changes in ALS.
Abstract Counterfactual quantum communication is one of the most interesting facets of quantum communication, allowing two parties to communicate without any transmission of quantum or classical ...particles between the parties involved in the communication process. This aspect of quantum communication originates from the interaction-free measurements where the chained quantum Zeno effect plays an important role. Here, we propose a new counterfactual quantum communication protocol for transmitting an entangled state from a pair of electrons to two independent photons. Interestingly, the protocol proposed here shows that the counterfactual method can be employed to transfer information from house qubits to flying qubits. Following this, we show that the protocol finds uses in building quantum repeaters leading to a counterfactual quantum network, enabling counterfactual communication over a linear quantum network.
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