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In this paper, we propose a phased array antenna design for 5G mobile communication repeater. The proposed antenna has a gain of more than 10 dBi in the entire beam scanning range and has robustness against the interference problem with the adjacent device or deterioration due to the environment change, and thus has high portability and scalability.

This paper presents the design of an internally fed dual-band dual-polarized repeater antenna covering 2.4 GHz Bluetooth or Industrial, Scientific, and Medical (ISM) band and 3.5 GHz 5G cellular communication for wearable application. By exciting an unsymmetrical slot structure loaded at two sides of the feeding port located between an external metal frame and an internal ground, we can easily tune the antenna for dual-band operation. More importantly, this internal ground can be designed as an empty metallic cavity housing electronic components, therefore minimizing the electromagnetic interference brought by them. This proposed type of antennas can be widely applicable in smartwatch, smartband and swallowable capsule intended for human health monitoring.

This paper proposes a novel wireless power transfer (WPT) system powering multiple loads. The repeater coils are used to transmit the power over a long distance. Every two repeater coils form a repeater unit, which corresponds to a load. For each transmitting coil, a capacitor is connected in series with it and a LCC compensation circuit is used for each receiving coil, which forms an S-LCC compensation topology. It is proven that the constant voltage characteristics can be obtained for each load when neglecting the coils’ parasitic resistances, which facilitates independent load power control.

PCB traces have high-frequency losses due to skin effect and dielectric losses which result in inter symbol interference (ISI), as the signal passes through cable and PCB traces. A limiting ReDriver, which acts as a repeater and includes a continuous time equalizer, removes the ISI which results in a longer signal reach. A CMOS limiting ReDriver channel operating up to 5.4Gbps and programmable preemphasis and de-emphasis to be compliant with some of the standards like display port (DP) and USB, is presented. It has programmable peaking gain up to 12dB at 2.7GHz with 1.5dB steps to compensate for the channel loss and a programmable output swing control of 400mVpp up to 1100mVppd. It has been implemented in 0.14 um CMOS technology and consumes 37.5mA to 55.5mA per channel from a 1.8V supply, depending on selected output swing and emphasis level. It uses common mode keeper, far-end termination detector and incoming squelch detector to work inside a protocol based ReDriver chip.

A near-field wireless power transfer (WPT) with magnetic resonant coupling (MRC) offers a dynamic means for charging various electric apparatuses. This paper presents the modeling and characteristics of a system with a resonant wired-2-coil repeater that can charge devices in any available space using a repeater wire. Moreover, resonant frequencies are discussed, and a method to tune the frequencies is described. Experimental results show that the modeling and tuning methods are valid and that the system can maintain a power transfer efficiency of more than 80% even when the repeater wire is 10-m long.

This paper reports the main achievements in the development of photonic RF payload solutions for telecommunication satellites based on a multiple-frequency conversion scheme. Representative models of photonic payload equipment, including photonic frequency generation assembly and frequency-converters, have been integrated and proven in a system environment. The end-to-end RF performance for various configurations and frequency plans were tested at ambient temperature. The test plan includes forward and return repeater configurations, with photonic frequency down-conversion from 30 to 20 GHz with up to 6-local oscillators in the case of a Ka-band multi-beam broadband mission. In addition, thermal tests were run over the [−5°C, +65°C] temperature range. The end-to-end RF performances of the photonic repeater demonstrator were assessed in detail experimentally and compared to theoretical predictions. These results are a major step towards new payload solution with enhanced capacity and in-orbit re-configurability.

In this paper, the optimal repeater number and size are analyzed for multi-walled carbon nanotube interconnects by using the particle swarm optimization (PSO) algorithm. Genetic algorithm (GA) is also used to verify the corresponding results. Further, the neural network (NN) is trained to facilitate the EDA process. It is found that the computational time can be dramatically reduced with the implementation of NN.

A new low power clock distribution network with multi-threshold-voltage (multi-V t ) repeaters is presented in this paper. A repeater circuit with two inputs and two outputs is employed for suppressing leakage currents in gated clock distribution networks. The standby leakage power consumption is reduced by 50.93% with the proposed clock tree as compared to the conventional 3 level H-tree operating with a power supply voltage of 0.8V in a 45nm CMOS technology. In addition to providing significant power savings in idle clock distribution networks, the proposed circuit technique also lowers the total energy consumption of partially active networks. Depending on the percent of segments that experience local clock gating, the total energy consumed by the proposed clock network is 6.78% to 80.43% lower as compared to the conventional clock tree with a power supply voltage of 0.4V and a clock frequency of 10MHz.

This research meant for the design tracking unit that will use for Wildlife or Protected animal who live in national Park and the tracking method is used this APRS as the method for data packet will travel over RF which will be used as the communication protocol to track Wildlife Animal location inside the National Park where the wireless infrastructure network unavailable. Each node using GPS combined with Tiny microcontroller generated beacon signal included location and heath data encoded to APRS Protocol sent to low power Radio Transmitter module transmitted RF. to Outpost station where located in the middle of forest acted as Digital Repeater passed data to the Internet gateway coverage 2Km radius.

Aiming at the problem of time-delay repeater jamming in the sea surface target detection environment, it is difficult for radar to discriminate false targets from the time domain and frequency domain. This paper proposes an anti-time-delay repeater jamming method based on spatial position constraint. The spatial position constraint method is a good candidate, which combines the radar’s position obtained by radar altimeter with the target’s angle obtained by amplitude-comparison angle measurement, and then solves the desired range of the target. In the multi-target tracking mode, by comparing the measured range of the detected target with the expected range under the spatial constraint, it can be judged whether the target is located on the sea surface, thereby determining the target position and the trajectory, and eliminating the time-delay repeater jamming. By analyzing the radius of the spatial error region caused by the angle error and the delay corresponding to the radius, the obtained correlation threshold can as an assistant to discriminate the false target. This method reduces complicated signal processing and avoids excessive computation. The simulation results show that the proposed method can easily and effectively eliminate the time-delay repeater jamming and obtain the target position.

The authors are presenting a solution of the planning for the group of Unmanned Aerial Vehicles (UAV)’s flights for the decision of multiple tasks in the city (monitoring, data acquisition, transportations, urban survey, etc.) using information technology, graph theory, and mathematical models. The configuration and optimization of group flight routes for UAVs, depending on the target task, is considering. The algorithm of finding the Central Drone Repeater in a group of UAVs in flight for relaying control signals from/to other UAV is obtaining. optimization of flight routes for UAVs using GRID-analyze and optimization methods are considering.

The report proposes a method for calculating the electromagnetic field on rough terrain using a parabolic equation based on elevation data obtained from electronic terrain maps. The presence of inhomogeneous relief significantly affects the propagation of radio waves above the Earth's surface. Obstacles serve as a barrier, as well as with a special arrangement and geometry can be a natural repeater. The calculation of the electromagnetic field using the parabolic equation method with the step-by-step Fourier transform allows for a three-dimensional model of space to take into account the point-built inhomogeneity of the relief, if you specify the desired step.

International audience; We present our work on realizing two-branch fiber links enabling multiple-partner clock comparisons in Europe. We report in detail on the setup connecting two long haul links, and report for the relative frequency stability and accuracy. We report on a combined uptime of 90% for our dual-branch link during almost one month. We finally discuss the combined uncertainty contribution of the ensemble of the link architecture to a clock comparison. We show that the frequency transfer uncertainty is 2 × 10 −19 .

Quantum repeaters are foundational to establishing the long distance quantum communication channels necessary to create a global communication network [1]. A quantum memory capable of storing optical quantum states is an integral component of the quantum repeater.

Payloads of most common communication satellites consist of repeater units, antennas and interconnecting elements. These interconnecting elements also called transmission lines are coaxial cables and waveguides. From RF performance of view, insertion loss per meter of waveguide is a contributor to most of the system budgets, which makes the design of the waveguide runs critical. Although the design of waveguides are commonly known as an RF expertise, because of the need to survive under severe static/dynamic and thermal conditions, mechanical design and verification of waveguide runs and supporting structures require a specific mechanical engineering approach. Analysis of the waveguide run is performed first thermally and then structurally with the help of thermal analysis output. Thermal analysis is concluded with obtaining waveguide surface temperature which is approximately 90°C. In addition to analysis of quasi-static loads, using the temperature output thermoelastic analysis is run and compared with material allowable values. The resultant stresses and natural frequencies show that the design of the sample waveguide run withstands to the loads which the waveguide assembly will be subjected to during its entire life. In this study, basic mechanical design principles of waveguides will be explained and analysis results to confirm the design will be presented.

As a means of transportation, electric vehicles (EVs) are gradually replacing oil-fueled vehicles and widely seen in the field of vision. To facilitate the charging of electric vehicles, static charging stations and highway dynamic wireless power transfer (WPT) systems are being popularized and promoted in many countries. Aiming at the problem of multiple inverters and high costs in the dynamic WPT systems for EVs, this paper proposes a scheme of alternately arranging the active coils and the repeater coils at the transmitter sides, which has the advantage of lower economic costs and reduces the number of the power converters by half. Dynamic quasi-constant power wireless EV charging can be achieved by adjusting the input voltage of the active coil. A mathematical model including three different operating modes during the dynamic process is developed to analyze the output power and system efficiency, and design the system parameters. The simulation results of the 1 kW system verify the validity of the proposed wireless EV charging scheme.

In this paper, a novel wireless power transfer system (WPT) is designed for powering the multiple gate drivers in a modular multilevel converter. Considering that the gate drivers are usually distributed over a long distance, the repeater units are designed, which are placed coaxially along the power transfer route. Then the magnetic field can be enhanced by these repeater units and high system efficiency is ensured even with long power transfer distance. Each repeater unit corresponds to a load and consists of two repeater coils that are both bipolar. Moreover, the two bipolar coils in the same repeater unit are placed perpendicularly to remove the magnetic coupling between them. A suitable compensation topology is designed for the proposed WPT system, so that the constant voltage (CV) characteristic can be achieved for each load when neglecting the coil's parasitic resistance. Thus, the load power can be regulated independently without affecting each other, which greatly simplifies the power control design. Experimental results are provided to validate the proposed WPT system.

In quantum mechanics, a fundamental law prevents quantum communications to simultaneously achieve high rates and long distances. This limitation is well known for point-to-point protocols, where two parties are directly connected by a quantum channel, but not yet fully understood in protocols with quantum repeaters. Here we solve this problem bounding the ultimate rates for transmitting quantum information, entanglement and secret keys via quantum repeaters. We derive single-letter upper bounds for the end-to-end capacities achievable by the most general (adaptive) protocols of quantum and private communication, from a single repeater chain to an arbitrarily-complex quantum network, where systems may be routed through single or multiple paths. We analytically establish these capacities under fundamental noise models, including bosonic loss which is the most important for optical communications. In this way, our results provide the ultimate benchmarks for testing the optimal performance of repeater-assisted quantum communications., End-to-end results first appeared in arXiv:1601.00966 (2016). Please cite as: "S. Pirandola, Commun. Phys. 2, 51 (2019); see also arxiv:1601.00966 (2016)"

We proposed a distributed optic fiber vibration sensing system that can realize a sensing distance of more than 160 km without a repeater. The system’s optical structure is based on the Mach–Zehnder and Sagnac hybrid interference technique. To increase the monitoring distance, we used a reflective erbium-doped fiber amplifier (EDFA) instead of a traditional reflector at the end of the sensing system. In addition, a phase-generated carrier was applied to eliminate the parasitic interferometric effects of Rayleigh scattering.

Near-field wireless power transfer (WPT) via magnetic resonant coupling (MRC) has become significant as a means of supplying power to devices using electricity. Because the transfer distance is short, however, wireless MRC-WPT systems require bringing a receiver near the transmitter, such as one connected from a power outlet. We thus propose a novel power transfer system with a wired three-coil repeater combining wireless and wired coils coupled by magnetic resonance. The system consists of a transmitter, one or two receivers, and a repeater connected with three coils. The wired three-coil repeater enables use of the system over a wide area or long distance. We also present an equivalent circuit model for the system and derive equations for calculating the transfer efficiency. Experimental results demonstrate that the proposed system can achieve efficiency of more than 60% for both straight and triangular repeater structures with up to a 10-m distance between the transmitter and receiver.

High efficiency power transfer in a magnetically coupled resonant wireless power transfer (MCR-WPT) system is only happened at a specific distance. In most applications, the distance between the transmitter and the receiver could be changed. To overcome this boundary, a reconfigurable three coil wireless power transfer system is proposed in this paper to maintain high power transfer efficiency over a long distance. The repeater coil consists of switches which are used to adjust the coupling coefficient and improve the transmission quality according to the change of distance between the transmitter and receiver. The principle of this reconfigurable structure is explained with the theoretical analysis and verified with experimental measurements.

This paper proposes a method to represent 3-coil wireless power transfer (WPT) system consisting of transmitter (TX), receiver (RX) and repeater (RP) by equivalent transmission line model. The method is based on matrix reduction technic, in which the impedance matrix dimension of any cascade WPT systems can be reduced to 2×2. The system is designed to operate at 13.56MHz. The proposed method provides a better understanding of the 3-coil WPT system under the scope of nominal T transmission line model.

The vision to develop quantum networks entails multi-user applications, which require the generation of long-distance multi-party entangled states. The current rapid experimental progress in building prototype-networks calls for new design concepts to guide future developments. Here we describe an experimentally feasible scheme implementing a two-dimensional repeater network for robust distribution of three-party entangled states of GHZ type in the presence of excitation losses and detector dark counts — the main sources of errors in real-world hardware. Our approach is based on atomic or solid state ensembles and employs built-in error filtering mechanisms peculiar to intrinsically two-dimensional networks. This allows us to overcome the performance limitation of conventional one-dimensional ensemble-based networks distributing multi-party entangled states and provides an efficient design for future experiments with a clear perspective in terms of scalability.

In this study, we implemented a high-performance multichannel repeater, both for FM and T-Digital Multimedia Broadcasting (DMB) signals using a Field Programmable Gate Array (FPGA). In a system for providing services using wireless communication, a radio-shaded area is inevitably generated due to various obstacles. Thus, an electronic device that receives weak or low-level signals and retransmits them at a higher level is crucial. In addition, parallel implementation of digital filters and gain controllers is necessary for a multichannel repeater. When power level is too low or too high, the repeater is required to compensate the power level and ensure a stable signal. However, analog- and software-based repeaters are expensive and they are difficult to install. They also cannot effectively process multichannel in parallel. The proposed system exploits various digital signal-processing algorithms, which include modulation, demodulation, Cascaded Integrator Comb (CIC) filters, Finite Impulse Response (FIR) filters, Interpolated Second Ordered Polynomials (ISOP) filters, and Automatic Gain Controllers (AGCs). The newly proposed AGC is more efficient than others in terms of computation amount and throughput. The designed digital circuit was implemented by using Verilog HDL, and tested using a Xilinx Kintex 7 device. As a result, the proposed repeater can simultaneously handle 40 FM channels and 6 DMB channels in parallel. Output power level is also always maintained by the AGC.

Quantum memories for light are important components for future long distance quantum networks. We present on-chip quantum storage of telecommunications band light at the single photon level in an ensemble of erbium-167 ions in an yttrium orthosilicate photonic crystal nanobeam resonator. Storage times of up to 10 $\mu$s are demonstrated using an all-optical atomic frequency comb protocol in a dilution refrigerator under a magnetic field of 380 mT. We show this quantum storage platform to have high bandwidth, high fidelity, and multimode capacity, and we outline a path towards an efficient erbium-167 quantum memory for light., Comment: 12 pages, 4 figures

In recent years, the demand of train-commuting nomadic users for the Internet has been a huge challenge for train and mobile operators. Consequently, train operators have started to deploy in-train repeater systems to increase mobile users' service quality. These systems generally follow the structure of static deployments. However, in contrast to a static deployment where the system is set up once using constant parameters that are based on an initial measurement, the train will commute in dense urban city centers and sparsely populated rural areas. We propose a holistic model that helps to understand the role of each system component, namely, cabin pathloss, repeater model, window penetration loss, and outdoor pathloss, in which each individual element can be measured independently. We parametrize the model by measuring an existing in-train repeater deployment of a high-speed train. Finally, we have analyzed the operation of the complete system for two extreme cases of deployment strategy: simple rural and optimized track side. We show that the main benefit of the tested system is visible in the nonoptimized rural deployment. However, the optimized deployment also benefits from the repeater setup.

Two wireless nodes outside each others radio range can communicate via a node in between, known as a relay node. A relay node may be a simple repeater or a fully functional entity depending upon the deployment scenario. In a two-way relay communication (TWRC), Physical-Layer network coding (PNC) exploits the superimposed nature of electromagnetic waves at the relay node to improve the throughput performance. Synchronization of information from two end users is critical when exchanging information via a relay node. Traditionally in PNC, modulation constellations sent from the two end users are chosen to be the same. In this paper, we investigate the performance of a PNC-based TWRC system in a Rayleigh fading scenario when the modulation constellation of one end user is rotated with respect to the modulation constellation at the other end user. The analysis shows that the rotated-QPSK gives distinct decision regions when the modulation constellation of QPSK and rotated-QPSK are superimposed, unlike the traditional (QPSK)(QPSK) transmission. Simulation results for the symbol error rate (SER) at the relay node shows the loss in performance of (QPSK)-(rotated-QPSK) scheme compared to the (QPSK)(QPSK) scheme due to phase rotation.

This paper introduces a simple measurement methodology that can identify extreme cases of multipath propagation for in-train repeater (ITR) deployments, which may cause performance impairments for users. Differential timing advance measurements allow to detect the relative power of multipath components in the range of -20. . . 20 dB, as we have verified through laboratory measurements. The experimental results for an existing ITR deployment inside an express passenger train show that this method can, in fact, be used to pinpoint the specific locations for which the interplay between the base station configuration and the ITR is still not optimal. Therefore, it is possible to use the proposed method to continuously collect measurement points, e.g., by crowdsourcing from standard handsets running on Android. This enables to continually improve deployments with active components such as ITRs.

We present a "hybrid quantum repeater" protocol for the long-distance distribution of atomic entangled states beyond qubits. In our scheme, imperfect noisy entangled pairs of two qudits, i.e., two discrete-variable $d$-level systems, each of, in principle, arbitrary dimension $d$, are initially shared between the intermediate stations of the channel. This is achieved via local, sufficiently strong light-matter interactions, involving optical coherent states and their transmission after these interactions, and optical measurements on the transmitted field modes, especially (but not restricted to) efficient continuous-variable homodyne detections ("hybrid" here refers to the simultaneous exploitation of discrete and continuous variable degrees of freedom for the local processing and storage of entangled states as well as their non-local distribution, respectively). For qutrits we quantify the light-matter entanglement that can be effectively shared through an elementary lossy channel, and for a repeater spacing of up to 10 km we show that the realistic (lossy) qutrit entanglement is even larger than any ideal (loss-free) qubit entanglement. After including qudit entanglement purification and swapping procedures, we calculate the long-distance entangled-pair distribution rates and the final entangled-state fidelities for total communication distances of up to 1280 km. With three rounds of purification, entangled qudit pairs of near-unit fidelity can be distributed over 1280 km at rates of the order of, in principle, 100 Hz., Comment: 23 pages, 9 figures

We present a multiplexed quantum repeater protocol based on an ensemble of laser-cooled and trapped rubidium atoms inside an optical ring cavity. We have already demonstrated strong collective coupling in such a system and have constructed a multiplexing apparatus based on a two-dimensional acousto-optical deflector. Here, we show how this system could enable a multiplexed quantum repeater using collective excitations with non-trivial spatial phase profiles (spinwaves). Calculated entanglement generation rates over long distances reveal that such a multiplexed ensemble-cavity platform is a promising route towards long distance quantum entanglement and networking.

Objectives We assessed the clinical usefulness of repeater F-waves (Freps) analysis in amyotrophic lateral sclerosis (ALS), using an automated computerized system (F Wave Analyzer). Methods Forty consecutive F-waves were recorded from the ulnar and peroneal nerve in 52 patients with ALS and 52 healthy control subjects. Data were imported into the F Wave Analyzer which identifies Freps and groups them. Parameters of Freps and non repeater F-waves (Fnonreps) were compared. Results Total number of repeating neurons, Freps persistence (100xFreps/40stimuli) and Index Total Freps (100xFreps/total number of F-waves) were significantly higher in the ALS compared to the control group (P ≤ 0.005). There were no consistent differences of F-wave latency or amplitude measurements between Freps and Fnonreps for both studied groups, with the exception of prolonged Freps minimum latency in ALS. Conclusion In ALS, the high numbers of Freps, reduced overall F-wave persistence and increased F-wave amplitude measurements in a relatively unaffected nerve-muscle complex reflects excitability alterations of the corresponding motor neuron pool. Overall, automatic analysis facilitates accurate and fast detection of Freps and could be useful in other clinical settings. Significance Analysis of repeater F-waves is expected to provide new insight regarding ALS pathophysiology and utilized for monitoring in clinical drug trials.

We propose a Bell measurement-free scheme to implement a quantum repeater in GaAs/AlGaAs double-quantum-dot systems. We prove that four pairs of double quantum dots compose an entanglement unit, given that the initial state is singlet states. Our scheme differs from the famous Duan–Lukin–Cirac–Zoller (DLCZ) protocol in that Bell measurements are unnecessary for the entanglement swapping, which provides great advantages and conveniences in experimental implementations. Our scheme significantly improves the success probability of quantum repeaters based on solid-state quantum devices.

With the introduction of PAM-4 signaling at 56Gb/s and the decreased benefits of CMOS scaling for high-speed mixed-signal designs, SerDes designers and system architects are faced with severe performance versus power budget constraints. Power management and energy efficiency have become the main drivers for system design. However, industry standards such as EEE have failed to keep up with efficiency demands. In this context the choice between a so-called analog mixed signal (AMS) SerDes architecture vs. an ADC-DSP-based one has been debated at length. AMS provides significantly lower maximum power [2, 4] while ADC-DSP provides higher link margin [1] thus avoiding expensive and power hungry repeater ICs that largely negate the power advantage of AMS SerDes in a system. AMS provides an easier and cheaper approach to implement multi-tap DFEs [3] compared to DSP where it is typically very expensive to implement more than a 1-tap DFE. This paper will show an ADC-DSP SerDes transceiver with a 2-tap DFE is capable of operating error-free over a 38dB link yet having an overall power budget similar to AMS. The same basic SerDes architecture is implemented (Fig. 6.2.1) with minor differences in 16nm and 7nm FinFET, however, power scaling is incorporated into the 7nm version only.

The enormous availability of data on the internet and the increased computational power available in the cloud require a constant increase in the bandwidth needed to transport data across the network. In order to mitigate the cost of infrastructure, the industry has proposed standards for 56Gb/s PAM-4 interfaces that can support legacy channels in conjunction with forward error correction (FEC) techniques. The reduced signal to noise ratio (SNR) available with PAM-4 modulation vs. NRZ requires sophisticated signal processing, making DSP-based solutions very attractive in terms of performance but, so far, at the expense of extra power vs. classical analog solutions. This paper demonstrates that this trade-off can be broken and presents a compact ADC/DAC DSP-based long-reach transceiver in 7nm FinFET technology that operates seamlessly from 3.5-to60Gb/s in PAM-4 (from 1-to-30Gb/s in NRZ mode) and consumes less than 250mW at 56Gb/s. The presented IP extends the deployment of DSP-based transceivers from repeater/re-timer applications to big ASICs with a very large number of ports.

It has recently been suggested in this journal by Benford (2019) that "Lurkers" in the form of interstellar exploration probes could be present in the solar system. Similarly, extraterrestrial intelligence could send long-lived probes to many other stellar systems, to report back science and surveillance. If probes and planets with technological species exist in more than a handful of systems in our galaxy, it is beneficial to use a coordinated communication scheme. Due to the inverse square law, data rates decrease strongly for direct connections over long distances. The network bandwidth could be increased by orders of magnitude if repeater stations (nodes) are used in an optimized fashion. This introduction to a series of papers makes the assumptions of the communication scheme explicit. Subsequent papers will discuss technical aspects such as transmitters, repeaters, wavelengths, and power levels. The overall purpose is to gain insight into the physical characteristics of an interstellar communication network, allowing us to describe the most likely sizes and locations of nodes and probes., Comment: Update to match version published in AJ

Recent experimental breakthroughs in satellite quantum communications have opened up the possibility of creating a global quantum internet using satellite links. This approach appears to be particularly viable in the near term, due to the lower attenuation of optical signals from satellite to ground, and due to the currently short coherence times of quantum memories. The latter prevents ground-based entanglement distribution using atmospheric or optical-fiber links at high rates over long distances. In this work, we propose a global-scale quantum internet consisting of a constellation of orbiting satellites that provides a continuous, on-demand entanglement distribution service to ground stations. The satellites can also function as untrusted nodes for the purpose of long-distance quantum-key distribution. We develop a technique for determining optimal satellite configurations with continuous coverage that balances both the total number of satellites and entanglement-distribution rates. Using this technique, we determine various optimal satellite configurations for a polar-orbit constellation, and we analyze the resulting satellite-to-ground loss and achievable entanglement-distribution rates for multiple ground station configurations. We also provide a comparison between these entanglement-distribution rates and the rates of ground-based quantum repeater schemes. Overall, our work provides the theoretical tools and the experimental guidance needed to make a satellite-based global quantum internet a reality., Comment: 22 pages, 11 figures. Minor changes; close to the published version

We demonstrate a Hong-Ou-Mandel interferometer in the domain of spin waves inside a multimode quantum memory. The ac-Stark-modulation-based protocol constitutes a bedrock for a multiplexed photon generator or a quantum repeater with error correction.

Quantum repeaters, which are indispensable for long-distance quantum communication, are necessary for extending the entanglement from short distance to long distance; however, high-rate entanglement distribution, even between adjacent repeater nodes, has not been realized. In a recent work by C. Jones, et al., New J. Phys. 18, 083015 (2016), the entanglement distribution rate between adjacent repeater nodes was calculated for a plurality of quantum dots, nitrogen-vacancy centers in diamond, and trapped ions adopted as quantum memories inside the repeater nodes. Considering practical use, arranging a plurality of quantum memories becomes so difficult with the state-of-the art technology. It is desirable that high-rate entanglement distribution is realized with as few memory crystals as possible. Here we propose new entanglement distribution scheme with one quantum memory based on the atomic frequency comb which enables temporal multimode operation with one crystal. The adopted absorptive type quantum memory degrades the difficulty of multimode operation compared with previously investigated quantum memories directly generating spin-photon entanglement. It is shown that the present scheme improves the distribution rate by nearly two orders of magnitude compared with the result in C. Jones, et al., New J. Phys. 18, 083015 (2016) and the experimental implementation is close by utilizing state-of-the-art technology., Comment: 8 pages, 6 figures

In this paper, a coherent multistatic radar network with a novel system architecture is presented, which circumvents the general problems of clock distribution and phase noise related signal-to-noise ratio (SNR) issues. The proposed network consists of a variable number of multiple-input multiple-output (MIMO) radar sensors and a variable number of repeater tags, all of which operate incoherently on the hardware level. In a minimum configuration, the network only consists of one MIMO radar sensor and a repeater tag. The theory behind such a multistatic network is mathematically derived and simulations are presented to show key aspects of the network, i.e. multistatic range and Doppler measurements as well as high resolution angle estimation exploiting a very large virtual aperture spanning the whole network. Measurements with one sensor and one repeater tag at 77 GHz are carried out to verify the simulations. The measurements show that the bistatic path between the sensor and repeater tag retains coherency., publishedVersion

We propose a strategy to reduce the propagation delay of microprocessors’ digital bus lines at very low costs in terms of area overhead, power consumption and power-delay product. Likewise some solutions adopted in industry nowadays, our strategy inserts in the bus lines repeaters implemented as a chain of inverters with increasing size. In this paper, we derive new expressions to determine the optimum number of inverters to be used within each repeater, and the optimum number of repeaters to insert in the bus lines. Our derived expressions yield to bus implementations with significant lower cost in terms of area overhead and power consumption than alternative solutions in literature. Considering a 32 nm technology as a significant example, we show that, compared to the traditional solution that inserts repeaters implemented as a single inverter, our strategy enables reductions up to 84% in terms of area overhead, up to 65% in power consumption, and up to 66% in power-delay product. Compared to three recent alternative solutions in the literature, our strategy enables reductions up to 88% in terms of area overhead, up to 48% in power consumption, and up to 43% in power-delay product. Therefore, our approach is particularly suitable to the growing market of mobile applications that require low cost in terms of power consumption and chip area.

Target echo cancellation is an ingenious method that protects the target of interest (TOI) from being detected by radar. Interrupted-sampling repeater jamming (ISRJ) is a novel deception jamming method for linear frequency modulation (LFM) radar countermeasures, which has been applied in target echo cancellation recently. Compared with the conventional cancellation method, not only can the target echo be successfully cancelled at radar receiver, but a train of false targets is also produced and forms deception jamming by applying the ISRJ technique. In this paper, an improved radar target echo cancellation method based on ISRJ is proposed that utilizes an extra frequency shifting modulation on the intercepted LFM radar signal. The jammer power is more efficiently utilized by the proposed method. Moreover, more flexible multi-false-target deception jamming can be obtained by adjusting the interrupted sampling frequency. The real target remains effectively protected by the false preceding target in the presence of amplitude mismatch of cancellation signal and target echo. Numerical simulations and measured data experiments are conducted to demonstrate the effectiveness of the proposed method.

We measure Hong-Ou-Mandel interference between weak coherent pulses retrieved from room-temperature rubidium vapor quantum memories operating via Electromagnetically-Induced Transparency. The interference visibility of V = (46.8 ± 3.4)% makes the system suitable for Quantum Repeater applications.

The goal of this work is to implement the possibility of digital reception and transmission of a received signal with changing its characteristics. The special software capable of generating, receiving and transmitting digital signals has been developed in the LabVIEW environment, using the NI USRP-2920 hardware platform. It allows to solve practical problems, such as the organization of radio communications between employees at the different offices, factories, etc.

We propose a nested quantum repeater architecture that mitigates quantum memory decoherence by optimizing the memory access time. This maximizes the distillable entanglement rate in the remote entangled state for technologically feasible repeater parameter regimes.

CAPS is an integrated system of navigation and communication. The orbit position of AsiaSat-3S satellite has been pushed from 105.5E to 147.5E. It has become a SIGSO satellite, which plays a certain role in improving the constellation DOP of CAPS navigation system. According to the characteristic parameters of AsiaSat-3S satellite (mainly including orbit parameters, polarization parameters, frequency offset parameters, etc.), this paper expounds the changes of azimuth, elevation angle and polarization angle of 16-meter paraboloid antenna in Tianjin pointing and tracking AsiaSat-3S satellite in CAPS ground system, and analyzes the dynamic changes of frequency offset of AsiaSat-3S satellite transponder through the spontaneous receiving of navigation signals The parameter model prediction of CAPS repeater navigation system has a good reference value.

Communication over a quantum broadcast channel with cooperation between the receivers is considered. The first form of cooperation addressed is classical conferencing, where Receiver 1 can send classical messages to Receiver 2. Another cooperation setting involves quantum conferencing, where Receiver 1 can teleport a quantum state to Receiver 2. When Receiver 1 is not required to recover information and its sole purpose is to help the transmission to Receiver 2, the model reduces to the quantum primitive relay channel. The quantum conferencing setting is intimately related to quantum repeaters, as the sender, Receiver 1, and Receiver 2 can be viewed as the transmitter, the repeater, and the destination receiver, respectively. We develop lower and upper bounds on the capacity region in each setting. In particular, the cutset upper bound and the decode-forward lower bound are derived for the primitive relay channel. Furthermore, we present an entanglement-formation lower bound, where a virtual channel is simulated through the conference link. At last, we show that as opposed to the multiple access channel with entangled encoders, entanglement between decoders does not increase the classical communication rates for the broadcast dual.

Feasible distribution of quantum entanglement over long distances remains a fundamental step towards quantum secure communication and quantum network implementations. Quantum repeater nodes based on quantum memories promise to overcome exponential signal decay inherent to optical implementations of quantum communication. While performance of current quantum memories hinders their practical application, multimode solutions with multiplexing can offer tremendous increase in entanglement distribution rates. We propose to use a wavevector-multiplexed atomic quantum memory (WV-MUX-QM) as a fundamental block of a multiplexed quantum repeater architecture. We show the WV-MUX-QM platform to provide quasi-deterministic entanglement generation over extended distances, mitigating the fundamental issue of optical loss even with currently available quantum memory devices, and exceeding performance of repeaterless solutions as well as other repeater-based protocols such as temporal multiplexing. We establish the entangled-bit (ebit) rate per number of employed nodes as a practical figure of merit reflecting the cost-efficiency of larger inter-node distances., Comment: 13 pages, 9 figures