Search

Abstract With the accelerated deployment of 5G massive multi‐input multi‐output (MIMO)‐structured base stations (BSs), accurate and efficient testing of massive MIMO arrays is essential to ensure that the 5G massive MIMO antenna array can perform as expected. The increasing trend of both antenna element and array physical size makes massive MIMO antenna pattern measurement in the direct‐far‐field OTA environment unrealistic due to the signal attenuation, long measurement time, and ultra‐high test system construction cost. Therefore, the necessity of a compact, efficient, low‐complex, yet accurate OTA test method is evident, especially for 5G massive MIMO BS arrays. This paper proposes a novel multi‐probe‐enabled midfield (MF) OTA test method for 5G massive MIMO devices in compact measurement settings where antenna pattern measurement can be efficiently performed. The detailed theoretical analysis for the 5G massive MIMO array MF antenna pattern reconstruction method is presented, and the simulated validation results based on the typical 5G BS antenna arrays are provided and analysed, which demonstrate the effectiveness of the proposed MF OTA test method and can provide insights into the radio frequency parametric measurement for 5G massive MIMO devices.

Abstract Automotive antennas are gaining importance due to their increasingly important role for autonomous driving with the development of the Internet of Vehicles. However, over‐the‐air testing on automotive antennas is difficult owing to its large volume and complex body structure. Plane wave generators can approximate uniform plane waves in the near field of the device under test, which can greatly reduce the measurement distance and thereby decreasing the cost compared with direct far‐field solutions. This letter designs three plane wave generators for three quiet zone sizes selected according to the vehicle structure at 5.9 GHz, achieving quiet zone sizes of 1.45 m ×0.23 m, 2.9m ×0.56 m, and 3.9 m ×1.27 m, respectively. Within the three quiet zones, amplitude deviations of 0.82, 0.34, and 0.34 dB and phase deviations of 9.4∘, 6.72∘ and 1.42∘ are realized, respectively, according to the numerical simulations. Uncertainty analysis is further implemented to investigate the robustness of the designed PWGs proposed in this letter.

The combined treatment method integrated photothermal therapy (PTT) with chemotherapy is extremely promising owing to the synergistic therapeutic effect as compared to single PTT or chemotherapy. To facilitate more novel and facile photothermal-chemotherapy drugs as well as promote controllable combination therapy, we have developed a mild and facile method to fabricate polymer polypyrrole (PPy)-doxorubicin (DOX) nanoparticles (NPs) as pH-responsive drug nanocarriers for synergistic photothermal-chemotherapy. In the nanoplatform, poly-L-lysine (PLL)-modified PPy serves as the photothermal material, and (DOX) molecules are adopted as the chemotherapy agent. Based on the cross-linking reaction of glutaraldehyde, DOX molecules are flexibly and efficiently assembled on the surface of PLL-modified PPy NPs. The obtained PPy-DOX NPs possess high photothermal effect, superior loading capacity of DOX, and controlled drug release behavior. The combination photothermal-chemotherapy based on PPy-DOX NPs has significantly enhanced the antitumor therapy effect. In general, the designed PPy-DOX NPs may be a potential drug delivery nanoplatform for cancer combination therapy.

Orthogonal frequency division multiplexing (OFDM) continues to be deployed in 5G communication systems and is likely to be used in beyond 5G (B5G) communication systems as well, due to its many advantages. However, one major drawback with OFDM systems is its high peak-to-average power ratio (PAPR), especially with large bandwidth transmissions. In this paper, we have provided a regularization optimization based flexible hybrid companding and clipping scheme (ROFHCC) used for PAPR reduction in OFDM systems. To reduce the design complexity, the companding function has two parts. It restrains the signal samples with amplitudes over a given value to a constant value for both peak power reduction and small power compensation. For signals with samples less than a given amplitude, they are expanded by a linear companding function. We build a regularization optimization model to jointly optimize the companding distortion as well as the continuity of the companding function for bit error rate (BER) performance as well as power spectral density (PSD) performance. Simulation results indicate that for the same PAPR performance, the proposed companding scheme has an advantage over the referenced companding schemes. For example, when the average signal power is normalized to be 1, we choose both PAPR for ROFHCC scheme and two-piecewise companding (TPWC) scheme as 4 dB, then we can find that at $BER=10^{-4}$ , the minimum required $E_{b}/{N_{0}}$ for ROFHCC scheme is around 2.3 dB lower than TPWC scheme.

With the advent of 5G, multimedia services in wireless communication networks will grow dramatically. So far, many researches have focused on improving security, throughput and channel capacity to support multimedia services. In this paper, a new system model of full-duplex (FD) two-way amplify-and-forward (AF) relay network with simultaneous wireless information and power transfer is presented, where two FD legitimate nodes with two single-antenna communicate with each other via energy-constrained AF relay with multiple antennas, and there is a half-duplex node with single antenna who intends to eavesdrop. This paper targets to maximize the secrecy sum rate of the system by designing the transmit beamforming vector of relay under power constraint and zero-forcing constraint, where two energy harvesting protocols, namely, power splitting and time switching are considered. However the maximization problem is a non-convex optimization, and it is very complex to solve. Therefore a linear method is used to find the lower bound of the secrecy sum rate and the non-convex problem is transformed into a convex optimization problem. After that, an iterative algorithm based on difference-of-convex programming is proposed to solve this convex optimization problem. The simulation results show the good convergence of the proposed iterative algorithm and also the superiority of secrecy sum rate of our proposed scheme compared with two traditional schemes.

With the new distribution demands emerging continuously in the last decade, the distribution mode is changing gradually in various applications, such as e-commerce, emergency relief supplies distribution, the last-mile delivery, and so on. We formulate vehicle routing problem with pickup and delivery (VRPPD), while simultaneously considering multiple arrival time and traffic congestion constraints. Our model focuses on the clear changes of the distribution mode to meet the fast-delivery requirements in the last decade, which is characterized by the multi-batch arrival of goods in 24 hours and time-varying congestion in various time windows. Besides, we propose dynamic memory memetic algorithm, which updates its dynamic memory by whether to promote populations to find new better solutions or not. This is an effective acceleration mechanism to promote the population progress. Meanwhile, dynamic memory memetic algorithm determines the serious congestion tasks in the delivery route and transforms them into normal congestion or even non-congestion tasks. Test sets with 30 test problems are constructed by using real distribution data from Alibaba Cloud and traffic congestion data from Baidu Map in Shanghai. By comparing with four compared algorithms, the effectiveness, efficiency, and robustness of our proposed algorithm in non-congestion and congestion tests are simultaneously demonstrated.

The digital optical fiber repeater (DOFR) is an important infrastructure in the LTE networks, which solve the problem of poor regional signal quality. Various types of conventional measurement data from the LTE network cannot indicate whether a working DOFR is present in the cell. Currently, the detection of DOFRs relies solely on maintenance engineers for field detection. Manual detection methods are not timely or efficient, because of the large number and wide geographical distribution of DOFRs. Implementing automatic detection of DOFR can reduce the maintenance cost for mobile network operators. We treat the DOFR detection problem as a classification problem and employ a deep convolutional neural network (DCNN) to tackle it. The measurement report (MR) we used in this paper are tabular data, which is not an ideal input for DCNN. We propose a novel MR representation method that takes the overall MR data of a cell as a sample rather than a single record in the table, and represents the MR data as a pseudo-image matrix (PIM). The PIM will be used as the input for training DCNN, and the trained DCNN will be used to perform DOFR detection tasks. We conducted a series of experiments on real MR data, and the classification accuracy can achieve 93%. The proposed AI-based method can effectively detect the DOFR in a cell.

New flexible electronic materials and devices have been developed rapidly in nearly a decade from the proposition,discovery,implementation to application.The impact of its strong fold ability and multi-capacity composite structures to technological development and system applications will be enormous.Two mainstream flexible implementation methods were compared:the material-induced flexibility and the structure-induced flexibility.The research progress of domestic and international in related fields was analyzed,including infrastructure,process and potential application directions,and the technical problems faced were summarized.According to the basic research status,flexible electronic devices will have mature application technology innovations achievements in the next few years,new and unprecedented wearable communication,wearable computing,distributed energy,environmental sensing,conformal display devices and devices will be formed.

Sensors are used to sense the state information of physical entities in the Internet of Things (IoT). Thus, a large amount of dynamic real-time data is generated. The entity similarity search based on the quantitative dynamic sensor data is thus worth studying. To the best of our knowledge, there is no research on the entity similarity search based on feature data selection for the quantitative dynamic sensor data in the IoT. This paper proposes a selection mechanism for the entity main features (SMEF). The SMEF is a feature data selection method based on the quantitative dynamic sensor data. It uses the feature matrix to delete the irrelevant entity features, applies an improved relief algorithm (iRelief) to calculate the feature data relevance and proposes a three-component storage relation table of the entities, models, and features (TEMF) for the dynamic feature weights calculation. The experimental results show that the similarity search algorithm based on feature data selection can improve the average search accuracy by more than 10%, as well as increase the search speed and reduce the data transmission and storage costs.

The conventional broadband impedance matching network in low-pass structure cannot present adequate broadband impedance rotation for the optimum broadband operation of the power amplifier (PA), resulting in performance variations and degradations. The underlying constraint is the phenomenon of opposite impedance rotation. Against such a backdrop, this paper presents a methodology using the band-pass topology to compensate the frequency-variable response of the PA. The CGH40010F from Cree is used to verify the effectiveness of this compensation method. The experimental results are in good agreement with the simulation. The proposed PA yields good gain flatness (±0.5 dB), input/output return loss (>13 dB), and high power added efficiency (>60 %) over the band from 1.7 to 2.7 GHz. After digital predistortion, the measured adjacent channel power ratio is about -55 and -50 dBc at ±5 and ±10 MHz offset when the PA is driven by 5- and 10-MHz WCDMA signals at 6.5 ~ 7 dB power back-off.

This paper presents a novel compact single-layer ultra-wideband phase shifter using weakly coupled lines, which contains a main line and a reference line. The basic equations of this phase shifter are calculated based on the even-odd mode theory. Then, the parameters are determined in the design procedure. A compact ultra-wideband 90° phase shifter is designed, fabricated, and measured for demonstration. The measured results, in good agreement with the EM simulation, show that this phase shifter can provide a wide bandwidth from 1.36 to 4.53 GHz (107.6%) with a phase deviation of only ±5°. Meanwhile, return loss better than 10 dB and insertion loss less than 1.25 dB can be obtained.

This paper presents a novel wide-band filtering three-port coupler with inherent DC-blocking function, which is simply comprised of a power divider with wideband filtering function and a broadband phase shifter with a modified coupled line. For demonstration, a designed prototype operating at 3 GHz is simulated, fabricated, and measured. From the simulated and measured results, the coupler shows a 49% filtering bandwidth with 12-dB return loss and 90° ± 590°phase shifting. The amplitude imbalance between the two output ports is less than 0.5 dB. The all-passband isolation is below -13 dB and the 25.7-dB upper stopband rejection is up to 5.4 GHz. Good agreement between the simulated and measured results validates the proposed idea. Hence, the proposed coupler is well suited for the applications of wideband, filtering, and single-layer circuitry integration.

In wireless rechargeable sensor networks for mobile multimedia services, the multi-hop transmission method is often used to reduce the distance of a single hop to save energy. However, the sensor nodes in special locations always carry more forwarding load,which causes energy holes. These sensor nodes in energy hole have the higher energy consumption and the less residual energy, which makes them very fragile and easy to exhaust energy. If a sensor node dies, the structure of the network will be changed and the original function will be affected. In this paper, an energy-balanced joint routing and charging framework is proposed to balance the energy consumption between sensors. By analyzing the network model, the proposed framework is decomposed into a routing strategy and a charging strategy. Considering the impact of the routing structure on sensors energy consumption, the goal of the routing strategy is designed to optimize the routing tree corresponding to the mobile charger staying at each sensor node. Furthermore, the proposed charging strategy prefers the charging path with the best balance of the total energy consumption of sensor nodes during one charging trip. In order to solve these optimization problems, the simulated annealing algorithms, including the proposed random solution generation method and acceptance rules, are used to obtain a fast convergence. The simulation results show that the proposed joint routing and charging framework has better energy balance performance than the traditional scheme.

This paper presents a broadband filtering patch antenna. This antenna consists of a rectangular patch, a rectangular ground plane, and an upright substrate. A coplanar waveguide (CPW) with T-probe is printed on the front side of the substrate, which can engender the broadband characteristic. On the back side, two transverse stubs cross the slots of CPW. The two transverse stubs can not only broaden the bandwidth but also improve the selectivity of the realized gain and reflection coefficient. Two U-slots are etched on the patch for providing a radiation null at the lower band edge as well as increasing the selectivity of out-of-band edge. Ultimately, an impedance bandwidth of 71.17% (2.48–5.22 GHz) and an average realized gain of 4.2 dBi are obtained. Moreover, two radiation nulls occur at 2.25 and 5.3 GHz. The simulated results are in good agreement with the measured results.

Modeling and solving multi-robot task allocation with definite path-conflict-free handling is an important research, especially in real working environments. Some of the research lines are unable to obtain definite path-conflict-free solutions for multi-robot task allocations, such as using the penalty-term method in the fitness function to restrict the survival probabilities of the solutions with path conflicts. In some cases, these solutions are only able to satisfy the objective of minimizing task time. We formulate this problem based on grid maps, while focusing on the frequently used cooperative task allocation. In our model, two subtasks of each cooperative task must be executed by two robots, simultaneously. We propose vitality-driven genetic task allocation algorithm (VGTA), which is able to simultaneously minimize task time and realize definite conflict-free path planning. VGTA consists of local operators, such as random mutations, greedy crossovers, and vitality selection. Meanwhile, VGTA includes schedule conflict and path conflict handling strategies. In path conflict handling strategy, we not only consider the common path conflicts in a grid cell, but also focus on the path conflicts between robots when exchanging positions in the adjacent grid cells. Besides, we construct our benchmarks based on real working environments, such as factory, powerhouse, and airport environments. Experimental results indicate that VGTA's search capability and computation cost are satisfactory. Meanwhile, its solutions are able to be really executed.

Hybrid precoding (HP) techniques based on partially connected structure (PCS) are widely studied in millimeter-wave (mmWave) MIMO communication systems due to low hardware cost as well as low energy consumption. Many efficient HP schemes based on PCS have recently been proposed, which require that the baseband precoding (BP) matrix of the digital domain to be a diagonal or square matrix. To avoid the interference from multiple streams of a single-user, the number of data streams for a single-user should not exceed the rank of the equivalent baseband MIMO channel (EBMC) before BP. Hence, these schemes are only reliable to the case that the EBMC matrix is full rank. However, the EBMC matrix may be rank-deficient due to the geometrical change and misplacement of the transceiver in practice. In this paper, we focus on the HP with PCS and propose a family of effective iterative matrix factorization (IMF) algorithms for HP designs, which are suitable for rank-deficient EBMC. We firstly propose an IMF-HP algorithm based on traditional design, which approximates the performance of the fully digital precoder by utilizing an alternate optimization strategy. In particular, we present a successive interference cancelation combined with IMF for HP design (SiC-IMF-HP) to further achieve higher throughput and lower complexity. Simulation results show that the proposed SiC-IMF-HP algorithm performs better than other recently proposed hybrid precoding schemes based on PCS when the number of data streams equals to the number of RF chains. The proposed algorithms both enjoy an acceptable computational complexity.

In recent years, with the rapid deployment of various Internet of Things (IoT) devices, it becomes a crucial and practical challenge to enable real-time search for objects, data, and services in the Internet of Everything. The IoT data prediction model can not only provide solutions for the real-time acquisition of the IoT sensor data but also provide more meaningful applications than the traditional IoT event detection model. In this paper, we use the complex time series formed by various types of sensors to establish a multi-dimensional feature selection model and a dynamic sensor-data prediction model. Compared with the traditional data prediction model, our model improves the accuracy and stability of the long-term prediction results of the IoT sensor data. Finally, we evaluate our prediction model using the Intel Berkeley Research Lab sensor data with an accuracy of over 98% and 92% accuracy on the Chicago Park District weather&water data.

Influence maximization is the problem of finding a certain amount of seed nodes that can trigger the largest expected number of remaining nodes under a pre-defined influence propagation model. However, most studies in this field apply online social network analysis methods mechanically and take commodity marketing in a broad sense as the research background, whose models are relatively simple, lacking characterization of specific business situation. Membership is a kind of classical marketing method. By selling membership, the company provides differentiated services to members and ordinary users, stimulating the former to consume. In this paper, we focus on the membership business model and study the membership-based influence maximization problem. First, due to the models used by predecessors failing in meeting the particularity of the membership, a novel influence propagation model membership-based influence cascade (MBIC) is proposed. According to the characteristics of membership, the MBIC model divides the influence propagation process into two stages, the influence stage and the reference stage. At the same time, the concepts of activity and intimacy are introduced to better model real social networks. Then, we propose the influence-reference rank (MBIC) algorithm that quantifies the ability of nodes at each stage in the MBIC to solve the membership-based influence maximization problem. Finally, experiments using real-world dynamic social networks with up to 1.4 million edges are conducted. The experimental results show that the influence-reference rank (IRR) achieves a better performance than several alternative algorithms under acceptable complexity conditions under MBIC model.

As a new wireless access technology, Narrow Band IoT (NB-IoT) enables low-power wide-area coverage services and can be applied to many domains. Emerging applications such as smart traffic, shared bicycles and shared cars have put forward more stringent requirements for connectivity. In order to get higher QoS, an enhancement access algorithm is proposed for the complex service scenario of NB-IoT, in which the network terminals are clustered based the distance from base station and terminal traffic intensity, and allocated reuse preamble code to improve network access capacity. The capacity is modeled and analyzed to evaluate the enhanced access algorithm based on clustering-reuse preamble allocation (ERA-CRPA). The experimental results show that the ERA-CRPA can effectively reduce the probability of random access preamble collision, further improve the access efficiency and increase the equivalent capacity of NB-IoT network.

Massive multiple-input-multiple-output (MIMO) is known as a large-scale antenna technology and has been enabled for the fifth generation (5G) mobile communication systems. The over-the-air (OTA) testing of massive MIMO antenna system has attracted a lot of attention in terms of evaluating the radio performance of a 5G base station (BS). As a promising OTA test methodology, the sectored multi-probe anechoic chamber (MPAC) setup is employed for the performance testing of massive MIMO BS. However, the system cost and installation are still an issue to be considered in practice (e.g., the anechoic chamber and multiple probes), though it can accurately reconstruct the flexible propagation channels by channel emulation methods. This paper proposes a virtual OTA test framework for the performance testing of massive MIMO BS on the basis of MPAC setups. As an alternative, the proposed virtual OTA test system adopting the concept of virtual probes solves the inconveniences and limitations of the actual probe installation in MPAC setups. The BS array responses to the actual probes of MPAC setups are generated in a phase matrix for the virtual probes. First, in this paper, the system description of virtual OTA testing is given. Then, the emulation method of spatial clusters is presented for the virtual OTA testing. Finally, simulations are performed with good channel emulation accuracy.

This paper introduces a benchmark dataset to the research article entitled “Ensemble framework by using nature inspired algorithms for the early-stage forest fire rescue - a case study of dynamic optimization problems”, by Zhang et al. [7]. Rescue ensemble that consists of rescue simulator and rescue algorithm is characterized by supporting the dynamic simulation of forest fire rescue. The purpose of rescue algorithm is to minimize the longest flight time of aircraft group II and the newly-increased burnt forest cost in one period, simultaneously. The map information in our dataset is from Google map and relevant parameters are also from the actual situation data. The benchmark contains 10 different maps that researchers can use to evaluate their own algorithms and compare their performance with our algorithm.

This paper presents a novel dual-band filtering balanced-to-unbalanced impedance transforming out-of-phase power divider using a simple admittance inverter with an extreme high frequency ratio and arbitrary power division, which is composed of stepped-impedance transmission lines. Based on the traditional transmission-line theory and ABCD/V matrix, the closed-formed analytical equations and complete design procedure are derived and provided for the filtering differential-mode transmission with high frequency ratio and good dual-band common-mode suppression. For demonstration, a designed prototype operating at 1 and 6.4 GHz are simulated, fabricated, and measured. The measured results agree well with the EM simulation perfectly.

A concurrent dual-band voltage-controlled oscillator (VCO) with independently tunable dual oscillation frequencies is proposed. A shared square open-loop dual-mode resonator and two varactor diodes are the basic units offering flexible tuning for the dual-band operation. A back-to-back varactor diode between the split of the resonator controls the odd-mode resonant frequency, and a single varactor diode is placed at the center of the resonator to adjust the even-mode resonant frequency. By combining the other four resonators with the shared dual-mode resonator, two distinct three-pole tunable bandpass filters (BPF) are designed as two frequency selective elements. Based on the two elements, a parallel-feedback concurrent dual-band VCO is fabricated with independently-tuned dual oscillation frequencies. Moreover, the mathematical deductions are analyzed to optimize the tuning ranges of the dual-oscillation frequencies and the circuit sizes. The measured results show that the two oscillation frequencies cover a tuning range of 5.114-5.28 GHz and 7.61-7.97 GHz, respectively.

This paper presents a novel structure for realizing a coupler with controllable power divisions, which is composed by two couplers and two phase shifters cascaded between them. This structure is applicable to constructing couplers with extremely-wide-range tunable power division, and the phase-difference performances can be predicted and controlled flexibly. In this paper, the rigorous design equations and methodologies are exhibited. For verification, two prototypes with rat-race and quadrature operations are fabricated and measured, and the measured results sufficiently confirm this topology to be effective and correct.

This paper presents a two-port dual-band pattern diversity patch antenna. The antenna consists of a rectangular patch, a rectangular ground plane, and an upright feeding network. The folding microstrip line and the new coplanar waveguide (CPW) structure are printed on two sides of the single feeding network with a size of 35 × 14.5 × 1 mm3. Therefore, two slots of the new CPW are able to generate in phase and out of phase electric fields, respectively, so that the patch is excited by the even and odd mode in lower common band and by the higher-order modes in upper common band. A prototype of the antenna is fabricated and measured. As a result, the lower common operating frequency band is 14% (2.453-2.821 GHz) and the upper common band is 16% (5.876-6.892 GHz). Moreover, the measured maximum peak gains are 4.0 dBi for Port 1 and 8.6 dBi for Port 2 in the lower common frequency band. In the upper common frequency band, 5.6 dBi for Port 1, and 4.5 dBi for Port 2 are obtained. The satisfactory isolation (|S12|

In this paper, a balanced-to-balanced power divider with a wideband filtering function is proposed. The power divider is simply composed of coupled-line sections, λ/4 lines and isolation resistors, and explicit design methodology is given. From the simulated and measured results, the power divider shows 49% differential-mode filtering bandwidth with two additional transmission zeros introduced, and the common-mode transmission is suppressed below -12 dB over 141% frequency bandwidth. This power divider can be a candidate for constructing fully-balanced systems.

Multiple-input multiple-output (MIMO) over-the-air (OTA) testing of wireless devices has become increasingly attractive in radiated performance evaluation. As one of the OTA testing methods, the radiated two-stage (RTS) method achieves flexible channel models with low-system cost. However, the existing MIMO OTA testing using RTS method is valid only for single carrier frequency application. This paper applies the RTS method to multiple carrier frequency applications [carrier aggregation (CA)]. Two setups are presented to discuss system cost and calibration time. To validate the RTS OTA testing for CA, the transfer matrices from the OTA antenna ports to device under test antenna ports in three types of RF shielded enclosure are investigated. The results demonstrate that the applied RTS method for CA works better in anechoic chambers. One calibration matrix might need to be adopted for each component carrier when the frequency separation of component carriers is large.

In this paper, the capacity improvement of full-duplex (FD) device-to-device (D2D) underlaying cellular networks (CNs) is analyzed. A single-cell environment is considered with one half-duplex (HD) base station, multiple HD cellular user equipments (CUEs), and one pair of FD D2D user equipments (DUEs). The BS is equipped with M multiple antennas, and one pair of FD DUEs is permitted to share the same resource with M out of K uplink HD CUEs, which will lead to a more complex interference environment. First, a novel interference-limited area-based (ILA-based) scheme is proposed to manage the co-channel interference from CN CUEs to FD DUEs. The ILA-based scheme does not allow the coexistence of HD CUEs and FD DUEs if the HD CUEs are located in any region of the two ILAs. Next, a senior ILA-based (SILA-based) scheme is proposed to reduce the complexity of the ILA-based scheme, in which only a common ILA is designed for both FD DUEs instead of the two ILAs in the ILA-based scheme. Then, the lower bounds of the ergodic capacity for FD D2D communications with imperfect self-interference cancellation (SIC) are derived in closed-forms with the ILA-based scheme and the SILA-based scheme. Furthermore, the capacity gain of the FD D2D communications is analyzed, and the numerical results show that the capacity improvement of the FD D2D communications is much greater than the traditional HD D2D communication if the sufficient SIC is achieved.

A concurrent dual-band six-port receiver based on real-valued time-delay neural network (RVTDNN) is proposed in this paper to retrieve two baseband signals from a dual-band radio frequency signal, concurrently. Different from the traditional six-port correlator, the new passive circuit correlator, which is composed of one power divider and three quadrature couplers, has three inputs and three outputs, resulting in the decreased hardware complexity as well as circuit size, and a reduced power consumption for the system. The new six-port correlator, its output power as well as the baseband signal recovery theory are described and analyzed in detail. The calibration algorithm based on the RVTDNN is adopted to verify the feasibility of the concurrent dual-band receiver based on the proposed correlator circuit. Finally, a practical wideband six-port receiver test bench, which operates from 2 to 3 GHz, is built and tested using the common modulated signals. The calculated error vector magnitudes are all less than 2% verifying the correctness of this novel system implementation approach.

In this paper, a simple and compact planar balanced-to-unbalanced in-phase power divider with arbitrary terminated impedances is proposed based on the coupled-line structure and a single grounded resistor. By using the even-/odd-mode analysis and the traditional transmission-line theory, the complete design procedure and analytical equations are obtained to achieve good performances for differential-mode transmission, common-mode suppression, phase difference, arbitrary terminated impedances, and isolation. For demonstration, two different prototypes with 50-to-50 Ω matching and complex impedance transformation are designed, fabricated, and measured. Good agreement can be observed between simulated and measured results.

High-performance single-ended wideband and balanced bandpass filters loaded with steppedimpedance stubs are proposed in this paper. For the proposed wideband filter and the differential mode of the proposed balanced filter, two transmission zeros near the passband are realized by using simple stepped-impedance stubs, which enhances the passband selectivity of these new filters. The analytical and accurate design equations for transmission poles and zeros of these single-ended and balanced filters are provided based on the scattering-parameters theory. The single-ended bandpass filter, employing a T-shaped structure to produce a wide passband, is achieved with 3-dB fractional bandwidth of 79.33%, 19-dB passband return loss, and 35-dB harmonic suppression (1.56f0-2.51f0, f0 is the center frequency of the wide passband). The 3-dB differential-mode fractional bandwidth of 33% with 22-dB passband return loss and the 30-dB harmonic suppression (1.29f0-2.67f0) are obtained in the proposed balanced bandpass filter. In addition, by inserting open-circuit stubs into the proposed balanced bandpass filter, over 25-dB common-mode suppression is obtained from 0 to 2.67f0. Good agreement is observed between the simulation and measurement results.

A single-feed dual-band dual-sense circularly polarized (CP) stacked patch antenna with a small frequency ratio is proposed for Chinese 842.5/922.5-MHz radio frequency identification (RFID) reader applications. Two elliptical-ring patches are configured orthogonally to operate at different frequency bands with different senses of circular polarization. A π-type dual-band complex impedance transformer is modified with asymmetric open-ended stubs to easily tune the input matching for both bands. Measured impedance bandwidth is 2.99% (824-849 MHz) for the lower band and 2.72% (908-933 MHz) for the upper band, in which the input return loss is greater than 10 dB. The measured 3-dB axial ratio (AR) bandwidths for the lower and upper bands are 1.07% (838-847 MHz) and 1.19% (918-929 MHz), respectively. The measured frequency ratio is 1.10. The measured gain is more than 4.5 dBic over both bands. Therefore, the proposed antenna can be a good candidate for Chinese RFID readers operating in the bands of 840-845 MHz and 920-925 MHz.

Duty cycle design is an important topic in body area networks. As small sensors are equipped with the limited power source, the extension of network lifetime is generally achieved by reducing the network energy consumption, for instance through duty cycle schemes. However, the duty cycle design is a highly complex NP-hard problem and its computational complexity is too high with exhaustive search algorithm for practical implementation. In order to extend the network lifetime, we proposed a novel quantum immune clonal evolutionary algorithm (QICEA) for duty cycle design while maintaining full coverage in the monitoring area. The QICEA is tested, and a performance comparison is made with simulated annealing (SA) and genetic algorithm (GA). Simulation results show that compared to the SA and the GA, the proposed QICEA can extending the lifetime of body area networks and enhancing the energy efficiency effectively.

A low energy clustering method of body area networks based on fuzzy simulated evolutionary computation is proposed in this paper. To reduce communication energy consumption, we also designed a fuzzy controller to dynamically adjust the crossover and mutation probability. Simulations are conducted by using the proposed method, the clustering methods based on the particle swarm optimization and the method based on the quantum evolutionary algorithm. Results show that the energy consumption of the proposed method decreased compare with the other two methods, which means the proposed method significantly improves the energy efficiency.

A new and accurate edge extension formula based on the Taguchi method is proposed to calculate the resonant frequency of electrically thin and thick rectangular patch antennas with an air gap (RPAAG) and rectangular patch antennas without an air gap. Based on 3205 antennas data random distribution in the electrical substrate thickness h/λd ranging from 0.001 to 0.2 and the dielectric constant ranging from 1.0 to 10.2, the edge extension formula is created with the Taguchi method. The resonant frequencies predicted using the proposed formula are in better agreement with simulated and measured results than those calculated with the existing formulas in other literatures, especially for electrically thick substrates. Furthermore, experimental results for the RPAAG are given, which shows that h/λd should be less than 0.13 in the design of a capacitively fed RPAAG.

In this paper, a wideband filtering power divider (PD) with ultra-wideband harmonic suppression and isolation is proposed. The dual coupled-line sections are embedded to the conventional quarter-wavelength transmission lines, which helps to extend the passband of the PD. With the introduction of the short-circuit stubs shunted at the output ports and the coupled lines with the open-circuit stubs, the ultra-wide stopband can be implemented more efficiently, thus resulting in five transmission zeros from 2 to 6 GHz. Furthermore, the improved isolation structure with series connected a resistor and a capacitor can be utilized to realize the ultra-wide isolation frequency band. Using a single resistor between two output ports, we have achieved an excellent in-band isolation. For demonstration, a wideband filtering PD operating at 1 GHz with a 20-dB bandwidth of 50% and an ultra-wide stopband better than 20 dB from 2 to 6 GHz is designed, fabricated, and measured. The measured results agree well with the anticipation.

This paper proposes a novel planar dual-band coupled-line balun with impedance transformation and high isolation. Closed-form design equations are obtained based on the classical even-odd mode equivalent approach. For convenience of designing and synthesizing such a novel dual-band balun, the practical ranges of the frequency ratio, terminated impedances, and two free variables are provided under the conventional microstrip fabrication constraints. By adopting four coupled-line sections, six transmission-line stubs, and an isolation resistor, a microstrip prototype balun working at 1.0/2.6 GHz is designed, fabricated, and measured. There is a good agreement between the simulated and measured results. The wide bandwidths of 290 MHz from 0.83 to 1.12 GHz and 270 MHz from 2.44 to 2.71 GHz are obtained with the measured return losses (|S11|, |S22|, |S33|) and the isolation (|S23|) better than 10 dB, which effectively confirm the proposed theoretical predictions.

A novel miniaturised wideband bandpass filter (BPF) based on harmonic suppressed dual transmission lines (DTLs) is introduced with enhanced upper stopband rejection and passaband selectivity. The transmission and harmonic suppression characteristics of series and parallel connected DTLs are analysed adopting even–odd mode method. To verify the proposed structure, a high selective wideband BPF centred at 1.86 GHz with a fractional bandwidth of 93.5% is designed and fabricated. The upper stopband is extended up to 8.8 GHz (4.7f0) with the suppression level of above 35 dB. Furthermore, a size reduction of 30% can be achieved in proposed BPF, compared with conventional wideband BPF based on quarter‐wavelength transmission lines.

Based on the feature of projection operator under box constraint, by using convex analysis method, this paper proposed three robust linear systems to solve a class of quadratic optimization problems. Utilizing linear matrix inequality (LMI) technique, eigenvalue perturbation theory, Lyapunov-Razumikhin method, and LaSalle’s invariance principle, some stable criteria for the related models are also established. Compared with previous criteria derived in the literature cited herein, the stable criteria established in this paper are less conservative and more practicable. Finally, a numerical simulation example and an application example in compressed sensing problem are also given to illustrate the validity of the criteria established in this paper.

In this paper, a novel L network (LN) is presented, which is composed of a frequency-selected section (FSS) and a middle stub (MS). Based on the proposed LN, a tri-band T-junction power divider (TTPD) with impedance transformation and independent power division ratios is designed. Moreover, the closed-form design theory of the TTPD is derived based on the transmission line theory and circuit theory. Finally, a microstrip prototype of the TTPD is simulated, fabricated, and measured. The design is for three arbitrarily chosen frequencies, 1 GHz, 1.6 GHz, and 2.35 GHz with the independent power division ratios of 0.5, 0.7, and 0.9. The measured results show that the fabricated prototype is consistent with the simulation, which demonstrates the effectiveness of this proposed design.

A novel wideband monopole antenna employing periodically loaded parallel-plate lines is presented in this paper. The proposed antenna consists of a main square patch, a rectangular ground plane, and a periodical structure which is printed on both sides of substrate. A strong electromagnetic coupling technique is used to design the element that enhances impedance bandwidth and decreases the side-lobe level throughout the effective bandwidth. The antenna achieves a wide impedance bandwidth of about 61.1% or ranging from 2.16 to 4.06 GHz, an omnidirectional far-field pattern, and a peak radiation gain of 2.37 dBi. Finally, the proposed antenna is analyzed and measured. The measured results show satisfactory performance and good agreement with the simulated results.

In this paper, a novel perturbation approach for implementing the independently reconfigurable dual-mode dual-band substrate integrated waveguide (SIW) filter is proposed. Dual-frequency manipulation is achieved by adding perturbation via-holes (the first variable) and changing the lengths of the interference slot (the second variable) in each cavity. The independent control of the upper passband only depends on the second variable while the lower passband is independently tuned by combining the two variables. Using such a design method, a two-cavity dual-band SIW filter is designed and experimentally assessed with four via-holes and an interference slot in each cavity. The dual-band filter not only has a frequency ratio (fR) ranging from 1.14 to 1.58 but also can be considered as a single passband one with a tunable range of 40.5% from 1.26 GHz to 2.12 GHz. The scattering parameters |S11| and |S21| are in the range of -10.72 dB to -37.17 dB and -3.67 dB to -7.22 dB in the operating dual bands, respectively. All the simulated and measured results show an acceptable agreement with the predicted data.

In this paper, the spoof surface plasmon polaritons (SSPPs) transmission line (TL) of periodical grooved bow-tie cells is proposed. The complex propagation constant and characteristic impedance of the SSPPs TLs and microstrip lines (MLs) are extracted using the analytical method of generalized lossy TL theory. The properties of the SSPPs TLs with different substrates and the same geometrical configuration are experimented. Then, for comparison, two ML counterparts are also experimented, which shows that the SSPPs TL is less sensitive to the thickness, dielectric constant and loss tangent of the chosen substrate below the cutoff frequency, compared with the ML ones. The single-conductor co-planar quasi-symmetry unequal power divider based on this SSPPs TL is presented in microwave frequencies. For experimental validation, the 0-dB, 2-dB, and 5-dB power dividers are designed, fabricated, and measured. Both simulated and measured results verify that the unequal power divider is a flexible option, which offers massive advantages including single-conductor co-planar quasi-symmetry structures, wide-band operation, and convenient implementations of different power-dividing ratios. Hence, it can be expected that the proposed unequal power dividers will inspire further researches on SSPPs for future design of novel planar passive and active microwave components, circuits and systems.

A rigorous mathematical explanation and accurate numerical prediction for asymmetrical passive intermodulation (PIM) distortions of memristors are investigated in this article. This theoretical explanation is based on behavior models of memristors representing the interrelation between terminated voltages and currents. The simulated single-tone and two-tone signal spectrums for extremely low-frequency (Hz) and microwave (GHz) applications verify our proposed mathematical approach and the new discovery of asymmetrical PIM distortions. This presented method provides an innovative choice to model and simulate the external performance of circuits and systems with asymmetrical PIM distortions in the future.

This paper presents a radiation pattern reconfigurable Yagi-Uda antenna based on graphene operating at terahertz frequencies. The antenna can be reconfigured to change the main beam pattern into two or four different radiation directions. The proposed antenna consists of a driven dipole radiation conductor, parasitic strips and embedded graphene. The hybrid graphene-metal implementation enables the antenna to have dynamic surface conductivity, which can be tuned by changing the chemical potentials. Therefore, the main beam direction, the resonance frequency, and the front-to-back ratio of the proposed antenna can be controlled by tuning the chemical potentials of the graphene embedded in different positions. The proposed two-beam reconfigurable Yagi-Uda antenna can achieve excellent unidirectional symmetrical radiation pattern with the front-to-back ratio of 11.9 dB and the10-dB impedance bandwidth of 15%. The different radiation directivity of the two-beam reconfigurable antenna can be achieved by controlling the chemical potentials of the graphene embedded in the parasitic stubs. The achievable peak gain of the proposed two-beam reconfigurable antenna is about 7.8 dB. Furthermore, we propose a four-beam reconfigurable Yagi-Uda antenna, which has stable reflection-coefficient performance although four main beams in reconfigurable cases point to four totally different directions. The corresponding peak gain, front-to-back ratio, and 10-dB impedance bandwidth of the four-beam reconfigurable antenna are about 6.4 dB, 12 dB, and 10%, respectively. Therefore, this novel design method of reconfigurable antennas is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems.

A novel coupled-line structure is proposed to design dual-band and high-power Gysel power dividers with inherent impedance-transforming functions. Based on traditional even- and odd-mode technique, the analytical design methods in closed-form formula are obtained and the accurate electrical parameters analysis is presented. Due to the usage of coupled-line sections, more design-parameter freedom and a wider frequency-ratio operation range for this kind of dual-band Gysel powder divider are obtained. Several numerical examples are designed and calculated to demonstrate flexible dual-band applications with different impedance-transforming functions. A practical microstrip power divider operating at 2 GHz and 3.2 GHz is designed, fabricated, and measured. The good agreement between the calculated and measured results verifies our proposed circuit structure and analytical design approach.