WILBERT

Description: Turbo codes, prevalent in most modern cellular devices, are set to be replaced by LDPC codes as the code for forward error correction. This transition was ushered in mainly because of the high throughput demands for 5G New Radio (NR). The new channel coding solution also needs to support incremental-redundancy hybrid ARQ, and a wide range of blocklengths and coding rates, with stringent performance guarantees and minimal description complexity. In this article, we first briefly review the requirements of the new channel code for 5G NR. We then describe the LDPC code design philosophy and how the broad requirements of 5G NR channel coding led to the introduction of novel structural features in the code design, culminating in an LDPC code that satisfies all the demands of 5G NR.

Description: Convolutional neural networks (CNNs) can be remarkably effective for recognizing two-dimensional and three-dimensional (3-D) actions. To further explore the potential of CNNs, we applied them in the recognition of 3-D motion-captured sign language (SL). The sign's 3-D spatio-temporal information of each sign was interpreted using joint angular displacement maps (JADMs), which encode the sign as a color texture image; JADMs were calculated for all joint pairs. Multiple CNN layers then capitalized on the differences between these images and identify discriminative spatio-temporal features. We then compared the performance of our proposed model against those of the state-of-the-art baseline models by using our own 3-D SL dataset and two other benchmark action datasets, namely, HDM05 and CMU.

Description: This letter proposes a novel ternary-event-based particle filtering ( $text{TEB-PF}$ ) framework by introducing the ternary-event-triggering mechanism coupled with a non-Gaussian fusion strategy that jointly incorporates point-valued, quantized, and set-valued measurements. In contrast to the existing binary-event-triggering solutions, the $text{TEB-PF}$ is a distributed state estimation architecture where the remote sensor communicates its measurements to the estimator, residing at the fusion centre, in a ternary-event-based fashion, i.e., holds on to its observation during idle epochs, transfers quantized ones during the transitional epochs, and only communicates raw observations during event epochs. Due to joint utilization of quantized and set-valued measurements in addition to the point-valued ones, the proposed $text{TEB-PF}$ simultaneously reduces the communication overhead, in comparison to its binary triggering counterparts, while also improving the estimation accuracy specially in low communication rates.

Description: A new control scheme for eliminating garbage collection during high-speed analysis of big-graph data stored in NAND flash memory is proposed and evaluated. During big-graph analysis, intermediate results of the analysis are stored in NAND flash memory and updated repeatedly. Under a conventional control scheme, excessive data copying, called “garbage collection,” occurs because overwriting data to NAND flash memory is prohibited. Such excessive data copying degrades performance of big-graph analysis. In contrast, under the proposed control scheme, the controller of NAND flash memory writes the intermediate results, which are updated at the same time, to the same block of NAND flash memory, and the excessive data copying is eliminated completely because all the data in the block can be erased at the same time before the intermediate results are updated. As a result, the proposed scheme shortens analysis time by 88 percent and increases analysis speed for big graphs 8.7 times. The proposed scheme can be applied to three-dimensional NAND flash memory and increases analysis speed 9.5 times. Also, the proposed scheme can be applied to an emerging high-density memory such as three-dimensional vertical chain-cell phase-change memory. These results show that the proposed control scheme enables high-speed analysis of big graphs.

Description: Due to the huge routing algorithm search space for 2D mesh based Network-on-Chip (NoC), Divide-Conquer method is presented to effectively explore the search space. When using Divide-Conquer method, a large number of routing algorithms will be created. In order to get the final results in an acceptable time, a precise metric is needed to measure routing performance and discard the poor performance routings. In this paper, we propose a new routing performance metric, namely, network pressure. Network pressure has the following three advantages: (1) it could measure the whole network congestion state; (2) network pressure of a network and that of its partial component is highly related, under the same routing; (3) it is closely related with routing performance. Based on network pressure and Divide-Conquer method, high performance routing could be achieved. The obtained routing is called suboptimal routing due to the following two reasons: (1) there is only a little gap between its performance and that of the fully adaptive routings under both transpose1 and transpose2 traffics. (2) the search space of routing algorithms is systematically and widely exploited.

Description: Today, security can no longer be treated as a secondary issue in embedded and cyber-physical systems. Therefore, one of the main challenges in these domains is the design of secure embedded systems under stringent resource constraints and real-time requirements. However, there exists an inherent trade-off between the security protection provided and the amount of resources allocated for this purpose. That is, the more the amount of resources used for security, the higher the security, but the fewer the number of applications which can be run on the platform and meet their timing requirements. This trade-off is of high importance since embedded systems are often highly resource constrained. In this paper, we propose an efficient solution to maximize confidentiality, while also guaranteeing the timing requirements of real-time applications on shared platforms.

Description: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.

Description: The 2-D/3-D hybrid discontinuous Galerkin time-domain (DGTD) method is efficient to deal with structures that contain elements capable of 2-D simplification. To separate 2-D elements from 3-D ones, a criterion for approximation error manipulation is required. However, in the latest reported technique, this kind of criterion is derived from the causality principle and the Courant–Freidrichs–Lewy constraint, and thus is indirect and inessential to 2-D simplification. As a result, some elements capable of 2-D simplification are unnecessarily flagged as 3-D ones, deteriorating efficiency dramatically. Moreover, controlling absolute error, the traditional criterion is not flexible for structures with complex mode distribution. In this paper, a novel criterion is proposed. Compared with the traditional one, this new criterion controls comparative error instead of absolute error, thus enhancing accuracy and flexibility. Besides, for the time-adaptive updating algorithm, the proposed criterion is derived directly from the discretized matrix equations of the DGTD method, rendering it straightforward and efficient. Finally, the 2-D/3-D DGTD with the proposed criterion is integrated with the modified nodal analysis technique for the analysis of power-ground plate pairs with decoupling capacitors. The accuracy, flexibility, and efficiency enhancement of the proposed criterion are demonstrated by comparison with commercial software and the traditional method.

Description: This paper discusses a novel optimization technique for broadband reflective-type phase shifters (RTPS). The performance characteristics of an RTPS, including its achievable maximum phase shift and the corresponding average loss, are calculated on the basis of simulated or measured varactor data. In addition, the root-mean-square (rms) errors are evaluated to determine the broadband performance of the device. To extract the characteristics, a reciprocal, lossless matching network with arbitrary output impedance is connected in series to the varactor. The results are plotted on Smith charts, which yield an intuitive representation of the matching network area to achieve the design goals. The technique is verified by realizing a WR-3 band (220–325 GHz) RTPS microwave monolithic integrated circuit realized in a 50-nm metamorphic high electron mobility transistor InGaAs technology. The measured phase shift is 118° at the center frequency of 240 GHz with a bandwidth of 62 GHz. The rms phase and amplitude errors are lower than 5.6° and 0.67 dB, respectively.

Description: This paper reports on the design and optimization of MEMS-tunable evanescent-mode cavity-based bandpass filters with continuously variable center frequency within an octave tuning range. The devised filters are manufactured using silicon-micromachining techniques that enable their actualization for frequencies located in the millimeter-wave (30–100 GHz) regime. An RF design methodology that takes into consideration all microfabrication-induced constrains—e.g., nonvertical wall profiles and finite MEMS deflection—enables high unloaded factor ( $Q_{u}$ ) and also minimizes bandwidth (BW) variation within the octave tuning range is reported. Furthermore, a new passively compensating package-integrated input/output feeding structure that enables optimal impedance matching over the entire tuning range is also presented. In order to evaluate the devised RF design methodology, a filter prototype was manufactured and measured at Ka-band. It exhibits a measured frequency tuning between 20 and 40 GHz (2:1 tuning range), relative BW between 1.9 and 4.7%, insertion loss between 3.1 and 1.1 dB, and input reflection below 15 dB. This paper also explores important tradeoffs between mechanical stability and insertion loss by comparing creep-resistant to pure-Au tuning diagrams.

Description: Limited sensitivity and sensing range are arguably the greatest challenges in microwave sensor design. Recent attempts to improve these properties have relied on metamaterial (MTM)-inspired open-loop resonators coupled to transmission lines (TLs). Although the strongly resonant properties of the resonator sensitively reflect small changes in the environment through a shift in its resonance frequency, the resulting sensitivities remain ultimately limited by the level of coupling between the resonator and the TL. This paper introduces a novel solution to this problem that employs negative-refractive-index TL MTMs to substantially improve this coupling so as to fully exploit its resonant properties. A MTM-infused planar microwave sensor is designed for operation at 2.5 GHz, and is shown to exhibit a significant improvement in sensitivity and linearity. A rigorous signal-flow analysis of the sensor is proposed and shown to provide a fully analytical description of all salient features of both the conventional and MTM-infused sensors. Full-wave simulations confirm the analytical predictions, and all data demonstrate excellent agreement with measurements of a fabricated prototype. The proposed device is shown to be especially useful in the characterization of commonly available high-permittivity liquids as well as in sensitively distinguishing concentrations of ethanol/methanol in water.

Description: This paper presents the analytical design of transmission-type arbitrary prescribed wideband flat group delay (GD) circuits (type-I and type-II) using $lambda $ /4 coupled lines. The GD circuit type-I consists of two sections of coupled lines, whereas the GD circuit type-II consists of $lambda $ /4 transmission lines (TLs) at input and output, in addition to coupled lines. The additional $lambda $ /4 TLs at input–output ports in GD circuit type-II provide more freedom to obtain larger GD, as compared to type-I, without fabrication difficulties. The analytical analysis shows that the wideband flat GD response can be obtained by selecting the appropriate even- and odd-mode impedances of coupled lines and the characteristic impedance of TLs. To obtain the arbitrary prescribed wideband flat GD response, the closed-form analytical design equations are provided. For experimental validation of the proposed structures, prototypes of GD circuits (type-I and type-II) are designed and fabricated at the center frequency of 2 GHz. The measurement results agree well with the simulation and theoretical predicted results.

Description: A coupled-line coupling structure is proposed for the design of quasi-elliptic bandpass filters (BPFs). The coupled-line structure functions as the input coupling structure for a BPF and introduces one pair of symmetrical transmission zeros at around the cutoff frequencies. Equivalent circuit models play an important role in the design of microwave filters. Accordingly, this paper undertakes a major effort to develop the equivalent circuit of the coupling structure. The equivalent circuit is in a form that can be readily used in combination with a given direct-coupled filter. The coupling structure can serve as a basic building block for the design of quasi-elliptic BPFs. As demonstrated by the theoretical and experimental treatment, the coupling structure can be used to transform a Chebyshev filter into a quasi-elliptic filter.

Description: In this contribution, a novel method to design broadband nonreciprocal phase shifters (NRPS) is illustrated: this new topology is based on the combination of two directive-distributed amplifiers with a four-port phase-shifting network. The presented approach includes explicit design formulae allowing for arbitrary differential-phase implementation. Extensive design description of a 180° NRPS, acting as broadband differential-phase inverter, is also provided. The $3.5 times 3.4$ mm 2 demonstrator, realized in 0.5 $mu text{m}$ GaN HEMT technology, has an average zero insertion loss up to 25 dBm of input power, 180° ± 2° differential-phase shift, and good port matching over the 3–7-GHz operating bandwidth.

Description: This paper presents the design, fabrication, and characterization of a zero-bias quasi-optical terahertz detector based on monolithically integrated heterostructure backward diodes (HBDs) for operation at G-band. The reported detectors consist of HBDs with $0.7 times 0.7 ~mu text{m}^{2}$ active device area and submicrometer-scale airbridges, integrated with lens-coupled high-impedance planar folded dipole antennas. Measurements of the HBD detector show that a peak-measured detector sensitivity of approximately 2400 V/W and a minimum noise equivalent power (NEP min ) of 2.14 pW/ $surd $ Hz have been obtained at 170 GHz. If an antireflection coating was used on the lens, a sensitivity of approximately 3500 V/W and NEP min of 1.48 pW/ $surd $ Hz is projected. The radiation patterns of the quasi-optical detector in both $E$ - and $H$ -planes have been measured, and good agreement has been achieved between simulation and measurement. The performance of this detector can be further improved by scaling the HBD device active area. The reported approach using monolithically integrated heterostructure backward tunneling diodes and submicrometer airbridges is promising for developing high performance and compact detectors and focal-plane arrays for millimeter-wave and terahertz sensing and imaging applications.

Description: Differences in the material reflection are required for any contrast in microwave- and millimeter-wave (mm-wave) imaging systems. Therefore, the dielectric properties, which determine the reflection of materials, need to be characterized. The characterization of skin and other biological tissue is, therefore, necessary, to apply imaging systems for instance in cancer diagnosis. In this paper, short, coherent mm-wave pulses (wavelets) are generated and their reflection on dispersive materials is studied. The reflections of wavelets on porcine skin and water are examined in time and frequency domain. A first-order Debye model is fitted to the reflection coefficient in frequency domain to quantify material dispersion. The frequency-dependent reflection on dispersive materials causes a distortion of the wavelets in the time domain. The startup behavior of the pulses is examined by simulation and measurements. The rise time of the pulses is identified as a feature in time domain for wavelets reflected on dispersive media. Together with other features characteristic for a pulse, for instance the wavelet amplitude, this enables identification of dispersive materials by reflectometry measurements, making it suitable for applications in mm-wave imaging systems.

Description: Stochastic network optimization problems entail finding resource allocation policies that are optimum on an average but must be designed in an online fashion. Such problems are ubiquitous in communication networks, where resources such as energy and bandwidth are divided among nodes to satisfy certain long-term objectives. This paper proposes an asynchronous incremental dual decent resource allocation algorithm that utilizes delayed stochastic gradients for carrying out its updates. The proposed algorithm is well-suited to heterogeneous networks as it allows the computationally-challenged or energy-starved nodes to, at times, postpone the updates. The asymptotic analysis of the proposed algorithm is carried out, establishing dual convergence under both, constant and diminishing step sizes. It is also shown that with constant step size, the proposed resource allocation policy is asymptotically near-optimal. An application involving multicell coordinated beamforming is detailed, demonstrating the usefulness of the proposed algorithm.

Description: Deploying a massive number of antennas at the base station side can boost the cellular system performance dramatically. This however involves significant additional radio-frequency (RF) front-end complexity, hardware cost, and power consumption. To address this issue, the beamspace-multiple-input-multiple-output (beamspace-MIMO)-based approach is considered as a promising solution. In this paper, we first show that the traditional beamspace-MIMO suffers from spatial power leakage and imperfect channel statistics estimation. A beam combination module is hence proposed, which consists of a small number (compared with the number of antenna elements) of low-resolution (possibly one-bit) digital (discrete) phase shifters after the beamspace transformation module to further compress the beamspace signal dimensionality, such that the number of RF chains can be reduced beyond beamspace transformation and beam selection. The optimum discrete beam combination weights for the uplink are obtained based on the branch-and-bound (BB) approach. The key to the BB-based solution is to solve the embodied subproblem, whose solution is derived in a closed-form. Thereby, a sequential greedy beam combination scheme with linear-complexity (w.r.t. the number of beams in the beamspace) is proposed. Link-level simulation results based on realistic channel models and long-term-evolution parameters are presented which show that the proposed schemes can reduce the number of RF chains by up to $text{25}%$ with a one-bit digital phase-shifter-network.

Description: We present a method for joint optimization of transmitter in-phase, quadrature and interpolarization time skew, amplitude mismatch, and bias voltages. The method is based on a cooperative coevolutionary genetic algorithm with fitness functions extracted from a directly detected reference quadrature amplitude modulation (QAM) signal generated at the transmitter. As a calibration method, it is able to find the values that will statically generate the best possible constellation. To the extent of the simulation investigations conducted, the algorithm is capable to calibrate time skews, bias voltages, IQ phase imbalances, and relative amplitude imbalances with standard deviation of residual error as low as 0.24 ps, 0.019 V, 0.56°, and 0.003, respectively, for a dual-polarization IQ modulator with $V_{pi } = text{4},text{V}$ and a 16-QAM reference signal operating at 16 GBd. An experimental demonstration is also reported.

Description: Presents the front cover for this issue of the publication.

Description: Presents the President’s message for this issue of the publication.

Description: Presents information on Microwave Week 2018.

Description: Presents information on the IMS 2018 Boot Camp.

Description: Presents information on the MTTS Ph.D. Student Sponsorship Initiative and Graduate Student Challenge.

Description: Presents information on the Spring ARFTG 2018 Microwave Measurement Conference.

Description: Presents information on the IMS2018 MicroApps conference.

Description: Since their conception in the early 1900s, radar systems have mostly used a single RF beam to probe the environment in search of objects of interest. Traditionally, this is accomplished by scanning the beam over a defined region and using time of flight to determine the range of objects located within the beam. As such, a key figure of merit is the spatial extent, or angular divergence, of the RF beam because it defines the lateral (or cross-range) resolution of detectable objects, while the operational bandwidth (BW) of the radar determines the range resolution of detectable objects. In combination, these two metrics often define the overall capability of the radar system.

Description: Presents information on global MTTS society education initiatives.

Description: Presents information on the RWW 2019 conference.

Description: Presents information on the WiSNET 2019 conference.

Description: A 128 Gbit/s free-space laser link demonstration has been presented. We use a simulated atmosphere system with a tunable 1 km equivalent weak turbulence channel. Eye diagrams and constellation diagrams were observed. Bit error rate curves of back to back transmission and that in a simulated atmospheric channel are measured. The results show that the receiving sensitivities can be better than –37.3 dBm at the rate of 128 Gbit/s in a turbulence channel. To the best of our knowledge, it is the first time that the transmission performance of high speed space laser in a tunable atmospheric channel is studied.

Description: Visible light communication devices have attracted significant attention recently due to their advantageously high transmission rates. It has been shown that current density and device capacitance has a significant effect on the frequency of visible-light GaN communication devices. We demonstrate a similar linear relationship in a micro-light emitting device (LED) between the −3 dB response frequency, current density, and device diffusion capacity. An experiment was conducted in which, when the device’s single light-emitting unit size is between 60–120 $mu text{m}$ , increasing the LED current density, the lifetime of the device is substantially reduced for the period of the device’s light emission process, and reducing device capacitance improved the device response frequency. To show the relationship between device capacitance and response frequency, four groups of devices with a single unit of the visible GaN communication device was reduced from 120 to 60 $mu text{m}$ , the current was set to 35 mA, and the matrix of devices was increased from $1times 1$ to $4times 4$ , generally, as the number of series increases, the capacitance decreases. As a result, the −3 dB device response frequency increased from 18 to 74 MHz and luminous efficiency increased from 37 to 74 lm/W, the linear relationship between capacitance and response frequency has been confirmed.

Description: A fully complementary metal-oxide-semiconductor compatible optical router is demonstrated. The router structure is built using the silicon-organic hybrid platform, while its mechanism is based on the directional coupler operation. The directional coupler waveguides are formed by the arrays of silicon nanowires, while the cladding and voids between the silicon nanowires are filled with an electro-optic polymer. Routing of the optical signal is demonstrated through the change of the coupling length of the directional coupler upon voltage application. The router is characterized by the short length directional coupler of $24~mu text{m}$ , and total footprint of $62~mu text{m}^{2}$ , high extinction ratio which reaches 33 dB and low insertion losses of 1.3 dB.

Description: In this letter, in order to improve avalanche characteristics in deep ultraviolet range and enhance fill factor, vertical 4H-SiC n-i-p-n avalanche photodiodes (APDs) are designed and fabricated, in which avalanche current flows through a forwardbiased p-n junction formed between the p epi-layer and the n-type substrate. Compared with a traditional n-i-p APD, no obvious difference of gain-voltage and photo-response characteristics is observed, indicating the feasibility of the proposed n-i-p-n device structure. When a partial trench isolation scheme is applied, the vertical n-i-p-n APD shows a high fill factor of 78.3% and a low-bias quantum efficiency of 66%.

Description: Recent steganalytic schemes reveal embedding traces in a promising way by using convolutional neural networks (CNNs). However, further improvements, such as exploring complementary data processing operations and using wider structures, were not extensively studied so far. In this letter, we design a new CNN in these aspects in order to better capture embedding artifacts. Specifically, on the one hand, we propose to process information diversely with a module called diverse activation module. On the other hand, we build a wide structure with parallel subnets using several filter groups for preprocessing. To accelerate the training process, we pretrain the subnets independently. Extensive experiments show that the proposed method is effective in detecting content-adaptive steganographic schemes.

Description: A 0.1-THz input coupler for HE 04 mode confocal gyrotron traveling-wave amplifiers is presented. A high-order HE 04 mode in confocal waveguide is efficiently excited from a TE 10 mode. The coupler consists of a Y-type power-divider and a mode-converting section. The wave is coupled with the confocal waveguide via two nonstandard rectangular apertures to maximize the coupling efficiency. The mode-converting section is enclosed with mode-selective grooves to suppress the unwanted modes and thus achieve a high efficiency over a broad frequency band. The prototype is fabricated and measured. Measurements are conducted utilizing two identical back-to-back connected couplers, and the measured performances show excellent agreement with the numerical one. Experimental results show that the coupler achieves a transmission of better than −3 dB in the frequency band from 92 to 110 GHz and a maximum transmission of −1 dB. The coupler exhibits high conversion efficiency, broad bandwidth, and flat transmission throughout the 1-dB bandwidth, which can also be used as a mode converter in cold test experiments of the interaction circuits.

Description: This paper presents a new method for designing multiband bandpass filters (BPFs). The filter consists of low-pass filter and two open stub-loaded shorted stubs. Multiple transmission zeros (TZs) are produced by the open stub-loaded shorted stub, and multiple passbands can be realized. For the first time, different numbers of open stubs are used to realize multiband BPFs with two to seven passbands. The center frequencies and the last passband bandwidth can be tuned in a certain range by adjusting the TZs and transmission poles. First, a wideband BPF is presented to introduce the design concept. Theoretical analysis is done to illustrate the design principle. Then, a wide single-band BPF and a dual-band BPF are designed to demonstrate the design method. The design procedure is summarized to guide the design process. Finally, tri-/quad-/quint-/sext-/sept-band BPFs are designed according to the design principle. All the BPFs are manufactured. Measured results show good agreement with simulated ones.

Description: This paper presents a W-band phased array receive front end in 32-nm CMOS silicon-on-insulator technology. The architecture is based on cascode low-noise amplifiers and passive switched LC 5-bit phase-shifters and with root-mean-square (rms) phase error of <3.5° at 88–93 GHz. The 4-bit equivalent (11°) rms phase error bandwidth is 88–98 GHz. An average system noise figure (NF) of 5.3 dB is obtained at 93–97 GHz with 18-dB gain and input $P_{mathrm{ 1dB}}$ of −25 dBm. The low-noise amplifier and phase-shifter front end consumes 24.3 mW including bias circuits. To the author’s knowledge, the front-end NF and power consumption are state of the art for silicon-based phased array receivers at W-band frequencies, and compares well with indium phosphide (InP) and gallium arsenide (GaAs) pseudomorphic high electron mobility transistor front ends.

Description: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.

Description: Presents the General Chair's welcome from the IMS 2018 Conference.

Description: Presents information on the IMA 2018 conference, including the opening and closing sessions.

Description: Presents information on the IMS 2018 conference.

Description: Presents information on the IMS2018 STEM Program.

Description: Presents information on the PAWR 2019 conference.

Description: Reports on MTTS society awards that were presented at te IMS 2018 conference.

Description: Having achieved "first light" immediately prior to the ceremony introducing it on 25 September 2016, China's 500-m aperture spherical radio telescope (FAST) is now being kept busy with commissions. Its innovative design requires ~1,000 points to be measured and driven instead of just the two axes of motion, e.g., azimuth and elevation for most conventional antennas, to realize pointing and tracking. We have devised a survey plan to exploit the full sensitivity of FAST, while minimizing the complexities involved during system operation. The 19-beam L-band focal plan array will be rotated to specific angles and receive continuous data streams, while the surface shape and the focal cabin stay fixed. Such a survey will cover the northern sky in about 220 full days. Our aim is to obtain data simultaneously for pulsar search, detection of neutral hydrogen (HI) galaxies, HI imaging, and radio transients through multiple back ends. These data sets could represent a significant contribution to all related fields in radio astronomy and remain relevant for decades.

Description: Presents information on the TWIOS 2019 conference.

Description: An efficient method based on a hybrid approach that combines extreme learning machine (ELM) technique and differential evolution (DE) algorithm is proposed to optimize the multipumped Raman fiber amplifier (RFA). The proposed method takes advantage of the fast learning speed and high generalization of the ELM as well as the strong global search capability of DE. From a novel perspective, we utilize ELM as a powerful learning tool to construct the nonlinear mapping between the pump parameters and gains of RFA. Instead of time-consuming integration of Raman coupled equations, the gains can be directly and accurately determined by the ELM model. To obtain a flat gain spectrum, DE algorithm is employed to find the optimal wavelengths and powers of pumps. The well-trained ELM model is incorporated into the evolution of DE to accelerate the search process. The results show that the designed RFAs with the optimized pump parameters achieve the desired gain performance and meanwhile maintain very low level of gain ripple. In comparison to other related methods, the proposed method significantly shortens the computation time and enhances the overall optimization efficiency, which offers potential for real-time adjustment and flexibility of RFA design.

Description: We propose and demonstrate a continuous-wave all-fiber ring laser generating cylindrical vector beams (CVBs) using a mode selective coupler (MSC) as transverse mode converter and mode splitter. The MSC is fabricated by a novel method free of pre-tapering, achieving LP 11 mode with a high purity of >96% near the wavelength of 1064 nm. The CVB fiber laser operates at a center wavelength of 1053.9 nm, with a 3-dB linewidth of less than 0.04 nm and a signal-to-background ratio of >60 dB. The laser slope efficiency is >9%. The radially and azimuthally polarized beams can be switched by adjusting the polarization controllers in the fiber ring cavity, with a high mode purity measured to be >96%.

Description: In this letter, a monolithically integrated ring laser is demonstrated and discussed with respect of potential application in optical gyroscope systems. The device has been realized using generic indium phosphide technology and fabricated on a multi-project wafer. The laser design uses a racetrack resonator with an arrayed waveguide grating as an intra-cavity wavelength filter. Measurement results proved the on-chip laser power of ca. 10 mW and single frequency operation with side mode suppression ratio over 50 dB. The laser is integrated with an interferometric detection circuit for monitoring the beating signal under rotation of the device.

Description: A sensing structure based on a cleaved silica microsphere is proposed for temperature sensing. The microsphere was cleaved using focused ion beam milling. The asymmetry in the structure introduced by the cut generates not only new cavities but also random interferometric reflections inside the microsphere. These two spectral components can be separated using low-pass and high-pass filters, respectively. The sensor response to temperature can be extracted from the cavities’ component using a correlation method. The device achieved a temperature sensitivity of −10.8 ± 0.2 pm/°C between 30 °C and 80 °C. The same effect is impossible to be obtained in a normal uncleaved microsphere. The random interferometric component did not provide any information on temperature using the same analysis. However, when changing the temperature, a new and completely distinct reflection spectrum with no apparent correlation with others at different temperatures was achieved.

Description: This letter proposes analytical expressions for the fusion of certain classes of labeled multiobject densities via Kullback–Leibler averaging. Specifically, we provide analytical fusion rules for the labeled multi-Bernoulli and marginalized $delta$ -generalized labeled multi-Bernoulli families of labeled multiobject densities. Information fusion via Kullback–Leibler averaging ensures immunity to double counting of information and is essential to the development of effective multiagent multiobject estimation.

Description: This letter investigates joint power control and user clustering for downlink nonorthogonal multiple access systems. Our aim is to minimize the total power consumption by taking into account not only the conventional transmission power but also the decoding power of the users. To solve this optimization problem, it is firstly transformed into an equivalent problem with tractable constraints. Then, an efficient algorithm is proposed to tackle the equivalent problem by using the techniques of reweighted $ell _1$ -norm minimization and majorization–minimization. Numerical results validate the superiority of the proposed algorithm over the conventional algorithms including the popular matching-based algorithm.

Description: Asynchronous logic offers the advantages of no clock tree, robust circuit operation, avoidance of worst-case timing margins, and a reduced emission spectrum. Thus, computational paradigms are sought to attain advantages of clockless logic by leveraging the complementary characteristics of emerging devices and CMOS transistors within novel circuit designs. This paper introduces Spin Torque Enabled NULL Convention Logic (STENCL), which exploits the physical characteristics of non-volatile Domain-Wall (DW) and memristive devices to realize the Quasi-Delay-Insensitive (QDI) NULL Convention Logic (NCL) asynchronous design methodology. First, a formal algorithm is developed to transform NCL-based threshold m-of-n gate realizations to STENCL, in order to generate the corresponding input memristance and NULL module memristance required for nominal currents achieving DW device biasing. Second, hysteresis and set/reset conditions are realized by determining the corresponding current fluctuations required to move the DW within each threshold logic gate to realize all 27 foundational NCL gate structures, which are then simulated to assess energy and delay metrics. Third, a case study of a four-stage pipelined 32-bit IEEE single-precision floating point co-processor implemented as a dual-rail STENCL architecture is compared to a conventional CMOS-based NCL design implemented by an IBM SOI1250 45nm CMOS process. Fourth, a sensitivity analysis is performed to assess the impact of write accuracy and drift on memristor and DW device operation. Results indicate that STENCL-based designs achieve between 2-fold to 20-fold reduction in energy consumption with up to 8-fold reduction in area, over an equivalent CMOS-based NCL design for 32-bit full adders. Comparisons for various four-stage pipelined 32-bit IEEE single-precision floating-point co-processors and ISCAS benchmarks further substantiate those benefits for operation within acceptable tolerances at identical process technology - odes.

Description: A general numerical scheme is proposed for the waveport modeling and scattering-parameter (S-parameter) extraction of inhomogeneous waveports with the discontinuous Galerkin time-domain method. In this scheme, the waveports are truncated with perfectly matched layers with a hybrid mesh automatically extruded from the mesh of the physical device to be simulated. The waveports are then excited by a total-field/scattered-field technique, with which the incident and scattered waves can be obtained for an accurate calculation of the S-parameters. A novel eigenmode solver is also developed to calculate the required modal profiles for the eigenmodes in both homogeneous and inhomogeneous waveports. Special attention is paid to the S-parameter extraction for evanescent modes, which has been a difficult task for time-domain simulations. Numerical examples are given to validate the proposed numerical scheme.

Description: This paper presents a new systematic and efficient method for the design of high-power varactor-based impedance tuners. By incorporating the varactor losses and voltage handling capabilities, the method allows the impedance tuning range to be maximized and losses to be minimized under high-power operating conditions. A 2.2-GHz large-signal double-stub tuner has been designed using the proposed methodology and SiC varactor diodes. Using comprehensive large-signal measurements, a 25-W input power handling is demonstrated up to $Gamma _{max } approx ~0.8$ . Two-tone linearity measurements show an input third-order intercept point exceeding 50 dBm for most impedances. These results clearly demonstrate the feasibility of the proposed technique for the design of high-performance large-signal tuners.

Description: A direct matrix approach is presented for the first time to synthesize high selectivity in-line topology filters where multiple transmission zeros are generated and independently controlled by a set of frequency-variant couplings. As the resultant network only involves resonators cascaded one by one without any auxiliary elements (such as cross-coupled or extracted-pole structures), this paper provides the best synthesis solution in configuration simplicity for narrowband filters. Considering both the couplings and capacitances of a traditional low-pass prototype, a generalized transformation on the admittance matrix is introduced as the basis of the synthesis, which allows more than one cross-coupling to be annihilated in a single step, while generating a frequency-variant coupling simultaneously. It is then shown that the in-line topology as well as some other unique topologies can be determined by applying a specific sequence of the transformations. For the validation, a group of examples with synthesis as well as experimental results are demonstrated.

Description: We propose two-photon absorption light-induced self-written (LISW) waveguide formation using short-wavelength infrared pulse laser light. It is suitable and efficient for single-mode optical interconnection, and also promising for small-core single-mode optical interconnection. The approach offers the possibility of not only decreasing the insertion loss, but also reducing the interconnection task time. We assessed this approach for single-mode optical interconnection. We obtained an LISW waveguide loss of about 0.06 dB for an LISW waveguide length of 100 μ m and a connection loss per facet of about 0.37 dB. We also presented the results on the interconnection between high-numerical-aperture small-core thermally-diffused expanded-core single-mode fibers having the mode field diameters of about 3 μ m by using the same approach. The results showed the present approach to be a promising alternative route for efficient interconnection of small-core single-mode optical devices, such as silicon nanowires with appropriate configurations.

Description: The improved performance of Si quantum dot-based silicon nitride light-emitting devices with the inserted hole-blocking nc-Si layer was investigated. An enhanced electroluminescence (EL) efficiency of 200% from the SiN x -based LEDs is demonstrated through H 2 plasma treatment of the inserted nc-Si layer. The enhancement of an EL efficiency is depended on time for plasma treatment. Moreover, the injected current of the devices with H 2 plasma treatment is significantly higher than that of the device without H 2 plasma treatment under the same driving voltage. The Z-parameter of the devices increases from 1.25 to 1.41 after H 2 plasma treatment of inserted nc-Si layer. The inserted nc-Si layers with and without H 2 plasma treatment were further investigated by the Raman spectroscopy and the Fourier transform infrared absorption spectroscopy, respectively. It is suggested that the improved EL efficiency is due to the suppression of nonradiative recombination, which resulted from the hydrogen passivation that effectively reducing Si-related defect states of the inserted nc-Si layer.

Description: By transferring the colloidal suspensions of ferroferric-oxide (Fe 3 O 4 ) nanoparticles (FONPs) onto a quartz plate, zero-dimension FONPs saturable absorber (SA) is successfully fabricated and employed in a Tm:Lu 3 Al 5 O 12 (Tm:LuAG) bulk laser. The properties of the FONPs-SA including Raman response, nonlinear optical response, and broad-band spectral absorption from 1800 nm to 2500 nm are measured. With the as-prepared FONPs-SA, laser pulses with the shortest duration of 600 ns, a maximum repetition rate of 96 kHz and maximum pulse energy of $4.9~mu text{J}$ are obtained, corresponding to a maximum peak power of 8.2 W. This is the first experimental demonstration of the zero-dimension FONPs-SA as Q-switch in $2~mu text{m}$ spectral region and even longer wavelength mid-infrared spectral region, to the best of our knowledge, which indicates that the zero-dimension FONPs-SA can act as a promising optical modulator in mid-infrared spectral region.

Description: Faster-than-Nyquist (FTN) signaling by introducing controlled inter-symbol interference (ISI) has been viewed as a potential technique in future communication systems due to its higher spectrum efficiency. In order to achieve the high transmission rate, the effective receivers have to been designed to suppress the ISI and extract the transmit signals. Therefore, we propose a channel shortening-based maximum-likelihood sequence estimation (MLSE) scheme. In this scheme, the length of the shortening channel can be optimized for the different time-squeezing factor, which determines the transmission rate and ISI in FTN systems, to achieve a good tradeoff between the detection performance and the implementation complexity. The simulation analysis results show that the proposed MLSE equalizer with optimized channel shortening can achieve a good tradeoff between the performance and the complexity.

Description: We demonstrate the first experimental evaluation of a 10Gb/s optical matchline (ML) memory architecture that designates successfully whether an incoming 2-bit optical address is identical to the optical address stored in an optical content addressable memory (CAM) line. The optical CAM line is formed by two optical CAM cells, with every cell comprising a monolithically integrated InP flip-flop and an SOA-MZI-based XOR gate, while the ML is completed by a subsequent wavelength multiplexing element and a semiconductor optical amplifier-cross gain modulation gate. Error-free operation at 10Gb/s has been obtained for 2-bit optical addresses and for both content addressing and write memory functionalities.

Description: This letter investigates methods to detect graph topological changes without making any assumption on the nature of the change itself. To accomplish this, we merge recently developed tools in graph signal processing with matched subspace detection theory and propose two blind topology change detectors. The first detector exploits the prior information that the observed signal is sparse w.r.t. the graph Fourier transform of the nominal graph, while the second makes use of the smoothness prior w.r.t. the nominal graph to detect topological changes. Both detectors are compared with their respective nonblind counterparts in a synthetic scenario that mimics brain networks. The absence of information about the alternative graph, in some cases, might heavily influence the blind detector's performance. However, in cases where the observed signal deviates slightly from the nonblind model, the information about the alternative graph turns out to be not useful.

Description: Accurate and fast thermal estimation is important for the runtime thermal regulation of modern microprocessors due to excessive on-chip temperatures. However, due to the nonlinear relationship between the leakage power and temperature, full-chip thermal estimation methods suffer slow speed and scalability issue when the increasing static leakage power is considered. In this work, we propose a new fast leakage-aware full-chip thermal estimation method. Unlike traditional methods, which use iteration to handle the leakage-temperature nonlinearity dependency issue, the new method applies a dynamic linearization algorithm, which adaptively transforms the original nonlinear thermal model into a number of local linear thermal models. In order to further improve the thermal estimation efficiency, a specially-designed adaptive model order reduction method is integrated into the thermal estimation framework to generate local compact thermal models. Our numerical results show that the new method is able to accurately estimate full-chip transient temperature distribution by fully considering the nonlinear leakage-temperature dependency with fast speed. On different chips with core number ranging from 9 to 36, it achieved 85 $times$ to 589 $times$ speedup in average against traditional iteration based method, with average thermal estimation error to be around 0.2 $^{circ}mathrm{C}$ .

Description: Convolutional Neural Networks (CNNs) have shown a great deal of success in diverse application domains including computer vision, speech recognition, and natural language processing. However, as the size of datasets and the depth of neural network architectures continue to grow, it is imperative to design high-performance and energy-efficient computing hardware for training CNNs. In this paper, we consider the problem of designing specialized CPU-GPU based heterogeneous manycore systems for energy-efficient training of CNNs. It has already been shown that the typical on-chip communication infrastructures employed in conventional CPU-GPU based heterogeneous manycore platforms are unable to handle both CPU and GPU communication requirements efficiently. To address this issue, we first analyze the on-chip traffic patterns that arise from the computational processes associated with training two deep CNN architectures, namely, LeNet and CDBNet, to perform image classification. By leveraging this knowledge, we design a hybrid Network-on-Chip (NoC) architecture, which consists of both wireline and wireless links, to improve the performance of CPU-GPU based heterogeneous manycore platforms running the above-mentioned CNN training workloads. The proposed NoC achieves 1.8× reduction in network latency and improves the network throughput by a factor of 2.2 for training CNNs, when compared to a highly-optimized wireline mesh NoC. For the considered CNN workloads, these network-level improvements translate into 25 percent savings in full-system energy-delay-product (EDP). This demonstrates that the proposed hybrid NoC for heterogeneous manycore architectures is capable of significantly accelerating training of CNNs while remaining energy-efficient.

Description: This paper presents for the first time the design, fabrication, and demonstration of a dielectric waveguide (DWG)-based ortho-mode sub-THz interconnect channel for planar chip-to-chip communications. By combining the proposed new transition of microstrip line with DWG orthogonally, the ortho-mode transition is constructed to form an ortho-mode channel. The measured minimum insertion losses for the $E_{y11}$ mode and the $E_{x11}$ mode are 6.6 dB with 20.3-GHz 3-dB bandwidth and 6.5 dB with 55.2-GHz 3-dB bandwidth, respectively. The simulation and measurement results agree well with each other.

Description: This paper proposes a topology of a broadband Wilkinson power divider based on the segmented structure. The segmented structure is formed by many transmission line segments in shunt with grounded capacitors and series resistor–capacitor networks. Each transmission line segment has the length of a fraction of a quarter of the wavelength (or $lambda $ /4) and the summed length of all segments remains $lambda $ /4. The segmented structure resembles a multiorder matching network and can extend the operation bandwidth through concurrent matching at multiple frequencies. Theoretically, the operation bandwidth can keep increasing with the increased number of segments. Practically, the widest achievable bandwidth is limited by the implementable component values. The theoretical background of the proposed broadband topology is explained. The guideline of designing the proposed power divider is provided. A power divider prototype with the structure of three segments is designed and fabricated. The measurement results, matching the simulations, show the state-of-the-art −20-dB operation bandwidth of 101%, if compared with all the published Wilkinson power dividers having a total length of $lambda $ /4.

Description: A tool that creates realtime interactive color maps for scientific visualization helped enhance the dynamics of a major research project for the Climate, Ocean, and Sea Ice Modeling team at Los Alamos National Laboratory.

Description: This article presents a taxonomy of spatial interaction patterns and techniques and discusses specific examples.

Description: In situ processing produces reduced size persistent representations of a simulations state while the simulation is running. The need for in situ visualization and data analysis is usually described in terms of supercomputer size and performance in relation to available storage size.

Description: Art historians have traditionally used physical light boxes to prepare exhibits or curate collections. On a light box, they can place slides or printed images, move the images around at will, group them as desired, and visual-ly compare them. The transition to digital images has rendered this workflow obsolete. Now, art historians lack well-designed, unified interactive software tools that effectively support the operations they perform with physi-cal light boxes. To address this problem, we designed ARIES (ARt Image Exploration Space), an interactive image manipulation system that enables the exploration and organization of fine digital art. The system allows images to be compared in multiple ways, offering dynamic overlays analogous to a physical light box, and sup-porting advanced image comparisons and feature-matching functions, available through computational image processing. We demonstrate the effectiveness of our system to support art historians tasks through real use cases.

Description: Ad for COMPSAC 2018.

Description: Front cover to the January/February 2018 issue of IEEE Internet Computing

Description: List of Editorial Board and staff associated with this issue of IEEE Internet Computing

Description: Presents the table of contents for this issue of this publication.

Description: The two articles in this special section represent ongoing Internet of Things applications in the context of Europe trying to make solutions usable to people in daily times.

Description: The architectural elements of the Internet that led to its great success are now, paradoxically, the source of its severest problems. For example, the use of autonomous systems to distribute governance has allowed rapid growth and scaling but has made the network unmanageable and unable to provide end-to-end quality of service. This article examines this and other key design elements of Internet architecture and shows how they have contributed to its success and how they now constrain it. I then use this framework to identify some key challenges that need to be addressed in the next phase of Internet research.

Description: A photonic-waveguide at real nano-scales based on the concept of hybridization of plasmonic and photonic modes is designed and fabricated. A high-index layer of silicon to control vertical and lateral confinement is introduced under the nano-confinement layer of thermally grown SiO 2 , which together with optimized waveguide-width provides low-loss guidance of hybrid-plasmonic-mode. A 11-nm thick SiO 2 on silicon provides us an optical-confinement at real nano-scales with an acceptably low loss of 7 dB/cm. Also, the proposed device exhibits ultra-low dispersion on introducing a grating in the silicon layer. In addition, the dispersion value “crosses zero-dispersion” many times over a broad range of wavelength.

Description: A photonic multiple microwave frequency measurement system is presented and demonstrated based on a swept frequency silicon microring resonator (MRR). The drop-port of a high-Q MRR is employed as a periodic narrowband scanning filter driven by a sawtooth voltage signal. The unknown frequency can be mapped to time interval between pulse appearances when scanning the modulated signal and the frequency-to-time mapping is established. In the experiments, we obtain a measurement range of 25 GHz with an error of ±510 MHz. Meanwhile, the measurement resolution for multi-frequency measurement is about 5 GHz. Our scheme offers a simple structure, low-cost solution, capability of multiple frequency measurement, and potential of chip-integration.