Showing papers on "Bandwidth (signal processing) published in 2016"
TL;DR: This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.
Abstract: Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.
2,380 citations
TL;DR: In this article, the small-signal impedance of three-phase grid-tied inverters with feedback control and phase-locked loop (PLL) in the synchronous reference ( d-q ) frame is analyzed.
Abstract: This paper analyzes the small-signal impedance of three-phase grid-tied inverters with feedback control and phase-locked loop (PLL) in the synchronous reference ( d-q ) frame. The result unveils an interesting and important feature of three-phase grid-tied inverters – namely, that its q–q channel impedance behaves as a negative incremental resistor. Moreover, this paper shows that this behavior is a consequence of grid synchronization, where the bandwidth of the PLL determines the frequency range of the resistor behavior, and the power rating of the inverter determines the magnitude of the resistor. Advanced PLL, current, and power control strategies do not change this feature. An example shows that under weak grid conditions, a change of the PLL bandwidth could lead the inverter system to unstable conditions as a result of this behavior. Harmonic resonance and instability issues can be analyzed using the proposed impedance model. Simulation and experimental measurements verify the analysis.
825 citations
TL;DR: It is shown that the best strategy depends on the target SNR regime, and guidelines to characterize the optimal choice as a function of the system parameters are provided.
Abstract: The massive amounts of bandwidth available at millimeter-wave frequencies (above 10 GHz) have the potential to greatly increase the capacity of fifth generation cellular wireless systems. However, to overcome the high isotropic propagation loss experienced at these frequencies, highly directional antennas will be required at both the base station and the mobile terminal to achieve sufficient link budget in wide area networks. This reliance on directionality has important implications for control layer procedures. In particular, initial access can be significantly delayed due to the need for the base station and the user to find the proper alignment for directional transmission and reception. This article provides a survey of several recently proposed techniques for this purpose. A coverage and delay analysis is performed to compare various techniques including exhaustive and iterative search, and context-information-based algorithms. We show that the best strategy depends on the target SNR regime, and provide guidelines to characterize the optimal choice as a function of the system parameters.
318 citations
TL;DR: In this article, a method for designing multi-wavelength metasurfaces using unit cells with multiple meta-atoms, or meta-molecules, was presented.
Abstract: Metasurfaces are nano-structured devices composed of arrays of subwavelength scatterers (or meta-atoms) that manipulate the wavefront, polarization, or intensity of light. Like other diffractive optical devices, metasurfaces suffer from significant chromatic aberrations that limit their bandwidth. Here, we present a method for designing multiwavelength metasurfaces using unit cells with multiple meta-atoms, or meta-molecules. Transmissive lenses with efficiencies as high as 72% and numerical apertures as high as 0.46 simultaneously operating at 915 nm and 1550 nm are demonstrated. With proper scaling, these devices can be used in applications where operation at distinct known wavelengths is required, like various fluorescence microscopy techniques.
301 citations
TL;DR: In this paper, an improved distributed secondary control scheme for dc microgrids is proposed, which can remove the dc voltage deviation and improve the current sharing accuracy by using voltage-shifting and slope-adjusting approaches simultaneously.
Abstract: This paper proposes an improved distributed secondary control scheme for dc microgrids (MGs), aiming at overcoming the drawbacks of conventional droop control method. The proposed secondary control scheme can remove the dc voltage deviation and improve the current sharing accuracy by using voltage-shifting and slope-adjusting approaches simultaneously. Meanwhile, the average value of droop coefficients is calculated, and then it is controlled by an additional controller included in the distributed secondary control layer to ensure that each droop coefficient converges at a reasonable value. Hence, by adjusting the droop coefficient, each participating converter has equal output impedance, and the accurate proportional load current sharing can be achieved with different line resistances. Furthermore, the current sharing performance in steady and transient states can be enhanced by using the proposed method. The effectiveness of the proposed method is verified by detailed experimental tests based on a 3 × 1 kW prototype with three interface converters.
270 citations
03 Apr 2016
TL;DR: The targets for NB-IoT are described, coverage, capacity, latency, and battery life analysis are presented, and a preliminary system design is presented.
Abstract: In 3GPP, a narrowband system based on Long Term Evolution (LTE) is being introduced to support the Internet of Things. This system, named Narrowband Internet of Things (NB-IoT), can be deployed in three different operation modes - (1) stand-alone as a dedicated carrier, (2) in-band within the occupied bandwidth of a wideband LTE carrier, and (3) within the guard-band of an existing LTE carrier. In stand-alone operation mode, NB-IoT can occupy one GSM channel (200 kHz) while for in-band and guard-band operation modes, it will use one physical resource block of LTE (180 kHz). The design targets of NB-IoT include low-cost devices, high coverage (20-dB improvement over GPRS), long device battery life (more than 10 years), and massive capacity. Latency is relaxed although a delay budget of 10 seconds is the target for exception reports. The specifications for NB-IoT are expected to be finalized in 2016. In this paper, we describe the targets for NB-IoT and present a preliminary system design. In addition, coverage, capacity, latency, and battery life analysis are also presented.
246 citations
TL;DR: The concept of Ultra-Massive Multiple Input Multiple Output (UM MIMO) communication is introduced as a way to increase the communication distance and the achievable capacity of THz-band communication networks.
229 citations
16 May 2016
TL;DR: The technical differences between a wideband spread spectrum (LoRa- like) and an ultra narrowband (Sigfox-like) network will be explained and evaluated and simulations show that adaptation of frequency and modulation is imperative for efficiently dealing with varying contention and interference in long range unlicensed networks.
Abstract: A broad range of emerging applications require very low power, very long range yet low throughput communication. Different standards are being proposed to meet these novel requirements. In this paper, the technical differences between a wideband spread spectrum (LoRa-like) and an ultra narrowband (Sigfox-like) network will be explained and evaluated. On the physical layer, simulation results show that an ultra narrowband network has a larger coverage, while wideband spread spectrum networks are less sensitive to interference. When considering the contention between nodes and interference between different networks, simulations show that adaptation of frequency and modulation is imperative for efficiently dealing with varying contention and interference in long range unlicensed networks. Depending on network load, size and distance, a device in a wideband network can send 6 times more packets to the base station when there is active rate and frequency management and an intra-technology control plane.
221 citations
TL;DR: A novel tapped delay line RF canceller architecture with multiple non-uniform pre-weighted taps to improve system isolation by cancelling both the direct antenna coupling as well as multipath effects that comprise a typical interference channel is presented.
Abstract: In-band full-duplex wireless communications are challenging because they require the mitigation of self-interference caused by the co-located transmitter to operate effectively. This paper presents a novel tapped delay line RF canceller architecture with multiple non-uniform pre-weighted taps to improve system isolation by cancelling both the direct antenna coupling as well as multipath effects that comprise a typical interference channel. A four-tap canceller prototype was measured over several different operating conditions, and was found to provide an average of 30 dB signal cancellation over a 30 MHz bandwidth centered at 2.45 GHz in isolated scenarios. When combined with an omni-directional high-isolation antenna, the canceller improved the overall analog isolation to 90 dB for these cases. In an indoor setting, the canceller suppressed a +30 dBm OFDM signal by 22 dB over a 20 MHz bandwidth centered at 2.45 GHz, and produced 78 dB of total analog isolation. This complete evaluation demonstrates not only the performance limitations of an optimized multitap RF canceller, but also establishes the amount of analog interference suppression that can be expected for the different environments considered.
201 citations
TL;DR: In this paper, an acoustic metamaterial consisting of curled, hollow, dead-end channels, which can totally absorb sound in a band of low frequencies, is presented, and the position and width of the band can be tuned by adjusting the lengths and number of channels in a unit cell, respectively.
Abstract: Sound absorption is a significant issue in acoustics and relevant to many applications, but current approaches suffer from either bulky dimensions or narrow bandwidth. The authors create an acoustic metamaterial consisting of curled, hollow, dead-end channels, which can totally absorb sound in a band of low frequencies. The position and width of the band can be tuned by adjusting the lengths and number of channels in a unit cell, respectively.
199 citations
TL;DR: The findings indicate that deploying the full-duplex principle can indeed also be feasible in mobile devices, and thus be one potential technology in, for example, 5G and beyond radio systems.
Abstract: In this article, we address the challenges of transmitter-receiver isolation in mobile full-duplex devices, building on shared-antenna-based transceiver architecture. First, self-adaptive analog RF cancellation circuitry is required, since the ability to track time-varying self-interference coupling characteristics is of utmost importance in mobile devices. In addition, novel adaptive nonlinear DSP methods are also required for final self-interference suppression at digital baseband, since mobile-scale devices typically operate under highly nonlinear low-cost RF components. In addition to describing the above kind of advanced circuit and signal processing solutions, comprehensive RF measurement results from a complete demonstrator implementation are also provided, evidencing beyond 40 dB of active RF cancellation over an 80 MHz waveform bandwidth with a highly nonlinear transmitter power amplifier. Measured examples also demonstrate the good self-healing characteristics of the developed control loop against fast changes in the coupling channel. Furthermore, when complemented by nonlinear digital cancellation processing, the residual self-interference level is pushed down to the noise floor of the demonstration system, despite the harsh nonlinear nature of the self-interference. These findings indicate that deploying the full-duplex principle can indeed also be feasible in mobile devices, and thus be one potential technology in, for example, 5G and beyond radio systems.
TL;DR: Simulation results on NPRACH performance including detection rate, false alarm rate, and time-of-arrival estimation accuracy are presented to shed light on the overall potential of NB-IoT systems.
Abstract: Narrowband Internet of Things (NB-IoT) is an emerging cellular technology that will provide improved coverage for massive number of low-throughput low-cost devices with low device power consumption in delay-tolerant applications. A new single tone signal with frequency hopping has been designed for NB-IoT physical random access channel (NPRACH). In this letter, we describe this new NPRACH design and explain in detail the design rationale. We further propose possible receiver algorithms for NPRACH detection and time-of-arrival estimation. Simulation results on NPRACH performance including detection rate, false alarm rate, and time-of-arrival estimation accuracy are presented to shed light on the overall potential of NB-IoT systems.
TL;DR: This paper presents the first linear bulk CMOS power amplifier (PA) targeting low-power fifth-generation (5G) mobile user equipment integrated phased array transceivers and achieves the highest measured PAE values among published K-and Ka-band CMOS PAs.
Abstract: This paper presents the first linear bulk CMOS power amplifier (PA) targeting low-power fifth-generation (5G) mobile user equipment integrated phased array transceivers. The output stage of the PA is first optimized for power-added efficiency (PAE) at a desired error vector magnitude (EVM) and range given a challenging 5G uplink use case scenario. Then, inductive source degeneration in the optimized output stage is shown to enable its embedding into a two-stage transformer-coupled PA; by broadening interstage impedance matching bandwidth and helping to reduce distortion. Designed and fabricated in 1P7M 28 nm bulk CMOS and using a 1 V supply, the PA achieves +4.2 dBm/9% measured $P_{\text {out}}$ /PAE at −25 dBc EVM for a 250 MHz-wide 64-quadrature amplitude modulation orthogonal frequency division multiplexing signal with 9.6 dB peak-to-average power ratio. The PA also achieves 35.5%/10% PAE for continuous wave signals at saturation/9.6 dB back-off from saturation. To the best of the authors’ knowledge, these are the highest measured PAE values among published ${K}$ - and Ka -band CMOS PAs.
TL;DR: This article presents an indoor multiuser terahertz system with array-of-subarrays architecture to accommodate hardware constraints as well as channel characteristics in the terAhertz band to alleviate spectrum limitation of current wireless systems.
Abstract: Enabling terahertz communications will alleviate the spectrum limitation of current wireless systems. This article presents an indoor multiuser terahertz system with array-of-subarrays architecture to accommodate hardware constraints as well as channel characteristics in the terahertz band. Specifically, the difference between terahertz and millimeter-wave communications is first clarified. Then the advantage of the array-of-subarrays structure is explained through comparison with the fully connected structure in both spectral and energy efficiency. Furthermore, a distance-aware multi-carrier scheme with the array-of-subarrays structure is introduced for wideband terahertz communications. Finally, the associated open issues and future research directions are discussed.
TL;DR: A new 3D-stacked DRAM architecture, called Simultaneous Multi-Layer Access (SMLA), is proposed, which increases the internal DRAM bandwidth by accessing multiple DRAM layers concurrently, thus making much greater use of the bandwidth that the TSVs offer.
Abstract: 3D-stacked DRAM alleviates the limited memory bandwidth bottleneck that exists in modern systems by leveraging through silicon vias (TSVs) to deliver higher external memory channel bandwidth. Today’s systems, however, cannot fully utilize the higher bandwidth offered by TSVs, due to the limited internal bandwidth within each layer of the 3D-stacked DRAM. We identify that the bottleneck to enabling higher bandwidth in 3D-stacked DRAM is now the global bitline interface, the connection between the DRAM row buffer and the peripheral IO circuits. The global bitline interface consists of a limited and expensive set of wires and structures, called global bitlines and global sense amplifiers, whose high cost makes it difficult to simply scale up the bandwidth of the interface within a single DRAM layer in the 3D stack. We alleviate this bandwidth bottleneck by exploiting the observation that several global bitline interfaces already exist across the multiple DRAM layers in current 3D-stacked designs, but only a fraction of them are enabled at the same time.We propose a new 3D-stacked DRAM architecture, called Simultaneous Multi-Layer Access (SMLA), which increases the internal DRAM bandwidth by accessing multiple DRAM layers concurrently, thus making much greater use of the bandwidth that the TSVs offer. To avoid channel contention, the DRAM layers must coordinate with each other when simultaneously transferring data. We propose two approaches to coordination, both of which deliver four times the bandwidth for a four-layer DRAM, over a baseline that accesses only one layer at a time. Our first approach, Dedicated-IO, statically partitions the TSVs by assigning each layer to a dedicated set of TSVs that operate at a higher frequency. Unfortunately, Dedicated-IO requires a nonuniform design for each layer (increasing manufacturing costs), and its DRAM energy consumption scales linearly with the number of layers. Our second approach, Cascaded-IO, solves both issues by instead time multiplexing all of the TSVs across layers. Cascaded-IO reduces DRAM energy consumption by lowering the operating frequency of higher layers. Our evaluations show that SMLA provides significant performance improvement and energy reduction across a variety of workloads (55p/18p on average for multiprogrammed workloads, respectively) over a baseline 3D-stacked DRAM, with low overhead.
TL;DR: In this paper, a planar shared-aperture dual-band dual-circular polarization (CP) array antennas are implemented on a single-layer substrate and extended to a larger array easily.
Abstract: This paper presents a new approach to implement planar shared-aperture dual-band dual-circular polarization (CP) array antennas. The antennas can be fabricated on a single-layer substrate and extended to a larger array easily. In this approach, each array element is obtained by connecting two patches working at different frequencies directly. To form arrays with higher gain, two kinds of feed networks are described, which can be applied in systems where narrowband and wideband are needed, respectively. One is using the conventional feed network and the other is using the sequential rotation technique to further improve the CP axial ratio (AR) performance. Two prototype arrays with $4 \times 4$ elements are fabricated and tested in $X/Ku$ bands. Experimental results show that good CP characteristics are obtained, which agree well with the simulation results. For the first narrow-band prototype array, the 3-dB AR bandwidth is around 1.5% for both bands. For the second array using the sequential rotation technique, the bandwidth of return loss and AR are wider. In the lower band centered at 12.1 GHz, the ${-}10\hbox{-}\text{dB}$ return loss bandwidth is 8.3% and the 3-dB AR bandwidth is 14.2% [right-hand CP (RHCP)]; in the higher band centered at 17.4 GHz, the corresponding data are 18.9% and 14.9% [left-hand CP (LHCP)], respectively.
TL;DR: A monopolar patch antenna with a V-shaped slot for car-to-car (C2C) and wireless local area network (WLAN) communications is presented and three resonances found in the operating frequency bandwidth resulted in a wideband characteristic.
Abstract: A monopolar patch antenna with a V-shaped slot for car-to-car (C2C) and wireless local area network (WLAN) communications is presented in this paper. To widen the impedance bandwidth of the antenna, techniques for adding a shorting pin and a V-shaped slot are applied to an equilateral triangular patch. By properly placing the shorting pins on an equilateral triangular patch, two operating modes, i.e., TM10 and TM20, are obtained. The presence of the V-shaped slot can generate an additional TM11 mode. These three resonances found in the operating frequency bandwidth resulted in a wideband characteristic. The proposed antenna can operate from 4.82 to 6.67 GHz for the reflection coefficient $\le -$ 10 dB with the gain of around 5.0 dBi. In addition, an omnidirectional radiation pattern is yielded by a coaxial center-fed probe excitation. The antenna has a thickness of 0.09 $\boldsymbol{\lambda}_\mathbf{g}$ (at the center frequency of 5.5 GHz), which is easily hidden on the roof of a vehicle for C2C communication. This proposed design can also be used as indoor base-station antennas for WLAN communication.
TL;DR: In this paper, the authors present a direct-conversion quadrature transmitter and receiver chipset at 240 GHz, which is implemented in a 0.13-μm SiGe bipolar-CMOS technology.
Abstract: This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz. It is implemented in a 0.13- $\mu{\hbox{m}}$ SiGe bipolar-CMOS technology. A wideband frequency multiplier ( $\times$ 16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens makes this chipset suited for applications requiring fixed and tunable LO. The chipset is packaged in a low-cost FR4 printed circuit board resulting in a complete solution with compact form-factor. At 236 GHz, the effective-isotropic-radiated-power is 21.86 dBm and the minimum single-sideband noise figure is 15 dB. The usable RF bandwidth for this chipset is 65 GHz and the 6-dB bandwidth is 17 GHz. At the system level, we demonstrate a high data-rate communication system where an external modem is operated in its two IF-bandwidth modes (250 MHz and 1 GHz). For the quadrature phase-shift keying modulation scheme, the measured data rate is 2.73 Gb/s (modem 1-GHz IF) with bit-error rate of ${\hbox{10}}^{-9}$ for a 15-cm link. The estimated data rate over the 17-GHz RF bandwidth is, hence, 23.025 Gb/s. Also, higher order modulation schemes like 16 quadrature amplitude modulation (QAM) with a data rate of 0.677 Gb/s and 64-QAM with a data rate of 1.0154 Gb/s (modem 250-MHz IF) is demonstrated. A second application demonstrator is presented where the wide tunable RF bandwidth of the chipset is used for material characterization. It is used to characterize an FR4 material (DE104) over the 215–260-GHz range.
TL;DR: A multi-wideband waveform design for the THz band is proposed, by exploiting the channel peculiarities including the distance-varying spectral windows, the delay spread and the temporal broadening effects to maximize the communication distance while satisfying the rate and the transmit power constraints.
Abstract: Terahertz band communication is envisioned as a key technology to satisfy the increasing demand for ultra-high-speed wireless links. In this paper, a multi-wideband waveform design for the THz band is proposed, by exploiting the channel peculiarities including the distance-varying spectral windows, the delay spread and the temporal broadening effects. This scheme allows the dynamical variation of the rate and the transmit power on each sub-window and improves the distance. Moreover, the closed-form expressions of the signal-to-interference-plus-the-noise and bit-error-rate for the multi-wideband waveform are derived, by considering the inter-symbol and inter-band interferences. Then, an optimization framework is formulated to solve for the multi-wideband waveform design parameters of the transmit power and the number of frames, with the aim to maximize the communication distance while satisfying the rate and the transmit power constraints. Four sub-optimal solutions are proposed and compared. The results show that the SINR increases with the transmit power and the number of frames, at the cost of the power consumption and the rate decrease. With the transmit power of 10 dBm, the largest distance to support 10 Gbps for the multi-path propagation is 4 m, which is realized via the power allocation scheme to minimize the power/bit on each sub-window and is 10% improvement over the fixed scheme. However, for the directional transmission, this scheme under-exploits the transmit power severely. Instead, the allocation scheme that minimizes the number of frames outperforms the other three schemes. In terms of the maximum distance that achieves 30 Gbps, this scheme reaches 22.5 m.
TL;DR: A photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented and the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented.
Abstract: 5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.
TL;DR: In this paper, the authors derive the asymptotic expansion of variable bandwidth kernels for arbitrary bandwidth functions and derive pointwise error estimates for the corresponding discrete operators which are based on finite data sets; generalizing a result of Singer which was restricted to fixed bandwidth kernels.
TL;DR: The use of OFDM technique reduces the integration complexity of the system where the parallel low pass filters are no longer needed to recover the transmitted data as in multicarrier DCSK scheme and the advantages of this new hybrid design are shown.
Abstract: In this paper, a multiuser OFDM-based chaos shift keying (MU OFDM-DCSK) modulation is presented. In this system, the spreading operation is performed in time domain over the multicarrier frequencies. To allow the multiple access scenario without using excessive bandwidth, each user has $N_P$ predefined private frequencies from the $N$ available frequencies to transmit its reference signal and share with the other users the remaining frequencies to transmit its $M$ spread bits. In this new design, $N_P$ duplicated chaotic reference signals are used to transmit $M$ bits instead of using $M$ different chaotic reference signals as done in DCSK systems. Moreover, given that $N_P , the MU OFDM-DCSK scheme increases spectral efficiency, uses less energy and allows multiple-access scenario. Therefore, the use of OFDM technique reduces the integration complexity of the system where the parallel low pass filters are no longer needed to recover the transmitted data as in multicarrier DCSK scheme. Finally, the bit error rate performance is investigated under multipath Rayleigh fading channels, in the presence of multiuser and additive white Gaussian noise interferences. Simulation results confirm the accuracy of our analysis and show the advantages of this new hybrid design.
TL;DR: An experimental simulation of environment-assisted coherent transport, using an engineered network of laser-written waveguides, with relative energies and inter-waveguide couplings tailored to yield the desired Hamiltonian.
Abstract: Transport phenomena on a quantum scale appear in a variety of systems, ranging from photosynthetic complexes to engineered quantum devices It has been predicted that the efficiency of coherent transport can be enhanced through dynamic interaction between the system and a noisy environment We report an experimental simulation of environment-assisted coherent transport, using an engineered network of laser-written waveguides, with relative energies and inter-waveguide couplings tailored to yield the desired Hamiltonian Controllable-strength decoherence is simulated by broadening the bandwidth of the input illumination, yielding a significant increase in transport efficiency relative to the narrowband case We show integrated optics to be suitable for simulating specific target Hamiltonians as well as open quantum systems with controllable loss and decoherence
TL;DR: This paper determines the localization accuracy of an agent, which is equipped with an antenna array and localizes itself using wireless measurements with anchor nodes, in a far-field environment with typical anchor deployments and antenna arrays.
Abstract: Location-aware networks are of great importance and interest in both civil and military applications. This paper determines the localization accuracy of an agent, which is equipped with an antenna array and localizes itself using wireless measurements with anchor nodes, in a far-field environment. In view of the Cramer–Rao bound, we first derive the localization information for static scenarios and demonstrate that such information is a weighed sum of Fisher information matrices from each anchor-antenna measurement pair. Each matrix can be further decomposed into two parts: 1) a distance part with intensity proportional to the squared baseband effective bandwidth of the transmitted signal and 2) a direction part with intensity associated with the normalized anchor-antenna visual angle. Moreover, in dynamic scenarios, we show that the Doppler shift contributes additional direction information, with intensity determined by the agent velocity and the root mean squared time duration of the transmitted signal. In addition, two measures are proposed to evaluate the localization performance of wireless networks with different anchor-agent and array-antenna geometries, and both formulae and simulations are provided for typical anchor deployments and antenna arrays.
TL;DR: An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters and paving the way for multiple on-chip microwave filters and channelizers.
Abstract: An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters. More than a decade bandwidth reconfigurability from 30 up to 440 MHz, with a passband ripple <1.9 dB is achieved by tailoring the Brillouin pump. The filter central frequency is continuously tuned up to 30 GHz with no degradation of the passband response, which is a major improvement over electronic filters. Furthermore, we demonstrate pump tailoring to realize multiple bandpass filters with different bandwidths and central frequencies, paving the way for multiple on-chip microwave filters and channelizers.
Patent•
14 Jun 2016
TL;DR: In this paper, a tunable duplexer circuit is described, wherein the frequency response as well as bandwidth and transmission loss characteristics can be dynamically altered, providing improved performance for transceiver front-end applications.
Abstract: A tunable duplexer circuit is described, wherein the frequency response as well as bandwidth and transmission loss characteristics can be dynamically altered, providing improved performance for transceiver front-end applications. The rate of roll-off of the frequency response can be adjusted to improve performance when used in duplexer applications. A method is described where the duplexer circuit characteristics are optimized in conjunction with a specific antenna frequency response to provide additional out-of-band rejection in a communication system. Dynamic optimization of both the duplexer circuit and an active antenna system is described to provide improved out-of-band rejection when implemented in RF front-end circuits of communication systems. Other features and embodiments are described in the following detailed descriptions.
TL;DR: Some numerical results are shown to highlight the effectiveness of the new technique to devise high-performance radar waveforms complying with the spectral compatibility requirements.
Abstract: Radar signal design in spectrally dense environments is a very challenging and topical problem. This letter deals with the synthesis of waveforms optimizing radar performance while satisfying multiple spectral compatibility constraints. Unlike some counterparts available in the open literature, a specific control on the interference energy radiated on each shared bandwidth is enforced. To tackle the resulting NP-hard optimization problem, a polynomial computational complexity procedure based on semidefinite relaxation (SDR) and randomization is developed. Hence, some numerical results are shown to highlight the effectiveness of the new technique to devise high-performance radar waveforms complying with the spectral compatibility requirements.
TL;DR: A scheme for photonic generation of linearly chirped microwave waveforms with a large time-bandwidth product (TBWP) based on an optically injected semiconductor laser is proposed and demonstrated and the flexibility for tuning the center frequency, bandwidth and temporal duration is demonstrated.
Abstract: A scheme for photonic generation of linearly chirped microwave waveforms (LCMWs) with a large time-bandwidth product (TBWP) is proposed and demonstrated based on an optically injected semiconductor laser. In the proposed system, the optically injected semiconductor laser is operated in period-one (P1) oscillation state. After optical-to-electrical conversion, a microwave signal can be generated with its frequency determined by the injection strength. By properly controlling the injection strength, an LCMW with a large TBWP can be generated. The proposed system has a simple and compact structure. Besides, the center frequency, bandwidth, as well as the temporal duration of the generated LCMWs can be easily adjusted. An experiment is carried out. LCMWs with TBWPs as large as 1.2x105 (bandwidth 12 GHz; temporal duration 10 μs) are successfully generated. The flexibility for tuning the center frequency, bandwidth and temporal duration is also demonstrated.
TL;DR: A top-injected coupled resonator based wide locking range technique is proposed in the frequency doublers to minimize the required injection power to cover the chirp bandwidth plus enough PVT variation margin, and therefore reduce the power consumption of the local-oscillating (LO) distribution network.
Abstract: A fully-integrated 77 GHz frequency doubling two-path phased-array frequency-modulated continuous-wave (FMCW) transceiver for automotive radar applications is proposed. By utilizing the frequency doubling scheme, the chirp bandwidth is improved, and the complexity of the frequency synthesizer and the insertion loss of the local-oscillating (LO) distribution network are both reduced. Top-injected coupled resonator based wide locking range technique is proposed in the frequency doublers to minimize the required injection power to cover the chirp bandwidth plus enough PVT variation margin, and therefore reduce the power consumption of the LO distribution network. Current-reused coupled resonator technique is utilized to implement the LO phase shifting in each receiving path. The digitally controlled artificial dielectric-based transmission lines are inserted in the low noise amplifiers to provide the operation frequency calibration capability. The receiving two-path signals are converted into intermediate frequency by low flicker noise current-mode passive mixers and then combined in the trans-impedance amplifier, followed by the reconfigurable analog baseband processing. Fabricated in 65 nm CMOS, the FMCW transceiver has achieved 1.93 GHz maximum chirp bandwidth, $12.9\sim 13.2$ dBm maximum transmitting power, and $47.8\sim 100.7$ dB programmable receiving conversion gain. The transceiver consumes 343 mW power and 4.64 mm2 chip area including all of the pads.
TL;DR: In this paper, a low profile printed slot antenna using wideband artificial magnetic conductor (AMC) is presented with improved radiation performance, which achieves a wide impedance bandwidth in the measured frequency range of 7.96-12.56 GHz for X-band applications.
Abstract: In this paper, a novel design of low profile printed slot antenna using wideband artificial magnetic conductor (AMC) is presented with improved radiation performance. For this purpose, the radiating slots with three unequal arms fed by coplanar waveguide are employed for broadening the impedance bandwidth with three resonances. It achieves a wide impedance bandwidth in the measured frequency range of 7.96–12.56 GHz ( $S_{11}\leq -10$ dB) for X-band applications. By loading a novel wideband planar AMC surface as the antenna ground plane, the radiation properties of this printed slot antenna are enhanced. This design includes the measured −10 dB impedance bandwidth from 5.75 to 14.51 GHz (86.48%). The proposed wideband planar AMC design operates at the frequency of 10.15 GHz with ±90° reflection phase bandwidth of 8–12.38 GHz (43.15%). The AMC surface is designed with the $5\times 8$ array of periodic patches which are developed underneath the broadband printed slot antenna. In comparison with the proposed design without AMC, the printed slot antenna loaded with AMC introduces 62.82% size reduction, a bandwidth enhancement of 41.65%, and better impedance matching. It also contributes considerable features like a low profile antenna with unidirectional radiation patterns and an increased gain of more than 10.6 dBi.