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Showing papers on "Frequency band published in 2011"


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method based on the kurtosis of the envelope spectrum amplitudes of the demodulated signal, rather than on the filter time signal, to detect transients with smaller signal-to-noise ratio comparing to the spectral kurtogram.

487 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.
Abstract: We have shown experimentally that it is possible to propagate and use the properties of twisted non-monochromatic incoherent radio waves to simultaneously transmit to infinity more radio channels on the same frequency band by encoding them in different orbital angular momentum states. This novel radio technique allows the implementation of, at least in principle, an infinite number of channels on one and the same frequency, even without using polarization or dense coding techniques. An optimal combination of all these physical properties and techniques represents a solution for the problem of radio band congestion. Our experimental findings show that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.

468 citations


Journal ArticleDOI
TL;DR: This brief addresses the problem of control for active vehicle suspension systems in finite frequency domain by using the generalized Kalman-Yakubovich-Popov (KYP) lemma to improve the ride comfort and suppresses the vibration more effectively for the concerned frequency range.
Abstract: This brief addresses the problem of control for active vehicle suspension systems in finite frequency domain. The performance is used to measure ride comfort so that more general road disturbances can be considered. By using the generalized Kalman-Yakubovich-Popov (KYP) lemma, the norm from the disturbance to the controlled output is decreased in specific frequency band to improve the ride comfort. Compared with the entire frequency approach, the finite frequency approach suppresses the vibration more effectively for the concerned frequency range. In addition, the time-domain constraints, which represent performance requirements for vehicle suspensions, are guaranteed in the controller design. A state feedback controller is designed in the framework of linear matrix inequality (LMI) optimization. A quarter-car model with active suspension system is considered in this brief and a numerical example is employed to illustrate the effectiveness of the proposed approach.

344 citations


Journal ArticleDOI
TL;DR: This design provides an effective and feasible way to construct broad band absorber in stealth technology, as well as the enhanced transmittance devices.
Abstract: We propose a design of an extremely broad frequency band absorber based on destructive interference mechanism. Metamaterial of multilayered SRRs structure is used to realize a desirable refractive index dispersion spectrum, which can induce a successive anti-reflection in a wide frequency range. The corresponding high absorptance originates from the destructive interference of two reflection waves from the two surfaces of the metamaterial. A strongly absorptive bandwidth of almost 60GHz is demonstrated in the range of 0 to 70GHz numerically. This design provides an effective and feasible way to construct broad band absorber in stealth technology, as well as the enhanced transmittance devices.

315 citations


Journal ArticleDOI
TL;DR: This communication presents a new antenna system designed for cognitive radio applications that has been simulated with the driving motor being taken into consideration and a good agreement is found between the simulated and the measured antenna radiation properties.
Abstract: This communication presents a new antenna system designed for cognitive radio applications. The antenna structure consists of a UWB antenna and a frequency reconfigurable antenna system. The UWB antenna scans the channel to discover “white space” frequency bands while tuning the reconfigurable section to communicate within these bands. The frequency agility is achieved via a rotational motion of the antenna patch. The rotation is controlled by a stepper motor mounted on the back of the antenna structure. The motor's rotational motion is controlled by LABVIEW on a computer connected to the motor through its parallel port. The computer's parallel port is connected to a NPN Darlington array that is used to drive the stepper motor. The antenna has been simulated with the driving motor being taken into consideration. A good agreement is found between the simulated and the measured antenna radiation properties.

203 citations


Patent
11 Mar 2011
TL;DR: In this article, the authors describe a peer-to-peer (P2P) communication protocol on an unlicensed spectrum with network assistance, where a user equipment (UE) may communicate with a wide area network (WAN) to establish P2P communication with at least one other UE on a first frequency band.
Abstract: Techniques for establishing and maintaining peer-to-peer (P2P) communication are described. In an aspect, P2P communication on an unlicensed spectrum may be established and maintained with network assistance. In one design, a user equipment (UE) may communicate with a wide area network (WAN) to establish P2P communication with at least one other UE on a first frequency band that is not licensed to the WAN. For example, the UE may receive an assignment of at least one frequency channel in the first frequency band for P2P communication. The UE may then communicate peer-to-peer with the other UE(s) on the at least one frequency channel. The UE may also communicate with the WAN to maintain P2P communication with the other UE(s), e.g., to switch to another frequency channel if necessary.

199 citations


Journal ArticleDOI
TL;DR: It is conceptualized that even isolated alterations in gamma or low frequency oscillations may impact the interactions of high and low frequency bands that are involved in key cognitive functions and may be critical for deciphering the complex electrophysiological abnormalities observed in schizophrenia patients.
Abstract: There is growing recognition that neural oscillations are important in a wide range of perceptual and cognitive functions. One of the key issues in electrophysiological studies of schizophrenia is whether high or low frequency oscillations, or both, are related to schizophrenia because many brain functions are modulated with frequency specificities. Many recent electrophysiological studies of schizophrenia have focused on high frequency oscillations at gamma band and in general support gamma band dysfunction in schizophrenia. We discuss the concept that gamma oscillation abnormalities in schizophrenia often occur in the background of oscillation abnormalities of lower frequencies. The review discusses the basic neurobiology for the emergence of oscillations of all frequency bands in association with networks of inhibitory interneurons and the convergence and divergence of such mechanisms in generating high vs low frequency oscillations. We then review the literature of oscillatory frequency abnormalities identified in each frequency band in schizophrenia. By describing some of the key functional roles exerted by gamma, low frequencies, and their cross-frequency coupling, we conceptualize that even isolated alterations in gamma or low frequency oscillations may impact the interactions of high and low frequency bands that are involved in key cognitive functions. The review concludes that studying the full spectrum and the interaction of gamma and low frequency oscillations may be critical for deciphering the complex electrophysiological abnormalities observed in schizophrenia patients.

198 citations


Patent
Shin Young Shik1, Dae-Hyun Sim1, Chang Seok Lee1, Beom-Soo Cho1, Kim Hyun Soo1, Kim Se Yeon1 
20 May 2011
TL;DR: In this article, the authors proposed a method and system for wireless charging using a radio wave, which includes scanning the radio wave of an access point, determining an available charging frequency band among frequency bands, sending the access point a request for transmitting a charging radio wave at the charging frequency bands and switching power output from an antenna, to a battery circuit.
Abstract: A method and system for wireless charging using a radio wave. The method includes scanning a radio wave of an access point, determining an available charging frequency band among frequency bands, sending the access point a request for transmitting a charging radio wave at the charging frequency band, and switching power output from an antenna, to a battery circuit.

194 citations


Journal ArticleDOI
TL;DR: This paper considers average transmit and interference power constraints for both schemes, proposes two algorithms that acquire the optimal sensing time and power allocation under imperfect spectrum sensing for the two schemes, and discusses the effect of the average transmitand interference power constraint on the optimal Sensing time.
Abstract: Cognitive radio is an emerging technology that aims for efficient spectrum usage by allowing unlicensed (secondary) users to access licensed frequency bands under the condition of protecting the licensed (primary) users from harmful interference. The latter condition constraints the achievable throughput of a cognitive radio network, which should therefore access a wideband spectrum in order to provide reliable and efficient services to its users. In this paper, we study the problem of designing the optimal sensing time and power allocation strategy, in order to maximize the ergodic throughput of a cognitive radio that employs simultaneous multiband detection and operates under two different schemes, namely the wideband sensing-based spectrum sharing (WSSS) and the wideband opportunistic spectrum access (WOSA) scheme. We consider average transmit and interference power constraints for both schemes, in order to effectively protect the primary users from harmful interference, propose two algorithms that acquire the optimal sensing time and power allocation under imperfect spectrum sensing for the two schemes and discuss the effect of the average transmit and interference power constraint on the optimal sensing time. Finally, we provide simulation results to compare the two schemes and validate our theoretical analysis.

183 citations


Patent
15 Jul 2011
TL;DR: In this article, a clear channel assessment threshold for use when a wireless device is to transmit in a wireless network that operates on a channel in a radio frequency band is adjusted by an amount depending on the type of interference detected in the received energy.
Abstract: Techniques are provided to adaptively adjust a clear channel assessment threshold for use when a wireless device is to transmit in a wireless network that operates on a channel in a radio frequency band. A first wireless device, configured to wirelessly communicate with one or more second wireless device in the wireless network, receives energy on the channel in the frequency band, analyzes the received energy to detect interference on the channel and determines a type of interference detected in the received energy. The clear channel assessment threshold is adjusted by an amount depending on the type of interference detected.

181 citations


Journal ArticleDOI
TL;DR: Three models of a constant-phase element consisting of passive R and C components are described, which can be used for practical realization of fractional analog differentiators and integrators, fractional oscillators, chaotic networks or for analog simulation of fractionsal control systems.
Abstract: SUMMARY The paper describes models of a constant-phase element consisting of passive R and C components. The models offer any input impedance argument (phase) between −90° and 0° over a selectable frequency band covering several decades. The design procedure makes it possible to choose values of average phase, phase ripple, frequency bandwidth, and total number of R and C elements. The model can cover three frequency decades with as few as five resistors and five capacitors. The models can be used for practical realization of fractional analog differentiators and integrators, fractional oscillators, chaotic networks or for analog simulation of fractional control systems. Copyright © 2011 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a single-layer antenna composed of a square ground plane embedded with two unequal-size inverted-L strips around two opposite corners is capable of generating a resonant mode for exciting two orthogonal E vectors.
Abstract: This letter presents a new design for a circularly polarized square slot antenna (CPSSA). The proposed single-layer antenna composed of a square ground plane embedded with two unequal-size inverted-L strips around two opposite corners is capable of generating a resonant mode for exciting two orthogonal E vectors. In this model, compared to the previous CPSSA structures, the impedance bandwidth and the axial ratio bandwidth of antenna are increased, which is four times wider than the impedance bandwidth of previous similar designs. The designed CPSS antenna with size 60 × 60 × 0.8 mm3 operates over the frequency band between 2.67 and 13 GHz (4.74:1, 132%) for VSWR <; 2, exhibiting a 32.2% (4.9-6.9 GHz, 1.5:1) circular polarization (CP) bandwidth. Throughout this letter, the improvement process of the axial ratio (AR) and S\\ properties are presented and discussed in detail.

Patent
31 Aug 2011
TL;DR: In this paper, a relay extension system is provided to minimize the investment costs when adding a new service to a new frequency band by using a twisted pair cable and a coaxial cable.
Abstract: PURPOSE: A relay extension system is provided to minimize the investment costs when adding a new service to a new frequency band. CONSTITUTION: A remote distribution unit(40) converts a twisted pair signal of a fixed band into an RF(Radio Frequency) signal. The remote distribution unit relays the RF signal through an antenna. At least one additional remote distribution unit(46) is connected to the remote distribution unit by the twisted pair cable and a coaxial cable. The additional remote distribution unit is transmitted to the twisted pair signal of the added band through the twisted pair cable. The additional remote distribution unit changes the twisted pair signal of the transmitted additional band into the RF signal. The additional remote distribution unit transmits the RF signal through to the remote distribution unit to the coaxial cable.

Patent
03 Feb 2011
TL;DR: In this article, a three-band antenna device with resonance generation includes a dielectric layer having an upper surface and a lower surface, a grounding element, a first radiating element, and a second radii element.
Abstract: A three-band antenna device with resonance generation includes a dielectric layer having an upper surface and a lower surface, a grounding element, a first radiating element, and a second radiating element. The first radiating element is arranged on the upper surface for providing a first frequency band. The second radiating element is arranged on the lower surface and stacked below the first radiating element via the dielectric layer for providing a second frequency band, so as to generate a parasitic capacitance therebetween. A third frequency band is provided by the resonance of the parasitic capacitance and the parasitic inductance in the second radiating element.

Patent
Dennis Hui1, Jiann-Ching Guey1
07 Nov 2011
TL;DR: In this article, a self-interference cancellation (SIC) precoder is used to place nulls at each of its receive antennas digitally at baseband for one or more frequency bands.
Abstract: A system and method to perform Full Duplex (FD) Space Division Duplex (SDD) communication using a Self-Interference Cancelling (SIC) precoder that applies different antenna phase shifts and amplitude scales to the transmitted signals to force them to be in the null space of the selected receive antennas. Thus, a wireless communication unit can place nulls at each of its receive antennas digitally at baseband for one or more frequency bands. The SIC precoder may be computed based on the self-interference channel from the transmit chain(s) to the receive chain(s). Different SIC precoders may be adaptively selected and stored digitally for different frequency bands. Subsequent single or multi-user precoder can be applied in concatenation with the SIC precoder to transmit signals to one or more users while receiving signals from one or more users simultaneously over the same frequency band.

Journal ArticleDOI
TL;DR: In this paper, a new ultra wideband circular monopole antenna with an acceptable band-rejection characteristic is investigated, which is created by means of an electromagnetic band-gap (EBG) structure.
Abstract: In this letter, a new compact ultra wideband circular monopole antenna with an acceptable band-rejection characteristic is investigated. This rejection band is created by means of an electromagnetic band-gap (EBG) structure. The EBG structure that is used here is a mushroom-like structure. An equivalent circuit model is employed to investigate the stopband characteristic of the EBG. The operation frequency band is 3.1-10.6 GHz with a rejection band of 0.7 GHz around 5.5 GHz. Accurate and high rejection is achieved. The proposed model is implemented, and the measured results are in good agreement with simulated ones.

Patent
23 Jun 2011
TL;DR: In this paper, an electronic device is disclosed comprising an acceleration sensor operable to generate an acceleration signal, and a free fall detector operating in response to the acceleration signal is disabled when a magnitude of the frequency response within one of a plurality of frequency bands exceeds a threshold, wherein each frequency band corresponds to one of the normal operating modes.
Abstract: An electronic device is disclosed comprising an acceleration sensor operable to generate an acceleration signal, and a free fall detector operable to detect a free fall event in response to the acceleration signal. A frequency response of the acceleration signal is measured, and the free fall detector is disabled when a magnitude of the frequency response within one of a plurality of frequency bands exceeds a threshold, wherein each frequency band corresponds to one of a plurality of normal operating modes.

Journal ArticleDOI
TL;DR: In this paper, the authors presented a novel ultra wideband (UWB) bandpass filter with a notched band using a ring resonator, and measured the 3 dB fractional bandwidths (FBWs) were 1028% and 1033% with and without the notched bands, respectively.
Abstract: This letter presents a novel ultra-wideband (UWB) bandpass filter (BPF) with a notched band using a ring resonator Bandwidths of the ring resonator with two stepped-impedance stubs are calculated by examining the relations between resonant frequencies and the characteristic impedance of the ring Stepped-impedance ports are used to obtain improved return losses in a high-frequency band Interdigital-coupled feed lines with an asymmetric structure embedded in the stepped-impedance ports are developed to avoid wireless local-area network (WLAN) signals at 5 GHz band Measured results show that 3 dB fractional bandwidths (FBWs) are 1028% and 1033% with and without the notched band, respectively Measured insertion loss of the notched band within the UWB is 1114 dB at 541 GHz

Journal ArticleDOI
TL;DR: A novel method of selecting subject and class specific frequency bands based on the analysis of a channel‐frequency matrix, which is applicable to other kinds of single‐trial EEG classifications that are based on modulations of brain rhythms, by no means limited to motor imagery‐based BCI applications.
Abstract: EEG-based discrimination among motor imagery states has been widely studied for brain-computer interfaces (BCIs) due to the great potential for real-life applications. However, in terms of designing a motor imagery-based BCI system, a lot of research in the literature either uses a frequency band of interest selected manually based on the visual analysis of EEG data or is set to a general broad band, causing performance degradation in classification. In this article, we propose a novel method of selecting subject and class specific frequency bands based on the analysis of a channel-frequency matrix, which we call a channel-frequency map. We operate the classification process for each frequency band individually, i.e., spatial filtering, feature extraction, and classification, and determine a class label for an input EEG by considering the outputs from multiple classifiers together at the end. From our experiments on a public dataset of BCI Competition IV (2008) II-a that includes four motor imagery tasks from nine subjects, the proposed algorithm outperformed the common spatial pattern (CSP) algorithm in a broad band and a filter bank CSP algorithm on average in terms of cross-validation and session-to-session transfer rate. Furthermore, a considerable increase of classification accuracy has been achieved for certain subjects. We also would like to note that the proposed data-driven frequency bands selection method is applicable to other kinds of single-trial EEG classifications that are based on modulations of brain rhythms, by no means limited to motor imagery-based BCI applications. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 123–130, 2011 (WCU (World Class University) Program (R31-10008-0) through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology.)

Patent
Hang Jin1, Li Guo1, Paul J. Stager1, Neil R. Diener1, Matthew A. Silverman1 
07 Jul 2011
TL;DR: In this article, the nulling filter is applied to the received energy at the plurality of antennas to produce a spatially filtered output, which is evaluated to determine whether to send a transmission on the channel in the unlicensed frequency band.
Abstract: At a wireless device operating in an unlicensed frequency band, energy received at a plurality of antennas is analyzed to detect interference on a channel in the unlicensed frequency band. The type of interference detected in the received energy is determined. Parameters are then generated for a nulling filter based on the type of interference detected in the received energy. The nulling filter is applied to the received energy at the plurality of antennas to produce a spatially filtered output. The spatially filtered output is evaluated to determine whether to send a transmission on the channel in the unlicensed frequency band.

Journal ArticleDOI
TL;DR: In this paper, the performance of a resonant vibration-based energy harvesting system utilizing a strongly nonlinear attachment was investigated and it was shown that with proper design, significant performance gains can be realized as compared with a tuned linear attachment.
Abstract: This work considers the performance of a resonant vibration-based energy harvesting system utilizing a strongly nonlinear attachment. Typical designs serving as the basis for harvesting energy from ambient vibration typically employ a linear oscillator for this purpose, limiting peak harvesting performance to a narrow band of frequencies about the resonant frequency of the oscillator. Herein, in an effort to maximize performance over the broader band of frequency content typically observed in ambient vibration measurements, we employ an essentially nonlinear cubic oscillator in the harvesting device and show that, with proper design, significant performance gains can be realized as compared with a tuned linear attachment. However, we also show that the coexistence of multiple equilibria due to the nonlinearity can degrade system performance, as the system can be attracted to a low amplitude state that provides reduced harvested power. Finally when multiple equilibria exist in the system, the basins of attraction for the stable states are determined and related to the expected response of the system.

Proceedings ArticleDOI
03 Apr 2011
TL;DR: In this paper, a simple model, in the frequency band up to 100 MHz, was derived by considering the noise generated at the source and taking into account the effect of the channel.
Abstract: This paper reviews existing noise models including both background and impulsive noise for the in-home PLC scenario, highlighting similarities and differences. With reference to the impulsive noise, it is shown that a simple model, in the frequency band up to 100 MHz, can be derived by considering the noise generated at the source and taking into account the effect of the channel. Capacity considerations are then made, comparing erasure decoding strategies or full decoding strategies.

Journal ArticleDOI
TL;DR: In this paper, the authors describe the design and the use of different types of antennas for the satellite communication service in the frequency band width in the Ka-band and describe the characteristics of these antennas.
Abstract: Ka-band payloads are becoming more and more popular for satellite communication. The wider band width in Ka-band allows a better satisfaction of the increasing demand for capacity. In addition to the use of more resources, a more efficient use of the available resources will become key for a successful development of satellite communication services. Modern antenna concepts allow a high frequency reuse scheme and, therefore, an extreme efficient use of the most rare resource in satellite communication, the frequency band width. In this paper, we describe the design and the use of different types of such antennas.

Journal ArticleDOI
TL;DR: In this paper, the authors presented a novel -band wideband circularly polarized 64-element microstrip antenna array with double application of the sequential rotation feeding technique, which can find good applications in aerospace, radar, and communication systems.
Abstract: A novel -band wideband circularly polarized 64-element microstrip antenna array is presented in this letter. It is developed with double application of the sequential rotation feeding technique. The array employs corner-truncated microstrip patches as the basic element, and then a four-element array as the subarray. By applying the sequential rotation technique twice to design the feed networks, a full 64-element array with good performance is obtained. A prototype of the full array was constructed and tested. The measurement results show that both the reflection coefficient of less than 10 dB and axial ratio of less than 3 dB have been achieved over a frequency band of 27-31 GHz; this corresponds to a wide bandwidth of 13.8%. Due to its planar configuration, the proposed array can find good applications in aerospace, radar, and communication systems.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a novel printed monopole antenna with constant gain over a wide bandwidth for ultra wideband applications with desired notch-band characteristic, which consists of a square-ring radiating patch with a pair of T-shaped strips protruded inside the square ring and a coupled Tshaped strip and a ground plane with a protruded strip, which provides a wide us able fractional bandwidth of more than 130% (3.07-14.6 GHz).
Abstract: A novel printed monopole antenna with constant gain over a wide bandwidth for ultra wideband applications with desired notch-band characteristic is presented. The proposed antenna consists of a square-ring radiating patch with a pair of T-shaped strips protruded inside the square ring and a coupled T-shaped strip and a ground plane with a protruded strip, which provides a wide us able fractional bandwidth of more than 130% (3.07-14.6 GHz). By using the square-ring radiating patch with a pair of T-shaped strips protruded inside it, the frequency bandstop performance is generated, and we can control its characteristics such as band-notch frequency and its bandwidth by electromagnetically adjusting coupling between a pair of T-shaped strips protruded inside the square ring. The designed antenna has a small size of 12 × 18 mm2, or about 0.15λ × 0.25λ at 4.2 GHz, while showing the band-rejection performance in the frequency band of 5.05-5.95 GHz.

Journal ArticleDOI
Yue-Ying Chen1, Yong-Chang Jiao1, Gang Zhao1, Fan Zhang1, Zhen-Lin Liao1, Yu Tian1 
TL;DR: In this article, a dual-band coplanar waveguide (CPW)-fed slot antenna with a C-shaped grounded strip is proposed for dual-sense circularly polarized radiation.
Abstract: A novel dual-band coplanar waveguide (CPW)-fed slot antenna with a C-shaped grounded strip is proposed for dual-sense circularly polarized radiation. The circular polarization in the lower band is achieved by the slots loaded in two opposite corners, and the C-shape grounded strip can offer a current path for the upper band. A rectangular tuning stub protruded into the slot from the signal strip of the CPW is used to obtain good impedance matching over the whole frequency band. Axial-ratio (AR) bandwidth can be significantly enhanced through tuning the horizontal length of the C-shaped grounded strip. The antenna has been investigated numerically and experimentally. Experimental results show that the antenna possesses the measured 10-dB return loss impedance bandwidth of 106.9% (1.01-3.33 GHz). The measured 3-dB AR bandwidths for the lower and upper bands can be up to 32.35% (1.41-1.96 GHz) and 5.6% (2.45-2.59 GHz), respectively.

Proceedings ArticleDOI
05 Jun 2011
TL;DR: Low-weight channel coding is proposed as a novel mechanism to reduce interference in pulse-based nanonetworks and it is shown that by appropriately choosing the weight of a code, interference can be mitigated.
Abstract: Nanotechnology is providing the engineering community with a new set of tools to design and manufacture integrated devices just a few hundred nanometers in total size. Communication among these nano-devices will boost the range of applications of nanotechnology in several fields, ranging from biomedical research to military technology or environmental science. Within the different alternatives for communication in the nanoscale, recent developments in nanomaterials point to the Terahertz band (0.1-10 THz) as the frequency range of operation of future electromagnetic nano-transceivers. This frequency band can theoretically support very large bit-rates in the short range, i.e., for distances below one meter. Due to the limited capabilities of individual nano-devices, pulse-based communications have been proposed for electromagnetic nanonetworks in the Terahertz band. However, the expectedly very large number of nano-devices and the unfeasibility to coordinate them, can make interference a major impairment for the system. In this paper, low-weight channel coding is proposed as a novel mechanism to reduce interference in pulse-based nanonetworks. Rather than utilizing channel codes to detect and correct transmission errors, it is shown that by appropriately choosing the weight of a code, interference can be mitigated. The performance of the proposed scheme is analytically and numerically investigated both in terms of overall interference reduction and achievable information rate, by utilizing a new statistical interference model. The results show that this type of network-friendly channel coding schemes can be used to alleviate the interference problem in nanonetworks without compromising the individual user information rate.

Journal ArticleDOI
TL;DR: In this article, a vertical vibration model of human body is introduced to make the modeling of seat suspension systems more precise, and a dynamic output feedback controller of order equal to the plant is designed, where an effective multiplier expansion is used to convert the controller design to a convex optimization problem.

Journal ArticleDOI
TL;DR: In this paper, the design and realization of a novel wideband two-layer 4 × 4 Butler matrix in substrate integrated waveguide (SIW) technology is addressed, and the two-level, low-loss, wideband SIW transition is designed and optimized using its equivalent circuit model.
Abstract: The design and realization of a novel wideband two-layer 4 × 4 Butler matrix in substrate integrated waveguide (SIW) technology are addressed. The two-layer SIW design is exploited through a two-fold enhancement approach. The two-layer topology is first explored in a simple matrix layout with minimum number of components. A space saving design is then proposed making optimum use of the two-layer topology and the SIW technology leading to a significant size reduction. A two-level, low-loss, wideband SIW transition is designed and optimized using its equivalent circuit model. The two corresponding Butler matrix prototypes are optimized, fabricated and measured. Measured and simulated results are in good agreement. Isolation characteristics better than -15 dB with input reflection levels lower than - 12 dB are experimentally validated over 24% frequency bandwidth centered at 12.5 GHz. Measured transmission magnitudes and phases exhibit good dispersive characteristics of 1 dB, around an average value of -6.8 dB, and 10° with respect to the theoretical phase values, respectively, over the entire frequency band. The impact of the measured transmission phases and magnitudes on the radiation pattern of a 4-element antenna array is also investigated.

Journal ArticleDOI
TL;DR: In this paper, a seismic interferometry method was proposed to extract reflection responses from low-frequency noise signals from the coda of transmissions, which can be used to characterize the lithosphere below an array of receivers.