Showing papers in "Radioengineering in 2015"
TL;DR: In this paper, the authors classify all memristors into three classes called Ideal, Generic, or Extended Memristors, and define new concepts such as Continuum-memory memristor, POP (acronym for Power-Off Plot), DC V-I Plot, and Quasi DC V -I Plot.
Abstract: This paper classifies all memristors into three classes called Ideal, Generic, or Extended memristors. A subclass of Generic memristors is related to Ideal memristors via a one-to-one mathematical transformation, and is hence called Ideal Generic memristors. The concept of non-volatile memories is defined and clarified with illustrations. Several fundamental new concepts, including Continuum-memory memristor, POP (acronym for Power-Off Plot), DC V-I Plot, and Quasi DC V-I Plot, are rigorously defined and clarified with colorful illustrations. Among many colorful pictures the shoelace DC V-I Plot stands out as both stunning and illustrative. Even more impressive is that this bizarre shoelace plot has an exact analytical representation via 2 explicit functions of the state variable, derived by a novel parametric approach invented by the author.
344 citations
TL;DR: In this article, the authors introduce graphene properties in the microwave range, and present a paradigm of novel graphene-based devices and applications in the micro-wave/RF frequency range.
Abstract: In view to the epochal scenarios that nanotech- nology discloses, nano-electronics has the potential to introduce a paradigm shift in electronic systems design similar to that of the transition from vacuum tubes to semi- conductor devices. Since low dimensional (1D and 2D) nano-structured materials exhibit unprecedented electro- mechanical properties in a wide frequency range, includ- ing radio-frequencies (RF), microwave nano-electronics provides an enormous and yet widely undiscovered opportunity for the engineering community. Carbon nano- electronics is one of the main research routes of RF/micro- wave nano-electronics. In particular, graphene has shown proven results as an emblematic protagonist, and a real solution for a wide variety of microwave electronic devices and circuits. This paper introduces graphene properties in the microwave range, and presents a paradigm of novel graphene-based devices and applications in the micro- wave/RF frequency range.
91 citations
TL;DR: Developing of such VLC links with a view to implementing ubiquitous broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM) or carrier-less amplitude and phase modulation (CAP) in conjunction with equalization techniques is discussed.
Abstract: 5G networks have to offer extremely high capacity for novel streaming applications. One of the most promising approaches is to embed large numbers of cooperating small cells into the macro-cell coverage area.
Alternatively, optical wireless based technologies can be adopted as an alternative physical layer offering higher data rates. Visible light communications (VLC) is an emerging technology for future high capacity communication links (it has been accepted to 5GPP) in the visible range of the electromagnetic spectrum (~370–780 nm) utilizing light-emitting diodes (LEDs) simultaneously provide data transmission and room illumination. A major challenge in VLC is the LED modulation bandwidths, which are limited to a few MHz. However, myriad gigabit speed transmission links have already been demonstrated.
Non line-of-sight (NLOS) optical wireless is resistant to blocking by people and obstacles and is capable of adapting its’ throughput according to the current channel state information. Concurrently, organic polymer LEDs (PLEDs) have become the focus of enormous attention for solid-state lighting applications due to their advantages over conventional white LEDs such as ultra-low costs, low heating temperature, mechanical flexibility and large photoactive areas when produced with wet processing methods.
This paper discusses development of such VLC links with a view to implementing ubiquitous broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM) or carrier-less amplitude and phase modulation (CAP) in conjunction with equalization techniques. Finally, this paper will also summarize the results of the European project ICT COST IC1101 OPTICWISE (Optical Wireless Communications - An Emerging Technology) dealing VLC and OLEDs towards 5G networks.
68 citations
TL;DR: A microwave sensor based on an ar- tificial transmission line is proposed for non-invasive blood glucosemonitoring and responded to by the commercial full-wave numerical simulation tool COMSOL Multiphysics and virtually tested by means of numerical simulations.
Abstract: In this paper, a microwave sensor based on an ar- tificial transmission line is proposed for non-invasive blood glucosemonitoring. Acorrespondingnumericalmodelofthe sensorimplementedinmicrostriptechnologyiscreatedinthe commercial full-wave numerical simulation tool COMSOL Multiphysics and virtually tested by means of numerical sim- ulations. Blood-glucose solution models with various blood glucose concentrations are used as a model of a biological tissue under test. Furthermore, a possible methodology for performing non-invasive tests is proposed. Sensitivity of the sensor developed here is compared to a sensor based on a section of a conventional microstrip transmission line of the same length and width.
39 citations
TL;DR: In this paper, a profoundly different modeling approach is proposed, which is mathematically equivalent to window-based modeling, but due to its numerical stability, it definitely smoothes the above problems away.
Abstract: The paper refers to problems of modeling and computer simulation of generic memristors caused by the so-called window functions, namely the stick effect, nonconvergence, and finding fundamentally incorrect solutions. A profoundly different modeling approach is proposed, which is mathematically equivalent to windowbased modeling. However, due to its numerical stability, it definitely smoothes the above problems away.
36 citations
TL;DR: This paper analyzes the impact of hardware impairments at relay node and source node by evaluating outage probability based on the effective signal to noise and distortion ratio (SNDR) and proposes energy harvesting protocol at the relay and source nodes.
Abstract: In this paper, we analyze the impact of hardware impairments at relay node and source node (i.e. imperfect nodes) on network performance by evaluating outage probability based on the effective signal to noise and distortion ratio (SNDR). Especially, we propose energy harvesting protocol at the relay and source nodes, namely, power switching imperfect relay (PSIR) and power switching imperfect source (PSIS). Aiming to determine the performance of energy constrained network, we first derive closed-form expressions of the outage probability and then the throughput can be maximized in delay-limited transmission mode. The simulation results provide practical insights into the impacts of hardware impairments and power switching factors of the energy harvesting protocol on the performance of energy harvesting enabled two-way relaying network.
36 citations
TL;DR: In this article, the authors measured the transition process from the high to low resistivity states, i.e., the reset process of resistive switching based memristors based on Ni/HfO2/Si- n+ structures, and developed an analytical model for their electrical characteristics.
Abstract: We have measured the transition process from the high to low resistivity states, i.e., the reset process of resistive switching based memristors based on Ni/HfO2/Si- n+ structures, and have also developed an analytical model for their electrical characteristics. When the char- acteristic curves are plotted in the current-voltage (I-V) domain a high variability is observed. In spite of that, when the same curves are plotted in the charge-flux domain (Q-), they can be described by a simple model containing only three parameters: the charge (Qrst) and the flux (rst) at the reset point, and an exponent, n, relating the charge and the flux before the reset transition. The three parame- ters can be easily extracted from the Q- plots. There is a strong correlation between these three parameters, the origin of which is still under study.
35 citations
TL;DR: The resulting continuous and differentiable DAE set captures accurately the dynamics of the original model, delivers well-behaved numerical solutions in software, and may be integrated into a commercially-available circuit sim- ulator.
Abstract: This work presents a continuous and differen- tiable approximation of a Tantalum oxide memristor model which is suited for robust numerical simulations in soft- ware. The original model was recently developed at Hewlett Packard labs on the basis of experiments carried out on a memristor manufactured in house. The Hewlett Packard model of the nano-scale device is accurate and may be taken as reference for a deep investigation of the capabilities of the memristor based on Tantalum oxide. However, the model contains discontinuous and piecewise differentiable func- tions respectively in state equation and Ohm's based law. Numerical integration of the differential algebraic equation set may be significantly facilitated under substitution of these functions with appropriate continuous and differentiable ap- proximations. A detailed investigation of classes of possible continuous and differentiable kernels for the approximation of the discontinuous and piecewise differentiable functions in the original model led to the choice of near optimal can- didates. The resulting continuous and differentiable DAE set captures accurately the dynamics of the original model, delivers well-behaved numerical solutions in software, and may be integrated into a commercially-available circuit sim- ulator.
29 citations
TL;DR: This paper utilizes memristors as configurable linear resistors and proposes memristor-based bandpass filters that feature suppression of parasitic frequency pass bands and widening of the desired rejection band.
Abstract: The recent implementation of the fourth fundamental electric circuit element, the memristor, opened new vistas in many fields of engineering applications. In this paper, we explore several RF/microwave passive circuits that might benefit from the memristor salient characteristics. We consider a power divider, coupled resonator bandpass filters, and a low-reflection quasi-Gaussian lowpass filter with lossy elements. We utilize memristors as configurable linear resistors and we propose memristor-based bandpass filters that feature suppression of parasitic frequency pass bands and widening of the desired rejection band. The simulations are performed in the time domain, using LTspice, and the RF/microwave circuits under consideration are modeled by ideal elements available in LTspice.
28 citations
TL;DR: In this article, a multilayered FSS with non-resonant unit cells in each layer allows inphase transmission of waves radiated from the antenna over a 3dB bandwidth of about 50%.
Abstract: Gain enhancement of a wide slot antenna over a wide frequency band using a low profile, second order bandpass frequency selective surface (FSS) as a superstrate is presented in this paper. The proposed multilayered FSS with non-resonant unit cells in each layer allows inphase transmission of waves radiated from the antenna over a 3dB bandwidth of about 50%. The design allows an enhancement of up to 4 dBi in the antenna gain over the entire frequency band (5-8 GHz) of operation. The FSS provides a very low insertion loss between the two transmission poles along with a linearly decreasing transmission phase over the band. The composite structure shows an impedance bandwidth (-10 dB) of 65% with an average gain between 6-8 dBi over the frequency band with a peak gain of 9 dBi. Measurement results of the fabricated prototype matches well with the predicted values.
TL;DR: In this paper, an electronically polarization reconfigurable circular patch antenna, with fixed resonant frequency and operating at Wireless Local Area Network (WLAN) frequency band (2.4-2.48 GHz), is presented.
Abstract: In this paper, an electronically polarization re-configurable circular patch antenna, with fixed resonantfrequency and operating at Wireless Local Area Network(WLAN) frequency band (2.4–2.48 GHz,) is presented. Thestructure of the proposed design consists of a circularpatch as a radiating element fed by a coaxial probe, coop-erated with four equal-length slits etched on the edge alongthe x-axis and y-axis. A total of four switches were usedand embedded across the slits at specific locations, thuscontrolling the length of the slits. By activating and deacti-vating the switches (ON and OFF) across the slits, the cur-rent on the patch is changed, thus modifying the electricfield and polarization of the antenna. Consequently, thepolarization excited by the proposed antenna can beswitched into three types; linear polarization, left-handcircular polarization or right-hand circular polarization.This paper proposes a simple approach that enablesswitching the polarizations and excites at the same oper-ating frequency. Simulated and measured results of theideal case (using copper strip switches) and the real case(using PIN diode switches) are compared and presented todemonstrate the performance of the antenna.
TL;DR: Robust and imperceptible nonblind color image watermarking algorithm is proposed, which benefit from the fact that watermark can be hidden in different color channel which results into further robustness of the proposed technique to attacks.
Abstract: Internet has affected our everyday life drastically. Expansive volumes of information are exchanged over the Internet consistently which causes numerous security concerns. Issues like content identification, document and image security, audience measurement, ownership, copyrights and others can be settled by using digital watermarking. In this work, robust and imperceptible nonblind color image watermarking algorithm is proposed, which benefit from the fact that watermark can be hidden in different color channel which results into further robustness of the proposed technique to attacks. Given method uses some algorithms such as entropy, discrete wavelet transform, Chirp z-transform, orthogonal-triangular decomposition and Singular value decomposition in order to embed the watermark in a color image. Many experiments are performed using well-known signal processing attacks such as histogram equalization, adding noise and compression. Experimental results show that the proposed scheme is imperceptible and robust against common signal processing attacks.
TL;DR: In this article, a lowpass filter is designed using open complementary split ring resonator and a tapered dumbbell shaped DGS is placed under the OCSRRs to extend the stopband.
Abstract: . A compact (0.16 g × 0.08 g ) and wide stop-band lowpass filter design using open complementary split ring resonator (OCSRR) and defected ground structure (DGS) is presented in this paper. Low pass filter is con-structed using two cascaded stages of OCSRR. Since the rejection bandwidth of the OCSRR is narrow, tapered dumbbell shaped DGS section is placed under the OCSRR to enhance the bandwidth. The cutoff frequency (f c ) of the proposed lowpass filter is 1.09 GHz. The rejection band-width of the filter covers the entire ultra wideband spec-trum. Hence the spurious passband suppression is achieved up to 10 f c . The designed filter has been fabri-cated and validated by experimental results. Keywords Lowpass filter, defected ground structure (DGS), open complementary split ring resonator (OCSRR) 1. Introduction On the motive of conventional filter design methods such as stepped impedance and open stub suffering from poor skirt characteristics and spurious passband, re-searchers have paid great attention over the past few years in designing a compact and sharp cutoff lowpass filters with spurious free wide stopband. Lowpass filter using different defected ground structures (DGS), photonic bandgap (PBG) structures and electromagnetic bandgap structures have been proposed in various literatures [1–9]. Sharp cutoff and low insertion loss lowpass filter using a complementary split ring resonator (CSRR) is reported in [3]. Cascaded stages of CSRR with open stub configura-tion, exhibiting sharp cutoff lowpass response are pre-sented in [4]. Planar photonic bandgap (PBG) structures involving compact microstrip resonating cell (CMCR) are utilized to design a lowpass filter with wide stopband [5]. Recently, a lowpass filter with very sharp transition band using OCSRR is demonstrated in [6]. In this paper, a new technique is proposed to reduce the size of the lowpass filter and to obtain the wide spurious free stopband. The lowpass filter is designed using open complementary split ring resonator and a tapered dumbbell shaped DGS is placed under the OCSRRs to extend the stopband. The proposed lowpass filter is smaller and outperforming the existing filters in terms of insertion loss level, roll off rate and rejection bandwidth. Figure 1 shows the schematic of OCSRR printed on the microstrip line. This structure is first proposed in [6] for designing a sharp cutoff lowpass filter with compact size. OCSRR is a negative image of the open split ring resonator. To study the frequency response characteristics of the OCSRR, this structure is designed on Rogers 5880 substrate with a dielectric constant of 2.2 and a substrate thickness of 0.381 mm and simulated using an Ansys full wave simulator.
TL;DR: In this article, a planar waveguide was realized on a modified dispersion equation and was schemed for 633 nm, 964 nm, 1310 nm and 1550 nm wavelength.
Abstract: This paper reports on a technology for realization of an optical planar waveguide layer on duroid substrate and on FR4 fiber reinforced board material printed circuit boards. Waveguide core material was EpoCore polymer and for claddings we used EpoClad polymer. Design of the presented planar waveguides was realized on the bases of modified dispersion equation and was schemed for 633 nm, 964 nm, 1310 nm and 1550 nm wavelength. Waveguiding properties were measured by dark mode spectroscopy while propagation optical loss measurement was done by the fiber probe technique at wavelegnth 633 nm (He-Ne laser). The samples had optical losses lower than 0.5 dB/cm. The best sample has optical losses around 0.25 dB/cm.
TL;DR: The paper compares the boundary surfaces using cross-sections in three projection planes, for the four changes of Chua’s circuit parameters, finding that in a variation of the parameters presented, the boundary surface will separate even single scroll chaotic attractors from each other.
Abstract: The paper compares the boundary surfaces using cross-sections in three projection planes, for the four changes of Chua’s circuit parameters. It is known that due to changing the parameters, the Chua’s circuit can be characterized not only by stable limit cycle, but also by one double scroll chaotic attractor, two single scroll chaotic attractors or other two stable limit cycles. Chua’s circuit can even start working as a binary memory. It is not known yet, how changes in parameters, and consequently in attractors in the circuit, will affect the morphology of the boundary surface. The boundary surface separates the double scroll chaotic attractor from the stable limit cycle. In a variation of the parameters presented in this paper, the boundary surface will separate even single scroll chaotic attractors from each other. Dividing the state space into regions of attraction for different attractors, however, remains fundamentally the same.
TL;DR: A novel quasi-coherent noise jamming method is proposed against linear frequency modulation signal and pulse compression radar and simulation results and circuit engineering implementation validate that the jamming signal covers real target effectively.
Abstract: A novel quasi-coherent noise jamming method is proposed against linear frequency modulation (LFM) signal and pulse compression radar. Based on the structure of digital radio frequency memory (DRFM), the jamming signal is acquired by the pseudo-random sequence phase-modulation of sampled radar signal. The characteristic of jamming signal in time domain and frequency domain is analyzed in detail. Results of ambiguity function indicate that the blanket jamming effect along the range direction will be formed when jamming signal passes through the matched filter. By flexible controlling the parameters of interrupted-sampling pulse and pseudo-random sequence, different covering distances and jamming effects will be achieved. When the jamming power is equivalent, this jamming obtains higher process gain compared with non-coherent jamming. The jamming signal enhances the detection threshold and the real target avoids being detected. Simulation results and circuit engineering implementation validate that the jamming signal covers real target effectively.
TL;DR: The work presented in this paper is aimed at the implementation of a real-time multiple-input multiple-output (MIMO) imaging radar used for area surveillance and demonstrates the practical feasibility of the implementation.
Abstract: The work presented in this paper is aimed at the implementation of a real-time multiple-input multiple-output (MIMO) imaging radar used for area surveillance. In this radar, the equivalent virtual array method and time-division technique are applied to make 16 virtual elements synthesized from the MIMO antenna array. The chirp signal generater is based on a combination of direct digital synthesizer (DDS) and phase locked loop (PLL). A signal conditioning circuit is used to deal with the coupling effect within the array. The signal processing platform is based on an efficient field programmable gates array (FPGA) and digital signal processor (DSP) pipeline where a robust beamforming imaging algorithm is running on. The radar system was evaluated through a real field experiment. Imaging capability and real-time performance shown in the results demonstrate the practical feasibility of the implementation.
TL;DR: In this paper, a frequency-reconfigurable coplanar-waveguide (CPW) fed monopole antenna using switchable stubbed ground structure is presented, where four PIN diodes are employed in the stubs stretching from the ground to make the antenna reconfigurable in three operating modes.
Abstract: A frequency-reconfigurable coplanar-waveguide (CPW) fed monopole antenna using switchable stubbed ground structure is presented. Four PIN diodes are employed in the stubs stretching from the ground to make the antenna reconfigurable in three operating modes: a single-band mode (2.4-2.9 GHz), a dual-band mode (2.4 to 2.9 GHz/5.09-5.47 GHz) and a triple-band mode (3.7 to 4.26 GHz/5.3-6.3 GHz/8.0-8.8 GHz). The monopole antenna is resonating at 2.4 GHz, while the stubs produce other operating frequency bands covering a number of wireless communication systems, including WLAN, WiMAX, Cband, and ITU. Furthermore, an optimized biasing network has been integrated into this antenna, which has little influence on the performance of the antenna. This paper presents, compares and discusses the simulated and measured results.
TL;DR: This paper proposes a new method for designing the polynomial-interpolation-type noninteger-delay filter with a new structure formulation based on the discrete Pascal transform and Pascal interpolation, which is more suited for fast delay tuning.
Abstract: This paper proposes a new method for designing the polynomial-interpolation-type noninteger-delay filter with a new structure formulation. Since the design formu- lation and the new realization structure are based on the discrete Pascal transform (DPT) and Pascal interpolation, we call the resulting filter Pascal noninteger-delay filter. The kth-order Pascal polynomial is used to pass through the given (k + 1) data points in achieving the kth-order Pascal filter. The Pascal noninteger-delay filter is a real- time filter that consists of two sections, which can be real- ized into the front-section and the back-section. The front- section contains multiplication-free digital filters, and the number of multiplications in the back-section just linearly increases as order becomes high. Since the new Pascal filter has low complexity and structure can adjust non- integer delay online, it is more suited for fast delay tuning. Consequently, the polynomial-interpolation-type delay filter can be achieved by using the Pascal approach with high efficiency and low-complexity structure.
TL;DR: An efficient parallel processing architecture using multi-core Digital Signal Processor (DSP) is presented to improve the capability of real-time imaging for Frequency Modulated Continuous Wave Synthetic Aperture Radar (FMCW SAR).
Abstract: This paper presents an efficient parallel processing architecture using multi-core Digital Signal Processor (DSP) to improve the capability of real-time imaging for Frequency Modulated Continuous Wave Synthetic Aperture Radar (FMCW SAR). With the application of the proposed processing architecture, the imaging algorithm is modularized, and each module is efficiently realized by the proposed processing architecture. In each module, the data processing of different cores is executed in parallel, also the data transmission and data processing of each core are synchronously carried out, so that the processing time for SAR imaging is reduced significantly. Specifically, the time of corner turning operation, which is very time-consuming, is ignored under computationally intensive case. The proposed parallel architecture is applied to a compact Ku-band FMCW SAR prototype to achieve real-time imageries with 34 cm × 51 cm (range × azimuth) resolution.
TL;DR: The computer-assisted vision system created for the detection of the disposable anesthetic respiratory masks provided the classification of defects which may be common to both rubber and plastic parts of the masks.
Abstract: The article concerns the computer-assisted vision system created for the detection of the disposable anesthetic respiratory masks. This article provides the classification of defects which may be common to both rubber and plastic parts of the masks. The defects were divided into groups and the nature of them was investigated. The algorithms and methods for the detection of defective products were based on the segmentation of image and the detection of uneven contours. The experiment results are presented in this work. With reference to the results, the most effective masks’ filters were identified. The achieved specificity of the algorithm is 100 % and the sensitivity is 100 %.
TL;DR: This paper proposes a resource allocation scheme that gradually varies frequency resource share with distance from the eNodeB for both macrocells and femtocells in order to attain better utilization of the resources.
Abstract: The Fractional Frequency Reuse (FFR) is a resource allocation technique that can effectively mitigate inter-cell interference (ICI) in LTE based HetNets and it is a promising solution. Various FFR schemes have been suggested to address the challenge of interference in femtocell systems. In this paper, we study the scopes of interference mitigation and capacity improvement. We propose a resource allocation scheme that gradually varies frequency resource share with distance from the eNodeB for both macrocells and femtocells in order to attain better utilization of the resources. This is performed effectively using three layers in the cell. The proposal also employs high number sectors in a cell, low interference and good frequency reuse. Monte-Carlo simulations are performed, which show that the proposed scheme achieves signifi- cantly better throughput compared to the existing FFR schemes.
TL;DR: In this paper, vowel polygons, exactly their parameters, are chosen as the criterion for achievement of differences between normal state of speaker and relevant speech under real psychological stress, and selected 6 methods based on cross-correlation of different features were classified by the coefficient of variation and for each individual vowel polygon, the efficiency coefficient marking the most significant and uniform differences between stressed and normal speech were calculated.
Abstract: Using vowel polygons, exactly their parameters, is chosen as the criterion for achievement of differences between normal state of speaker and relevant speech under real psychological stress. All results were experimentally obtained by created software for vowel polygon analysis applied on ExamStress database. Selected 6 methods based on cross-correlation of different features were classified by the coefficient of variation and for each individual vowel polygon, the efficiency coefficient marking the most significant and uniform differences between stressed and normal speech were calculated. Using the mean of cross- correlation values received for area difference with vector length and angle can be classified as the best method for observing generated differences. Generally, best results for stress detection are achieved by vowel triangles created by /i/-/o/-/u/ and /a/-/i/-/o/ vowel triangles in formant planes containing the fifth formant F5 combined with other formants.
TL;DR: In this article, the authors derived a general form of DEM that holds for any ideal memristor and showed that it is always a nonlinear equation of the first order; the PSM forms are found for memristors which are governed by DEMs of the Bernoulli and the Riccati types.
Abstract: Ideal memristor is a resistor with a memory, which adds dynamics to its behavior. The most usual char- acteristics describing this dynamics are the constitutive relation (i.e. the relation between flux and charge), or Parameter-vs-state map (PSM), mostly represented by the memristance-to-charge dependence. One of the so far unheeded tools for memristor description is its differential equation (DEM), composed exclusively of instantaneous values of voltage, current, and their derivatives. The article derives a general form of DEM that holds for any ideal memristor and shows that it is always a nonlinear equation of the first order; the PSM forms are found for memristors which are governed by DEMs of the Bernoulli and the Riccati types; a classification of memristors according to the type of their dynamics with respect to voltage and cur- rent is carried out.
TL;DR: In this paper, the level crossing rate of a macrodiversity SC receiver and two micro-diversity SC receivers is evaluated using closed-form expressions for Gamma shadowing severity.
Abstract: Macrodiversity system including macrodiversity SC receiver and two microdiversity SC receivers is consid- ered in this paper. Received signal experiences, simultane- ously, both, long term fading and short term fading. Microdiversity SC receivers reduce Rayleigh fading effects on system performance and macrodiversity SC receivers mitigate Gamma shadowing effects on system performance. Closed form expressions for level crossing rate of microdi- versity SC receivers output signals envelopes are calcu- lated. This expression is used for evaluation of level crossing rate of macrodiversity SC receiver output signal envelope. Numerical expressions are illustrated to show the influence of Gamma shadowing severity on level crossing rate.
TL;DR: In this article, the design of current mode low-pass ladder filters based on CMOS technology is described. The filters are derived from passive RLC ladder filter proto-types using new CMOS lossy and lossless integrators.
Abstract: This paper describes the design of current mode low-pass ladder filters based on CMOS technology. The filters are derived from passive RLC ladder filter proto- types using new CMOS lossy and lossless integrators. The all-pole and Elliptic approximations are used in the pro- posed low-pass filter realizations. The proposed two types of filter can be electronically tuned between 10 kHz and 100 MHz through bias current from 0.03 µA to 300 µA. The proposed filters use 1.5 V power supply with 3 mW power consumption at 300 µA bias current. The proposed filters are resistorless, use grounded capacitors and are suitable for further integration. The total harmonic distor- tion (THD) of the low-pass filters is less than 1% over the operating frequency range. PSPICE simulation results, obtained by using TSMC 0.18µm technology, confirm the presented theory.
TL;DR: The lookup table (LUT) method is introduced, which possesses the advantages of ultra-high speed, high accuracy and low memory usage, and without adding fre- quency index to the lookup table, the estimator can realize wideband application.
Abstract: The time-consuming phase ambiguity resolu- tion makes the uniform circular array (UCA) interferometer not suitable for real-time direction-of-arrival (DOA) estima- tion. This paper introduces the lookup table (LUT) method to solve this problem. The key of the method is that we look up the ambiguity numbers instead of the eventual DOA from the table, and then the DOA is obtained by relatively small amount of calculation. This makes it possible that we are able to shrink the table size while maintain the DOA estima- tion accuracy. The table addresses cover all possible mea- sured phase differences (PDs), which enables the method to be free of spatial scanning. Moreover, without adding fre- quency index to the lookup table, the estimator can realize wideband application. As an example, a field-programmable gate array (FPGA) based DOA estimator with the estimation time of 180 ns is presented, accompanied by the measured results. This method possesses the advantages of ultra-high speed, high accuracy and low memory usage.
TL;DR: This paper presents a new design of dual-band bandpass filters using coupled stepped-impedance reso- nators for wireless systems that uses multiple couple stubs to tune the passband frequencies and the filter characteristics are improved using defected ground technique.
Abstract: This paper presents a new design of dual-band bandpass filters using coupled stepped-impedance reso- nators for wireless systems. This architecture uses multiple couple stubs to tune the passband frequencies and the filter characteristics are improved using defected ground struc- ture (DGS) technique. Measurement results show insertion losses of 0.93 dB and 1.13 dB for the central frequencies of 2.35 GHz and 3.61 GHz, respectively. This filter is de- signed, fabricated and measured and the results of the simulation and measurement are in good agreement.