Location service for wireless network using improved RSS-based cellular localisation

Value-added services, especially in mobile environments, have recently become the key component of making more profit and attracting more subscribers. One of the most commonly used such service is location-based advertiser services. The main issue which should be considered in providing such services is determining the position of the mobile terminals precisely. In this paper, one pattern recognition localisation method based on the signal strength appropriated for implementing a location-based service is presented. The main aim is to introduce some practical solutions to decrease error and computational load and also eliminate the necessity of updating the database. Practical results illustrate high accuracy of this technique and its suitability to apply in such services. The mean error declines to 9.7 m and mean error corresponding to CDF = 67% and CDF = 95% are less than 11 m and 23 m, respectively. We also present a location-based advertising service, in which the customer’s interests and local time are considered, in order to enhance the efficiency and individualism of this service.     

A 6-GHz capacitively-coupled Colpitts CMOS quadrature voltage controlled oscillator

In this work a new low-noise low-power Colpitts quadrature voltage controlled oscillator (QVCO) made by coupling two identical current-switching differential Colpitts voltage controlled oscillators (VCO) is proposed; coupling of the VCOs is done using some capacitors in an “in-phase anti-phase” scheme. In this coupling configuration first harmonics (as well as higher harmonics) from each VCO are injected to the other VCO, as opposed to coupling schemes in which only even harmonics are injected. An analysis of the linearized circuit which confirms 90° phase difference between output signals of the proposed circuit is presented. Since no extra noise sources or power consumption are introduced to the core VCOs, the proposed QVCO achieves low phase noise performance and low power consumption. The proposed circuit is designed and simulated in a commercial 0.18 μm CMOS technology. The simulated phase noise of the proposed QVCO at 3 MHz offset frequency is ?138.3 dBc/Hz, at 6 GHz. The circuit dissipates 8.16 mW from a 1.8 V supply and its frequency can be tuned from 5.6 to 6.3 GHz.     

Efficient architectures for modulo 2n − 2 arithmetic units

Moduli of the 2ⁿ and 2ⁿ ± 1 forms are usually employed in designs that adopt the residue number system. However, in several cases such as in finite impulse response filters and communication components, a modulo value equal to 2ⁿ ? 2 can be used. So far, modulo 2ⁿ ? 2 arithmetic units have been based either on look-up tables or on generic modulo arithmetic units. In this work, by taking advantage of the properties of modulo 2ⁿ ? 2 arithmetic, we propose efficient modulo 2ⁿ ? 2 multi-operand adder, multiplier as well as squarer architectures. The proposed circuits are based on the corresponding ones for modulo 2^n?1 ? 1 arithmetic and some simple logic. Experimental results validate that the proposed circuits achieve significant area and delay savings compared to those previously presented.     

Microwave Sintering of Bi2Te3- and PbTe-Based Alloys: Structure and Thermoelectric Properties

Microwave sintering is well known as an expeditious process in applications involving ceramics and biomaterials. For powders in the nanometer range, rapid microwave heating could reduce material exposure to elevated temperatures, thus preserving nanostructures in the resulting materials. To investigate the potential of this technique for thermoelectric (TE) materials, we have prepared samples of bismuth-telluride- and lead-telluride-based alloys from powders, for both materials, having sizes of partially agglomerated particles distributed from 0.15 μm to 7 μm. Sintering of the cold-pressed powders was carried out in a microwave furnace for 900 s at temperatures in the range of 583 K to 623 K for bismuth telluride and 793 K to 813 K for lead telluride specimens. For optimized sintering times and temperatures, the samples obtained showed relative densities of almost 95%. Scanning electron microscopy shows some residual porosity and a reduction of grain size, up to a factor of 5 for PbTe, compared with optimized hot-extruded specimens. For bismuth telluride samples, the TE performance in the range of 300 K to 460 K is poor, which is attributed to the arbitrary texture obtained from cold pressing of a highly anisotropic alloy prior to its sintering. In contrast, PbTe exhibits isotropic properties, hence deficiency of texturing is not expected to have a negative impact on its TE properties. Harman measurements show a value of ZT = 0.42 at 617 K for PbTe p-type sintered samples, which is comparable to hot-extruded alloys from similar powders. The present work demonstrates that microwave sintering is a promising alternative to other powder consolidation techniques for polycrystalline materials exhibiting isotropic TE properties.     

Macro cellular network transition from traditional frequency range to 28 GHz millimeter wave frequency band

The target of this article is to analyze the impact of transition from cellular frequency band i.e. 2.1 GHz to Millimeter Wave (mmWave) frequency band i.e. 28 GHz. A three dimensional ray tracing tool “sAGA” was used to evaluate the performance of the macro cellular network in urban/dense-urban area of the Helsinki city. A detailed analysis of user experience in terms of signal strength and signal quality for outdoor and indoor users is presented. Indoor users at different floors are separately studied in this paper. It is found that in spite of considering high system gain at 28 GHz the mean received signal power is reduced by almost 16.5 dB compared with transmission at 2.1 GHz. However, the SINR is marginally changed at higher frequency. Even with 200 MHz system bandwidth at 28 GHz, no substantial change is witnessed in signal quality for the outdoor and upper floor indoor users. However, the users at lower floors show some sign of degradation in received signal quality with 200 MHz bandwidth. Moreover, it is also emphasized that mobile operators should take benefit of un-utilized spectrum in the mmWave bands. In short, this paper highlights the potential and the gain of mmWave communications.     

Improvement in the Durability and Heat Conduction of uni-leg Thermoelectric Modules Using n-type Mg2Si Legs

We have fabricated several kinds of uni-leg thermoelectric (TE) modules using Sb-doped n-type Mg₂Si. In order to evaluate the influence of the structure of the modules on their durability with respect to heat-cycling, modules of two different types were evaluated. One was a conventional-structured module, in which the upper and lower surfaces of the legs were each fixed to a ceramic substrate. The other was a ‘half skeleton’ module, in which the ‘cold-side’ substrate was removed and a thermal-conductive sheet was used instead of a ceramic plate for the cold-side insulator. From the result of this evaluation, it was confirmed that, although some variation in the output power was observed for the ‘half-skeleton’ module, the power variation was markedly less than for the conventional-structured module. Additionally, to improve the output power of the module, we replaced the Al₂O₃ substrate with Si₃N₄, which has a higher thermal conductivity than the Al₂O₃ substrate. The observed output power of a module (25 mm × 24 mm × 8.3 mm) fabricated using the Si₃N₄ substrate was 1,293 mW at ΔT = 500 K. The output value of the module using the Si₃N₄ plate was improved by 29 % compared with the output value of the module using the Al₂O₃ substrate. Moreover, based on the structures of these modules, a 36 mm × 41 mm × 8.3 mm module was fabricated. The expected value of the output power of the module was 1.9 W at ΔT = 500 K.     

Influence of Gaussian Beam on Terahertz Radar Cross Section of a Conducting Sphere

In RCS estimation, usually a plane wave is assumed; while in real measurements at terahertz frequencies, generally a Gaussian beam or a similar beam source is adopted. In this paper, the RCS of a conducting sphere is discussed under the condition that the incident wave is a Gaussian beam. In the estimation, the influence of 2.52 THz collimated laser beam on RCS is discussed and the RCS changing with scattering angle and some other factors is obtained; at the same time, the comparisons between different incident beams, plane wave and Gaussian beam, are also given. The estimation results show that choosing a beam width of 40 mm is appropriate when the sphere radius is 10 mm and the distance between the sphere and the beam source is 1 m.     

Programmable Switched Capacitor Finite Impulse Response Filter with Circular Memory Implemented in CMOS 0.18 μm Technology

This paper presents a programmable multi-mode finite impulse response (FIR) filter implemented as switched capacitor (SC) technique in CMOS 0.18 μm technology. Intended application of the described circuit is in analog base-band filtering in GSM/WCDMA systems. The proposed filter features a regular structure that allows for elimination of some parasitic capacitances, thus significantly improving the filtering accuracy. Due to its modularity that allows for dividing the circuit into two separate sections, the circuit can be easily reconfigured to work as either infinite impulse response (IIR) or as finite impulse (FIR) filter. One of the key components that allows for this multi-mode operation is the proposed programmable and ultra low power multiphase clock circuit. The 24-taps filter for the sampling frequency of 30 MHz dissipates power of 4.5 mW from a 1.8 V supply.     

Diagnostics of Analog Circuits Based on LS-SVM Using Time-Domain Features

Most researchers use wavelet transforms to extract features from a time-domain transient response from analog circuits to train classifiers such as neural networks (NNs) and support vector machines (SVMs) for analog circuit diagnostics. In this paper, we have proposed some new feature selection methods from a time-domain transient response, and compared the diagnostic results based on a least squares SVM (LS-SVM) using different time-domain feature vectors. First, we have improved two traditional feature selection methods: (a) using the mean and standard deviation in wavelet transform features, and (b) using the mean, standard deviation, skewness, kurtosis, and entropy in statistical property features. Then, a conventional time-domain feature vector based on the impulse response properties of a control system has been proposed. The simulation experiments for a leapfrog filter and a nonlinear rectifier show that: (1) the two improved methods have better accuracy than the traditional methods; (2) the proposed conventional time-domain feature vector is effective in the diagnostics of analog circuits—over 99 % for both of the two example circuits; (3) the proposed diagnostic method can diagnose soft faults, hard faults, and multi-faults, regardless of component tolerances and nonlinearity effects.     

Research into Influence of Gaussian Beam on Terahertz Radar Cross Section of a Conducting Cylinder

In RCS measurement, usually the incident beam is a Gaussian beam or a similar beam source; however, in the theoretical RCS estimation, usually a plane wave is assumed as the incident beam for sake of simplicity. In this paper, the RCS of an infinite perfect conducting cylinder is estimated. In the estimation, the influence of a 2.52 THz laser beam on RCS is studied and the RCS in dependence with scattering angle and some other factors is obtained after the change of RCS equation; meanwhile, comparisons of RCS when the incident beam is a plane wave and a Gaussian beam respectively, are also given. The estimation results show, when the cylinder radius is 10 mm, choosing a beam width of 40 mm can keep the relative error less than 0.48 dB.     

Output-Mirror-Tuning Terahertz-Wave Parametric Oscillator with an Asymmetrical Porro-Prism Resonator Configuration

We demonstrate a terahertz-wave parametric oscillator (TPO) with an asymmetrical porro-prism (PP) resonator configuration, consisting of a close PP corner reflector and a distant output mirror relative to the MgO:LiNbO₃ crystal. Based on this cavity, frequency tuning of Stokes and the accompanied terahertz (THz) waves is realized just by rotating the plane mirror. Furthermore, THz output with high efficiency and wide tuning range is obtained. Compared with a conventional TPO employing a plane-parallel resonator of the same cavity length and output loss, the low end of the frequency tuning range is extended to 0.96 THz from 1.2 THz. The highest output obtained at 1.28 THz is enhanced by about 25%, and the oscillation threshold pump energy measured at 1.66 THz is reduced by about 4.5%. This resonator configuration also shows some potential to simplify the structure and application for intracavity TPOs.     

A 2.65 W high-fidelity filterless class D audio amplifier using multiple loop filters

The design of a 2.65 W, high-fidelity, filterless Class D audio amplifier in a standard 0.5 μm CMOS technology is proposed in this paper, where an architecture with multiple loop filters is utilized. This structure attenuates residual clock signals around the loop allowing very low total harmonic distortion (THD) and intermodulation distortion to be achieved in conjunction with high power supply rejection ratio (PSRR). The active area of this circuit is about 1.5 × 1.5 mm². The THD + N is <0.03 % at 1 kHz input frequency and 100 mW output power. The PSRR is ?80 dB at 217 Hz and maximum output power at 10 % THD is 2.658 W. A Figure of merit is defined to estimate the excellent performance which can meet the demands of portable communication devices greatly.     

VLSI design of lossless frame recompression using multi-orientation prediction

Pursuing an experience of high-end visual quality drives human to demand a higher display resolution and a higher frame rate. Hence, a lot of powerful coding tools are aggregated together in emerging video coding standards to improve coding efficiency. This also makes video coding standards suffer from two design challenges: heavy computation and tremendous memory bandwidth. The first issue can be properly solved by a careful hardware architecture design with advanced semiconductor processes. Nevertheless, the second one becomes a critical design bottleneck for a modern video coding system. In this article, a lossless frame recompression using multi-orientation prediction technique is proposed to overcome this bottleneck. This work is realised into a silicon chip with the technology of TSMC 0.18 µm CMOS process. Its encoding capability can reach full-HD (1920 × 1080)@48 fps. The chip power consumption is 17.31 mW@100 MHz. Core area and chip area are 0.83 × 0.83 mm² and 1.20 × 1.20 mm², respectively. Experiment results demonstrate that this work exhibits an outstanding performance on lossless compression ratio with a competitive hardware performance.     

Weibull Raindrop-Size Distribution and its Application to Rain Attenuation from 30 GHz to 1000 GHz

A weibull raindrop-size distribution is fitted to the measurements of rainfall observed using a distrometer in Tokyo. A propagation experiment at 103 GHz is also introduced. The rain attenuation is calculated by considering the Mie scattering for the Marshall-Palmer, Best, Joss-Thomas-Waldvogel, Gamma and Weibull raindrop-size distributions. The results of frequency characteristics from the Weibull raindrop-size distribution agrees well with some experimental data for the millimeter and submillimeter waves above 30 GHz. The quick read table is calculated for the rain attenuation from 30 GHz to 1000 GHz.     

Comparison among mathematical models of the photovoltaic cell for computer simulation purposes

This paper presents a comparison among mathematical models used in the simulation of solar photovoltaic modules that can be easily integrated with power electronic converters. In order to perform the analysis, three models available in literature and also the physical model of the module in software PSIM® are used. Some results regarding the respective I × V and P × V curves are presented, while some advantages and eventual limitations are discussed. Besides, a DC–DC buck converter performs maximum power point tracking by using perturb and observe method, while the performance of each one of the aforementioned models is investigated.     

A new multi-resolution hybrid wavelet for analysis and image compression

Most of the current image- and video-related applications require higher resolution of images and higher data rates during transmission, better compression techniques are constantly being sought after. This paper proposes a new and unique hybrid wavelet technique which has been used for image analysis and compression. The proposed hybrid wavelet combines the properties of existing orthogonal transforms in the most desirable way and also provides for multi-resolution analysis. These wavelets have unique properties that they can be generated for various sizes and types by using different component transforms and varying the number of components at each level of resolution. These hybrid wavelets have been applied to various standard images like Lena (512 × 512), Cameraman (256 × 256) and the values of peak signal to noise ratio (PSNR) obtained are compared with those obtained using some standard existing compression techniques. Considerable improvement in the values of PSNR, as much as 5.95 dB higher than the standard methods, has been observed, which shows that hybrid wavelet gives better compression. Images of various sizes like Scenery (200 × 200), Fruit (375 × 375) and Barbara (112 × 224) have also been compressed using these wavelets to demonstrate their use for different sizes and shapes.     

Giga-hertz rate single slope conversion technique with 512-phase RTWO

In this paper, an 8-bit 1.2 Gsample/s single-slope ADC architecture is presented. The proposed technique utilizes the picosecond-accurate phases of a rotary traveling wave oscillator (RTWO). The proof-of-concept test chip is fabricated in a 0.18-μm CMOS process and occupies 1.3 mm  ×  1.3 mm of die area. Power consumption is 36 mW for the core and 135 mW for on-chip clocks.     

A reconfigurable two-stage cyclic ADC for low-power applications in 3.3 V 0.35 µm CMOS

This article presents a reconfigurable pipeline analog-to-digital converter (ADC) using a two-stage cyclic configuration. The ADC consists of two stages with 1.5 effective bit resolution, two reference circuits for voltage and current biasing, and a clock generator and timing circuit. Throughout the development of this ADC, several techniques were combined for reducing the power consumption as well as for preserving the converter linearity. To reduce the power consumption, the circuit has a single operational trans-conductance amplifier shared by both pipeline stages. To keep conversion linearity, circuits such as the bootstrapped complementary metal-oxide semiconductor (CMOS) transmission gates and a robust comparator topology were implemented. The circuit can be configured to perform conversion between 7 and 15 bit resolutions, and it works with the master clock frequency in the range of 1 kHz to 40 MHz. The circuit has been prototyped in a 3.3 V 0.35 µm CMOS process and consumes 14.1 mW at 40 MHz and 8 MSample/s sampling rate. With this resolution and sampling rate, it achieves 60.1 dB SNR, 56.57 dB SINAD and 9.1 bit ENOB at 0.666 MHz input frequency and 53.6 dB SNR, 52.4 dB SINAD and 8.6 bit ENOB at 3.85 MHz input frequency. The technological FOM obtained was 13.2 A s/m².     

A high-resolution multi-phase delay-locked loop with offset locking technique

In this work, we propose a new type of high-resolution delay-locked loop (DLL) which achieves the performance of high-resolution output by offset locking techniques without restrictions of intrinsic delay in the delay cell. Compared to traditional multi-phase clock generator, this architecture has the features of small size, low jitters, low-power consumption and high resolution. This DLL has been fabricated in 0.35 μm complementary metal-oxide-semiconductor (CMOS) process. The measured root-mean-square and peak-to-peak jitters are 2.89 ps and 31.1 ps at 250 MHz, respectively. The power dissipation is 68 mW for a supply voltage of 3.3 V. The maximum resolution of this work is 144 p and the intrinsic delay of 0.35 μm CMOS process is 220 ps. Comparing with intrinsic delay, the improvement of maximum resolution is 34.5%.     

A two-pole tunable filter with constant fractional-bandwidth characteristics

In this paper, a tunable filter with constant fractional bandwidth is designed and fabricated on ε_r = 2.2, h = 0.508 mm duroid substrates. A new mixed electrical and magnetic coupling scheme is introduced by this structure to achieve an overall constant coupling coefficient during the tuning range, which can meet the requirement of constant fractional bandwidth. A detailed analysis on the external quality (Q_ext) and coupling coefficient is presented. Two-chip capacitors (C_M = 1 pF), using radio frequency (RF) and microwave capacitors, were used to enhance Q_ext. The Q_ext (22 ± 3) shows a relatively small variation over the entire tuning range. The tunable constant fractional-bandwidth filter shows a tuning range of 1.28–1.86 GHz, a 3-dB bandwidth of 5.3 ± 0.6% and an insertion loss of 5.11–2.69 dB. The measured and simulation results are in a good agreement.