Furthermore, the high-isolation hybrids designed in Section 2 have a significant bandwidth, on the range of the octave. One of the devices is an all-lumped variant, with only concentrated components, and therefore minimum occupied surface. The designs have been developed with the aid of commercial software ADS from Agilent TM , v.2009A, and their electromagnetic planar simulator, MOMENTUM, was extensively used.
Metamaterial structures have been extensively applied in microwave frequency bands for providing enhancement in active and passive devices. Metamaterials have been applied to design and improve microwave devices such as transmission lines, antennas, absorbers, etc. [1-5]. After their realization and successful applications in microwave frequencies, tremendous efforts raised to take advantage of their extra ordinary features in terahertz and optical frequencies. Terahertz absorbers using metamaterials have been developed due to their wide range of employments in terahertz detectors, sensors, stealth applications and so forth. Recently graphene, one layer of carbon atoms in hexagonal lattice, has received special interest in terahertz and optical frequencies due to its beneficial effects specifically its dynamically tunable property.
As one of the essential components for the multiband and wireless communication systems, electrically tunable multiband bandpass ﬁlters (BPFs) have developed rapidly due to their potential for reducing system size, complexity and the cost in fabrication in recent years. Therefore, aggressive investment has been done based on diﬀerent kinds of tuning devices. Recently, the tunable ﬁlters based on varactor diodes have been gaining much attention.
with nitrogen, tellurium and chromium diffused sapphire waveguides were also investigated. The simulation and layout of optical waveguide devices, including 1x2 GaN splitters, Mach-Zehnder interferometers and asymmetric twin waveguide devices, were performed using a commercial software package using the beam propagation method. As-grown GaN materials were characterized by using cathodoluminescence, optical transmission measurement, atomic force microscopy and prism coupling. GaN waveguides, 1x2 splitters and Mach-Zehnder interferometers were fabricated and tested at visible wavelengths using HeNe and a tunable Argon laser. The end faces of the waveguide chips were polished by using the sample preparation techniques used in transmission electron microscopy. The morphology of the rib waveguides were
To build an RF MEMS structure with micromachining, the wafer could be processed using conventional processes to create transmission line capacitors and inductors that are required before the RF MEMS processing starts. A resist layer is then deposited and patterned to protect this part of the circuit from the RF MEMS processing steps. This layer can be removed at the completion of RF MEMS fabrication. The surface micromachining involves the selective adding and removing of metal, dielectric and sacrificial layers on the substrate surface. Depending on the step, either a metal or a dielectric or a sacrificial layer is then deposited, patterned and etched. This sequence of steps is repeated until the required RFMEMS three-dimensional structure is completed. The process employs four masks for device fabrication and one additional mask for the fabrication of package structure. Four inches quartz wafers are used for the device fabrication. The package structures are patterned in the form of rings of SU8-10 on standard silicon substrate. The released structures of tunable low pass filters are subjected to wafer level packaging using chip on wafer bonding with the help of Fine Tech Fine Placer Flip Chip Bonding. Further, the effects of introducing thick metal for DC actuation in the ground plane (Type A in Figure 1) and thin metal for DC actuation (Type B in Figure 1) are studied.
multiplexing and demultiplexing applications in interval of 1.45 µm to 1.65 µm wavelength band, which including the short, conventional, long, and ultra long wavelength band. Moreover we have taken into account a comparison between these new materials within operating design parameters of conventional AWG devices such as diffraction order, length difference of adjacent waveguides, focal path length, free spectral range or region, maximum number of input/output wavelength channels, and maximum number of arrayed waveguides. As well as we have employed these materials based AWG to include Multi band applications under the effect of ambient temperature variations.
Figure 4 shows the projected band dispersion diagram along the wave propagation direction with the ﬁrst and second TM propagating modes of the inﬁnite WMM with symmetry that corresponds to Fig. 1(b). Simulations were performed with FDTD-method using a package MEEP. Here we represent frequencies without any normalization for better ability of comparison with experimental data. But wave vector is normalized in usual manner for dispersion diagrams of the periodical structures. Diﬀerent types of dispersion curves correspond to various values of parameter a (2.0; 2.5; 3.0; 3.5; 4.0) mm. Parameter b is ﬁxed ( b = 6 . 5 mm). Zeroth-order band gap (0–16 GHz), 1st band gap (22–35 GHz) and 2nd one are marked by shaded area (for the case a = 4 mm). These data are in good agreement with obtained experimental and theoretical results for the spatially restricted structure. (Fig. 2 and Fig. 3). As can be seen in Fig. 4, the width of band gaps increases with the parameter a decreasing. Moreover, dispersion curve becomes ﬂatter. Under condition a → 0, dispersion curves transform into straight lines. It is clear that in this case wire structure is the “condensed metal”, and its band gap “character” of spectrum disappears. Indeed, the rows of wires along axis Ox transform into metal sheets that completely reﬂect the incident radiation. It should be noted that low-frequency boundaries of the ﬁrst and second band gaps do not depend on parameter a . Additional numerical calculations show that these boundaries are shifted by varying parameter b . Therefore, the dispersion and spectral properties of the wire structure are controlled by geometrical sizes of the wire medium unit cell. For example, one can change the zeroth- order band gap width and accordingly eﬀective plasma frequency by means of mechanical changing of the parameter a value (see Fig. 1(a)). Changing parameter b provides additional possibility for the WMM dispersion properties tuning.
Especially for the goal of describing the levels of complexity in the evolution of brain function and activity from simpler invertebrates to mammals, concepts are called for that recognize features such as the following. We have no idea how much of the brain waves are attributable to “familiar” sources such as synaptic potentials. We have no idea how much interneuronal communication is attributable to all-or-none impulses and classical synaptic potentials. We know that graded presynaptic activity happens and causes graded transmission. Many neurons are permanently without spikes and an unknown additional number may sometimes function without spikes. We know of several mechanisms contributing to synchronization but probably not all of them. Their relative roles in different brain structures may vary widely. One example is the electrical, nonsynaptic connection that passes only slow events (Watanabe and Bullock 1960); this synchronizes cardiac ganglion activity in lobsters and may be widespread in vertebrate brains without having been noticed. If our belief is correct, much of the nonrhythmic compound field potentials we see - which means most of the activity - is not truly stochastic but has unrevealed structure and this may be the domain of evolution. We don’t know what causes EEGs of large sharks and frogs to be so much smaller than those of large dolphins and mice. We can’t explain the strong tendency for a wide range of FFT frequency components to vary in coherence together - and similarly for bicoherence. We are far from an adequate natural history of the signs of activity in organized populations of neurons in different regions, states, stages and species.
of two subset with 192 male and 192 female speakers . The corresponding speech signals are those which are transmitted through different telephone handsets. This typically helps in the investigation of telephone transducer effects on speech. For STCTIMIT which is single channel, the speech signals were sent through a real and, in contrast to NTIMIT, all these can be turned as the derivation of wideband speech [6-11]. While some are telephony are containing narrowband speech. The sampling is at the rate of 8 kHz with a range of 200 Hz to 3.4 kHz. Inspite of all these it is to be noted that there is no availability of real world wideband telephony speech corpus. Several versions of wideband speech codes like G.722 (1988), G.722 (1999) G.722.2 (2001) and G.711.1 (2008) have been into operation with several techniques like ADPCM, 3GPP  and wideband PCM. It is interesting to note that the wideband telephony speech transmission system is wide available and adaptable. In contrast to ever increasing mobile networks citing this, it its essential to have wideband system in the TIMIT for a wide range of scientific investigations. There are several advantages and applications associated with WBSTS. The integrated speech recognition system provides remote dictation or spelling. This was not a possible case with the earlier telephony system.
2.2. UWB Lower Band and Upper Band Filters Design The configuration of the UWB lower band filter is shown in Figure 4(a), to obtain much tighter coupling between the input/output ports and the E-shaped SIR, the capacitive S-L cross-coupled feed structure is proposed in this filter. The coupling scheme is shown in Figure 4(b) and the signal transmits from port 1 to port 2 through two paths: the signal of path 1 is mainly coupled into the E-shaped resonator through a parallel coupling-line structure; meanwhile, the direct signal of path 2 from port 1 to port 2 through weakly coupling is formed by capacitive S-L cross-coupled feed structure. Beyond the passband, transmission zeros may generate owing to the interaction of the signals from the two coupling paths.
Abstract—The ultra-wideband characteristic basis function method (UCBFM) is an eﬃcient approach for analyzing wideband scattering problems because ultra-wide characteristic basis functions (UCBFs) can be reused for any frequency sample in the range of interest. However, the errors of the radar cross section calculated by using the UCBFs are usually large at low frequency points. To mitigate this problem, an improved UCBFM is presented. Improved UCBFs (IUCBFs) are derived from primary characteristic basis functions and secondary level characteristic basis functions (SCBFs) by applying a singular value decomposition procedure at the highest frequency point. This method fully considers the mutual coupling eﬀects among sub-blocks to obtain the SCBFs. Therefore, the accuracy is improved at lower frequency points because of the higher quantity of current information contained in the IUCBFs. Numerical results demonstrate that the proposed method is accurate and eﬃcient.
Three tunable slots are used in this antenna design as the basic radiation element to achieve three concurrent tunable frequency bands covering the range from 0.6 to 2.7 GHz. Due to the limited tuning range of a single slot, the desired system frequency range is divided into three sub-ranges: 0.6 to 1.1 GHz (low range), 1 to 2.5 GHz (middle range) and 1.9 to 2.7 GHz (high range), which are covered by slots 1, 2 and 3 in Fig. 2(c), respectively. One of the key objectives of this tunable tri-band antenna design is to achieve independent tunability of each band, which means tuning any one slot of the antenna should not affect the other two slots. The requirement for a low antenna profile in modern mobile handsets, where the internal space is extremely limited, makes this particular task difficult. Therefore, the location and polarisation of each slot needs to be carefully chosen in order to minimise the mutual coupling between radiating elements.
derivatives, which enlarges the memory requirement. So in , the AWE based on the CBFM, is proposed to analyze the wide-band electromagnetic scattering problems. An adaptive modiﬁed CBFM combined with the MBPE technology is proposed in  to analyze the wide-band and wide-angle electromagnetic scattering problems. Although the above mentioned two methods utilize the CBFM to accelerate solving speed of the interpolation point and to reduce memory consumption, both the methods need to recalculate the characteristic basis functions (CBFs) at each interpolation point. Hence, in , an ultra-wideband CBFM (UCBFM) is proposed to analyze the wide-band electromagnetic scattering problems without having the requirement to repeatedly construct the CBFs at each frequency. The CBFs constructed at the highest frequency point, termed ultra-wideband CBFs (UCBFs), entail the electromagnetic behavior at lower frequency range; thus, it implies that they can also be employed at lower frequency points without going through the time consuming step of reconstruction. However, the errors of the RCS calculated by the UCBFs are usually large at lower frequency points because of weak universality of the UCBFs. In , the construction of the UCBFs is improved by considering the CBFs constructed at the lowest frequency point. An improved UCBFM (IUCBFM) is presented in . This method fully considers the mutual coupling eﬀects among the sub-blocks to obtain the secondary level CBFs (SCBFs) with a stronger universality, such that the improved UCBFs (IUCBFs) contain more current information, and to improve the calculation accuracy at lower frequency points. Although the accuracy of the above methods is improved, it should be noted that the number of IUCBFs is unnecessarily high and that the computational complexity will be increased when applying the IUCBFs to the lower frequency points. In this paper, an adaptive IUCBFM (AIUCBFM) is presented. The proposed method adaptively divides the given frequency band into multiple sub-bands keeping the number of the IUCBFs under consideration, which leads to smaller number of IUCBFs at the lower sub-frequency band. The RCS data are then calculated utilizing the IUCBFs obtained at the highest frequency point in each sub-band. The smaller number of IUCBFs results in a substantial time-saving in the ﬁll procedure of the reduced matrix at the lower frequencies. Finally, the wide RCS data over the given frequency band are obtained by splicing the RCS data in each frequency band.
and 2.5G GPRS/EDGE standards. A combination of frequency bands will have to be supported to reduce the cost and size of the mobile devices . Consequently, the increase in complexity of the mobile devices translates into greater challenges and more stringent requirements on the design of front end passive components, including filters, switches and power amplifiers (PA) [36, 37, 38]. Frequency-agile and multifunctional circuits are highly desirable in communications systems, radars, sensor networks, and biomedical devices also. Tunable elements are the key components in achieving the frequency tunability. Great efforts have been made on developing tunable components such as antennas, filters, matching networks, couplers, dividers and phase shifter etc. Though various tuning techniques have been utilized in achieving frequency tunability including semiconductor varactors -, ferroelectric thin films -, and RF MEMS , , those techniques can achieve a reasonable capacitance tuning capability only. The Amorphous ferromagnetic wires have demonstrated the tuning of transmission characteristics by DC current based on giant magneto impedance effect [49- 51]. Ferromagnetic thin films have also been actively explored for high-performance microwave devices. RF devices have been done using yttrium iron- garnet (YIG) [52-53] and tuned with external magnetic field but these are difficult to integrate with planar RF/microwave circuit.
Although this and other results for white noise driven systems found wide applications in engineering problems (see, ), the noises in reality are not white indeed. At most, they are approximately white and, in general, far from being white. Fleming and Rishel  wrote that the real noises are wideband and white noises are the ideal case of wideband noises. When the parameters of white and wideband noises are sufficiently close to each other, white noises take place of wideband noises to make mathematical models simpler. Respectively, for more adequate estimation and control results, a mathematical method of handling and working with wideband noises is required.
interpretation strong coupling refers to Rabi splitting. Rabi coupling is a manifestation of the interaction of electromagnetic radiation on resonance with an atomic or molecular transition of sufficient intensity that the two level is system is driven repeatedly from ground to excited state and back again. Is an oscillation that leads to a splitting in the observed absorption/emission band that is related to strength of the coupling, i.e. the interaction of transition dipole moment with the electric field. It is derived from the first- order time-dependent perturbation solution of the Schrödinger equation. In understanding what various authors mean by strong coupling it is important to bear in mind that reports of Rabi oscillations require excitation of an isolated two-level system in an optical cavity with a high-quality factor, an intense excitation source that is precisely on resonance or very near resonance. Many of these aspects are lacking in the reports of layers on Ag that have been presented as evidence of strong coupling.
This paper investigates a planar band antenna that cover UWB bandwidth of 9 GHz (3.1 to 12.1GHz) suitable for, WLAN, Wi-MAX, Medical Application, and radar imaging technology, PC Peripherals, Wireless USB The antenna has a low profile and can be easily embedded into the display of a laptop computer. Return loss of the UWB antenna are examined experimentally. UWB complements currently deployed wireless networks in the WLAN environment, plus it extends high bit- rate, multimedia connectivity to WPANs supporting PC, CE and cellular devices. This combination will enable true convergence of electronics and mobile communications REFERENCES
PHONETIC CLASSIFICATION ON WIDE BAND AND TELEPHONE QUALITY SPEECH PHONETIC CLASSIFICATION ON WIDE BAND AND TELEPHONE QUALITY SPEECH Benjamin Chigier Speech Technology Group Artificial Intelligence Lab[.]
Low-cost and low-power receivers have gained importance due to increasing demands from wireless communication systems. In traditional digital communications, the RF signal is down converted to lower frequencies by means of analog mixers and filters. Current attempts in wireless communications are towards digitizing the received signal as close to the antenna as possible. Therefore, analog-to-digital converter (ADC) should be placed as near as possible to the antenna. After the ADC, with the use of robust digital signal processing (DSP) techniques, digital circuits will implement complicated filtering, down conversion and demodulation. In future receivers, antenna, LNA and ADC will be individual blocks only. All other functions will be processed in the DSP part. As a result a minimal set of RF and analog component will be required, as depicted in Figure 1.1. However, in such receivers, the ADC must achieve a high linearity in order to be able to digitize the input signal with minimal inter-modulation of interferers and exhibit a thermal and quantization noise floor well below the signal level at the output. The level of noise reduction varies different applications, which maybe in the range of 40-100 dB. For some applications a radio-frequency (RF) filter may be necessary to remove out-of-band noise so as to relax the dynamic range of the ADC.
to that of short wire pairs , resulting from antiparallel currents in parallel metallic segments. The electromagnetic response can be tuned by changing the geometry parameters of the front structure, back ring and spacing between them. To maximize the absorption of the MA, both the transmission and reflection should be minimized. Thus, the impedance of the absorber should be tuned to match approximatively that of free space on one side and mismatch on the other side in the absorption band. This can lead to a minimal reflectance, a minimal transmission and hence a maximal absorbance. Because of the coupling between the back ring and front patch as well as the front ring, there may exist two resonances. The wide-band property of the MA could be realized by making different resonances overlap. The polarization- insensitive and wide-angle property could be realized by improving the symmetry of the unit cell . Because of this, square patches and rings, which have good symmetry, are adopted.