Showing papers on "Frequency band published in 2005"

Impedance, bandwidth, and Q of antennas

Abstract: To address the need for fundamental universally valid definitions of exact bandwidth and quality factor (Q) of tuned antennas, as well as the need for efficient accurate approximate formulas for computing this bandwidth and Q, exact and approximate expressions are found for the bandwidth and Q of a general single-feed (one-port) lossy or lossless linear antenna tuned to resonance or antiresonance. The approximate expression derived for the exact bandwidth of a tuned antenna differs from previous approximate expressions in that it is inversely proportional to the magnitude |Z'/sub 0/(/spl omega//sub 0/)| of the frequency derivative of the input impedance and, for not too large a bandwidth, it is nearly equal to the exact bandwidth of the tuned antenna at every frequency /spl omega//sub 0/, that is, throughout antiresonant as well as resonant frequency bands. It is also shown that an appropriately defined exact Q of a tuned lossy or lossless antenna is approximately proportional to |Z'/sub 0/(/spl omega//sub 0/)| and thus this Q is approximately inversely proportional to the bandwidth (for not too large a bandwidth) of a simply tuned antenna at all frequencies. The exact Q of a tuned antenna is defined in terms of average internal energies that emerge naturally from Maxwell's equations applied to the tuned antenna. These internal energies, which are similar but not identical to previously defined quality-factor energies, and the associated Q are proven to increase without bound as the size of an antenna is decreased. Numerical solutions to thin straight-wire and wire-loop lossy and lossless antennas, as well as to a Yagi antenna and a straight-wire antenna embedded in a lossy dispersive dielectric, confirm the accuracy of the approximate expressions and the inverse relationship between the defined bandwidth and the defined Q over frequency ranges that cover several resonant and antiresonant frequency bands.

Electronic endoscope apparatus

Abstract: An electronic endoscope (10) and a processor (11) of an electronic endoscope apparatus (2) transmit and receive signals via radio waves within a predetermined frequency band to which plural channels are allocated. The electronic endoscope has a transmission frequency band switching circuit (42) which switches between a first and second transmission frequency bands, and a first channel detection circuit (43) for detecting an available channel. The processor has a reception frequency band switching circuit (62) which switches between a first and second receptionfrequency bands,and a second channel detection circuit (63) for detecting an available channel. The transmission and reception frequency band switching circuits automatically switch the transmission and reception frequency bands according to detection results of the first and second channel detection circuits.

Stacked multi-resonator antenna

Abstract: An antenna structure comprising a ground plane, a feed line and at least one resonator element that is embedded in a dielectric substrate and which is meandering in shape such that it includes at least two adjacent resonator segments. As a result, the resonator element resonates in two separate frequency bands. A second resonator element is preferably provided, the second resonator element being dimensioned to resonate in a frequency band located on one side of a third operating frequency band, the feed line and ground plane being arranged to cause a resonance in a frequency band located on the other side of the third operating frequency band. During use, the combined effect of the resonance of the second resonator element and of the feed line and ground plane is to cause the antenna structure to resonate in the third operating frequency band.

Application of time-frequency domain reflectometry for detection and localization of a fault on a coaxial cable

Abstract: In this paper, we introduce a new high-resolution reflectometry technique that operates simultaneously in both the time and frequency domains. The approach rests upon time-frequency signal analysis and utilizes a chirp signal multiplied by a Gaussian time envelope. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. This latter capability is of particular interest when testing communication cables and systems. Sensitivity in detecting the reflected signal is provided by a time-frequency cross-correlation function. The approach is verified by experimentally locating various types of faults, located at various distances, in RG 142 and RG 400 coaxial cables.

Removal of power-line interference from the ECG: a review of the subtraction procedure

Abstract: Modern biomedical amplifiers have a very high common mode rejection ratio. Nevertheless, recordings are often contaminated by residual power-line interference. Traditional analogue and digital filters are known to suppress ECG components near to the power-line frequency. Different types of digital notch filters are widely used despite their inherent contradiction: tolerable signal distortion needs a narrow frequency band, which leads to ineffective filtering in cases of larger frequency deviation of the interference. Adaptive filtering introduces unacceptable transient response time, especially after steep and large QRS complexes. Other available techniques such as Fourier transform do not work in real time. The subtraction procedure is found to cope better with this problem. The subtraction procedure was developed some two decades ago, and almost totally eliminates power-line interference from the ECG signal. This procedure does not affect the signal frequency components around the interfering frequency. Digital filtering is applied on linear segments of the signal to remove the interference components. These interference components are stored and further subtracted from the signal wherever non-linear segments are encountered. Modifications of the subtraction procedure have been used in thousands of ECG instruments and computer-aided systems. Other work has extended this procedure to almost all possible cases of sampling rate and interference frequency variation. Improved structure of the on-line procedure has worked successfully regardless of the multiplicity between the sampling rate and the interference frequency. Such flexibility is due to the use of specific filter modules. The subtraction procedure has largely proved advantageous over other methods for power-line interference cancellation in ECG signals.

Frequency band-gap measurement of two-dimensional air/silicon phononic crystals using layered slanted finger interdigital transducers

Abstract: In this paper, we investigate the frequency band-gap features of micromachined air/silicon phononic band structures using layered slanted finger interdigital transducers (SFIT). In order to achieve the applications of phononic crystals on the microelectromechanical system related components, the frequency band-gap widths of surface waves are studied both theoretically and experimentally in micrometer scale phononic crystals. For further integration with the complementary metal-oxide semiconductor processing techniques, silicon is chosen as the base material of the two-dimensional phononic crystals in this study. To cover the frequency band-gap width of the phononic crystal, the wideband SFIT- and the SFIT∕ZnO∕Si-layered structures in the measurement are analyzed and discussed. For layered structures, the dispersive relation is calculated by the effective permittivity approach, and the frequency response of the layered SFIT is then simulated by the coupling-of-modes model. The frequency band-gap width and ...

Slim Multi-Band Antenna Array For Cellular Base Stations

Abstract: This invention is in the field of base station antennas for wireless communications. The present invention refers to a slim multi-band antenna array for cellular base stations, which provides a reduced width of the base station antenna and minimizes the environmental and visual impact of a network of cellular base station antennas, in particular in mobile telephony and wireless service networks. A multiband antenna array comprises a first set of radiating elements operating at a first frequency band and a second set of radiating elements operating at a second frequency band, said radiating elements being smaller than λ/2 or smaller than λ/3, being (λ) the longest operating wavelength. The ratio between the largest and the smaller of said frequency bands is smaller than 2.

Wideband microstrip-fed monopole antenna having frequency band-notch function

Abstract: A novel and compact ultra-wideband (UWB) microstrip-fed monopole antenna having frequency band notch function is presented. To increase the impedance bandwidth of an antenna, a narrow slit is used. By inserting a modified inverted U-slot on the proposed antenna, the frequency band notch characteristic is obtained. The designed antenna satisfies the voltage standing wave ratio requirement of less than 2.0 in the frequency band between 3 and 11 GHz while showing the band rejection performance in the frequency band of 5.0 to 5.9 GHz.

Allocation of radio resource in orthogonal frequency division multiplexing system

Abstract: An uplink capacity is increased by a method in which more than two mobile stations simultaneously use a radio resource allocated to one mobile station. A method of allocating a radio resource in an orthogonal frequency division multiplexing system comprises receiving data associated with a radio resource allocation map from a base station, wherein the radio allocation map comprises control parameters for transmitting uplink data to the base station. The control parameters comprises orthogonal pilot pattern indicator for using orthogonal pilot patterns associated with supporting at least concurrent dual transmission by at least one mobile station, and for use in the same frequency band and same time duration. The orthogonal pilot patterns comprises at least a minus pilot being used for an uplink basic allocation unit. The mobile station then transmits uplink data to the base station by using the orthogonal pilot patterns.

Method and device for amplification of data signals over power lines

Abstract: A device for bi-directional amplification of data signals over power lines is disclosed. In one embodiment, the device includes a bandpass filter, a frequency converter and an amplifier. The bandpass filter filters out undesired frequencies and the frequency converter converts the frequency band of the data signals to a different frequency band. The output of the filter is provided to the amplifier for amplifying the frequency converted data signals for transmission over power line.

EMI reduction in switched power converters using frequency Modulation techniques

Abstract: Frequency-modulation techniques have been used to reduce electromagnetic interference (EMI) produced by the clock of digital systems working in the range of hundreds of megahertz. The working principle consists of modulating the original constant clock frequency in order to spread the energy of each single harmonic into a certain frequency band, thus reducing the peak amplitude of EMI at harmonic frequencies. Nowadays, the switching frequency of power converters has increased up to values that make interesting the application of such techniques to reduce EMI emissions due to switching of power circuits. This paper presents the theoretical principles of frequency modulation using deterministic profiles for the modulating function. It shows the effectiveness of such methods in terms of EMI reduction for different modulation profiles and other parameters. The method is compared with other methods using random modulation. Tests carried out on a buck converter are presented for experimental validation of the method. A short discussion on optimal modulation profiles and parameters is also included.

Signal repeater system

Abstract: Analogue signal repeater system, (1) where frequency converting repeaters (6-9, 10-13)' of super-heterodyne or super­regenerative type realised with any of discrete semiconductors, MMIC semiconductors, ASIC semiconductors are applied to optimize signal dynamics by avoiding echo between repeaters (6-9, 10-13) and where each information channel (15, 16) in the system only needs two frequency bands, where each second repeater (7, 9, 12, 10) of the signal cascade (2, 14) repeating the signals within the same frequency band to increase isolation against interference between repeaters and against reflections and signal echo.

Source-antennas for transmitting/receiving electromagnetic waves

Abstract: The present invention relates to a source-antenna for transmitting/receiving electromagnetic waves comprising an array of n radiating elements (11 3 , 11 4) operating in a first frequency band, means (20) with longitudinal radiation operating in a second frequency band, the array and the means with longitudinal radiation having a substantially common phase centre, the n radiating elements being arranged symmetrically about the longitudinal-radiation means, and each element (11 3 , 11 4) of the array consisting of a radiating element of the travelling wave type.

Deembedding static nonlinearities and accurately identifying and modeling memory effects in wide-band RF transmitters

Abstract: In this paper, a robust modeling technique for memoryless wide-band radio frequency transmitters using a dynamic exponential weighted moving average algorithm is developed and tested. To improve the relatively limited accuracy of the conventional Wiener model in predicting the response of dynamic nonlinear transmitters, a new augmented Wiener model is proposed along with its parameter-identification procedure. The accuracy of the augmented Wiener model is compared with that of the conventional Wiener model by using an L-band 60-W peak-envelope-power GaAs field-effect-transistor push-pull amplifier-based transmitter, which is driven by a two-carrier wide-band code-division multiple-access signal.

Silencer design by using array resonators for low-frequency band noise reduction

Abstract: Helmholtz resonators are often used to reduce noise. They are particularly useful when noise has a narrow frequency band. In this study we aim to broaden its narrow band characteristics by combining many resonators. Serial and parallel arrangements of resonators have been tested to obtain broader impedance mismatch characteristics in the broader band. Theoretical and experimental results explain these characteristics in the absence of mean flow. The serial arrangement mainly increases the peak of TL at the resonance frequency. But the parallel arrangement logarithmically increases the peak of TL and expands the bandwidth. The change of acoustic characteristics is explained by introducing an “equivalent impedance analysis.” This shows that the transmission loss has a maximum value when the distance between resonators is λ∕4 of its wavelength. In this study we propose a novel design method that optimizes the arrangement of resonators while keeping the volume minimized. Various transmission loss characterist...

N-th order curve fit for power calibration in a mobile terminal

Abstract: A method for calibrating the output power of a mobile terminal using at least a second order curve fit to describe a power amplifier gain (PAG) setting versus output power characteristic of a power amplifier in a transmitter of the mobile terminal is provided. For each of an upper-band frequency, a mid-band frequency, and a lower-band frequency of a frequency band, multiple measurements of the output power of the mobile terminal are made corresponding to multiple values of the PAG setting, and a curve fit is performed, thereby calculating coefficients defining a polynomial describing the PAG setting versus output power characteristic. Using the polynomials describing the PAG setting versus output power characteristic of the power amplifier for each of the upper-band, mid-band, and lower-band frequencies, values of the PAG setting are determined for each desired output power level for each desired frequency within the frequency band.

Methods of ground based beamforming and on-board frequency translation and related systems

Abstract: Methods are provided to operate a communications system including a satellite and a satellite gateway. In particular, a feeder link may be provided between the satellite and the satellite gateway over a feeder link frequency band for communication of information between the satellite gateway and the satellite. A service link may be provided between the satellite and at least one radioterminal in a coverage area of the satellite over a service link frequency band. Moreover, the feeder link and service link frequency bands may be different. In addition, a frequency segment of the feeder link may be linearly translated from the feeder link frequency band to the service link frequency band to provide a frequency segment of the service link. Related satellites are also discussed.

Electromagnetic-bandgap layers for broad-band suppression of TEM modes in power planes

Abstract: A practical set of engineering design equations are derived for predicting stopband performance of electromagnetic-bandgap (EBG) structures within parallel power planes. The EBG circuits suppress the TEM-mode noise within parallel plates used within digital power distribution networks. Stopbands are realized over designed frequency bands of interest in the microwave spectrum. The mathematical relationships between the physical hardware and the electrical models are clearly stated. Several examples are given and proof-of-concept experiments are described and compared to the predicted results with good agreement.

Influence of the electrical parameters on the input impedance of a fractal structure realised on silicon

Abstract: We study here samples having “fractal tree” patterns. The frequency response analysis of their input impedance “ Z in ” has revealed the existence of a frequency band in which the input impedance Z in ≈( iω ) η , η being a fraction. The argument of Z in is constant, situated between 0 and −π/2 and called constant phase angle. This zone depends on the number of iterations for the patterns concerned and on the magnitude of parameters R s , C p and R p of the electrical model. We demonstrate here another approach in the utilisation of deterministic fractal, from an electronic component angle. Obtained by microelectronical process, this component can be used in stabilizer circuit such as phase correctors. The manufacturing process employed has aided in mastering the technological aspects (conducting trace length, oxide thickness, plate surface) of parameters of the electrical model which play a very important role in the choice of the frequency range in which the fractal zone must intervene. The objective was attained in two phases. At first, in simulation where the technological parameters were adjusted to obtain the appropriate electrical magnitudes was followed by the component manufacture based on simulation results. After, electrical measurements were undertaken on those components.

Ultra-wideband channel modeling on the basis of information-theoretic criteria

Abstract: We present results of two ultra-wideband (UWB) channel measurement campaigns in the 2-5 GHz frequency band, and use Akaike's Information Criterion (AIC) to determine suitable distributions for the channel impulse response taps. Despite the large bandwidth, AIC supports the complex Gaussian tap distribution, with mean depending on the measurement setting. We estimate the empirical covariance matrix of the channel impulse response, and demonstrate that the number of corresponding significant eigenvalues scales approximately linearly with bandwidth, albeit we find that channel taps are correlated

Applications of Space Division Multiplexing and Those Performance in a MIMO Channel

Abstract: Currently, space division multiplexing (SDM), where individual data streams are transmitted from different antennas simultaneously, is expected to be a promising technology for achieving a high data rate within a limited frequency band in a multiple-input multiple-output channel. In this paper, transmitter and receiver architectures of SDM applications are described, and performance improvement with the increase of data streams is shown referring to results of computer simulations. In addition, channel coded systems are also evaluated.

Automatic therapy advisor

Abstract: A method of automatically determining which type of treatment is most appropriate for (or the physiological state of) a patient. The method comprises transforming one or more time domain measurements from the patient into frequency domain data representative of the frequency content of the time domain measurements; processing the frequency domain data to form a plurality of spectral bands, the content of a spectral band representing the frequency content of the measurements within a frequency band; forming a weighted sum of the content of the spectral bands, with different weighting coefficients applied to at least some of the spectral bands; determining the type of treatment (or physiological state) based on the weighted sum.

Method for uplink scheduling in communication system using frequency hopping-orthogonal frequency division multiple access scheme

Abstract: Disclosed is a method for uplink scheduling in a communication system. The method for uplink scheduling in a communication system having a cellular structure hopping between sub-channels according to a predetermined rule whenever a signal is transmitted The communication system dividing a whole frequency band into a plurality of sub-carrier bands and including the sub-channels which are sets of the sub-carrier bands. The method includes determining a number of sub-channels to be allocated to a mobile station such that throughput of the mobile station is maximized based on a first predetermined condition in which a mobile station having a superior channel state is allocated with a greater number of sub-channels than a mobile station having an inferior channel state, and determining a modulation and coding scheme level according to a signal-to-interference and noise ratio (SINR) of a downlink channel reported by the mobile station based on a second predetermined condition capable of improving a channel state of the mobile station having an inferior channel state.

Method and apparatus for transmitting/receiving channel quality information in a communication system using an orthogonal frequency division multiplexing scheme

Abstract: A method for transmitting channel quality information (CQI) from a receiver station to a transmitter station in a wireless communication system which includes diversity mode consisted of spaced apart subcarriers and band AMC mode consisted of a number of bands comprised of a predetermined number of adjacent subcarriers. The method comprises the steps of transmitting an average CINR(Carrier to Interference and Noise Ratio) value for a full frequency band if the receiver station operates in the diversity mode; transmitting a differential CINR of a predetermined number of bins if the receiver station operates in the band AMC mode.

Gyro-BWO experiments using a helical interaction waveguide

Abstract: A helically corrugated waveguide was used for a gyrotron backward-wave oscillator (gyro-BWO) experiment. A thermionic cathode was used to produce an electron beam of 90-215 keV in energy, 2-3 A in current, and pitch alpha of up to 1.6. The oscillator achieved high-efficiency frequency-tunable operation. At a fixed beam voltage of 185 kV and a current of 2 A, the output frequency was tuned by adjusting the magnetic field in the interaction cavity. A maximum power of 62 kW and a 3-dB frequency-tuning band of 8.0-9.5 GHz (17% relative tuning range) with a maximum electronic efficiency of 16.5% were measured. In addition, the interaction frequency could be tuned by varying the electron beam energy. At a fixed cavity magnetic field of 0.195 T, the output frequency and power from the gyro-BWO were measured as a function of tuning electron beam energy while the beam current was maintained at 2.5 A. A 3-dB relative frequency tuning range of 8% was measured when the electron beam voltage was changed from 215 to 110 kV.

Band‐notched ultra‐wideband circular‐disk monopole antenna with an arc‐shaped slot

Abstract: By embedding a simple arc-shaped slot in a circular-disk monopole antenna, an ultra-wideband (UWB, 3.1–10.6 GHz) operation with a controlled notched frequency band can be obtained. The arc-shaped slot is placed close to the boundary of the circular-disk monopole and has a length of about one-half wavelength of the desired notched frequency. The proposed slotted circular-disk monopole antenna showing UWB operation with a notched frequency band for rejecting the 5.8-GHz WLAN band is demonstrated. The effects of the dimensions of the arc-shaped slot on the notched frequency band are also analyzed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 188–191, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20766

Directional and band-gap behavior of periodic auxetic lattices

Abstract: The paper investigates the wave propagation characteristics of periodic two dimensional, auxetic lattice structures. Periodic structures in general feature unique wave propagation characteristics, whereby waves are allowed to propagate only within specific frequency bands. Two dimensional periodic structures complement this feature with a low frequency directional behavior. The combination of these unique characteristics makes two dimensional periodic structures ideal candidates for the design of pass-band directional mechanical filters. Focus is here placed on honeycomb lattice configurations. A sensitivity analysis is first presented to investigate the influence of band-gap and directional behaviors with respect to changes in the internal angle. The presented results demonstrate how re-entrant topologies feature enhanced wave attenuation capabilities with respect to hexagonal lay-outs. An optimization problem is then formulated by considering the internal angle as a design variable, and the width of the attenuation frequency ranges and angular range of propagation at low frequencies as objective functions. The identified optimal configurations feature combined properties which demonstrate the effectiveness of the analysis procedure.

Band‐notched ultra‐wideband planar‐monopole antenna

Abstract: An ultra-wideband (UWB) planar metal-plate monopole antenna with a band-notch characteristic is presented. The proposed planar metal-plate monopole antenna is embedded with an inverted U-shape slot, whose length is selected to be a half-wavelength at the desired notched frequency. By adjusting the slot length, the notched frequency band within the antenna's operating bandwidth can be easily controlled. A design example for an UWB (3.1–10.6 GHz) planar metal-plate monopole antenna with a notched frequency band at 5 GHz is demonstrated. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 217–219, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20592

Systems and methods with different utilization of satellite frequency bands by a space-based network and an ancillary terrestrial network

Abstract: A radioterminal communications system includes an ancillary terrestrial component configured to receive from at least some of a plurality of radioterminals using frequencies from a first satellite frequency band (e.g., an L-band) and to transmit to at least some of the plurality of radioterminals using frequencies from a second satellite frequency band (e.g., an S-band). The system further includes a space-based component configured to communicate with the plurality of radioterminals using at least some of the frequencies from the first satellite frequency band and/or at least some of the frequencies from the second satellite frequency band. In some embodiments the ancillary terrestrial component communicates with radioterminals using a Time Division Duplex (TDD) mode and the space-based component communicates with the same or other radioterminals using a Frequency Division Duplex (FDD) and/or a TDD mode.

Magnetic properties of s-shaped split-ring resonators

Abstract: We present a theoretical analysis of the radiation of an S-shaped split ring resonator (S-SRR) for the realization of a metamaterial exhibiting left-handed properties. It is shown that the structure is resonant due to its internal capacitances and inductances, which can be adjusted such that the electric plasma frequency and magnetic plasma frequency, both due to the S-SRR only, appear within the same frequency band. Using the same idea, we also present some extended S-shaped split-ring resonator structures with improved performance.