Showing papers on "Frequency band published in 2000"

3-D radar imaging using range migration techniques

Abstract: An imaging system with three-dimensional (3-D) capability can be implemented by using a stepped frequency radar which synthesizes a two-dimensional (2-D) planar aperture. A 3-D image can be formed by coherently integrating the backscatter data over the measured frequency band and the two spatial coordinates of the 2-D synthetic aperture. This paper presents a near-field 3-D synthetic aperture radar (SAR) imaging algorithm. This algorithm is an extension of the 2-D range migration algorithm (RMA). The presented formulation is justified by using the method of the stationary phase (MSP). Implementation aspects including the sampling criteria, resolutions, and computational complexity are assessed. The high computational efficiency and accurate image reconstruction of the algorithm are demonstrated both with numerical simulations and measurements using an outdoor linear SAR system.

Scattering of elastic waves by periodic arrays of spherical bodies

Abstract: We develop a formalism for the calculation of the frequency band structure of a phononic crystal consisting of nonoverlapping elastic spheres, characterized by Lam\'e coefficients which may be complex and frequency dependent, arranged periodically in a host medium with different mass density and Lam\'e coefficients. We view the crystal as a sequence of planes of spheres, parallel to and having the two-dimensional periodicity of a given crystallographic plane, and obtain the complex band structure of the infinite crystal associated with this plane. The method allows one to calculate, also, the transmission, reflection, and absorption coefficients for an elastic wave (longitudinal or transverse) incident, at any angle, on a slab of the crystal of finite thickness. We demonstrate the efficiency of the method by applying it to a specific example.

Coexistence techniques in wireless networks

Abstract: Techniques are provided for frequency coordination among two different wireless network protocols, such as the IEEE 802.11 and Bluetooth protocols, operating in proximity with one another. Coordination is accomplished by the use of a first radio transceiver operating in accordance with a first communication protocol (which may be the 802.11 protocol) and using a frequency band (which may be the 2.4 GHz band), a base station connected to a wired network and operating in accordance with the first communication protocol, a second radio transceiver operating in accordance with a second communication protocol (which may be the Bluetooth protocol) and using the frequency band, and a coordinator associated with the base station for, in turn, activating the first radio transceiver, deactivating the first radio transceiver, activating the second radio transceiver, and deactivating the second radio transceiver.

Multiple-frequency-tuned photonic bandgap microstrip structures

Abstract: Photonic bandgap (PBG) structures in microstrip technology have been recently proposed as efficient Bragg reflectors. The periodic patterns employed until now were formed by a distribution of nonconnected holes (cermet topology) etched in the ground plane or drilled in the dielectric substrate, giving rise to single-frequency-tuned band reflectors. In this letter, a novel pattern that follows a continuous profile (network topology) is proposed to simultaneously reject multiple frequency bands. It is formed by the addition of various sinusoidal functions tuned at the design frequencies. Measurements performed for two-and three-frequency-tuned PBG microstrip prototypes show that multiple deep and wide stopbands can be obtained using these novel devices.

Semi built-in multi-band printed antenna

Abstract: The present invention provides a miniature, built-in multi-band antenna which is suitable for use in future compact mobile terminals. According to exemplary embodiments, a semi built-in printed antenna is provided which includes patch elements of different sizes and capable of being tuned to different frequency bands. An internal patch element is located on a printed circuit board (PCB) within a communication device and another patch element is located outside the PCB. On each patch element is formed a slot which divides the patch element into sub-parts. Each sub-part of the internal patch element is structured so as to be resonant at a frequency in the same frequency band to which the internal patch element is tuned. Each sub-part of the external patch element is similarly structured but having a resonance with a larger bandwidth than the internal patch element and at a frequency band to which the external patch element is tuned. As a result, a high efficiency, broad band, multi-band, and surface mountable low profile antenna can be realized.

Surface-mounted antenna structure and communications equipment provided with the same

Abstract: PROBLEM TO BE SOLVED: To satisfy all the demands of band widening, miniaturizing and multi- banding. SOLUTION: A radiation electrode 3 is loop-shaped, an opening terminal 3a of this radiation electrode 3 is arranged opposite to a power feeding terminal side electrode portion via a gap, and a capacitor is formed between the opening terminal 3a and the power feed terminal side electrode portion. Since the interval between the resonance frequency of a fundamental mode and the resonance frequencies of a higher-order mode can be controlled variably by varying this capacitor, without markedly changing the resonance frequency in the fundamental mode of the radiating electrode 3, it is easy to design the respective resonance frequencies of the fundamental mode ands the higher-order mode, as demanded. Both the fundamental mode and the higher-order mode of the radiating electrode 3 can be utilized and multi-banding can be attained. Furthermore, an antenna 1 is mounted on a non-grounded area 16 of a mount board 15. Thus, both the widening of frequency band and miniaturizing of the antenna can be attained.

Apparatus for and method of embedding and extracting digital information, and medium having program for carrying out the method recorded thereon

Abstract: An apparatus for embedding information in a signal includes a band dividing device, a block divider, a quantization portion, a signal replacement portion, a mean difference addition portion, a mean calculation portion, and a band synthesis portion. The band dividing device divides the signal into transform coefficients over a plurality of frequency bands. The block divider divides one frequency band into a plurality of blocks in accordance with a previously determined block size. The quantization portion calculates for each block, a mean value M of the transform coefficients in the block, and subjects the mean value M to linear quantization, using a previously determined quantization step-size Q to calculate a quantization value. The signal replacement portion replaces the quantization value for each block, on the basis of the quantization value and the value of the information to be embedded. The mean difference addition portion subjects the replaced quantization value, for each block, to inverse linear quantization using the quantization step-size Q to calculate a mean value M′, and adds a difference DM between the mean value M′ and the mean value M to all the transform coefficients in the block. The mean calculation portion calculates a mean value LM of the transform coefficients in the frequency band after the addition of the difference DM. The band synthesis portion reconstructs a signal in which the information has been embedded using the frequency band after the addition of the difference DM and the other frequency bands.

Method permitting increased frequency re-use in a communication network, by recovery of transmitted information from multiple cochannel signals

Abstract: A method for use in a communication network having multiple users and limited bandwidth, wherein up to N users are allocated to the same frequency band at the same time, and the method provides for processing signals received at an M-element antenna array, using a cumulant-based signal recovery system to separate and recover the signals transmitted by the respective users.

Ultimate sensitivity of time-resolved optoacoustic detection

Abstract: The major limitation in sensitivity of the optical tomography is associated with strong optical attenuation in human tissues. Opto-acoustic tomography overcomes this limitation utilizing detection of acoustic waves instead of detection of transmitted photons. Exceptional sensitivity of the opto-acoustic tomography allows early detection of small tumors located dep in human tissues, such as breast. This paper demonstrates that an optimally designed opto-acoustic imaging system can detect early 1-mm tumors with minimal blood content of only 7 percent at the depth of up to 7-cm within the breast attenuating laser irradiation 3.3 times per each 1-cm of its depth. A theoretical consideration of the ultimate sensitivity of piezo-detection in a wide ultrasonic frequency band is developed. The detection sensitivity is presented as a function of the ultrasonic frequency, tumor dimensions and optical absorption coefficient. Comparative analysis of piezo and optical interferometric detection of opto-acoustic transients is presented. The theoretical models of piezo detection were developed for the open-circuit and short-circuit schemes of operation. The ultimate sensitivity limited by thermal noise of electric capacitor of the piezo-element was estimated. It was shown that the limit of detection depends on the frequency band, the electric capacity of the transducer and the sped of sound in the piezo-element. Comparative analysis of various piezo-materials was made from the point of view of their utility for sensitive opto-acoustic detection.

Propagation prediction techniques and antenna modeling (150 to 1705 kHz) for intelligent transportation systems (ITS) broadcast applications

Abstract: This paper discusses the basic aspects of radio-wave propagation and antenna modeling at 150 to 1705 kHz The paper contains descriptions of both sky-wave and ground-wave propagation-prediction models, in addition to the methodology used to analyze antennas that operate in this band A method of calculating and normalizing antenna gain for system computations is also discussed The sky-wave models described in this paper are valid from 150 to 1705 kHz The ground-wave models described in this paper are valid from 10 kHz to 30 MHz The propagation of radio waves from 150 to 1705 kHz includes both a ground wave and a sky wave, and is quite different from propagation at any other frequency The methods used for antenna modeling and analysis in this band are also quite unlike those in other bands The AM broadcast band of 535 to 1605 kHz is planned to be used in the advanced traveler information systems (ATIS) of intelligent transportation systems (ITS), to provide information such as road conditions, road hazards, weather, and incident reporting for rural travelers The band of frequencies from 285 to 325 kHz is presently being used in another application of ITS, called the Differential Global Positioning System (DGPS), which will be used for precision location of vehicles The propagation-prediction models and antenna-analysis methods described here can be used for designing systems and making performance predictions for both of these ITS applications, or for any other systems that operate in this band of frequencies from 150 to 1705 kHz Some examples of comparisons of measured and predicted data are also presented A computer program that includes all of these propagation-prediction models and antenna-modeling techniques was used

Dual band ultrasonic systems

Abstract: A dual-frequency band ultrasonic apparatus provides a first ultrasound signal to a region at a first frequency band and a second ultrasound signal at a second frequency band for monitoring the region. A processor controls the first and second ultrasound signals such that a predetermined phase relationship is achieved between the first frequency band signal and the second frequency band signal. The apparatus can employ a single transducer operable at both frequency bands or separate transducers for the first and second frequency bands.

Optoacoustic tomography of breast cancer with arc-array transducer

Abstract: The second generation of the laser optoacoustic imaging system for breast cancer detection, localization and characterization using a 32-element arc-shaped transducer array was developed and tested. Each acoustic transducer was made of 110-micrometers thick SOLEF PVDF film with dimensions of 1mm X 12.5mm. The frequency band of transducer array provided 0.4-mm axial in-depth resolution. Cylindrical shape of this 10-cm long transducer array provided an improved lateral resolution of 1.0 mm. Original and compact design of low noise preamplifiers and wide band amplifiers was employed. The system sensitivity was optimized by choosing limited bandwidth of ultrasonic detection 20-kHz to 2-MHz. Signal processing was significantly improved and optimized resulting in reduced data collection time of 13 sec. The computer code for digital signal processing employed auto- gain control, high-pass filtering and denoising. An automatic recognition of the opto-acoustic signal detected from the irradiated surface was implemented in order to visualize the breast surface and improve the accuracy of tumor locations. Radial back-projection algorithm was used for image reconstruction. Optimal filtering of image was employed to reduce low and high frequency noise. The advantages and limitations of various contrast-enhancing filters applied to the entire image matrix were studied and discussed. Time necessary for image reconstruction was reduced to 32 sec. The system performance was evaluated initially via acquisition of 2D opto-acoustic images of small absorbing spheres in breast-tissue-like phantoms. Clinical ex-vivo studies of mastectomy specimen were also performed and compared with x-ray radiography and ultrasound.

Method and apparatus for adaptively suppressing noise

Abstract: An apparatus and method for suppressing noise is presented. The apparatus may utilize a filter bank of bandpass filters to split the input noisy speech-containing signal into separate frequency bands. The overall average noise-to-signal ratio (NSR) of the input signal is estimated in the overall NSR estimator, which estimates the average noisy signal power in the input signal during speech activity and the average noise power during silence. Two indirect power measures are performed for each band, measuring a short-term power and a long-term power. The power estimation processes are adapted based on the signal activity indicated by the JVADAD. An NSR adapter adapts the NSR for each frequency band based on the long-term and short-term power measures, the overall NSR and the signal activity indicated by the JVADAD. The gain computer utilizes these NSR values to determine the gain factors for each frequency band.

MOSFET 1/f noise measurement under switched bias conditions

Abstract: A new measurement setup is presented that allows the observation of 1/f noise spectra in MOSFET's under switched bias conditions in a wide frequency band (10 Hz-100 kHz). When switching between inversion and accumulation, MOSFET's of different manufacturers invariably show reduced 1/f noise power density for frequencies below the switching frequency. At low frequencies (10 Hz), a 5-8 dB reduction in intrinsic 1/f noise power density is found for different devices, largely independent of the switching frequency (up to 1 MHz). The switched bias measurements render detailed wideband 1/f noise spectra of switched MOSFET's, which is useful for 1/f noise model validation and analog circuit design.

Speech decoding using mix ratio table

Abstract: A decoder compares a spectral envelope value y8 on a frequency axis with a predetermined threshold f9 to identify a voiced region and an unvoiced region. An excitation signal is produced by using excitations suitable for respective frequency regions. An encoder applies the nonuniform quantization to the period of the aperiodic pitch in accordance with its frequency of occurrence. The result of the nonuniform quantization is transmitted together with the quantization result of the unvoiced state and the periodic pitch as one code. A decoder obtains spectral envelope amplitude l8′ from the spectral envelope information, and identifies a frequency band e10′ where the spectral envelope amplitude value is maximized in each of respective bands divided on the frequency axis. A mixing ratio g8′, which is used in mixing a pitch pulse generated in response to the pitch period information and white noise, is determined based on the identified frequency band and voiced/unvoiced discriminating information. A mixing signal of each frequency band is produced in accordance with the mixing ratio. Then, the mixing signals of respective frequency bands are summed up to produce a mixed excitation signal x8′.

Animating by multi-level sampling

Abstract: We describe a method for synthesizing joint angle and translation data based on the information in motion capture data. The synthetic data is realistic not only in that it resembles the original training data, but in that it has random variations that are statistically similar to what one would find in repeated measurements of the motion. To achieve this result, the training data is broken into frequency bands using a wavelet decomposition, and the information in these bands is used to create the synthetic data one frequency band at a time. The method takes into account the fact that there are correlations among numerous features of the data. For example, a point characterized by a particular time and frequency band will depend upon points close to it in time in other frequency bands. Such correlations are modeled with a kernel-based representation of the joint probability distributions of the features. The data is synthesized by sampling from these densities and improving the results using a new iterative maximization technique. We have applied this technique to the synthesis of joint angle and translation data of a wallaby hopping on a treadmill. The synthetic data was used to animate characters that have limbs proportional to the wallaby.

High-frequency switch, high-frequency switch module, and wireless communication device

Abstract: A high-frequency switch circuit common to a plurality of frequency bands comprises a first high-frequency switch connected to first high-frequency signal input and output terminals and adapted to pass transmission signals of a first or a second frequency band and block received signals of the first and second frequency band; and a demultiplexer has a first high-frequency circuit which consists of a first phaser connected to the first terminal and a first bandpass filter succeeding to the first phaser, and a second high-frequency circuit which consists of a second phaser connected to the first terminal and a second bandpass filter succeeding to the second phaser. The transmission line in the first phaser has a line length such that the input impedance of the first high-frequency circuit is substantially open in the pass band of the second bandpass filter, whereas the transmission line in the second phaser has a line length such that the input impedance of the second high-frequency circuit is substantially open in the pass band of the first bandpass filter. Thus, the high-frequency switch circuit passes one of the received signals of the first and second frequency bands and blocks the other.

High-frequency composite switch component

Abstract: The present invention relates to a hybrid radio frequency (RF) switching device. It is an object of the invention to provide a hybrid RF switching device including fewer diodes and having a smaller size and high performance. To achieve the object according to the invention, the device includes first to fourth ports, a diode coupled between the first port and second port, a first transmission line having a length of λg/4 (where λg is a wave length of a frequency in a first frequency band), and a first element coupled in series with the first transmission line having an almost simple reactance component and nearly opening in a second frequency band. The first transmission line and first element are coupled in series between the second port and third port. The device further includes a second transmission line having a length of λd/4 (where λd is a wavelength of a frequency in the second frequency band), and a second element having an almost simple reactance component and nearly opening in the first frequency band. The second transmission line and second element are coupled in series between the second port and fourth port.

Simultaneous Diagonalization in the Frequency Domain (SDIF) for Source Separation

Abstract: Reverberant signals recorded by multiple microphones can be described as sums of sources convolved with different parameters. Blind source separation of this unknown linear system can be transformed to a set of instantaneous mixtures for every frequency band. In each frequency band, we may use the simultaneous diagonalization algorithms to separate the sources. In addition to our previous simultaneous diagonalization to minimize the Frobenius norm, we now propose another set of efficient simultaneous diagonalization algorithms based on Hadamard’s inequality to make the source separation feasible in the frequency domain.

Beat frequency modulation for plasma generation

Abstract: An apparatus and method for providing a modulated-bias plasma are described. In particular, a radio frequency (RF) source or collector includes one or more sources to provide differing driving frequencies or bias frequencies, respectively. These frequencies, over time, interfere with one another to produce beating at one or more controllable, infinitely variable beat frequencies. As a beat frequency has significantly fewer cycles per second than a driving or bias frequency, a modulated-bias plasma may be provided without turning power on and off as in conventional “pulsed” plasma systems. Beat frequencies facilitate modulation of the driving or bias frequencies, which may lie within a relatively narrow frequency band. Also, the use of a plurality of driving or bias frequencies facilitates use of more conventional RF sources or collectors owing to lower power requirements at each frequency. In accordance therewith, the apparatus and method described may be employed for plasma etching and/or plasma enhanced vapor deposition.

Multiple branch receiver system and method

Abstract: A receiver provides received analog signals to a plurality of channel branches, and on at least one of the channel branches, the frequency of the received analog signals is adjusted independent of the relative positions of the corresponding analog signals in the radio frequency (RF) spectrum. The analog signals on the channel branches are then combined, and the combined analog signals are converted into the digital domain. For example, the receiver comprises at least one antenna(s) which receives radio frequency (RF) analog signals. A channel branch arranger receives the analog RF signals from the antenna(s) and provides the RF analog signals to a plurality of channel branches. A frequency conversion arrangement comprising at least one frequency converter on at least a respective one of the channel branches adjusts the frequency band of the analog RF signals on the respective channel branch independent of the relative positions of the corresponding analog signals in the RF spectrum of the different channel branches. The analog signals on the channel branches are combined, and a single analog to digital converter converts the combined analog signals into digital signals. In converting the composite analog signals into the digital domain, the frequency bands of the analog signals are positioned in a plurality of Nyquist zone channels in the digital domain. By properly selecting the frequency bands for the analog signals on the channel branches and the sampling rate for the A/D converter, the available bandwidth for the A/D converter can be more efficiently used, and/or time coherence and/or phase coherence can be provided.

A fully integrated broadband direct-conversion receiver for DBS applications

Abstract: The key obstacle to successful integration of broadband receivers is that the wide-tuning range (C/sub H//C/sub L/>5) varactors required are not available in a standard process In addition, when external hyper-abrupt varactors are used, a separate high-voltage supply (eg 30 V) is required to cover the entire frequency band More recently, integrated wideband tuners have been reported using multiple wideband RC oscillators, but they require a complicated multi-loop architecture to achieve desired phase-noise performance Using multiple integrated LC voltage-controlled oscillators (VCO) (including resonators) a fully-integrated single-loop frequency synthesizer is possible which allows the development of a single-chip solution for broadband applications This results in a significant cost reduction and ease of system-board design

Limitations on impedance inversion of band-limited reflection data

Abstract: A seismic approximate impedance log is often the ultimate output in the sequence of seismic data‐processing steps. In principle, the true acoustic impedance is obtainable from the inversion of full‐band impulse response. Because the seismic data necessarily is band limited, its inversion obviously would produce an approximate impedance log. A question addressed is how the true and reconstructed logs are related and a mathematical relationship between the two is derived without the assumptions required in an existing derivation of the same result. The deductions also include the contribution of an individual seismic frequency in the reconstruction of the impedance and, in particular, a simple formula for the contribution of direct‐current (dc) frequency, which never is recorded but is required to supplement the inversion. Analytical expressions are derived for the reconstructed impedance corresponding to any given frequency band for two cases: a simple discontinuity and a bed sandwiched between two similar...

High frequency enhancement layer coding in wideband speech codec

Abstract: A speech coding method and device for encoding and decoding an input signal and providing synthesized speech, wherein the higher frequency components of the synthesized speech are achieved by high-pass filtering and coloring an artificial signal to provide a processed artificial signal. The processed artificial signal is scaled by a first scaling factor during the active speech periods of the input signal and a second scaling factor during the non-active speech periods, wherein the first scaling factor is characteristic of the higher frequency band of the input signal and the second scaling factor is characteristic of the lower frequency band of the input signal. In particular, the second scaling factor is estimated based on the lower frequency components of the synthesized speech and the coloring of the artificial signal is based on the linear predictive coding coefficients characteristic of the lower frequency of the input signal.

Analysis of coplanar waveguide-to-coplanar stripline transitions

Abstract: The coplanar waveguide (CPW)-to-coplanar stripline (CPS) transition is analyzed theoretically and experimentally in this paper. To characterize this transition in the lower frequency band, a simple equivalent-circuit model that consists of uniform and nonuniform transmission lines is established. The elements of this model can all be obtained by the closed-form formulas; hence, this model is suitable for computer-aided-design application. This model is then applied to design and analyze the CPW-to-CPS transitions with various structure parameters. In the higher frequency band, the partially prism-gridded finite-difference time-domain (FDTD) method is employed to take into account the bond-wire effect as well as the surface-wave leakage and space-wave radiation associated with the transition. In this study, results based on equivalent-circuit model, FDTD simulation, and measurement are compared. Good agreement among these results supports the usefulness of the proposed equivalent-circuit model and also validates the FDTD method. By using the equivalent-circuit model to optimize the transition configuration, the CPW-to-CPS transition with broad bandwidth and low insertion loss may be achieved.

Study of ultrasonic contrast agents using a dual-frequency band technique

Abstract: We have developed a dual-frequency band technique to study frequency-dependent phenomena associated with ultrasonic contrast agents. Our technique uses a superimposed high-frequency (10 MHz) broad-band ultrasound (US) pulse to investigate contrast agent interaction with a low-frequency (e.g., 0.5 MHz) ultrasonic field. Our digitally controlled system has the ability to produce two colinear, confocal US pulses at different center frequencies, to adjust the relative phasing and pulse repetition frequency of each pulse, and to acquire digital backscatter data. A series of experimental studies demonstrated that the high-frequency backscatter signal responded to several phenomena induced in contrast agent particles by the low-frequency beam. These phenomena included radial pulsations, nonlinear oscillations and depletion. Initial results also demonstrated a relative phase shift between the high- and low-frequency signals; this shift is due to a difference in sound velocity at these frequencies, and it may convey information about the contrast agent concentration.

Broad spectrum diffusion model for room acoustics ray-tracing algorithms

Abstract: Geometrical acoustics methods have already been transformed to account for diffusely reflecting boundaries. In randomized ray-tracing algorithms, the sound rays are either specularly reflected or scattered, according to the value of a random number which is compared with the diffusion factor. However, this method becomes inefficient if this factor depends on frequency, since the process must then be repeated for each frequency band. A method is proposed in this paper to compute all frequency components simultaneously in a single pass. The diffuse reflection model is based on the definition of a new concept: the “splitting coefficient,” which can differ from the diffusion factor. First, the randomized ray-tracing method is described and the diffusion model is applied to a single diffusing surface in free field. It is shown that the results computed by the program are in accordance with theoretical results. Then, the method is shown to work properly when it is applied to more realistic enclosures: This is p...