Showing papers on "Frequency band published in 2002"

Resource allocation for MIMO-OFDM communication systems

Abstract: Techniques to schedule terminals for data transmission on the downlink and/or uplink in a MIMO-OFDM system based on the spatial and/or frequency “signatures” of the terminals. A scheduler forms one or more sets of terminals for possible (downlink or uplink) data transmission for each of a number of frequency bands. One or more sub-hypotheses may further be formed for each hypothesis, with each sub-hypothesis corresponding to (1) specific assignments of transmit antennas to the terminal(s) in the hypothesis (for the downlink) or (2) a specific order for processing the uplink data transmissions from the terminal(s) (for the uplink). The performance of each sub-hypothesis is then evaluated (e.g., based on one or more performance metrics). One sub-hypothesis is then selected for each frequency band based on the evaluated performance, and the one or more terminals in each selected sub-hypothesis are then scheduled for data transmission on the corresponding frequency band.

Ultra wide bandwidth spread-spectrum communications system

Abstract: An ultra wide bandwidth, high speed, spread spectrum communications system uses short wavelets of electromagnetic energy to transmit information through objects such as walls or earth. The communication system uses baseband codes formed from time shifted and inverted wavelets to encode data on a RF signal. Typical wavelet pulse durations are on the order of 100 to 1000 picoseconds with a bandwidth of approximately 8 GHz to 1 GHz, respectively. The combination of short duration wavelets and encoding techniques are used to spread the signal energy over an ultra wide frequency band such that the energy is not concentrated in any particular narrow band (e.g. VHF: 30-300 MHz or UHF: 300-1000 MHz) and is not detected by conventional narrow band receivers so it does not interfere with those communication systems. The use of pulse codes composed of time shifted and inverted wavelets gives the system according to the present invention has a spatial resolution on the order of 1 foot which is sufficient to minimize the negative effects of multipath interference and permit time domain rake processing.

Sidelobe controlled radio transmission region in metallic panel

Abstract: A region in a metallic panel that facilitates the transmission of radio frequency signals. The metallic panel may be included in a window such as the window of a vehicle or building. For example, the metallic panel may be used for heating or to reflect infrared radiation. An aperture is formed in the metallic panel to enable radio frequency signals to be transmitted through the metallic panel. The design of the aperture may be selected to enable the transmission of the desired frequency band. Furthermore, the aperture is designed such that there is a taper in the transmission amplitude and/or the phase to suppress lobing effects on the other side of the aperture. In an embodiment in which the metallic panel is used to conduct electric current, the aperture may be oriented such that the current may flow between the openings of the aperture. Accordingly, there may be uniform heating across the metallic panel without blocking the transmission of radio frequency signals in the desired frequency band.

System and method for spectrum management of a shared frequency band

Abstract: A system and method for managing the spectrum utilization of a frequency band that is shared, both in frequency and time, by multiple devices. At one or more devices operating in the frequency band, pulses associated with signals occurring in the frequency band are detected by sampling part or all the frequency band for a time interval. From the detected signal pulses, the signals can be classified. In addition, overall spectrum activity can be measured. Using classification information for signals detected in the frequency band, policies can be executed so that a device may take certain actions in order to avoid interfering with other signals, or to optimize simultaneous use of the frequency band with the other signals. Signal detection occurs at one or more devices operating in a frequency band. Signal classification and measurement, as well as policy execution may occur within a processor of the same device where signal detection occurs, or in another device (located remotely or within the operating region of the frequency band).

An ensemble source spectra model for merchant ship-radiated noise.

Abstract: This paper presents an evaluation of the classical model for determining an ensemble of the broadband source spectra of the sound generated by individual ships and proposes an alternate model to overcome the deficiencies in the classical model. The classical model, proposed by Ross [Mechanics of Underwater Noise (Pergamon, New York, 1976)] postulates that the source spectrum for an individual ship is proportional to a baseline spectrum with the constant of proportionality determined by a power-law relationship on the ship speed and length. The model evaluation, conducted on an ensemble of 54 source spectra over a 30-1200-Hz to 1200-Hz frequency band, shows that this assumption yields large rms errors in the broadband source level for the individual ships and significantly overestimates the variability in the source level across the ensemble of source spectra. These deficiencies are a consequence of the negligible correlation between the source level and the ship speed and the source level and the ship length. The alternate model proposed here represents the individual ship spectra by a modified rational spectrum where the poles and zeros are restricted to the real axis and the exponents of the terms are not restricted to integer values. An evaluation of this model on the source spectra ensemble indicates that the rms errors are significantly less than those obtained with any model where the frequency dependence is represented by a single baseline spectrum. Furthermore, at high frequencies (400 to 1200 Hz), a single-term rational spectrum model is sufficient to describe the frequency dependence and, at the low frequencies (30 to 400 Hz), there is only a modest reduction in the rms error for a higher order model. Finally, a joint probability density on the two parameters of the single term model based on the measured histograms of these parameters is proposed. This probability density provides a mechanism for generating an ensemble of ship spectra.

A model for voltage-to-displacement dynamics in piezoceramic actuators subject to dynamic-voltage excitations

Abstract: A model that predicts the expansion of piezoceramic actuators when subject to dynamic-voltage excitations is developed as an extension of the classical Preisach model. The model is presented in a recursive form that is suitable for real-time implementation. The model uses measurements of the first-order reversal curves and the average rate of change of the input-voltage signal. The model is shown through experiments to offer high accuracy under voltage excitations covering a wide frequency band.

Ultra wide bandwidth communications method and system

Abstract: An ultra wide bandwidth, high speed, spread spectrum communications system uses short wavelets of electromagnetic energy to transmit information through objects such as walls or earth. The communication system uses baseband codes formed from time shifted and inverted wavelets to encode data on a RF signal. Typical wavelet pulse durations are on the order of 100 to 1000 picoseconds with a bandwidth of approximately 8 GHz to 1 GHz, respectively. The combination of short duration wavelets and encoding techniques are used to spread the signal energy over a an ultra wide frequency band such that the energy is not concentrated in any particular narrow band (e.g. VHF: 30-300 MHz or UHF: 300-1000 MHz) and is not detected by conventional narrow band receivers so it does not interfere with those communication systems. The use of pulse codes composed of time shifted and inverted wavelets gives the system according to the present invention has a spatial resolution on the order of 1 foot which is sufficient to minimize the negative effects of multipath interference and permit time domain rake processing.

System and method for real-time spectrum analysis in a communication device

Abstract: A spectrum analysis engine (SAGE) that comprises a spectrum analyzer component, a signal detector component, a universal signal synchronizer component and a snapshot buffer component. The spectrum analyzer component generates data representing a real-time spectrogram of a bandwidth of radio frequency (RF) spectrum. The signal detector detects signal pulses in the frequency band and outputs pulse event information entries output, which include the start time, duration, power, center frequency and bandwidth of each detected pulse. The signal detector also provides pulse trigger outputs which may be used to enable/disable the collection of information by the spectrum analyzer and the snapshot buffer components. The snapshot buffer collects a set of raw digital signal samples useful for signal classification and other purposes. The universal signal synchronizer synchronizes to periodic signal sources, useful for instituting schemes to avoid interference with those signals.

System and method for signal classiciation of signals in a frequency band

Abstract: A system and method for classifying signals occurring in a frequency band. One or more characteristics of one or more signals in the frequency band are detected using any suitable technology, such as a device that can generate characteristics of signal pulses detected in the frequency band. Data pertaining to the signal pulses is accumulated over time. The accumulated signal data is compared against reference data associated with known signals to classify the one or more signals in the frequency band based on the comparison. The accumulated data may include one or more characteristics selected from the group consisting of: pulse center frequency, pulse bandwidth, pulse duration, time between pulses and number of different active pulses, and wherein the reference data associated with each of a plurality of known signals comprises one or more characteristics selected from the group consisting of: pulse center frequency, pulse bandwidth, pulse duration and time between pulses. The accumulated signal data is compared against the reference data, and depending on the degree of match with reference data, a signal can be classified. Additional levels of signal classification processing may be performed.

Frequency range and explicit expressions for negative permittivity and permeability for an isotropic medium formed by a lattice of perfectly conducting $\Omega$ particles

Abstract: An analytical model is presented for a rectangular lattice of isotropic scatterers with electric and magnetic resonances. Each isotropic scatterer is formed by putting appropriately 6 $\Omega$-shaped perfectly conducting particles on the faces of a cubic unit cell. A self-consistent dispersion equation is derived and then used to calculate correctly the effective permittivity and permeability in the frequency band where the lattice can be homogenized. The frequency range in which both the effective permittivity and permeability are negative corresponds to the mini-band of backward waves within the resonant band of the individual isotropic scatterer.

Integrated tri-band antenna for laptop applications

Abstract: Integrated (embedded) tri-band antennas for use with portable devices such as laptop computers. In one aspect, an integrated tri-band antenna for a portable device comprises a first element having a resonant frequency in a first frequency band, a second element having a resonant frequency in a second frequency band, a third element having a resonant frequency in a third frequency band, and a ground element for grounding the first, second and third elements. The first, second and third elements and ground element may be metallic elements formed on a PCB (printed circuit board), wherein the first element is connected to a signal feed, and wherein the PCB is mounted to a metallic support frame of a display unit of the portable device.

Mobile communication device

Abstract: A mobile communications device has a multifrequency band antenna with a low band portion (LB) tuned to a low frequency band, and a first high band portion (HB 1 ) tuned to a first high frequency band at higher frequencies than the low frequency band. The low band portion (LB) and the first high band portion (HB 1 ) have a common first grounding point (GP 1 ), a common feeding point (FP) for feeding input signals to the antenna and for receiving signals from the antenna, and a first conductor portion (CP 1 ), which forms part of the low band portion (LB) and of the first high band portion (HB 1 ). The first conductor portion (CP 1 ) is electrically connected to the first grounding point (GP 1 ) and to the common feeding point (FP). A second high band portion (HB 2 ) is coupled to the first conductor portion (CP 1 ) and tuned to a second high frequency band at a higher frequency than the low frequency band and different from the first high frequency band. A switching network is connected between the second high band portion and ground, allowing the resonant frequency of the second high band portion to be varied, on the basis of a signal which depends on the operating mode of the device, thereby allowing four band operation.

Frequency hopping ofdma method using symbols of comb pattern

Abstract: Method for providing frequency-hopping OFDMA using symbols of comb pattern, the method including the steps of: a) assigning frequency domain signal X(k) of comb pattern (comb symbol, k is frequency index) to modulated data sequence, the comb symbol comprising predetermined number of sub carriers (sub carrier group) which are placed with predetermined interval in the whole available frequency band; b) getting the comb symbol hopped for the comb symbol to have independent frequency offset; and c) inverse fast fourier transforming the comb symbol to time domain signal x(n) (n is time index) and transmitting the signal.

Narrowband interference suppression in time-hopping impulse-radio systems

Abstract: Ultra-wideband (UWB) radio systems have drawn a lot of attention during the last few years. These systems use very low transmission power, spread over a bandwidth of several gigahertz. The very low transmission power and the large bandwidth used enable UWB radio systems to coexist with other narrowband systems over the same frequency band without interfering with the narrowband systems. Nevertheless, these narrowband systems may cause interference which jams the UWB receiver completely. Since standard narrowband interference suppression techniques are not applicable, techniques for interference suppression have to be developed. This paper presents novel narrowband interference suppression algorithms for UWB radio systems. Theoretical analysis of these algorithms reveal that they can eliminate the narrowband interference almost completely.

Efficient and scalable parametric stereo coding for low bitrate audio coding applications

Abstract: A method for decoding an encoded power spectral envelope of a stereo or multichannel signal having two channels, the encoded power spectral envelope being represented by a balance parameter for each frequency band indicating in each band a ratio of power in the two channels, a level parameter representing a total power of the two channel per frequency band, comprising the step of converting the balance and power parameters into power values of the first and second channels.

Characterization and modeling of in-building power lines for high-speed data transmission

Abstract: This paper analyzes the characteristics of power lines in the Singapore residential network in order to develop a channel model suitable to simulate its behavior for high-speed data transmission. The channel model, which describes the transfer function and noise characteristics of typical in-building power line channels in a frequency band from 1 to 10 MHz, is developed and tested through software simulation and hardware implementation. The transfer function is described by an echo model, and the noise spectrum is derived statistically from measurements on actual power lines. Some measurement results on power line impedance, noise, and attenuation are presented. The results are based on measurements between line and neutral conductors in a 230 V power line network. From the results obtained so far, the impedance, noise, and attenuation of power lines exhibit variations with frequency, time, and location.

Wideband signal transmission system

Abstract: Described is a transmission system (10) comprising a transmitter (12) for transmitting an input signal to a receiver (14) via a transmission channel (16). The transmitter (12) comprises a splitter (20) for splitting up the input signal into at least first and second frequency band signals. The transmitter (12) further comprises a first encoder (22) for encoding the first frequency band signal into a first encoded frequency band signal and a second encoder (24) for encoding the second frequency band signal into a second encoded frequency band signal. The transmitter (12) is arranged for transmitting the first and second encoded frequency band signals via the transmission channel (16) to the receiver (14). The receiver (14) comprises a first decoder (26) for decoding the first encoded frequency band signal into a first decoded frequency band signal and a second decoder (28) for decoding the second encoded frequency band signal into a second decoded frequency band signal. The receiver (14) further comprises a combiner (30) for combining the first and second decoded frequency band signals into an output signal and reconstruction means (48) for reconstructing the second decoded frequency band signal when the second decoded frequency band signal is not available. The transmission system (10) is characterized in that the reconstruction means (48) are arranged for reconstructing the second decoded frequency band signal from the first decoded frequency band signal. In this way, errors occurring in the receipt or decoding of the second frequency band signal can be concealed by reconstructing the missing part(s) on the basis of the first frequency band signal which was received and decoded correctly. Preferably, this reconstruction is done by means of bandwidth extension.

Gaussian mixture model based mutual information estimation between frequency bands in speech

Abstract: In this paper, we investigate the dependency between the spectral envelopes of speech in disjoint frequency bands, one covering the telephone bandwidth from 0.3 kHz to 3.4 kHz and one covering the frequencies from 3.7 kHz to 8 kHz. The spectral envelopes are jointly modeled with a Gaussian mixture model based on mel-frequency cepstral coefficients and the log-energy-ratio of the disjoint frequency bands. Using this model, we quantify the dependency between bands through their mutual information and the perceived entropy of the high frequency band. Our results indicate that the mutual information is only a small fraction of the perceived entropy of the high band. This suggests that speech bandwidth extension should not rely only on mutual information between narrow- and high-band spectra. Rather, such methods need to make use' of perceptual properties to ensure that the extended signal sounds pleasant.

Digital baseband receiver in a multi-carrier power amplifier

Abstract: A power amplifier system and method for locating carrier frequencies across a frequency band, identifying the modulation format of each carrier, and locating and suppressing undesired intermodulation distortion (IMD) products generated by the power amplifier. The system includes an amplifier for amplifying RF carrier signals in a main signal path, a variable phase shifter and variable attenuator on a feed forward path, and a tunable receiver that digitizes a portion of the frequency band to baseband. The tunable receiver includes a tunable voltage controlled oscillator which provides an oscillating frequency to a mixer and is phase-locked to a highly stable reference oscillator. The mixer downconverts a desired RF based on the oscillating frequency to IF. A filter passes only a selected portion of the IF signals, and the filter has a passband sufficient to discern both narrowband and wideband carriers and their associated IMD products. Based on the locations of the carrier frequencies, a processing unit determines the IMD locations of the carrier frequencies, determines the IMD locations, and adjusts the variable phase shifter and variable attenuator on the feed forward path until the IMD products in the main signal path are suppressed below a desired threshold.

Scanning receiver for use in power amplifier linearization

Abstract: A feed forward power amplifier system and method identify active channels across a frequency band to suppress unwanted intermodulation distortion (IMD) products in a communications signal such as a single- or multi-carrier communications signal. A scanning receiver identifies at least one active channel in a frequency band, and identifies at least one portion of the frequency band likely to include IMD products based upon the identified active channel(s). Based upon the identified portion of the frequency band, IMD products are suppressed from the communications signal, e.g., by controlling the magnitude and/or phase of a suppression signal mixed with the communications signal.

Vector network analyzer applique for adaptive communications in wireless networks

Abstract: A test signal generator at a transmitter station and a facsimile generator at a receiver station go through an acquisition and tracking process which aligns the two signals so that a logical processor can compute the frequency transfer function of the entire propagation path for use in an adaptive, concurrently sent communication signal. The frequency transfer function is conveyed back to the transmit end via a control channel permitting an adaptivity function at the transmit end to influence subsequent selection of communication parameters, among which are typically transmitted data rate, selection of modulation, selection of forward error correcting coding, and selection of frequency band for transmission. The same measurement is conveyed to an adaptivity function at the receive end for use in the communications receiver to select demodulator variables such as gain control, and equalization of amplitude and phase, versus frequency. The adaptivity function also permits interspersing of reverse-direction communications over the same frequency bands in a time-share mode between forward-direction and reverse-direction communication with the measurement signals having to be transmitted in only one direction. An alternate embodiment invention of this type is described which is additionally useful for mobile communications channels. Another variation embodiment is described for pure propagation measurements only, absent conveyance of end-user information.

System and handover mechanism in frequency multiple band environment and equipment therefor

Abstract: A mechanism for supporting the decision on performing a communication connection changeover of a subscriber terminal in a wireless communication network, in particular in a multiple band WLAN, is proposed. The subscriber terminal is able to communicate with an access node on two or more frequency bands. AP related communication information are detected which comprises, besides information indicating a multiple band capability, a traffic load, a frequency band coverage and/or a frequency channel information. The communication information are broadcasted, for example, by means of the AP beacon frame, processed and used for a decision on a communication connection changeover of the subscriber terminal.

Nonlinear synthetic wideband waveforms

Abstract: Radars commonly use wide bandwidth pulses to attain high range resolution. However, when such wideband pulses are unavailable (or otherwise undesirable), high range resolution can still be achieved by coherently combining a sequence of narrowband pulses spanning the desired bandwidth. Collectively, such narrowband pulse sequences are said to compose a "synthetic wideband waveform" (specific variants are also known by the names "stepped frequency waveform", "frequency jump burst" and "frequency jump train"). Prior publications and reports have examined synthetic wideband waveforms that distribute energy uniformly over the frequency band. Such waveforms require heavy spectral weighting, highly overlapped pulses and/or nonperiodic pulses to control the range sidelobes and grating lobes; unfortunately, undesirable attributes are associated with each of these. We formulate synthetic waveforms that distribute energy nonuniformly over the desired frequency band. These new waveforms are shown to offer improved performance (i.e., lower range sidelobes, higher gain, higher range resolution and/or reduced grating lobes) when compared with traditional approaches.

Cableran networking over coaxial cables

Abstract: A bi-directional coaxial cable communication network including at least one bi-directional coaxial cable (10) extending from a remote location to a location adjacent subscriber premises and carrying traffic in opposite direction (22) along respective frequency spectra which are separated by a separation frequency band and at least one bi-directional coaxial cable extending from the location adjacent subscriber premises to at least one outlet (24) at the subscriber premises and carrying traffic along the separation frequency band.

Multiband phased array antenna utilizing a unit cell

Abstract: A multi-band phased array antenna for radiating low frequency band signals and high frequency band signals. The multiband phased array antenna is formed from unit cells having waveguides for radiating high frequency band signals and end-fire radiating elements for radiating low frequency band signals. The unit cells have four walls with an open input end and an open radiating end. End-fire radiating elements are disposed on inner surfaces and outer surfaces of the four walls and radiate out the radiating end. Four waveguides are disposed together to radiate into the input end of the low frequency assembly.

Multi-channel self-interference cancellation method and apparatus for relayed communication

Abstract: Multi-channel self-interference cancellation is provided in relayed electromagnetic communication (Fig. 4) between a first device and one or more other devices on one or more shared frequency channels. Specifically, near signals are generated at the first device and transmitted to a relay station. A composite signal is received at the first device from the relay station containing relayed versions of the near signals and relayed versions of remote signals transmitted from the one or more other devices, the composite signal having frequency channels including the one or more shared frequency channels, each shared frequency channel occupied by at least one of the relayed near signals and one of the relayed remote signals. One or more cancellation signals are selectively generated, each having a frequency band corresponding to one of the shared frequency channels. The cancellation signals are combined with the composite signal to produce a desired signal representing the relayed remote signals.

Method and apparatus providing a dual mode VCO for an adaptive receiver

Abstract: An RF VCO (260A) forms, in the preferred embodiment, a part of a dual mode mobile station (100). Also disclosed is a method for operating the VCO. The VCO is operated in a first frequency band using a first inductance (300A) that forms part of a first resonant circuit (parallel resonance), and the VCO is switched for operation to a second frequency band by the closing a switch (M5) that causes a second resonant circuit (serial resonance) to be inductively coupled to the first resonant circuit. The second resonant circuit includes a second inductance (300B), and preferably includes at least one frequency tunable component, such as a varactor (VR3, VR4), for adjusting the resonant frequency of the second resonant circuit. The second inductance is center tapped, and the switch, such as a MOS transistor, is coupled in series between two ends of the center tapped inductance. The first frequency band may include 3.6 GHz (a double frequency GSM band) and the second frequency band may include 4.3 GHz (a double frequency WCDMA band). Additional operational bands can be also be used. In the preferred embodiment the first inductance forms part of a transformer primary fabricated in an integrated circuit, and the second inductance forms part of the transformer secondary that is fabricated in the integrated circuit so as to underlie the first inductance. A signal detector (D1, D2) may be provided that is responsive to a signal induced in the transformer secondary, and the signal detector has an output coupled to a closed loop control circuit (310) for controlling a magnitude of a signal output from the VCO. A further input to the closed loop control circuit may be a signal that is indicative of communication channel conditions, and the current consumption of the VCO circuit is maintained at a level that is adequate to ensure operation with the communication channel conditions. A passive buffering circuit (320) is provided for coupling an output of the VCO circuit to a further circuit, such as a mixer, thereby reducing the total VCO current considerably.