Showing papers on "Frequency band published in 1996"

Photonic Band Gap Materials

Abstract: An overview of the theoretical and experimental efforts in obtaining a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, is presented.

Radio communication device and radio communication method

Abstract: A radio communication device has a first transmission and reception circuit for transmitting and receiving a channel which is established in a first occupied frequency band according to a first access process, and a second transmission and reception circuit for transmitting and receiving a channel which is established in a second occupied frequency band which is established in a guard band in the first occupied frequency band according to a second access process.

Output Frequency Characteristics of Nonlinear Systems

Abstract: Some interesting properties of output frequencies of Volterra-type nonlinear systems are particularly investigated. These results provide a very novel and useful insight into the super-harmonic and inter-modulation phenomena in output frequency response of nonlinear systems, with consideration of the effects incurred by different nonlinear components in the system. The new properties theoretically demonstrate several fundamental output frequency characteristics and unveil clearly the mechanism of the interaction (or coupling effects) between different harmonic behaviors in system output frequency response incurred by different nonlinear components. These results have significance in the analysis and design of nonlinear systems and nonlinear filters in order to achieve a specific output spectrum in a desired frequency band by taking advantage of nonlinearities. They can provide an important guidance to modeling, identification, control and signal processing by using the Volterra series theory in practice.

Slow beam extraction by a transverse RF field with AM and FM

Abstract: A beam extraction method using a transverse rf electric field with amplitude and frequency modulation has been studied in order to develop an irradiation method which is synchronized with the breathing of a patient for high-quality charged particle therapy. The dependence of the extracted beam intensity on the voltage, the frequency band width and the center frequency of the transverse rf electric field has been investigated. The extracted beam intensity was slightly increased from that of the ordinary slow extraction method with a third order resonance. The response of the extracted beam intensity to the applied transverse rf electric field was as prompt as within 1 ms. The horizontal emittance of beams extracted by the present method was reduced by about 70% compared with that by the ordinary one due to utilizing a constant separatrix. Amplitude modulation can control the global beam spill structure. The frequency modulation reduced the effect of the current ripple of the main quadrupole magnets.

Dual band mobile station employing cross-connected transmitter and receiver circuits

Abstract: A multi-mode radiotelephone (10) includes at least one antenna (12) for transmitting and receiving RF signals within at least two frequency bands. The radiotelephone also includes a first receiver (30, 34) having an input coupled to the antenna for amplifying and down-converting RF signals within a first frequency band and a second receiver (30a, 34a) having an input coupled to the antenna for amplifying and down-converting RF signals within a second frequency band. The radiotelephone further includes a first transmitter (44, 46, 48) having an output coupled to the antenna for up-converting and amplifying RF signals within the first frequency band and a second transmitter (44a, 46a, 48a) having an output coupled to the antenna for up-converting and amplifying RF signals within the second frequency band. In accordance with this invention the first receiver and the second transmitter are disposed within a first circuit package (29a), and the second receiver and the first transmitter are disposed within a second circuit package (29b). The first and second circuit packages may be integrated circuits or hybrid (e.g., thick or thin film) circuits.

Plural frequency antenna feed

Abstract: Apparatus and method for providing an antenna feed (10) operative at different microwave frequency bands employ a circular waveguide (14) interconnecting an orthomode transducer (20) to a feed horn (16) thereby providing a feed (10) suitable for illuminating the reflector (54) of an antenna (12). The orthomode transducer provides for a coupling of waves in the first frequency band with both vertical and horizontally polarized waves. Included within the feed is a coupler assembly (26) of waves of the second frequency band operative via a sidewall of the circular waveguide. The coupler assembly includes plural identical coupling sections (28) each having a rectangular waveguide section contiguous and parallel to the circular waveguide with a row of apertures for coupling power into and out of the circular waveguide. Pairs of the coupling sections are disposed in orthogonal planes so as to introduce two linearly polarized waves which are perpendicular to each other. A slab (48) of dielectric material is placed in each of the coupling sections to match the phase velocity of waves in the coupling sections to waves in the circular waveguide at the second frequency band while mismatching the phase velocities at the first frequency band. The dispersion of the waveguides provides for interaction with electromagnetic waves in the second frequency band while inhibiting such interaction at the first frequency band.

Method for selecting a preferable wireless communications service provider in a multi-service provider environment

Abstract: A communication device locates a wireless service provider in a multi-service provider environment using a frequency band search schedule. The frequency band search schedule has a first or home band and a several other frequency bands in a predetermined order. The order of the frequency bands may be programmed by the user or by a home service provider over the air. The communication device searches for an acceptable service provider by examining the home band and then the other bands listed in the frequency band search schedule. The bands are examined in the order specified by the frequency band search schedule. An acceptable service provider is identified by comparing the identity of a service provider specified by an identifier received from a band being examined with a list of acceptable service providers.

Multi-frequency antenna

Abstract: The present invention relates to an antenna system which is capable of multiband operation from a single antenna aperture. The system provides a high degree of design freedom for achieving desired antenna pattern shapes for all relevant frequency bands. The system achieves this pattern shaping ability by utilizing a unique array configuration which is highly adaptable. The array configuration may include a center array element for each of the relevant frequency bands. In one embodiment of the present invention, a dual frequency band antenna is provided which includes a stacked patch element as the center element in a first frequency band and a crossed dipole element, mounted on top of the stacked patch, as the center element in the second frequency band.

Method of transmitting orthogonal frequency division multiplexing signal and receiver thereof

Abstract: An orthogonal frequency division multiplexing signal transmitted from the transmitting end to the receiving end intermittently includes a particular symbol S0 having a predetermined particular pattern in addition to a symbol Sm including data to be transmitted. At the receiving end, the variation in the receiving level and/or the variation in the frequency band of a received signal are detected and corrected on the basis of the received particular symbol S0. Since the particular symbol S0 has a particular pattern, the variation in the level and/or the variation in the frequency are strongly correlated with the variation in the receiving level and/or the variation in the frequency band of the received signal. Consequently, the variation in the receiving level and/or the variation in the frequency band of the received signal can be accurately detected from the particular symbol S0 and consequently high-precision correction can be made.

Digital continuous phase modulation for a dds-driven phase locked loop

Abstract: A system and method are provided in which a phase modulation generator is used to modulate the output signal of a DDS with a modulation index, h/N. The phase-modulated. DDS output drives a PLL, which is an upconversion stage for a radio transmitter, with the modulated DDS signal as the PLL's reference. The output of the PLL will have a modulation index of h. Consequently, the frequency band of the DDS output is significantly narrower than the frequency band of upconversion stages used in conventional transmitters, and there are significantly less spurious emissions in the transmitted signal. However, a transmitter employing the present phase-modulated DDS-driven PLL topology can still transmit over a relatively wide frequency band.

Frequency‐Dependent Dielectric Permittivity from 0 to 1 GHz: Time Domain Reflectometry Measurements Compared with Frequency Domain Network Analyzer Measurements

Abstract: Measurements on a seven-wire coaxial probe carried out with a cable tester in the time domain are compared with measurements carried out with a network analyzer in the frequency domain. Results are compared in the frequency domain and in the time domain. The frequency domain results of the time domain measurements are less smooth than the direct frequency domain measurements, but similar trends can be observed. The measurements carried out with the cable tester (Tektronix 1502B) clearly have a frequency content well above 3 GHz for measurements in air but with a very low signal-to-noise ratio for the higher frequencies. The useful frequency band for measurements carried out with a seven-wire probe depends on the dielectric properties of the material being measured. The higher the complex dielectric permittivity, the lower the useful frequency band. Methods are presented for calibrating seven-wire coaxial probes and measuring the frequency-dependent dielectric properties of soil samples using a combination of frequency and time domain analyses. The approach does not depend on a choice of frequency bandwidth. A Debye relaxation curve is capable of describing the frequency domain dielectric permittivity of sandy soils containing a soil solution with an electrical conductivity of approximately 0.4 S m−1. Results indicate an effective bandwidth of at least 0–1 GHz for sandy soils.

Video and data co-channel communication system

Abstract: In the present invention, ancillary data is modulated onto a carrier frequency which is within a low energy density portion of a frequency band of a video signal, and the modulated carrier data (44) is combined with the video signal (46) so that the modulated carrier is either in an active video region or in an overscan region of the video signal. The ancillary data may be spread over several frequencies and summed at the output of a decoder to enhance the legibility of the ancillary data at the output of the decoder. Frequency-stepping may be used to add the ancillary data at ones of a plurality of selected frequencies within the frequency band of the video signal. Then ancillary data may be hierarchically apportioned between respective uniquely specified sequential segments corresponding to many distribution points of the video signal.

Shared hybrid-fiber coax transmission system having increased bandwidth in the upstream and downstream directions

Abstract: Bandwidth is increased and noise may be reduced in a shared hybrid fiber-coax transmission system (10) by digitally modulating upstream information onto a high frequency band (e.g., 750-1000 MHz) and thereafter digitally regenerating both the high frequency upstream information as well as a portion of the downstream information not used for broadcast video (i.e., the 500-750 MHz band).

Antenna for a mobile computer

Abstract: Disclosed is an antenna mounted on a dielectric card with three pairs of dipoles. The dielectric card may be made of epoxy or epoxy glass or Teflon with glass fibers or any plastic with low dielectric loss and/or glass. Each dipole pair is designed to resonate at a different frequency band. Thus, for instance, a first pair provide signals in 800 MHZ range, a second dipole pair provide signals in the 1900 MHZ range and a third dipole pair provide signals in the 2400 MHZ range. With multiple dipoles the antenna can be used to provide wireless communications for several different frequency bands. The antenna card may hingeable or slideably mounted to a mobile computer. Thus, using a single antenna card a mobile computer can operate in several different frequency bands.

High-speed data communications modem

Abstract: A computer network for high-speed data communication, has a data transmission cable with a root and at least one leaf node. A signal conversion system (SCS) is attached to the root, and at least one client station is attached to a leaf node. The SCS consists of a transmitter that transmits down-stream data onto said cable in a first frequency band; and a receiver that receives data from said client stations on a second frequency band; wherein said down-stream data includes synchronization and acknowledgement signals. Each client station has a receiver that receives data on said first frequency band, and a transmitter that transmits data on a second frequency band according to synchronization signals received on said first frequency band. The computer network is controlled by a method comprising transmitting downstream from the signal conversion system (SCS) a control signal having synchronization information on a first frequency band, receiving said control signal at client stations, transmitting up-stream from said client stations to said SCS on a second frequency band, the transmission being timed with respect to said synchronization information, and acknowledging on said first frequency band successful receipt by said SCS of said up-stream transmission. The client station's transmission packets may include requests for reserved slots on said second frequency band for subsequent transmissions, and the SCS has a scheduler operable to determine a start time for requested reserved slots, and transmits the start time for the requested reserved slots. The client stations are operable to wait to continue transmission until after waiting for the start time. Other systems and methods are disclosed.

Transmitter and receiver for orthogonal frequency division multiplexing signal

Abstract: In a communication system, the energy of each bit of the inputted information bit string is diffused over the whole frequency band of the orthogonal carriers, and the energy of the plural bits is multiplexed onto each orthogonal carrier, As a result, even though frequency selective fading has occurred attenuation value of the energy of each bit is some remarkable degrading of the error rate can be alleviated, and changing of the data rate can be easily accommodated by modifying the number of the code multiplexing. In this way, a communication system can be realized which is able to alleviate the performance deterioration due to frequency selective fading, and to easily cope with a modification of the data rate.

Multi-channel synchronous companding system

Abstract: A multi-channel synchronous compander for hearing aids, in which the input signal from an input transducer is directed through a 2:1 front compressor, then through a band splitting filter to divide it into a desired number of frequency bands, then through expander/compressors to provide selected expansion/compression of each frequency band depending on the user's hearing impairment. The outputs of the expander/compressors are summed, amplified and directed to the hearing aid output transducer. The compressor and each expander/compressor are all controlled by control signals derived from the compressed signal level at the output of the front compressor. The use of common control signals for both the front end compression and the expansion removes the need for close matching of temporal performance and improves the output signal fidelity. The front compressor allows the filter capacitors to be reduced in size so that they can be integrated. Sounds above a high level threshold do not change the gain applied to input signal, even when changes are made in the expansion/compression ratios of the expander/compressors.

Subband image coding and decoding

Abstract: In encoding an input picture signal, the input signal is split by subband splitting into plural frequency bands for generating signals of plural frequency bands, and the signals of the respective frequency bands are quantized for generating quantized signals of the respective frequency bands. From these quantized signals of the respective frequency band, the coefficients existing at the same spatial positions of the respective layers resulting from spectrum splitting are extracted for generating a coefficient tree. This coefficient tree is S-scanned in a direction proceeding from the low frequency band towards the high frequency band for generating a scan sequence which is run-length encoded for generating encoded data. In decoding the encoded data, obtained as described above, is decoded by run-length decoding for generating a scan sequence from which a coefficient tree is re-constructed. The coefficients of the re-constructed coefficient tree located at the same spatial positions in the respective layers and the coefficients located at the same spatial positions are dequantized for generating signals of the plural frequency bands. These signals are decoded by subband decoding for reproducing the original input picture signal.

Digital cellular network/system with mobile stations communicating with base stations using frequency-hopping and having enhanced effect of interference diversity

Abstract: PCT No. PCT/FI93/00195 Sec. 371 Date Feb. 17, 1995 Sec. 102(e) Date Feb. 17, 1995 PCT Filed May 6, 1993 PCT Pub. No. WO93/22849 PCT Pub. Date Nov. 11, 1993A digital TDMA/FDMA (Time Division Multiple Access/Frequency division Multiple Access) cellular network system, suitable for a microcellular network and to maximize the advantage to be gained from interference diversity, including base stations forming radio cells, each having a determined static frequency of a channel of the cell and including a first transceiver continuously transmitting control data of the system concerning the cell at the control channel frequency, at least in one predetermined time slot of a TDMA frame. The TDMA frame of the first transceiver includes traffic channels at least in a part of the other time slots. Each base station further includes at least one second transceiver for the traffic channels. The system further includes mobile stations connected to the base stations via a radio path. The traffic channels of the second transceiver units use frequency-hopping, at least in a part of the radio cells, in such a way that, on those traffic channels aligned with the predetermined time slots of the control data of the cell in the first transceiver, substantially all frequencies of the available frequency band, except the control data transmission frequency determined for the cell, belong to the hopping sequence. On those traffic channels which are in the other time slots, substantially all frequencies of the available frequency band belong to the hopping sequence.

RFI suppression in multicarrier transmission systems

Abstract: Mutual radio frequency interference with amateur radio transceivers may be a very serious problem for VDSL systems that use a frequency band up to about 12 MHz. Discrete multitone (DMT) is a strong candidate for the very high-speed digital subscriber loop (VDSL) standard, but it has previously been thought that it is overly sensitive to RFI (both egress and ingress). This paper defines the problems and is a preliminary report on a combination of methods applicable to DMT that solves them.

Design and characterization of a 250-350-GHz fixed-tuned superconductor-insulator-superconductor receiver

Abstract: A fixed-tuned superconductor-insulator-superconductor (SIS) receiver has been designed to operate in the 250-350-GHz frequency band. This receiver has a double-side-band noise temperature of between 35 and 45 K, or about 3h/spl nu//k/sub B/, over its entire operating band. Extensive characterization of the receiver has been carried out using techniques developed for submillimeter waves. The input noise, side-band ratio, 1 dB compression point, optimum LO drive level, and vector near-field beam profile have all been measured experimentally. The measurement techniques and results are presented and discussed.

Using neural network for tool condition monitoring based on wavelet decomposition

Abstract: This paper presents a neural network application for on-line tool condition monitoring in a turning operation. A wavelet technique was used to decompose dynamic cutting force signal into different frequency bands in time domain. Two features were extracted from the decomposed signal for each frequency band. The two extracted features were mean values and variances of the local maxima of the absolute value of the composed signal. In addition, coherence coefficient in low frequency band was also selected as a signal feature. After scaling, these features were fed to a back-propagation neural network for the diagnostic purposes. The effect on tool condition monitoring due to the presence of chip breaking was studied. The different numbers of training samples were used to train the neural network and the results were discussed. The experimental results show that the features extracted by wavelet technique had a low sensitivity to changes of the cutting conditions and the neural network has high diagnosis success rate in a wide range of cutting conditions.

Radio communication system and communication terminal equipments thereof

Abstract: First and second radio communication units communicate using the frequency band of an existing microwave transmission system. A judgment whether the first communication unit is within communication range is performed based on information specifying the position of a base station of another radio communication system which is obtained therefrom. If found to be within communication range, the first communication unit shifts to a state and transmits a registration message to the second communication unit, which is then shifted to a transmission state. Interference in the existing microwave transmission system is prevented with a simple construction and without adding a circuit for confirming the present position of a communication unit.

Radio frequency leakage detection system for CATV system

Abstract: A communication circuit carries at least one signal including synchronizing intervals by which output of the signal by first apparatus coupled to the communication circuit is to be synchronized. A communication method includes selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals. A modulator is provided for selecting and modulating at least a portion of the duration of at least some of the synchronizing intervals. Another communication circuit carries at least a first signal including frequencies in at least a first frequency band. A method of determining whether the first signal is escaping from the circuit includes transporting along the circuit apparatus adapted for receiving the first signal, detecting whether a received signal includes frequencies in the first frequency band, and producing an indication that the received signal includes frequencies in the first frequency band. A detector is provided for transporting along the circuit for determining whether the first signal is escaping from the circuit. The detector is adapted for receiving the first signal, detecting whether a received signal includes frequencies in the first frequency band, and producing an indication that the received signal includes frequencies in the first frequency band.

Passive optical network for dense WDM downstream data transmission and upstream data transmission

Abstract: A passive optical network for the downstream dense wavelength division multiplexing communication of data between a host terminal complex (HTC) and a plurality of optical network units (ONUs), and for the upstream communication of data from the ONUs to the HTC. The network includes a routing device for distributing downstream data signals contained in a common frequency band among a plurality of fiber drop lines for providing a corresponding wavelength to a corresponding ONU. The routing device also combines upstream data signals contained in a frequency band other than the downstream common frequency band, which are input to the routing device on the plurality of fiber drop lines, to a multi-wavelength signal which is provided to the HTC. In a preferred embodiment, the upstream data signals are output by the routing device to a broadcast port.

Gigabit/s indoor wireless systems with directional antennas

Abstract: The design of a high speed (>150 Mb/s) wireless local area network (WLAN), requires that many factors be considered, including technical, economic, and regulatory. A major technical factor is the channel response behavior (multipath) in the indoor environment as a function of the frequency band, building type and radio system architecture. The consequences of designing indoor wireless systems with directional antennas at one or both ends of a line-of-sight (LOS) link are investigated. We determine how narrow the beamwidth must be so that the maximum data rate is not limited by multipath effects. For such beamwidths, simple unequalized two-level frequency shift keying (FSK) or phase shift keying (PSK) modems can be used in place of the more costly and complex "anti-multipath" modems, and data rates above 1 Gb/s may be achieved. The channel impulse response in an empty room is estimated using geometrical optics, observing that with directional antennas, multipath rays must arrive from the same direction as the LOS ray. The link outage probability is then estimated as a function of the antenna beamwidth, and guidelines are established for the selection of the frequency band and antenna placement. Experiments using a 19-GHz 622-Mb/s binary phase shift keying (BPSK) link and 15/spl deg/ beamwidth horn antennas in an office building with plaster walls and large metallized windows have demonstrated error-free performance on both LOS and non-LOS (NLOS) links.

Mode coupling by internal waves for multi‐megameter acoustic propagation in the ocean

Abstract: Broadband parabolic‐equation simulations have been performed with and without internal‐wave sound‐speed fluctuations. The simulations have a center frequency of 75 Hz, a bandwidth of 30 Hz, and a propagation range R of 1000, 2000, and 3000 km. For these cases it is found that acoustic propagation through internal waves is strongly nonadiabatic. In terms of modal travel times, low modes have a negative bias because they couple into higher, faster modes, while the higher modes show a positive bias, indicating preferential coupling into lower, slower modes. The lowest modes show the least travel‐time spread and bias, and these quantities increase rapidly with increasing mode number. Empirically and approximately it is found that bias grows like R2 and spread grows like R3/2. The modal power distributions over frequency are markedly different from the source distributions. Power is distributed roughly equally across the 30‐Hz frequency band for each mode, with 5.6‐dB scintillations consistent with an exponent...

Radio frequency circuit for portable radio communication device

Abstract: Band-pass filters (BPF1, BPF2), and (BPF3) correspond to the reception frequency band for FDD, the transmission band for FDD, and the band for TDD, respectively. An antenna (A1) is used in common for transmission and reception in the FDD and TDD systems. Another antenna (A2) is used for diversity reception in the FDD system. A controller (20) controls switches (SW1) through (SW4). When the FDD system is selected, the reception signal is sent from the antenna (A1) or (A2) through the filter (BPF1) to a reception amplifier (RA), and the transmission signal is sent from the transmission amplifier (TA) through the filter (BPF2) to the antenna (A1). When the TDD system is selected, the reception signal is sent from the antenna (A1) through the filter (BPF3) to the reception amplifier (RA), and the transmission signal is sent from the transmission amplifier (TA) through the filter (BPF3) to the antenna (A1).

Peer-peer frequency hopping spread spectrum wireless system

Abstract: A peer--peer frequency hopping spread spectrum wireless system allows the implementation of full duplex voice/data communications in a single hop peer--peer wireless system. The system uses frequency hopping spread spectrum technique. The frequency band is divided into signalling and message channels. The signalling channels use TDMA with a media access control(MAC) protocol developed for the wireless terminals to access the signalling channels. Once a wireless terminal accesses a time slot on a signalling channel, the corresponding hopping pattern on the message channel is assigned. The message channels use frequency hopping. The hopping patterns of the message channel are chosen such that there is no co-channel interference and minimum adjacent channel interference in the system. Either analog or digital modulation schemes can be used. Synchronization of a transmitter-receiver pair (user-pair) and among user-pairs are achieved through the use of the signalling channels.