Abstract: A power amplifier, particularly a gradient amplifier of a nuclear magnetic resonance tomography apparatus, has at least one switched output stage containing a power bridge circuit formed by a number of switch elements, the bridge circuit being connected to a floating intermediate circuit voltage, as well as at least one digital pulse width modulator that generates pulse-width-modulated control signals for all switch elements of the power bridge circuit from digital input signals in order to generate at least one output stage voltage according to an output stage switching clock.

Abstract: A set of formats and protocols is proposed for a satellite communications system. In these formats, a pilot signal (PS) is inserted after every 25 or 29 data symbols. The formats consist of SCPC frames (F) which may contain either data (D) and in-band signalling information (SU), or only signalling information (SU). In either case, the contents of each frame (F) are error-correction coded before transmission with the same coding rate. Each data frame (F) carries the data content of an integral number of input user data frames (M), each of which comprises four subframes. Different symbol transmission rates are used for different input data rates, the symbol transmission rates being selected so that their different synchronizing clock rates can easily be obtained from a common clock. Data bursts may be preceded by a constant power level preamble (P). The formats and protocols satisfy the requirements of a high data rate satellite communications system.

Abstract: This invention produces data packets that can vary in length and/or data compression ratio. First, an algorithm is employed to transform a data signal into fixed or variable length data packets at variable data compression ratios. If the algorithm produces fixed length data packets, the fixed length data packets are then converted to variable length data packets, which include only the valid data bytes of the fixed length data packets. Finally, the variable compression ratio, variable length data packets are provided with length codes at each end of each data packet to facilitate bidirectional searching and decompression. The transition from fixed to variable length data packets employs a buffer which stores the fixed length data packets until the fixed length data packets are converted to variable length data packets.

Abstract: A network transceiver is configured to receive a complex modulated carrier signal from another network transceiver via a network medium. The complex modulated carrier signal may be payload encoded utilizing one of a plurality of payload encoding specifications based on network distortion characteristics. The transceiver includes an A/D converter and a mixer circuit for generating a baseband I-signal and a baseband Q-signal and a slicer which scales the baseband signals to enable complex decoding constellation coordinates to be integer values and mapping calculations to be performed with integer values.

Abstract: A waveform equalizer which can improve a quality of a read signal by certainly correcting asymmetry in the read signal and a data reproducing apparatus using the waveform equalizer. The waveform equalizer performs a waveform equalization to the read signal and is constructed by: inclination discriminating means for detecting an ascending slope portion and a descending slope portion of the read signal; a filter for performing a filtering process to the read signal; and characteristics switching means for switching frequency characteristics of the filter in accordance with a discrimination output of the inclination discriminating means.

Abstract: An isolation system for terminating a phone line is provided. The invention may comprise a capacitive isolation barrier across which a digital signal is communicated. Clock recovery circuitry may be employed on one side of the isolation barrier to extract timing information from the digital signal communicated across the barrier. An isolated power supply may also be provided on the isolated side of the barrier, whereby direct current is generated in response to the digital data received across the isolation barrier. A bidirectional isolation system is provided whereby bidirectional communication of digital signals is accomplished using a single pair of isolation capacitors. In preferred embodiments, the digital data communicated across the barrier consists of digital delta-sigma data signals multiplexed in time with other digital control, signaling and framing information.

Abstract: At a transmitter, a measurement array is constructed from various combinations of frame bits, including at least one combination Which includes many frame bits and at least one combination which includes only a few frame bits. The measurement array is transmitted along with the frame bits. Upon receipt of the frame at a receiver, a parity check is performed on the received frame bits and on the measurement array, resulting in the creation of a symptomatic array. The symptomatic array can be accumulated during the course of successive frames. After a sufficiently high number of frames, it will become clear from the values of the elements in the accumulated symptomatic array which bits in the symptomatic array are saturated and which are not. The accumulated symptomatic array is then mapped to a BER estimate.

Abstract: The invention provides systems and methods that include, inter alia, wireless communication systems that integrate wireless receivers and transmitters with host computer platforms and that include a data access channel that delivers into the memory space of an application program digital data that is representative of a base band modulated signal. Accordingly, these systems can employ wideband digitization of an incoming signal, such as an RF signal, direct the digitized data into the application memory space of a general purpose workstation, and allow an application program operating on the general purpose work station to perform the digital signal processing that obtains the information encoded within the digitized signal.

Abstract: A digital phase locked loop (PLL) frequency synthesizer includes a 1-bit numerically controlled oscillator (NCO) to negate the requirement that a VCO frequency be an integer multiple of its reference frequency. Thus, in accordance with the principles of the present invention, a direct digital synthesizer (DDS) or numerically controlled oscillator (NCO) is used to form a frequency divider in a feedback path of a PLL. Thus, a synthesizer with fine frequency control and very fast settling time is disclosed. The conventional integer-ratio relationship between the reference frequency fREF and the synthesized output frequency signal fVCO is overcome by replacement of a conventional VCO divider in a feedback path of a digital PLL with a 1-bit NCO. This allows the reference frequency fREF to be greater than the channel spacing, i.e., the channel spacing can be smaller than the reference frequency fREF.

Abstract: The invention is a method of estimating the time and frequency response of at least one desired signal received by at least one antenna, based on Gradient Optimization techniques. Through the use of gradient optimization techniques and efficient DFT processing, the invention provides frequency response estimates that require fewer computations than prior art decision-directed channel estimation devices.

Abstract: There is provided a radio-signal transceiver including an antenna, a radio-signal receiver receiving a message having been received through the antenna, addressed to a calling number of the radio-signal transmitter, a main controller controlling an operation of the radio-signal receiver, an interface through which a command is input into the radio-signal receiver, an auxiliary controller analyzing the command and transmitting a signal indicative of an operation represented by the command, to the main controller, a display screen displaying the message, and a message analyzer analyzing the message and extracting data to be registered, the auxiliary controller making judgement as to whether a received message is able to be registered, based on analysis made by the message analyzer, and registering a received message automatically or manually, if a received message is judged to be able to be registered.

Abstract: A coding method for a pulse transmission system specifies temporal and/or non-temporal pulse characteristics according to temporal and/or non-temporal characteristic value layouts having one or more allowable and non-allowable regions. The method generates codes having predefined properties. The method generates a pulse train by mapping codes to the characteristic value layouts, where the codes satisfy predefined criteria. In addition, the predefined criteria can limit the number of pulse characteristic values within a non-allowable region. The predefined criteria can be based on relative pulse characteristic values. The predefined criteria can also pertain to spectral properties and to correlation properties. The predefined criteria may pertain to code length and to the number of members of a code family. The pulse train characteristics may pertain to a subset of the pulse train.

Abstract: A code specifies characteristics of pulses transmitted and received by an impulse transmission system. The invention provides methods for defining non-allowable regions within pulse characteristic value range layouts enabling non-allowable regions to be considered when generating a code. Various approaches are used to define non-allowable regions based either on the pulse characteristic value range layout or on characteristic values of one or more other pulses. Various permutations accommodate differences between temporal and non-temporal pulse characteristics. Approaches address characteristic value layouts specifying fixed values and characteristic value layouts specifying non-fixed values. When generating codes to describe pulses, defined non-allowable regions within pulse characteristic value layouts are considered so that code element values do not map to non-allowable pulse characteristic values.

Abstract: A system for synchronizing a clock includes a phase-locked loop (PLL) circuit that generates or receives (304) timing errors that are based on timing information from multiple timing sources. Gain blocks (214) weight (306) the timing errors, which are then combined (308) into a loop time error. A loop integrator (226) integrates (310) the loop time error to produce an input used to adjust (312) an oscillator frequency. A corresponding oscillator clock signal is fed back (240) to one or more phase detectors (206), which receive (302) timing reference signals and generate timing errors. When a timing errors indicates that a problem exists with a timing source, the impact of the problematic timing source is reduced (430, 504), or oscillator frequency adjustments are suspended (608). When used on a satellite (700), at least one of the timing errors can be based on times of transmit and times of arrival of time messages exchanged between the satellite and its neighbors (716).

Abstract: A variable bit rate coder, and an associated method, for encoding a frame of speech, such as frames of data generated during operation of a communication station operable in a cellular communication system. Selection of the coding rate is made responsive to indicia of actual coding performance of a coder at more than one coding rate.

Abstract: Carrier frequency and frames are synchronized in bursty data transmissions over unknown channels that cause inter-symbol interference. The synchronization procedure comprises two stages. The first stage performs a time-domain processing of samples to exploit a periodic signal repetition and to extract the coarse timing, the frequency offset and also to resolve frequency ambiguities. The second stage estimates the fine time offset of a received modulation signal. A coarse estimate of a frame start position of a received sequence of desired data samples may be improved by using the coarse timing estimate to generate frequency-domain received samples. A frequency-domain correlation is then determined between the frequency-domain received samples and noiseless samples. When using a fixed number of training samples, a “sandwich” preamble (“sandamble”) is utilized to achieve greater efficiency than a conventional repetition preamble.

Abstract: A receiver of a frequency-shift-keying, continuous-wave radar comprises at least sampling means taking real samples of the signals in each reception channel and extrapolation means, the extrapolation means producing fictitious samples synchronous with the real samples, the reception signals being formed out of real samples and fictitious samples. Application especially to radars fitted into automobiles.

Abstract: The invention determines the geographic location of a subscriber unit within a CDMA communication system. At least one base station transmits a spread spectrum signal with a chip code sequence unique to that base station. A subscriber unit receives the base station signal and transmits a spread spectrum signal with a unique chip code sequence time synchronized with the chip code sequence of the received base station signal. The base station receives the subscriber unit signal and compares the chip code sequence of the received subscriber unit signal with the chip code sequence signal transmitted by the base station to determine the location of the subscriber unit.

Abstract: A Code Division Multiple Assess (CDMA) receiving station includes first finger (310), a second finger (312), and a searcher (314). Assignment and deassignment of second finger (312) are made in part by determining the gap between the first finger and the second finger, or between the first finger and an energy peak detected by the searcher. Assignment and deassignment of second finger (312) are also made in part by selectively slowing the Time Tracking Loop (TTL) of both fingers when appropriate thresholds are crossed.

Abstract: Methods and systems are provided for channel tracking utilizing multi-pass demodulation in which, during the second pass, decoded symbols are treated as known symbols which are used to calculate the error term used in updating the propagation characterization during the second pass. This allows a higher bandwidth to be used for updating the propagation characterization while known symbols are being processed. In particular, the propagation characterization may be provided by a channel tracker or a multi-antenna receiver, such as an interference rejection/combining (IRC) system, with an impairment correlation matrix estimator or a combination of both.