Abstract: The levels of received time-division multiple access (TDMA) signals may vary widely from section to section. In DC-coupled amplifier circuits, the received signals are distorted by offset voltages. Conventional correcting or balancing methods use control mechanisms which do not allow for level variations or offset drift and tend to result in miscompensation of individual signal sections. Other methods depend on time intervals defined in the received signal and having a known average value. It is the object of the invention to provide a correcting method and a circuit arrangement for carrying out the same which achieve a self-adjusting, not widely varying (floating) correction value, thus avoiding miscompensation. This is accomplished by selecting the individual time slots in a comparator with the aid of limit value.

Abstract: Frame synchronization for data transmitted using quadrature amplitude modulation is achieved by providing that one symbol per frame is chosen from a larger signal point constellation than the remaining symbols. Thus, bits are assembled into groups of unequal size to control the mapping between the data and the signal points. Where constellations having a number of points not equal to a power of two, these may be coded in groups; or the data may be converted into a mixed-base number the bases of which correspond to the number of points in the respective constellations.

Abstract: The channels of a GPS receiver system are dynamically allocated during acquisition mode to hierarchically chain a slave channel module to a master channel. Each channel circuit includes two correlators, where each correlator receives a digitized received GPS signal and a delayed local PRN reference code signal to provide an output signal to an accumulator. During acquisition, the system provides two correlator channels where each channel includes two correlators for a total of four correllators. A PRN reference code signal is progressively delayed to provide a sequence of progressively delayed PRN reference code signals, where one of the sequence of progressively delayed PRN reference code signals are applied to each of the correlators. Each correlator channel also includes a digital mixer which receives a digitized GPS IF signal and a digital carrier reference signal and which provides the digitized received GPS signal.

Abstract: A method and apparatus for processing convolution coded data. The method and apparatus have lower computational requirements, while still reducing or eliminating errors caused by noise or distortion. A path metric value associated with each decoder state is updated upon the receipt of each incoming signal value. The path metric value is formed by: (1) identifying those permissible transition(s) to that decoder state that are represented by symbols having the minimum branch metric compared to the received signal value; (2) identifying those permissible transition(s) to that decoder state that originate from states with the minimum previously-computed path metric value; and (3) comparing the transitions identified in the first and second steps. From this comparison, the identity of the transition with the lowest path metric value is derived. Thereafter, the path metric chosen is stored for that given state.

Abstract: A method and apparatus are shown for generating and transmitting very short and widely separated high frequency sine-wave pulses of electromagnetic energy into space. A transistor, a charging capacitor, and an inductor are coupled into a first series loop path to form a discharge circuit. A bias voltage source, the same charging capacitor, and a charging resistor are coupled into a second series loop path to form a recharging circuit. The bias voltage source is selected to be capable of biasing the forward conduction path of the transistor near its breakdown condition. An original information signal is sampled upon each occurrence of a periodic reference signal, and the transistor is then triggered into its breakdown or avalanche mode. The starting times of successive transmitted pulses are modified in accordance with a pulse position modulation protocol.

Abstract: In a scanning receiver for receiving a signal by scanning the frequency of a received signal, the speed of a scanning operation is made fast with skipping non-modulated signals and digital signals. AF signal is changed into A/D converted values, and first and second amplitude distribution are respectively formed from A/D converted values. Non-modulated signal is discriminated based on the first amplitude distribution, and digital signal is discriminated based on the second amplitude distribution.

Abstract: An improved isolation circuit for protecting data communication equipment from high voltages on a transmission line has two mixers. The first dual balanced mixer (DBMX) translates a data signal on the transmission line to a high frequency and is coupled with an isolation circuit to the second DBMX. The second DBMX then translates the output of the first DBMX to an isolated data signal with the same frequency content as the original data signal.

Abstract: A decision directed carrier recovery circuit comprising a demodulator for adjusting a frequency and a phase of an input carrier to demodulate an original signal therefrom, a signal decision unit for deciding an output signal from the demodulator as a specified symbol, and a phase error detector for receiving the output signal from the demodulation and an output signal from the signal decision unit and detecting an phase error between the received signals using bit shifting instead of division.

Abstract: A self-timed interface (STI) in which a clock signal clocks bit serial data onto a parallel, electrically conductive bus and the clock signal is transmitted on a separate line of the bus. The received data on each line of the bus is individually phase aligned with the clock signal. The received clock signal is used to define boundary edges of a data bit cell individually for each line and the data on each line of the bus is individually phase adjusted so that, for example, a data transition position is in the center of the cell.

Abstract: A network port configurator device for automatically configuring a system having network workstations and corresponding network equipment of various physical protocols. The network port configurator comprises a plurality of input and output ports for receiving physical wiring to which the workstations and network equipment are attached. Detection circuitry attached to the input and output ports determine the physical protocol of the attached workstations and network equipment by determining a characteristic of the attached equipment. Examples of identifying characteristics include a characteristic impedance, a characteristic voltage, and a characteristic cable identification of the workstation. Logic circuitry uses this information to control a circuit switching mechanism that connects the input ports to the output ports.

Abstract: A high efficiency speech coding apparatus which can eliminate repetitions of high efficiency speech coding and decoding processes of a digital speech signal upon inter-office transit switching without employing a special exchange and a transit switching system which can prevent degradation in quality of speech information and increase in encode and decode processing delay upon transit switching are disclosed. The apparatus repetitively inserts a synchronizing signal into an output speech signal to an exchange and supervises an input speech signal from the exchange to detect a synchronizing signal in order to determine whether the destination of connection of the exchange is a subscriber line or another trunk circuit connected by way of another high efficiency coding apparatus.

Abstract: In each radio base station of a cellular mobile communication network in which a mobile station is communicative with the radio base stations through a time division multiplex radio link, a transmitter/receiver serves as a synchronization system in cooperation with a base station control unit (35) to synchronize a down-link radio signal generated from a transmission frame generator at a transmission time with a like down-link radio signal transmitted from a different one of the radio base stations. The synchronization system has a received frame regenerator for detecting a reception time of one of frames of an up-link radio signal directed from the mobile station to the different station. A timing controller calculates a time difference between the transmission and the reception time. Controlled by the control unit in accordance with the time difference, the timing controller controls, in turn, the transmission time.

Abstract: A data transmission scheme for use in a low channel bandwidth-to-modulation symbol rate ratio (BW:R.sub.S) application employing a linear modulator for producing in-phase and quadrature (I and Q) components of a data stream inputted at a predetermined symbol rate. This transmission method allows for the recovery of signals having unfavorable delay spread characteristics. That is, a specialized function is used to process the I and Q components, whose time domain transfer characteristic remains within a predetermined range of a data constellation point for a duration that exceeds 25 percent of a symbol period corresponding to the predetermined symbol rate. The processed response is then band-limited to produce a modulation signal that is usable in the low BW:R.sub.S application.

Abstract: Pluralities of estimated desired and interference signal sequence candidates corresponding to the states of transition of desired and interference signals estimated to receive are sequentially generated in a state estimation part 40, from which they are provided to a desired signal estimation part 10 and an interference signal estimation part 20. These estimation parts 10 and 20 generate estimated desired and interference signals from the sequence candidates in accordance with conversion parameters from a channel parameter estimation part 50. A signal of their sum is subtracted in an error estimation part 30 from a received signal to yield an estimation error signal .epsilon.. The state estimation part 40 estimates estimated desired and interference signal sequences for the generated sequence candidates.

Abstract: The present invention provides a novel Geometric Harmonic Modulation (GHM) system. The GHM system operates in two modes, a preamble mode and a traffic mode. During the preamble mode, n+1 frequencies are each offset by a predetermined phase offset in a transmit unit and passed through a channel to a receive unit. The set of phase offsets is used as the spreading code in the transmit unit, and also acts as an `address` of receive units to transmit to. The receive unit monitors preamble signals to determine the phase offsets. When it recognizes a set of phase offsets, or `address`, which pertains to itself, the receive unit stores the phase offsets and uses these phase offsets to despread and decode the appended message. After the preamble mode is finished, the transmit unit enters the traffic mode and requests the message to be transmitted from the message source. A traffic carrier waveform is created by multiplying tones, each having its specific phase offset.

Abstract: A numerically controlled oscillator that outputs a complex exponential value (sine and cosine). The numerically controlled oscillator inputs a scalar phase increment and uses the scalar phase increment to approximate a complex exponential phasor increment. A complex multiplier multiplies the exponential increment by an exponential value previously output from the oscillator to yield a multiplication result. A recursive amplitude normalizer, connected to the complex multiplier, normalizes the multiplication result to yield the complex exponential value.

Abstract: A monolithic direct digital UHF/L-Band receiver for receiving and processing a UHF/L-Band analog signal and deriving digitized samples, the receiver operating in a tuning frequency range centered at a center frequency and having a baseband frequency, a lower bandedge frequency, and an upper bandedge frequency. The receiver comprises: a substrate; an analog-to-digital converter, mounted on the substrate, for digitally sampling at a sample rate the UHF/L-Band analog signal; a heterodyning circuit, coupled to the analog-to-digital converter and mounted on the substrate, for mixing the digitally sampled signal with a mixing signal thereby shifting the center frequency of the tuning frequency range of the sampled signal to the baseband frequency; and means, coupled to the heterodyning circuit and mounted on the substrate, for decimation filtering and decimating the mixed signal to obtain a second sample rate lower than the sample rate.

Abstract: A jitter generating device for use in a data communication system. The device has a repeating unit with an input and an output connected in use to receive data from the data communication system and to repeat the data onto the data communication system respectively. A clock signal generator generates a clock signal which is fed to the repeating unit to control the rate at which data is output onto the data communication system. A clock phase (jitter) modulating unit modulates the phase of the clock signal output by the clock signal generator.

Abstract: Convolutionally encoded information subjected to channel intersymbol interference is decoded by calculating the minimum cost path through a trellis. The trellis terminates in known states. Exploiting the open architecture of the coprocessor, the minimum cost state is checked to ascertain if it is the known, that is, correct state and if it is not, the possible known states are searched by the DSP inside the ECCP active register and the state with the lowest cost amont the possible states is selected.

Abstract: A device and method of adjusting an equalizer in a digital communications receiver in response to relative velocity between the communications receiver and a communications transmitter. A radio frequency receiver receives a radio frequency signal from the communications transmitter through a communications channel, and an analog to digital converter digitizes a first portion of the radio frequency signal during a first time period, and generates a first data signal made up of digital samples. The analog to digital converter also digitizes a second portion of the radio frequency signal during a second time period and generates a second data signal, also made up of samples. A channel estimator estimates characteristics of the communications channel in response to a portion of the first data signal, and generates a first channel estimate in response thereto.