Abstract: A bandwidth stabilized PLL in an FPLL has an I channel including an I channel signal, having a pilot, and a Q channel signal. The DC offset, including the pilot, of the I channel signal is determined. The value of the pilot is found by subtracting the determined DC offset from the I channel signal. An error signal is developed from the known value of the transmitted pilot and the determined value of the pilot. The error signal is used to control a gain block for the Q channel for stabilizing the bandwidth of the PLL. Different embodiments are shown for controlling the gain of the PLL from both inside and outside of the PLL.

Abstract: A method for the transmission of digital signals, particularly in the AM bands (broadcasting bands), with high-level modulation, preferably 32 APSK or 64 ASPK, being used for data blocks to be transmitted. At the receiving end, time-periodic measurements of a noise are carried out and noise signals determined therefrom are subtracted from received signals.

Abstract: A method and apparatus providing for a multifrequency receiver with upstream switching of received frequencies. The invention is described in connection with a cable plant having a plurality of modems transmitting at a first frequency. It may be desirable to locate a second frequency having more desirable transmission characteristics and to cause the modems to transmit at the second frequency. It is disclosed to utilize an additional receiver coupled through a switch which may be used to both locate a desirable frequency and to facilitate automatic switching of the cable modems from the first frequency to the second frequency.

Abstract: A method and apparatus for avoiding and or recovering from the latch-up condition in a quantized feedback DC restorer circuit for use in a digital data communication system receiver. An automatic gain control (AGC) circuit controls the level of the received data by comparing the AGC output with a quantized output signal from the DC restorer. A carrier detect circuit detects the presence of data transitions in the quantized output signal, and in the absence of such transitions continuously ramps up the gain of the AGC until such transitions are detected. The carrier detect circuit can be further used to disable, either entirely or partially, the positive feedback path of the DC restorer in the absence of transition in the quantized output signal. The present invention further provides an inherent muting function of the DC restorer output signal in the absence of valid data transitions.

Abstract: This invention concerns a method of increasing coding levels. In this method, an increase in levels is achieved with multi-level coding, where uninterrupted periodic sequences such as an alternating current of the same frequency and phase relation are provided as the code elements, and where the code elements are flagged with respect to one another by changes in amplitude; this increase in levels is achieved by the fact that the next code element begins or ends either with a positive or negative half-period, so that two levels can be marked with one code element. This has the effect, for example, that six levels are obtained instead of three. In numbers, this means that with three levels and two, three, four and five places there are 9, 27, 81 and 243 combinations, and with six levels and two, three four and five places there are 36, 216, 1296 and 7776 combinations.

Abstract: A method of generating one or more pseudorandom noise (PN) sequences for use in spread spectrum communications includes the steps of providing data at an input of memory which stores bits associated with a pseudorandom noise (PN) sequence: changing the data; and for each of a plurality of changes of the data, providing a selected PN bit of the PN sequence at an output of the memory based on the data.

Abstract: When a mobile communication unit (e.g. a cellular telephone) is powered up, the unit must lock on to a local base station, or “acquire” a base station signal, to enable the user to send and receive calls. To lock on a local base station, the mobile unit must determine the delay at which the base station is sending the pseudo random (PN) code. This process is called the “acquisition.” The current art of acquiring a base station involves collecting a set of samples at a particular code phase, or delay, testing the collected sample, and repeating these steps using another code phase until the correct code phase is found. The present invention discloses a method and apparatus for collecting a set of samples at a particular code phase, and simultaneously testing the collected sample and collecting the next set of samples for another code phase.

Abstract: DVD reproducing apparatus which transmits variable-bit rate data on a digital serial bus having a predetermined transmission rate. The DVD reproducing apparatus reproduces data from a record medium in accordance with a control signal to produce variable rate data. The data rate of the variable rate data is detected at predetermined intervals of time, a rate of transmission of the variable rate data is established in accordance with the detected data rate, and the variable rate data is transmitted in accordance with the established transmission rate. The DVD reproducing apparatus includes an MPEG decoder which MPEG decodes the reproduced data and which generates the control signal in accordance with amounts of data stored within various buffers, such control signal being utilized to control the reproduction of the data from the record medium. A receiver, e.g.

Abstract: A method of simultaneous phase synchronization and decoding that makes use of the maximum likelihood criterion is provided. The method is applied to signal packets received at a receiver, wherein the signals have been subjected to convolution encoding at the transmitter. The method consists of calculating branch metrics taking account firstly of firm decisions calculated on the received symbols and secondly of a magnitude that takes account of the phase error between the carrier of the signal and the local oscillator signal used at the receiver, the magnitude weighting the decision variables constituted by the complex digital components of the received symbols. This magnitude is equal to &Sgr;*k for each of the paths studied where: &Sgr;k=&Sgr;Nn=0rk−n·d*k−n.

Abstract: A method provides for an improved compensation Fourier channel characteristics in a wireless communication embodiment. The method identifies one or more information carriers as pseudo pilot tones whose information may be realized to enhance the determination of the complex coefficient of the communication channel.

Abstract: A frequency demodulation apparatus and a method therefor using an arcsin approximation includes: an analog-to-digital converter (ADC) for sampling a frequency-modulated analog signal to convert the frequency-modulated analog signal into a digital signal, and for outputting the sampled values (S0˜Sn) of the digital signal; a first multiplier for multiplying sinusoidal first and second oscillation signals having a phase difference of 90°, by the sampled value Si(O≦i≦n) respectively, and outputting the products as the signals Ii and Qi; a low pass filter for low-pass-filtering the signals Ii and Qi and outputting the low-pass-filtered signals Ii′ and Qi′; a first de-emphasizer for de-emphasizing the high-frequency components of the signals Ii′ and Qi′ and outputting the de-emphasized signals Ii″ and Qi″; a frequency differentiator for delaying the signals Ii″ and Qi″, multiplying and then subtracting the delayed signals, and outputting the subtracti

Abstract: According to the invention, a method and an arrangement is provided for digital radio transmission of data between a fixed station (1) and at least one mobile station (2, 3) at one of a plurality of carrier frequencies (f1, f2, etc.) the data being transmitted in time slots (Z1, Z2 etc.) using time-division multiplex method (TDMA) and, in particular if so-called slow hopping RF modules are used, the change from one carrier frequency to another carrier frequency requiring at least a time period corresponding to one time slot. According to the invention, the data are transmitted in two successive active time slots (Z1, Z2) which are followed by an inactive time slot, in which no data are transmitted. The transmission in two successive time slots (Z1, Z2) takes place at the same carrier frequency.

Abstract: The DC offset error of a quadrature modulated RF signal is corrected by introducing a specific trial offset correction value, D, into the DC offset correction circuits 3, 4 or 5 times, by measuring the carrier power resulting from each trial introduction, and by using the information to determine the DC offset correction components, Icor and Qcor. According to an ideal case first embodiment, specific offset D is employed in three different measurement combinations to determine the correction factors Icor and Qcor. According to an alternative embodiment, a fourth offset correction measurement, needed to estimate a single offset control scale factor, is used to account for an unknown power scale factor A. According to a second alternative embodiment, five offset correction measurements are used to account for separate offset control scale factors for the I and Q channels.

Abstract: The present invention relates to a digital phase-locked loop (PLL) circuit producing an output pulse stream or clock pulses in phase with a reference clock input. The digital PLL circuit consumes reduced power during a phase error compensating operation. The digital PLL circuit of the present invention includes, inter alia, a phase comparator for detecting phase errors of an input signal and a feedback signal; a charge pump for sourcing and/or sinking current in response to control signals based on a phase error detected in the phase comparator; and a sensing circuit for detecting a simultaneous activation of the sourcing and the sinking of the charge pump and for generating a sensing signal corresponding to the simultaneous activation, whereby the phase comparator generates in response to the sensing signal the control signals to inactivate the sourcing and the sinking of the charge pump. The charge pump is also activated in response to the sensing signal.

Abstract: A generalized quadrature product subcarrier modulation system applies subcarrier modulation to quadrature modulated signals with constant envelope modulation suitable for efficient sinewave and squarewave subcarrier modulations. The quadrature subcarrier modulation enables the addition of new signals to the in-phase and quadrature phase signals with spectral isolation while maintaining a constant amplitude waveform.

Abstract: A receiver for enabling one-way communications in a GHM network which does not interfere with or reduce the capability of the GHM network. The receiver detects a small modulation factor signal present on the GHM signal normally transmitted by the GHM transmitter. If the frequency of the modulated signal corresponds to a pre-defined frequency, then the receiver generates a command signal to, for example, a relay, annunciator, or other external device. More particularly, and in one embodiment, the receiver includes a filter which partially isolates the GHM energy from the lower 60 Hz harmonics. The receiver also includes a envelope detector coupled to filter. The envelope detector is coupled to a frequency detector. The frequency detector is coupled to a command decoder. The command decoder determines whether a plurality of AM modulation frequencies are present on the received signal.

Abstract: In a PCM modem system in which equivalence classes are used to communicate information from a transmitter to a receiver, a method is provided to solve the problem of 180° phase reversals in the communications channel which result in a garbled transmission. This is accomplished by remapping the equivalence classes into a form that can be differentially encoded and decoded such that equivalence class identity is not lost during a phase reversal of the channel.

Abstract: A flexible BPSK (binary phase shift keying)/QPSK (quadrature phase shift keying) modulator of the wideband code division multiple access system. The flexible modulator includes a first link selecting unit for selecting a modulating type after receiving a signal of a reverse channel, alternately, an I (In-phase) signal and Q (quadrature) signal of a forward channel for which a spread modulation is to execute, a Hadamard spreading unit permits Hadamard code spreading modulation after receiving the I and Q signals from the first link selecting unit, and a spreading means for executing a spread modulation for a pseudo-noise (PN) code of the exchanged I and Q signals. The present invention can reduce the amount of hardware required by controlling a similar parts of the channel in a wideband code division multiple access system, especially a BPSK/QPSK modulation parts, by an external register and a flexible channel structure for joint control between channels.

Abstract: A frequency synthesizer of the phase locked loop type and particularly useful for frequency hopping applications includes means (8) for achieving fast frequency and phase lock. In one embodiment the synthesizer is steered to a new frequency value by a DAC 10 which controls a VCO (5) input voltage. Subsequently, the phase of the synthesizer output is locked to that of the reference frequency oscillator (1) by resetting the feedback frequency divider (6) at the point in time when a rising edge of the reference frequency is detected. In a second embodiment, rapid frequency and phase lock is achieved by resetting the feedback frequency divider (6) on every rising edge of the reference frequency while the feedback loop is disabled, until the detected phase difference between the reference frequency and the divided VCO frequency reaches a minimum value.

Abstract: A method 100 for improved decoding of received convolutionally coded input data uses data scaling to provide near ideal turbo decoding. The method includes a first step of loading 102 a portion of the input data into a buffer. A next step includes calculating 104 a mean of the data in the portion of the input data. A next step includes computing 106 a root-mean-square value of the portion of the input data using the mean from the calculating step. A next step includes deriving 108 a scaling factor from the root-mean-square value of the computing step, and a next step includes scaling 110 the portion of input data by the scaling factor of the deriving step.