Abstract: An orthogonal code division multiple-access communications system comprised of a plurality of transceivers respectively employing orthogonal noise code mate pairs of a type having autocorrelation functions upon detection which when linearly added together compress into a lobeless impulse and wherein the same single time slot is utilized by all of the users in the system. Each user is assigned a different unique noise code pair consisting of code mate pairs that are selected from a subset of multiplexed noise codes whose cross-correlation function value is equal to zero at a time when all the code mate pairs compress to an impulse, i.e. .tau.=0. The described arrangement enables random access, or direct call-up, to be accomplished with no interference between the users while using different noise codes for each user.

Abstract: A television transmission system for asynchronously transmitting a television picture as a plurality of video samples over a narrow bandwidth medium from at least one remote transmitting site to a receiver at a base station. Improved synchronization between the transmitter and receiver are achieved by a dotting pattern consisting of alternating logic ones and zeros being sent by the transmitter to precede the video samples such that a sampling clock at the receiver synchronizes to the phase of the dotting pattern and thereafter samples the video signal. The video signals are also preceded by at least one predetermined digital word which identifies the particular remote transmitter and prepares the receiver to begin receiving the video samples. DC restoration circuitry determines the average value of the incoming video signals and to add an appropriate DC offset to the video signals to correct for any change in the gray scale of the video samples.

Abstract: A wireless communication system for simultaneously operating a plurality of portable communication devices each having a fixed station on different frequencies within a specified area without harmful interference caused by receiver desensing and intermodulation products.

Abstract: A system for time-period modulating (TPM) a subcarrier in accordance with the amplitude of an input signal includes generating a ramp signal of constant slope, comparing the ramp signal with the input signal, and resetting the ramp signal when the ramp signal reaches the input signal. Each time the ramp signal is reset, a clock pulse is counted. These clock pulses are counted in cyclic groups of N. After each clock pulse is counted, the then attained count is converted to a value of a sinusoid about some reference. The values for each of N counts define one sinusoidal cycle of the modulated subcarrier. Converting these values to voltage levels produces a sinusoidal stepwave which has a period linearly proportional to the amplitude of the input signal at the time.

Abstract: A pulse interference cancelling system for spread spectrum signals utilized in a digital noise coded communications system. The system includes a first and second noise coded signal channel located in a noise coded signal receiver which also includes a demultiplexer for providing a pair of received noise coded signals which were initially generated, multiplexed and transmitted to the receiver. First and second coherent detector means are coupled to both signal channels, the first being directly coupled thereto so that no signal delay exists but the second is coupled to the two signal channels by means of respective first and second variable time delay circuits having a delay substantially equal to the bit width of each digital code as well as a vernier delay which is adapted to delay the phase of any received pulse interference in the respective channel so that it is exactly 180.degree. out of phase with the same undelayed pulse interference.

Abstract: A noise coded communications system which eliminates continuous wave (CW) interference while providing no loss or degradation of the desired signal includes the variable delay line and a linear adder coupled to the output of the front end section of a multiplexed noise coded receiver which further includes an active coherent detector comprised of a multiplier and an integrator. The variable delay line provides a delay whose order of magnitude is substantially equal to the bit width of the multi-bit binary noise code utilized and is further varied until any CW interference signal received along with the noise coded signal is shifted in phase by 180.degree. and inverted with respect to the input interference signal. The inverted interference signal and the non-inverted input interference signal are summed together in the linear adder whereupon a cancellation of the interference signal occurs while providing no degradation in the desired signal.

Abstract: A switching system for performing line to line or group to group switching of communication signals modulated by multiplexed noise codes. The noise codes comprise a subclass or set of multiplexed noise codes consisting of code mate pairs which provide an impulse autocorrelation function when detected and furthermore crosscorrelate to zero at a time when the code mate pairs compress to an impulse providing thereby orthogonal operation, meaning that there is no mutual interference between any of the input/output lines when the signals are translated thereon concurrently.

Abstract: An adaptive equalizer performs equalization at IF, demodulates the input signal and then generates the equalization coefficients at baseband from the demodulated data. Coefficient updating can be done on a non-real time basis and coefficients for individual bursts stored in a coefficient memory for retrieval when the same burst occurs in the next frame, thus obtaining a pseudo-continuous equalization for each burst. The error signal is derived from demodulated equalized data and correlated with demodulated unequalized data to generate the correlation coefficients, and individual error signals from each channel can be combined into a single composite error signal for correlation purposes.

Abstract: An FM discriminator useful in a modem circuit includes a tank circuit coupled to an input receiving an FSK input signal. The FSK input signal is resistively coupled to an input of an operational amplifier having its output also coupled to that input. The other input of the operational amplifier is connected to the tank circuit and to an input of a comparator. The other input of the comparator is connected to the output of a circuit which produces a signal that lags by 90 degrees the signal produced by the tank circuit. The output of the comparator is used to synchronously chop the output signal of the first operational amplifier in such a way as to pass the operational amplifier output signal when the comparator output signal is a "1" and to invert the operational amplifier output signal when the comparator output signal is a "0".

Abstract: Cancellation of pulse interference with no loss in the received level of the desired signal is obtained for a spread spectrum system which utilizes orthogonal multiplexed noise codes which when orthogonally multiplexed, matched filter detected and linearly added, compress to a lobeless impulse. The noise codes are comprised of binary noise codes which compress to a code bit width .tau.. The pulse interference is eliminated by means of a variable delay line and a linear adder coupled to the output of a linear adder which operates in combination with a pair of matched filters to provide a lobeless impulse signal. The delay line is varied to provide a 180.degree. phase shift for any pulse interference signal which occurs in time coincidence with the lobeless impulse. The original and phase shifted pulse interference signals are added together in the linear adder and in the process cancel one another while leaving the lobeless impulse signal with no reduction in signal amplitude.

Abstract: Substantially complete cancellation of continuous wave or slowly varying continuous wave interference with no loss in the received level of the desired signals is provided for a spread spectrum system which utilizes orthogonal multiplexed noise codes which when orthogonally multiplexed, detected in a matched filter detector and linearly added, compress to a lobeless impulse. The noise codes are comprised of binary digital noise codes which compress to a code bit width .tau.. The CW interference is eliminated by means of a variable delay line and a linear adder. The delay line operates to provide an interference signal from the input interference signal which is exactly 180.degree. out of phase with respect to the input interference signal. By adding the delayed signal to the input signal in the linear adder, a total cancellation of the interference signal occurs while the signal level of the noise coded communications signal remains unchanged.

Abstract: A pulse compressor for multiplexed noise codes generated with transposed code mate pairs and which comprise expanded noise codes of the code mates where the first expanded code is generated by delaying the inverse of one code mate by a predetermined time delay and adding it to the other code mate and wherein the second expanded code is generated by delaying the inverse of the other code mate, forming its complement and adding it to said one code mate. The means utilized comprises means for compressing the two expanded codes collectively by summing and differencing of the codes in a repetitive pipelined sequence until a final pair of codes are outputted which are lobeless and equal to the basic mate pair.

Abstract: A global positioning system comprises an RF receiver for receiving L.sub.1, L.sub.2 p-code or ca code modulated frequency outputs from one or more space vehicles, a multiplexer operably connected to the receiver multiplexes the L.sub.1 and L.sub.2 signals to the receiver, and code and carrier tracking loops operably connected to the receiver, each loop including a plurality of filters, one for tracking line-of-sight dynamics and another for determining ionosphere effects on the L.sub.1 and/or L.sub.2 signals.

Abstract: In a method for decoding a received biphase-coded signal, a signal edge (2) is detected and its polarity determined in intervals of two periods (2T) for reconstructing the transmitted data. This allows the transmission rate of the signals to be increased up to the maximum frequency limit of the logic family used. By this means data sets (B1-BN), for example in biphase-level code, can be transmitted with start characters (A) optimized for minimum time loss. A decoder can be implemented with very simple monostable multivibrators and a small number of gates. Since sampling controlled by means of a digital counter is not required, the transmission rate can be increased by a factor of 8 to 32.

Abstract: A frequency translator receives an input frequency signal and an offset frequency signal, and processes the signals digitally in order to obtain an output from a multiplexer. Pulse trains derived from the input frequency are provided to an N-bit shift register. The outputs from the shift register are provided to a multiplexer which is controlled by count signals from the offset frequency. The multiplexer provides, as its output, a single sideband output at a frequency equal to (f.sub.c -f.sub.os)/N, or (f.sub.c +f.sub.os)/N.

Abstract: A telemetry system for sensing remote physical events and for transmitting and boosting a digital data signal representing the sensed events on a transmission line, which comprises a master clock and a plurality of sensing stations for sensing local data. The sensing stations inject local data onto the transmission line as a digital data signal, and a controller/receiver receives the digital data. The master clock initializes the system timing and generates a sync signal. Each sensing station includes a booster subsystem for receiving the local digital data and for injecting the digital data onto the transmission line as a digital data signal. During system start up, each booster subsystem claims a slot, in accordance with an organizational process, for injecting the digital data signal onto the transmission line. The booster subsystem in each sensing station further includes a booster circuit for boosting the digital data signals which are propagating on the transmission line, as well as the sync signal.

Abstract: The described invention relates to a phase-locked loop circuit arrangement for synchronizing an oscillator to a Non-Return-To-Zero data signal in which a transition from one potential level to another represents a data transition from one binary value to another.A local clock signal is provided by means of a controllable oscillator and a phase comparator compares the phases of the data and clock singals with one another. The frequency of the oscillator is adjusted by means of a control signal in dependence upon an amount by which the phase of the data leads that of the clock signal and vice versa. In any cycle of the clock signal in which the phase of the clock signal leads that of the data and in which no data transition occurs the application of a control signal to the oscillator is inhibited.The invention is particularly applicable to teletext receivers.

Abstract: A transceiver for use with a digital telephone apparatus adapted to be connected for duplex communication to a telephone speech transmission line includes a receiving unit and a transmitting unit. The receiving unit processes an incoming serial ternary level signal stream composed of alternate mark inverted (AMI) encoded pulses and received from the transmission line. A compensation filter compensates distortions of the transmitted signals. A full wave rectifier circuit generates unipolar output signals. A pulse detection circuit derives rectangular pulses from the unipolar output signals. A phase-locked loop (PLL) circuit reconstructs a clock pulse train from the rectangular pulses. The transmitting unit receives an outgoing serial data stream from the telephone apparatus and internal clock pulses from that PLL circuit and includes means for converting the pulses of the outgoing data stream into AMI encoded signals.

Abstract: An orthogonal code division multiple access communications system is disclosed involving multiple users while providing orthogonal operation, meaning that there is substantially zero interference between users. All of the users employ a mutually different time permutation of the same multi-bit direct sequence pseudo noise code with a synchronous time reference for all of the users being established through a central node or station which communicates with all of the users preferably through a loopback synchronous timing scheme. Each pseudo noise code is followed by an extra processing bit that balances the number of one and zero bits in the composite information bit which has the effect of providing a code structure which will have a cross-correlation value of zero with the other time permutated codes which enables the system to operate as an orthogonal system.

Abstract: A portable frequency modulation transmitter (1) for voice or data is disclosed for operation at infrared frequencies. The transmitter comprises keyboard (200) or microphone (402) input capability and dual modes of use. In the data mode, carrier is generated when the keyboard is operated and is not generated when the keyboard is idle in order to conserve power. In the voice mode, either voice or data may be transmitted, data having priority over voice. A series connection of two variable modulus counters (302, 303) and other counters (304, 305, 306) provide a frequency shift keyed data signal, marker data signal, marker data frames between data frames, parity insertion and other features. In the event that the local battery power level falls below a particular level, a particular word is inserted in the applied binary data input.