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 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: 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: 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: 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: 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: An adaptive interference cancelling system for multibit spread spectrum noise codes wherein a plurality of users in a mobile subscriber access system each operates with a different noise code. Each user receives a composite signal which includes a desired noise coded signal from another user plus any unwanted interference noise coded signals from other like users in relatively close proximity. The RF demodulator or front end section of each user receiver is coupled to a bank of matched filters which selectively detect and identify any interfering codes. These interfering codes are then regenerated devoid of the desired signal to provide a coherent replica of the interference signal. The received composite signal and the coherent replica of one or more interference signals are applied to individual signal subtractor circuits which operate to cancel the interfering noise coded signals leaving the desired signal to be subsequently matched filter detected free of interference from other users.

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 multipath interference reduction system for mobile subscriber access systems, each occupying one of a plurality of time slot channels. Interference caused by multipath returns is eliminated in the receiver portion of digital signal communications apparatus by a plurality of cascaded signal subtraction units wherein the detected signal is successively delayed by increasing multiples of the pulsewidth of the main lobe, varied in amplitude and subtracted from itself until all the multipath amplitudes of significance are subtracted out of the composite received signal.

Abstract: Expanded multiplexed noise codes formed from code mate pairs of equal code length and having autocorrelation functions which upon detection provides an impulse autocorrelation function are generated by delaying one of the code mate pairs (code b) by a time delay less than its code length and adding it to the other code mate pair (code a) to form a first expanded code mate (code A) while a second expanded code mate (code B) is generated by forming the complement of the delayed code b and adding it to code a. Such partial overlapping results in expanded codes which also compress to an impulse when detected with a matched filter. These expanded codes, moreover, are utilized in multiplexed noise code modulated communications systems.

Abstract: Undesired intentional interference, i.e. jamming signals in a multiple acsing mobile subscriber system employing a plurality of subscriber communication terminals, selectively transmitting and receiving desired signals from one another via a central node or repeater station, is achieved by intercepting relatively strong jamming signals, also directly received by the various subscriber communication terminals, and transmitting the jamming signals to the central node where they are then retransmitted or relayed to the subscriber terminals in a dedicated orthogonal multiplexed channel relative to respective signal channels carrying desired communications signals. Each terminal includes means for demultiplexing the orthogonal channel and the signal channel. The relayed jamming signals are adjusted in amplitude and time position so that they are equal to and coincident in time with the directly received jamming signals.

Abstract: The described system utilizes a pair of antenna beam patterns, one of which s adapted to provide the desired signal and all interfering signals, and the other of which is adapted to provide only the interfering signals. The patterns are then combined to produce substantially only the desired signal as the combined output.

Abstract: A loop-around doppler canceling loop is employed between a master ground minal or node and a slave ground terminal or node for translating a doppler-free reference to the slave terminal by having a local voltage controlled oscillator (VCO) of frequency f at the master terminal lock to a frequency f.sub.o =f.sub.d where f.sub.o is frequency of the primary standard reference clock 8 at the master terminal and f.sub.d is the two-way doppler frequency that exists during transmission between the master and slave ground terminals by way of satellite.

Abstract: A time division multiple access mobile communications system employing frency division multiplexing and perfect noise codes to enable utilization of the system. A central node, or repeater, is employed, with all transmissions to it being performed at a first frequency, and with the frequency division multiplexing being such that all re-transmissions from the central node are performed at a second, different frequency. The noise codes employed are of a type termed code mates having correlation functions which upon detection provide an impulse autocorrelation function. The described arrangement enables random access, or direct call-up, to be accomplished with total non-interference between users. Large improvements in signal-to-noise power ratio and in signal-to-jamming power ratio will be seen to result.

Abstract: A bi-orthogonal PCM communications system employing multiplexed noise codes o provide enhanced protection against interference. Two system approaches are described--a first of which employs active, matched filter detection, whereas a second of which employs passive matched filter detection. The noise codes employed are of a type termed code mates having correlation functions which, upon detection, provide an impulse autocorrelation function. The described arrangements afford a transmission efficiency which extends towards Shannon's theorectical limit.

Abstract: The described system utilizes the interference cancelation technique disced in my pending U.S. Pat. application Ser. No. 114,547, filed Jan. 23, 1980, with narrow-band orthogonal addressing in providing improved system performance, but only with modest equipment requirements. Orthogonal narrow-band frequency division multiple access signaling is employed to initially accomplish call-up, with interference then being adaptively suppressed and an available voice channel selected for accomplishing the communication requirements.

Abstract: A tropospheric transmission system employing perfect noise codes in provig M fold diversity with a single antenna, while simultaneously reducing jamming interference by a factor 2M. The noise codes employed are of the type termed code mates having correlation functions which upon detection provide an impulse autocorrelation function. The described arrangement utilizes n bit perfect noise mate pair codes, with coherent separation and extraction of the uncorrelated returns from the tropospheric medium followed by optimal combination in a maximal ratio combiner.

Abstract: Code mates having cooperating autocorrelation functions to produce an impulse autocorrelation function are utilized. The code is bi-phase generated with phases of 0.degree. and 180.degree. and the mate code is bi-phase generated with phases of +90.degree. and -90.degree.. The resultant outputs are linearly combined to yield a single quaternary or quintuple code of the pseudo-noise class, that is, an impulse autocorrelation function. The quaternary code results when the code mates are binary codes. The quintuple code results when the code mates are ternary codes, where no output represents the third code.

Abstract: A time division multiple access mobile communications system employing a f-adaptive feature and perfect noise codes to enable utilization of the system. The self-adaptive feature permits switching to vacant channels as interfering users move to an occupied channel. The noise codes employed are of the type termed code mates having correlation functions which upon detection provide an impulse autocorrelation function. The described arrangement enables random access to be accomplished with minimal interference between users. Large improvements in signal-to-noise power ratio and in signal-to-jamming power ratio will be seen to result.

Abstract: An adaptive trunk data transmission system in which data bits to be communicated are not transmitted during certain fade durations of a multi-channel propagation characteristic, but are delayed instead, until the fade interval is over, when they are then transmitted.