Arthur A. Collins, Inc.

Jon W Bayless, Sr

Robert D Pedersen

Arthur A Collins

John C Bellamy, Ii

A slip-free timing adjustment system adjusts channel timing for a multiplexed digital data stream. The data stream in each of c time division channels (10, 11) is modified preparatory to switching in a digital time-division circuit switch (14). The multiplexed digital data stream may arrive at the switch at a rate R0. The switch clock rate may be at a rate R1. Rates R0 and R1 are potentially different. Signal means (12, 13) provide for inserting a variable length timing code, one bit at a time, in each of the c channels in each multiplexed digital data stream. The multibit timing code is composed of successive variable length code words of length L and L+1 bits. Adjustment means (18, 42) receives the multiplexed data stream and adjusts individual channel rates in each of the c channels. This includes means for altering the length of the variable length code words by adjusting code words of length L to code words of length L+1 when the input clock is slower than the switch clock and for adjusting code words of length L+1 equal to code words of length L when the input clock is faster than the switch clock. By this means, the respective clock rates are equalized by the adjustment of just a sufficient set of code words in each of said channels to result in equal rates. Means (24, 28, 25, 29, 43, 44, 45) provide for transmitting the adjusted time-division multiplexed channels to a digital-time-division switch (14) for channel switching under control of the switch clock (21).

Timing adjustment circuit for digital switching

A high density bandlimited digital transmission system with a transmitter and a receiver connected by a radio path with an end-to-end channel transfer function selected to form at the receiver either raised cosine pulses or partial response pulses. The transmitter is partitioned or divided into an active pulse forming network and a passive pulse shaping and bandlimiting network. The active and passive networks are concatenated and in combination provide an optimal transmitter-receiver combination for raised cosine or for partial response signaling. Transmit and receive filters provide optimal signal pulse shaping while meeting specified out-of-band signal suppression. In-phase and quadrature phase carriers (I and Q channels) work with rectangular or half-wave sinusoidal modulating pulses. Further, time-offset or time-coincident pulses on each of the respective I and Q channels are used. Multi-level embodiments are also disclosed. Receivers using time-offset modulation forms allowing coherent detection using VSB and SSB techniques with resulting simplification of the receiver structures. This mode of operation is possible without the use of sideband separation filters at the transmitter. Only the receiver structure is affected. Preferred embodiments are described that closely approach optimal performance and achieve information densities in the range from 1.75 to 4 bits per second per Hertz.

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Dallas, TX, United States of America

Jon W Bayless, Sr