Comsat Corporation

Communications Satellite Corporation

James R Thomas

Soheil I Sayegh

John James Poklemba

In a multi-channel demodulator, a detection-transition sample estimation scheme classified samples as left (L) or right (R) of a reference position within a symbol interval (,), or before (B) or after (A) a transition between symbols (,). When a sample is classified as L or B, the classification of the next sample is forced to R or A, respectively. A memory is provided for storing the contents of various registers when switching to processing of a different channel, and for retrieving from the memory stored data corresponding to previous processing of the different channel. Data read from the memory is written to a register downstream of the register from which it was taken when written to the memory. The read cycle of the memory is extended to ensure that a clock is available to load the data from memory into the downstream register after switching to the new channel.

Demodulation of asynchronously sampled data by means of detection-transition sample estimation in a shared multi-carrier environment

A time-shared multitask execution circuit for sharing registered digital hardware among a plurality of users is provided to achieve zero overhead switching while processing as few as 1 sample (in one clock cycle) for each user. The circuit comprises a three register bank, two switches, and a dual port RAM. On any given cycle of the clock, one register is processing data of a current user, one register is writing processed data of a prior user to the RAM, and one register is reading data of a subsequent user for processing from RAM. In this manner, processing, reading and writing are decoupled and proceed in parallel.

Method and apparatus for zero overhead sharing for registered digital

A coherent phase and frequency recovery method capable of rapidly recovering the phase and frequency of bursts of received signals from plural sources. The received signal is applied to a first input of a mixer, the output of which is amplified and applied to two feedback paths, one for frequency and the other for phase. The frequency path contains a loop filter driving a voltage-controlled oscillator, and the phase path a loop filter and amplifier. Initial estimates of the phase and frequency of the present burst are derived and injected into the respective feedback paths. The output of the phase path is applied to correct the phase of the output of the frequency path, which is then applied to a second input of the mixer.

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Sandy Spring, MD, United States of America

James R Thomas