Satellite communications link monitor

Claim 1

Automatic apparatus for measuring in real time, bit error rate of digital communication links and comprising: at a transmitter station, bit stream generator means for transmitting a bit stream comprising a selectively predetermined baseband first code sequence; digital communication link means for transmitting said bit stream to receiver stations; at a receiver station, means for receiving said bit stream from said digital link; bit error rate monitor means connected to said receiver means and comprising, bit phase lock loop means for automatically and sequentially acquiring bit synchronization of said received bit stream by locking directly to the bit phase thereof and for phase tracking variations in timing due to transmission thereof over said digital link to provide timing signals substantially in phase with said received bit stream; decoder means connected to the output of said receiver means for decoding said incoming bit stream to provide a code synchronization output; local bit stream generator means connected to the output of said loop means and to the output of said decoder means and being responsive thereto to produce a reference code sequence substantially identical to said first code sequence and in bit and code synchronism therewith before transmission thereof over said digital link; bit comparison means connected to the output of said receiver means and to the error pulse of said reference bit stream generator means to compare on a bit-by-bit basis said received bit stream with respect to said local code sequence to produce an output if a difference is sensed; counter means connected to the output of said comparison means; time base generator means for providing a selectively predetermined time base comprising a fixed number of bits to said counter means whereby the output of said counter means comprises the ratio of error pulses to said number of bits. storage means connected to the output of said counter means for storing the contents thereof each time base; and display means connected to the output of said storage means for displaying the contents thereof and comprising bit error rate of said bit stream.