Predictive signal cancellation for extracting 1 Mb/s MIL-STD-1553 component from composite high performance 1553 signal

A method for canceling out one of first and second data carrying signals transmitted as a combined signal to a receiver, said second signal having a frequency greater than said first signal, comprising:

• transferring the combined signals received to first and second paths for further processing;
• passing said first signal and filtering out said second signal from passing along said first path;
• passing said combined first and second signals along said second path for further processing while filtering out harmonics of said second signal from passing along said second path;
• transferring said first and second signals in said first path to a summing circuit after a given delay;
• determining zero crossings of said first signal passed in said second path;
• utilizing the zero crossings to generate a digital signal simulating the signal passed by said first path wherein rising edges of the zero crossings serve as starting points for digital representations of the positive and negative pulses, and responsive to:
• an identity of a terminal that is currently transmitted;
• a position of word/bits within a transmission of a current message from a terminal;
• values of prior Manchester half bits and sink types;
• and an identification of types of signal transitions;
• adjusting time delays of the generated digital signal to eliminate any time skew between first signals in the first and second signal paths;
• converting the generated digital signal into analog form;
• subtracting the analog form of the digital signal from the combined first and second signals transferred from said first path;
• and
• converting a resulting difference signal into digital form.

A method for generating a predictive cancellation signal, comprising:

• receiving a composite signal comprised of a first and a second data carrying signal, a frequency of said second signal being greater than a frequency of said first signal;
• separating said first signal from said first and second signals;
• detecting positive and negative zero crossings of the separated first signal to synthesize an estimate of said first signal;
• and
• subtracting the synthesized signal from said composite signal to recover said second signal.

Apparatus for synthesizing a first signal for use in the analysis of a composite signal comprised of a second signal combined with said first signal, said second signal having a higher frequency than said first signal, comprising:

• a unit for receiving said combined signals in analog form;
• an A/D converter for converting the combined signals;
• first and second output lines coupled to an output of said AID converter;
• a high pass filter coupled to said first output line for removing harmonics of the second signal;
• a low pass filter coupled to said second output line for removing the second signal;
• a summing circuit having first and second inputs;
• a delay circuit coupling an output of said high pass filter to said first input of said summing circuit to synchronize arrival of the signals at said first and second inputs;
• a zero-crossing detector coupled to an output of said low pass filter for detecting zero crossings in a positive and negative going direction of a signal passed by said low pass filter;
• a generator for generating a digital output representation of said first signal responsive to said zero-crossing detector;
• a circuit for adjusting the digital output of said generator to compensate for a timing skew between said signals in said first and second lines so that the signals in said first and second lines are in time synchronism when they reach said summing circuit;
• and
• said summing circuit subtracting the output of said generator from said combined first and second signals.