Adaptive acquisition of multiple access codes

A technique for matching the phases of two signals comprising:

• measuring the correlation between said signals at various points representing different signal phases;
• comparing the measured correlation to first and second threshold signals;
• adaptively increasing said first and second threshold signals each time a measured correlation exceeds said second threshold signal;
• and
• providing an indication of phase match at the phase corresponding to the correlation point representing the most recent correlation which exceeds said first or second threshold signal.

In a direct sequence spread spectrum communication system having a plurality of transmitters and receivers wherein each of said transmitters transmit a differently coded carrier for code division multiplexing, and each receiver generates a reference code which is a replica of the code received from a transmitter from which reception is desired for enabling multiple access reception, said receivers including correlation controlled phase matching structure for measuring the correlation between the received code and reference code at successive different code phases for determining a match of the code phases, the improvement in said correlation controlled phase matching structure comprising:

• means for establishing a first threshold signal and a second threshold signal having a magnitude greater than said first threshold signal;
• means for detecting when a measured correlation exceeds said first or second threshold signals;
• means for increasing the magnitude of said first and second threshold signals when a measured correlation exceeds said second threshold signal;
• means for providing an indication of code phase when said measured correlation exceeds said first or second threshold signals;
• and
• means for fixing the phase of the reference code at the phase represented by the most recent indication of code phase.

A technique for providing adaptive signal acquisition in a communication system comprising:

• transmitting a coded signal;
• receiving said transmitted signal;
• generating a reference code which is a replica of the transmitted code;
• changing the phase of the reference code at selected intervals;
• measuring the correlation between the transmitted code and reference code during said selected intervals;
• establishing a first threshold signal and a second threshold signal having a magnitude greater than said first threshold signal;
• comparing each measured correlation with said first and second threshold signals during each selected interval;
• increasing each threshold signal prior to the next selected interval when said measured correlation exceeds said second threshold signal, said threshold signals each being increased an amount equal to the difference between said measured correlation and said second threshold signal;
• providing an indication of signal acquisition when said measured correlation exceeds said first or second threshold signal;
• and
• fixing the phase of the reference code at the phase represented by the last provided indication when a predetermined time period has elapsed after said last indication.