Single-tone pseudorandom-based modems

A new technique for modulation and demodulation of serial data bits employing modified pseudorandom (PN) codes is presented in this paper. In this type of modem, the data bits are serially fetched into a maximum length PN generator, K-bits at a time. These K-bits are then used as the seeds of the PN generator to generate L-chips (n-bits/chip) frame. At the receiver side, each incoming frame is correlated with a reference PN sequence. An index to the lag at which the correlation has a maximum value is used to retrieve the transmitted data.