Third-generation TDRSS-compatible direct-sequence spread-spectrumdigital receiver

摘要

A digital communication receiver, called a third-generationnreceiver, has been developed. This receiver takes samples of thendirect-sequence spread signal at a nonzero intermediate frequency (IF)ninstead of the zero IF (baseband), and quantizes the samples bynemploying a 1-b analog-to-digital (A/D) converter at the receiver frontnend. These 1-b samples are digitally processed for pseudonoise (PN)ncode, carrier, bit synchronization, and bit decision with the use of annapplication-specific integrated circuit. The effects of the IF samplingnand 1-b A/D conversion on PN code synchronization are analyzed for a PNnspread-spectrum communication system with oversampling rate, e.g., 12nsamples per chip. In addition, the bit-error rate (BER) degradation duento the 1-b A/D conversion is studied by assuming perfect PN code,ncarrier, and bit synchronization. It is observed that the BERndegradation due to the 1-b A/D is significant, e.g., 2.4 dB, whenndecimation is made after IF sampling such that only one sample per chipnis used for bit decision. These analyzed BER results agree well with thensimulated results. However, if no decimation is made and oversampling isnused for bit decision, BER degradation due to 2-b A/D conversion isninsignificant, e.g., 0.6 dB