3RD-GENERATION TDRSS-COMPATIBLE DIRECT-SEQUENCE SPREAD-SPECTRUM DIGITAL RECEIVER

Recently, a digital communication receiver, called a third-generation receiver, has been developed, This receiver takes samples of the direc t-sequence spread signal at a nonzero intermediate frequency (IF) inst ead of the zero IF (baseband), and quantizes the samples by employing a 1-b analog-to-digital (A/D) converter at the receiver front end, The se 1-b samples are digitally processed for pseudonoise (PN) code, carr ier, bit synchronization, and bit decision with the use of an applicat ion-specific integrated circuit, In this paper, the effects of the IF sampling and 1-b A/D conversion on PN code synchronization are analyze d for a PN spread-spectrum communication system with oversampling rate , e.g., 12 samples per chip, In addition, bit-error rate (BER) degrada tion due to the 1-b AID conversion is studied by assuming perfect PN c ode, carrier, and bit synchronization, It is observed that BER degrada tion due to the 1-b A/D is significant, e.g., 2.4 dB, when decimation is made after IF sampling such that only one sample per chip is used f or bit decision, These analyzed BER results agree well with the simula ted results, However, if no decimation is made and oversampling is use d for bit decision, BER degradation due to 1-b AID conversion is insig nificant, e.g., 0.6 dB.