Abstract: Spectrum spreading techniques is used in CDMA communications systems, where that each subscriber within the communication system is assigned one pseudo noise code.
The number of codes equal to the number of subscribers to the communications system.
In this paper, we discuss a practical mechanism design of the Direct Sequence Spread Spectrum
(DSSS) system which is used in CDMA communication systems by using cyclone II EP2C20F484C7 FPGA from ALTERA placed on education and development board DE-1 with the following parameters:
-Clock frequency :FCLK=50MHz
-Modulation type of signal is: BPSK
-Frequency range is: (3Hz…..10 MHz ).
-Frequency Resolution is: (3Hz).
-Frequency of data impulses (FDATA=1KHz).
-Frequency of pseudo-noise code generator (PNCG): (FPNCG=50,100,500,1000 KHz).
-Spreading spectrum factor: KSS= (FPNCG/FDATA )=50,100,500,1000.
maximum length of PNCG for (10 bits) shift register is:{〖L_PNCG〗_ =(2^10-1)*T_PNCG}
-Signal amplitude (5V).
-Computer-controlled parameters: operating frequency, Spreading spectrum factor value.
-Possibility of updating: Increasing the spreading spectrum factor, Increasing the number of bits of the pseudo-random sequence generator so that the spectrum becomes more random, change modulation type, increase the frequency range up to 20 MHz

Keywords: DSSS, CDMA, BPSK, FPGA, PNCG, DDFS, DDS, Spread spectrum.

| DOI: 10.17148/ IMRJR.2024.010302