Dss

## PN sequence generation with Max length

x0= 1

x1= 0

x2 =0

x3 =0

N = 7 

for i in range(1,N+1):

  x3 =x2

  x2 =x1

  x1 = x0

  x0 =(x1^x3)

  print ('The PN sequence at step:',i)

  x = [x1, x2, x3]

  print ('x=',x)

m = [7,8,9,10,11,12,13,17,19]#

N = [2**mm-1 for mm in m]

print ('Table 9.1 Range of PN Sequence lengths')

print ('_________________________________________________________')

print ('Length of shift register (m) =',m)

print ('PN sequence Length (N) =',N)

print ('_________________________________________________________')

##Properties of PNsequence

from numpy import corrcoef as corr

from matplotlib.pyplot import plot,xlabel,ylabel,title,show

#Period of PN Sequence N = 7

#Properites of maximum-length sequence

#Assign Initial value for PN generator

x0= 1

x1= 0

x2 =0

x3 =0

N = 7 

one_count = 0

zero_count = 0

C=[]

C_level=[]

t=[]

for i in range(1,N+1):

  x3 =x2#

  x2 =x1#

  x1 = x0#

  x0 =(x1^x3)

  print ('The PN sequence at step :',i)

  x = [x1 ,x2 ,x3]

  print ('x=',x)

  C.append(x3)

  if(C[i-1]==1):

    C_level.append(1)

    one_count = one_count+1

  elif(C[i-1]==0):

    C_level.append(-1)

    zero_count = zero_count+1  

print ('Output Sequence : ',C) 

print ('Output Sequence levels :',C_level)

if(zero_count < one_count):

  print ('Number of 1s in the given PN sequence : ',one_count)

  print ('Number of 0s in the given PN sequence :',zero_count)

  print ('Property 1 (Balance property) is satisified')

Rc_tuo = corr(C_level,rowvar=N)

t = range(1,2*len(C_level)+1)

plot(t,C_level+C_level)

xlabel('                                        t')

title('Waveform of maximum-length sequence ')

show()

## Generation of waveforms in DSSS/BPSK spread spectrum transmitter

from numpy import ones ,sin , arange , hstack ,nditer , pi 

import numpy as np

from matplotlib.pyplot import plot , subplot , xlabel , ylabel , title , show

t =range(0,13+1)

N =7#

m=[7,8,9,5]

l=[2**n-1 for n in m]

print('/n Values of length',l)

wt=arange(0,0.01+1,0.01)

bt=hstack([[1*xx for xx in ones(N)],[-1*yy for yy in ones(N)]])

ct= [0,0,1,1,1,0,1,0,0,1,1,1,0,1]

ct_polar= [-1,-1,1,1,1,-1,1,-1,-1,1,1,1,-1,1]

mt= [a*b for a,b in nditer([bt,ct_polar])]

Carrier = [2*sin(wtt*2*pi) for wtt in wt]

st= []#

for i in range(0,len(mt)):

    st=st+[mt[i]*Cr for Cr in Carrier]

subplot(3,1,1)

plot(t,mt)

xlabel('                                                                t')

title('Product Signal m(t)')

subplot(3,1,2)

plot(Carrier)

xlabel('                                                               t')

title('Carrier Signal')

subplot(3,1,3)

plot(st)

xlabel('                                                               t')

title('DS/BPSK signal s(t)')

show()