forked from obada-a/AntennaProject
/
antenna_package.py
174 lines (147 loc) · 5.46 KB
/
antenna_package.py
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import math
from pylab import*
# the function takes in input the number of array elements "n" and
# the attenuation of the secondary lobes compared to the main lobe
def chebyParam( n , r ):
n = float(n)
r = float(r)
iterator = math.cosh(1/n * math.acosh(r))
a = (( iterator - 1 ) / 2 ).real
b = (( iterator + 1 ) / 2 ).real
#returns the list of chebyshev's parameters
return [ a , b ]
#chebyshev's parameters and optimized distance value btw array elements
def chebyParamOptimized(n , r , k0 ):
n = float(n)
r = float(r)
iterator = math.cosh(1/n * math.acosh(r))
a = (( iterator - 1 ) / 2 ).real
b = (( iterator + 1 ) / 2 ).real
optimized_dist = ( 2*math.pi - math.acos((1 - a)/b)) / k0
output = open("valori_a_b.txt",'a')
output.write(" a = " + str(a) + " b = " + str(b) + " N = " + str( n*2+1) + "\n")
output.close()
print( "N="+str(n*2+1) + " d=" + str(optimized_dist))
return [ a , b , optimized_dist]
# the function takes in input the chebyshev's parameters and returns the
# excitation coefficients
def excitCoeff( n , a, b):
if n not in range(2,5):
raise Exception("The number isn't in the range [ 2 , 4 ]")
# 5 elements array
def five_elem():
k0 = 2*a**2 + b**2 - 1
k1 = 4*a*b/2
k2 = b**2/2
return [ k0 , k1 , k2 ]
#7 elements array
def seven_elem():
k0 = 4*a**3 + 6*a*b**2 - 3*a
k1 = ( 12*a**2*b +3*b**3 - 3*b )/2
k2 = ( 6*a*b**2 )/2
k3 = b**3/2
return [ k0 , k1 , k2 , k3 ]
#9 elements array
def nine_elem():
k0 = -8*a**2 + 8*a**4 - 4*b**2 + 3*b**4 + 24*a**2*b**2 +1
k1 = (24*a*b**3 + 32*a**3*b - 16*a*b)/2
k2 = (4*b**4 - 4*b**2 + 24*a**2*b**2)/2
k3 = 8*a*b**3/2
k4 = b**4/2
return [ k0 , k1 , k2 , k3 , k4 ]
feed_coeff = { 2 : five_elem , 3 : seven_elem , 4 : nine_elem }
return feed_coeff[n]()
#the function takes in input the excitation coefficients, the distance between array elements,
#the angle of orientation
#returns the array factor
def arrayFactor( coeff , dist , angle , k0 ):
u = k0 * dist * cos((angle*pi)/180)
f = zeros(len(angle))
for item in range(0,len(angle)):
f[item] = coeff[0]
for item2 in range(1,len(coeff)):
f[item] = f[item] + 2*coeff[item2]*cos(item2*u[item])
return f
# Chebyshev sysnthesis
def chebyshevSynthesis( f0 , r , angle , gain , n ):
gain = 10**(array(gain)/10)
c = float(3*(10**8))
#wave length
r = 10**(r/20)
lambda_0 = c/float(f0)
k0 = 2*math.pi/lambda_0
psi = 90 - np.array(angle)
m = int(ceil(( n-1 )/2))
params = chebyParamOptimized( m , r , k0)
excitation_coeff = excitCoeff( m, params[0] , params[1] )
array_factor = np.array(arrayFactor( excitation_coeff, params[2] , psi , k0))
#square absolute value of the array factor
abs_array_factor = abs(np.array(array_factor))**2
# the sum of the absolute values of the excitation parameters
sum_coeff = sum( abs(array(excitation_coeff))**2)*2 - abs(excitation_coeff[1])**2
array_factor_gain = abs_array_factor/float(sum_coeff)
#the gain of the antenna
system_gain = array_factor_gain * gain
db_system_gain = 10*log10(system_gain)
max_gain = max(db_system_gain)
db_3_gain = 0
teta_3_db = -1
for item in range(1, len(angle)):
if db_system_gain[item] == db_3_gain :
teta_3_db = angle[item]
break
elif db_system_gain[item] < db_3_gain:
teta_3_db = angle[item - 1]
break
if teta_3_db == -1 :
print(" Impossible to calculate the beamwidth ")
print(teta_3_db)
bw = 2*teta_3_db
return [ array_factor , array_factor_gain , system_gain , max_gain , bw ]
def chebySynthesisDistance( f0 , r , angle , gain , n , dist ):
c = float(3*10**8)
r = 10**(r/20)
lambda_0 = c/float(f0)
k0 = 2*math.pi/lambda_0
psi = 90 - array(angle)
m = int(ceil((n-1)/2))
params = chebyParam( m , r )
excitation_coeff = excitCoeff( m , params[0] , params[1] )
array_factor = arrayFactor(excitation_coeff , dist , psi , k0 )
abs_array_factor = abs(array_factor)**2
sum_coeff = sum(abs(array(excitation_coeff))**2)*2 - abs(excitation_coeff[1])**2
array_factor_gain = abs_array_factor/float(sum_coeff)
system_gain = array_factor_gain*gain
db_system_gain = 10*log10(system_gain)
max_gain = max(system_gain)
db_max_gain = max(db_system_gain)
db_3_gain = db_max_gain - 3
print(db_system_gain)
teta_3_db = -1
for item in range(0, len(angle)):
if db_system_gain[item] == db_3_gain:
teta_3_db = angle[item]
break
elif db_system_gain[item] < db_3_gain:
teta_3_db = angle[item - 1]
break
if teta_3_db == -1 :
print(" Impossible to calculate the beamwidth ")
bw = 2*teta_3_db
return [ array_factor , array_factor_gain , system_gain , max_gain , bw ]
def plot_function(axes,values , names ):
m = values[0]
g=[]
for item in axes:
g.append(-1*item)
g = g[::-1]
axes = g + axes
values = array(list(values[::-1])+list(values))
plot(axes,values)
ylim(-60,35)
xlim(-90,90)
annotate(str(m)[0:5], xy=(5, m+6), xytext=(5, m+6),bbox=dict(boxstyle="larrow", fc="w"), rotation = 35)
grid(True)
ylabel(names[0])
xlabel(names[1])
title(names[2])