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{
"metadata": {
"name": ""
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h1>Chapter 8: Helical Antennas<h1>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 8-5.1, Page number: 309<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"from math import sqrt\n",
"\n",
"#Variable declaration\n",
"w = 5 #Width of flattened tubing at termination (mm)\n",
"Er = 2.7 #Relative permittivity of the sheet\n",
"Z0 = 50 #Characteristic impdence of the sheet\n",
"\n",
"#Calculation\n",
"h = w/((377/(sqrt(Er)*Z0))-2)\n",
"\n",
"#Result\n",
"print \"The required thickness of the polystyrene sheet is\", round(h,1),\"mm\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The required thickness of the polystyrene sheet is 1.9 mm\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 8-5.2, Page number:315<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"from math import sqrt, log10\n",
"\n",
"#Variable declaration\n",
"n = 16.0 #Number of turns (unitless)\n",
"C = 1 #Circumference (lambda)\n",
"S = 0.25 #Turn Spacing (lambda)\n",
"\n",
"#Calculation\n",
"hpbw = 52/(C*sqrt(n*S)) #Half power beamwidth (degrees)\n",
"ax_rat = (2*n + 1)/(2*n) #Axial ratio (unitless)\n",
"gain = 12*(C**2)*n*S #Gain of antenna (unitless)\n",
"gain_db = 10*log10(gain) #Gain of antenna (in dBi)\n",
"\n",
"print \"The half power beam width is\", hpbw, \"degrees\"\n",
"print \"The axial ratio is\", round(ax_rat,2)\n",
"print \"The gain is\", gain,\"or\",round(gain_db,1),\"dBi\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The half power beam width is 26.0 degrees\n",
"The axial ratio is 1.03\n",
"The gain is 48.0 or 16.8 dBi\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 8-5.3, Page number:316<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"from math import pi, sqrt, log10\n",
"\n",
"#Variable declaration\n",
"n = 10.0 #Number of turns (unitless)\n",
"S = 0.236 #Spacing between turns (lambda)\n",
"n_a = 4.0 #Number of helical antennas in the array (unitless)\n",
"\n",
"#Calculation\n",
"D = 12*n*S #Directivity of a single antenna(unitless)\n",
"Ae = D/(4*pi) #Effective aperture (lambda^2)\n",
"\n",
"A = sqrt(Ae) #Area of square/spacing between helixes (lambda)\n",
"Ae_total = Ae*n_a #Total effective aperture (lambda^2)\n",
"D_array = (4*pi*Ae_total) #Directivity of the array (unitless)\n",
"D_array_db = 10*log10(D_array) #Direcitivity of the array (dBi)\n",
"\n",
"#Result\n",
"print \"The best spacing between the helixes is\", round(A,1), \"lambda\"\n",
"print \"The directivity of the array is\", round(D_array),\"or\",round(D_array_db,1),\"dBi\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The best spacing between the helixes is 1.5 lambda\n",
"The directivity of the array is 113.0 or 20.5 dBi\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<h3>Example 8-16.1, Page number:347<h3>"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"from math import pi\n",
"\n",
"#Variable declaration\n",
"gain = 24.0 #Gain (dB)\n",
"alpha = 12.7 #Pitch angle (degrees)\n",
"c_lambda = 1.05 #Circumference (lambda)\n",
"s_lambda = 0.236 #Spacing between turns (lambda)\n",
"\n",
"#Calculation\n",
"D = 10**(gain/10) #Directivity (unitless)\n",
"L = D/(12*(c_lambda**2)) #Helix length (lambda)\n",
"n = L/s_lambda #Number of turns (unitless)\n",
"D = D/4 #Directivity for four 20-turn helixes(unitless)\n",
"Ae = D/(4*pi) #Effective aperture of each helix (lambda^2)\n",
"\n",
"#Result\n",
"print \"The Axial length is\", round(L),\"lambda\"\n",
"print \"The number of turns for the axial length is\",round(n)\n",
"print \"The effective aperture for 20 turns is\",round(Ae),\"lambda^2\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The Axial length is 19.0 lambda\n",
"The number of turns for the axial length is 80.0\n",
"The effective aperture for 20 turns is 5.0 lambda^2\n"
]
}
],
"prompt_number": 4
}
],
"metadata": {}
}
]
}
|
