{ "metadata": { "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "

Chapter 17: Antenna Temperature, Remote Sensing and Radar Cross Section

" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-1.1, Page number: 623

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi\n", "\n", "#Variable declaration\n", "Ta = 0.24 #Antenna temperature (K)\n", "ang = 0.005 #Subtended angle (degrees)\n", "hpbw = 0.116 #Antenna half power beamwidth (degrees)\n", "\n", "#Calculations\n", "Ts = Ta*(hpbw**2)/(pi*(ang**2/4))\n", "\n", "#Result\n", "print \"The averate temperature of the surface is\", round(Ts), \"K\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The averate temperature of the surface is 164.0 K\n" ] } ], "prompt_number": 1 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-1.2, Page number: 625

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi, sqrt\n", "\n", "#Variable declaration\n", "eff_aper = 500 #Antenna effective aperture (m^2)\n", "wave_lt = 20e-2 #Wavelength (m)\n", "Tsky = 10.0 #sky temperature (K)\n", "Tgnd = 300.0 #Ground temperature (K)\n", "beam_eff = 0.7 #Beam efficiency (unitless)\n", "aper_eff = 0.5 #Aperture efficiency (unitless)\n", "\n", "#Calculations\n", "phy_aper = aper_eff/eff_aper #Physical aperture (m^2)\n", "diam = 2*sqrt(phy_aper/pi) #Antenna diameter (m)\n", "diam_l = diam/wave_lt #Antenna diameter (lambda)\n", "\n", "ta_sky = Tsky*beam_eff #Sky contribution to antenna temp. (K)\n", "ta_side = 0.5*Tsky*(1-beam_eff) #Side-lobe contribution to antenna temp. (K)\n", "ta_back = 0.5*Tgnd*(1-beam_eff) #Back-lobe contribution to antenna temp. (K)\n", "\n", "Ta = ta_sky + ta_side + ta_back\n", "\n", "#Result\n", "print \"The total antenna temperature is\", Ta, \"K\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The total antenna temperature is 53.5 K\n" ] } ], "prompt_number": 2 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-2.1, Page number: 629

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Variable declaration\n", "Tn = 50.0 #Noise temperature (K)\n", "Tphy = 300.0 #Physical temperature (K)\n", "Eff = 0.99 #Efficiency (unitless)\n", "Tn_stg = 80.0 #Noise temperature of first 3 stages (K)\n", "gain_db = 13.0 #Gain (dB)\n", "Tphy_tr = 300 #Transmission line physical temperature (K)\n", "Eff_tr = 0.9 #Transmission line efficiency (unitless)\n", "\n", "#Calculations\n", "gain = 10**(gain_db/10)\n", "T_r = Tn_stg + Tn_stg/(gain) + Tn_stg/(gain**2)\n", " #Receiver noise temperature (K)\n", "Tsys = Tn + Tphy*(1/Eff - 1) + Tphy_tr*(1/Eff_tr - 1) + (1/Eff_tr)*T_r\n", " #System temperature (K)\n", "\n", "#Result\n", "print \"The system temperature is\", round(Tsys), \"K\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The system temperature is 180.0 K\n" ] } ], "prompt_number": 3 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-2.2, Page number: 630

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import sqrt\n", "\n", "#Variable declaration\n", "phy_aper = 2208 #Physical aperture (m^2)\n", "f = 1415e6 #Frequency (Hz)\n", "aper_eff = 0.54 #Aperture efficiency (unitless)\n", "Tsys = 50 #System temperature (K)\n", "bw = 100e6 #RF Bandwidth (Hz)\n", "t_const = 10 #Output time constant (s)\n", "sys_const = 2.2 #System constant (unitless)\n", "k = 1.38e-23 #Boltzmann's constant (J/K)\n", "\n", "#Calculations\n", "Tmin = sys_const*Tsys/(sqrt(bw*t_const)) #Minimum detectable temperature(K)\n", "eff_aper = aper_eff*phy_aper #Effective aperture (m^2)\n", "Smin = 2*k*Tmin/eff_aper #Minimum detectable flux density (W/m^2/Hz)\n", "\n", "#Result\n", "print \"The minimum detectable flux density is %.1e W/m^2/Hz\" % Smin" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The minimum detectable flux density is 8.1e-29 W/m^2/Hz\n" ] } ], "prompt_number": 7 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-3.1, Page number: 631

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi, log10\n", "\n", "#Variable declaration\n", "k = 1.38e-23 #Boltzmann's constant (J/K)\n", "trans_pow = 5 #Transponder power (W)\n", "r = 36000e3 #Distance (m)\n", "wave_lt = 7.5e-2 #Wavelength (m)\n", "ant_gain = 30 #Antenna gain (dB)\n", "earth_ant = 38 #Earth station antenna gain (dB)\n", "Tsys = 100 #Earth station receiver system temperature (K)\n", "bw = 30e6 #Bandwidth (Hz)\n", "\n", "#Calculations\n", "s_n = wave_lt**2/(16*(pi**2)*(r**2)*k*Tsys*bw)\n", "s_n = 10*log10(s_n) #Signal to Noise ratio (dB)\n", "\n", "trans_pow_db = 10*log10(trans_pow) #Transponder power (dB)\n", "erp = ant_gain + trans_pow_db #Effective radiated power (dB)\n", "\n", "s_n_downlink = erp + earth_ant + s_n #Signal to Noise ratio downlink(dB)\n", "\n", "#Result\n", "print \"The earth station S/N ratio is\", round(s_n_downlink,1), \"dB\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The earth station S/N ratio is 13.2 dB\n" ] } ], "prompt_number": 8 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-4.1, Page number: 634

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import exp\n", "\n", "#Variable declaration\n", "tf = 0.693 #Absorption co-efficient (unitless)\n", "Te = 305 #Earth temperature (K)\n", "Ta = 300 #Satellite antenna temperature (K)\n", "\n", "#Calculations\n", "Tf = (Ta - Te*exp(-tf))/(1-exp(-tf))\n", "\n", "#Result\n", "print \"The forest temperature is\", round(Tf), \"K\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The forest temperature is 295.0 K\n" ] } ], "prompt_number": 9 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 17-5.1, Page number: 639

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Variable declaration\n", "f = 10e9 #Frequency (Hz)\n", "wind_speed = 350 #Wind speed (km/h)\n", "c = 3e8 #Speed of light (m/s)\n", "vr = 1e3 #Differential velocity (m/h)\n", "\n", "#Calculations\n", "wave_lt = c/f #Wavelength (m)\n", "freq_shift = 2*(wind_speed*1000/3600)/wave_lt \n", " #Doppler Frequency shift (Hz)\n", "T = 1/(2*freq_shift) #Pulse repetition interval (s)\n", "prf = 1/T #Pulse repetition frequency (Hz)\n", "\n", "fmin = 2*(vr/3600)/wave_lt #Frequency resolution (Hz)\n", "N = 1/(round(fmin,1)*T) #Number of pulses \n", "\n", "#Result\n", "print \"The minimum pulse repetition frequency is\", round(prf,-3), \"Hz\"\n", "print \"The number of pulses to be sampled is\", round(N)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The minimum pulse repetition frequency is 13000.0 Hz\n", "The number of pulses to be sampled is 699.0\n" ] } ], "prompt_number": 14 } ], "metadata": {} } ] }