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+//Chapter 15: Antennas for Special Applications
+//Example 15-21.1
+clc;
+
+//Variable Initialization
+dia = 1000    //Diameter of asteroid (m)
+prc = 0.4     //Power reflection coefficient of asteroid (unitless)
+f = 4e9       //Frequency (Hz)
+P = 1e9       //Power (W)
+s = 20e3      //Asteroid speed (m/s)
+ast_dis = 0.4    //Distance of asteroid (AU)
+au = 1.5e11     //Astronomical Unit (m)
+c = 3e8       //Speed of light (m/s)
+k = 1.38e-23    //Boltzmann's constant (m^2 kg s^-2 K^-1)
+Tsys = 10      //System temperature (K)
+B = 1e6     //Bandwidth (Hz)
+snr = 10    //Signal to noise ratio (dB)
+eap = 0.75    //Aperture efficiency (unitless)
+
+sigma = prc*%pi*s**2    //Radar cross section (m^2)
+ast_dm = au*ast_dis    //Astroid distance (m)
+lmda = c/f     //Wavelength(m)
+
+d4 = (64*(lmda**2)*(ast_dm**4)*k*Tsys*B*snr)/((eap**2)*%pi*(sigma)*P)
+d = d4**(0.25)    //Diameter of dish (m)
+
+delf = 2*s/lmda    //Doppler shift (Hz)
+delt = 2*(ast_dm)/c    //Time delay (s)
+
+timp = ast_dm/s    //Time before impact (s) 
+
+
+//Result
+mprintf("The diameter of the dish is %.0f m",d)
+mprintf("\nThe doppler shift is %.1f Hz",delf)
+mprintf("\nThe time delay for the radar signal is %d s", delt)
+mprintf("\nThe time before impact is %d s", timp)