#calculate the max usable freq
#page no 621
#prob no. 17.1
#given
#TE10 mode in air dielectric mode with inside cross sectn=2cm*4cm
#Determination of cut-off freq
a=4.*10**-2;#largest dimn is used for calculation
c=3.*10**8;#Speed of light in m/s
#calculations
fc=c/(2*a);
#Determination of dominant mode of propagation over 2:1
MUF=2*fc;
#results
print 'The max usable freq is',MUF,'Hz'
#calculate the group velocity
#page no 624
#prob no. 17.2
#Determination of group velocity for waveguide in example 7.1
from math import sqrt
#given
f=5*10**9;#freq.in Hz
fc=3.75*10**9;#cut-off freq from eg.7.1
c=3.*10**8;#speed of light in m/s
#calculations
vg=c*sqrt(1-(fc/f)**2);
#results
print 'The group velocity is',vg,'m/s'
#calculate the froup velocity
#page no 624
#prob no. 17.3
#A waveguide with fc=10GHz.2 signal with frequency 12 & 17GHz propogate down=50m
from math import sqrt
#given
fc=10*10**9;c=3.*10**8;f1=12.*10**9;f2=17.*10**9;d=50.;
#calculations and results
#Determination of group velocity for 12GHz
vg1=c*sqrt(1-(fc/f1)**2);
print 'The group velocity for 12GHz signal is',vg1,'m/s'
#Determination of group velo for 17GHz
vg2=c*sqrt(1-(fc/f2)**2);
print 'The group velocity for 17GHz signal is',vg2,'m/s'
#Determination of time taken for 50m dist by f1
t1=d/vg1;
#Determination of time taken for 50m dist by f2
t2=d/vg2;
#Determination of diffn in the travel times for 2 signals
dela=t1-t2;
print 'The diffn in the travel times for 2 signals is',dela,'sec'
#calculate the phase velocity
#page no 627
#prob no. 17.4
#Determination of phase velo.with given 5GHz freq
from math import sqrt
#given
f=5.*10**9;c=3.*10**8;fc=3.75*10**9;#Cut-off freq refering eg.17.1
#calculations
vp=c/sqrt(1-(fc/f)**2);#Calculation of phase velo.
#results
print 'The phase velocity is',vp,'m/s'
#calculate the characteristic impedanccec of waveguide
#page no 628
#prob no. 17.5
from math import sqrt
#given
#determination of characteristic impedance of waveguide with given 5GHz freq
f=5*10**9;fc=3.75*10**9;#Refering in eg. 17.4
#calculations
Zo=377/sqrt(1-(fc/f)**2);
#results
print 'The characteristic impedance of waveguide is',round(Zo,3),'ohm'
#page no 631
#prob no. 17.7
#calculate the signal level in all cases
#A signal with level of 20dBm & insertion loss=1dB & coupling =20dB,directivity=40dB
#given
sig_in=20.;loss=1.;couple=20.;direct=40.;
#calculations and results
#Determination of signal level in main guide
sig_level_main=sig_in-loss;
print 'The signal level in main guide is ',sig_level_main,'dBm'
#Determination of signal level in secondary guide
sig_level_sec=sig_in-couple;
print 'The signal level in secondary guide is',sig_level_sec,'dBm'
#If signal dirn in main guide were reveresed,the signal level in sec gide would reduced by 40dB to
sig_sec_rev=(sig_level_sec)-(direct);
print 'The signal level from sec guide when reversed guide is',sig_sec_rev,'dBm'
#page no 642
#prob no. 17.8
#calculate the frequency of oscillation
#given
#A Gunn device with thickness=7um
d=7*10**-6;v=10**5;#Basic velocity of e
#calculations
t=d/v;#Basic velocity relation
#Determination of freq of oscillation
f=1/t;#Inverse of period is freq
#results
print 'The frequency of oscillation is',f,'Hz'
#page no 648
#prob no. 17.9
#calculate the duty cycle and length of pulse
#given
#A pulse magnetron with avg power=1.2kW & peak power=18.5kW & 1 pulse is generated every 10ms
Pavg=1.2*10**3;Pp=18.5*10**3;Tt=10.*10**-3;
#calculations
#Determination of duty cycle
D=Pavg/Pp;
#Determination of length of pulse
Ton=D*Tt;
#results
print 'The duty cycle is',round(D,3)
print 'The length of pulse is',round(Ton,5),'sec'
#page no 652
#prob no. 17.10
#calculate the gain and beam width in all cases
import math
#A pyramidal horn has aperture=58mm in E-plane & 78mm in H-plane & operates at 10GHz
#given
f=10*10**9;c=3.*10**8;dH=78.*10**-3;dE=58.*10**-3;
#calculations and results
#a)Determination of gain in dB
wl=c/f;#calculation of wavelength
G=(7.5*dE*dH)/(wl**2);
G_dBi=10*math.log10(G);#Converting to dBi
print 'a)The gain is',round(G_dBi,3),'dBi'
#b)Determination of beamwidth in H-palne
theta_H=(70*wl)/dH;
print 'b)The beamwidth in H-plane is',round(theta_H,3),'degree'
#c)Determination of beamwidth in E-plane
theta_E=(56*wl)/dE;
print 'c)The beamwidth in H-plane is',round(theta_E,3),'degree'
#page no 654
# problem no 17.11
#calculate the width and length of the antenna
#given
from math import sqrt
#for a square patch antenna
f=2*10**6;# freq of operation in Hz
Er=2;# relative permittivity
c=3*10**8;# velo of light
#calculations
#wavelength is given as
wl=c/(f*sqrt(Er));
#The antenna width and length are each approximately half of this.
w=wl/2;
l=wl/2;
#results
print 'The antenna width = ',round(w,2),'m ','and ','The antenna length = ',round(l,2),'m'
#page no 657
#prob no. 17.12
#calculate the received power
import math
#A radar Tx has power=10kW at freq=9.5GHz & target at 15km with cross sectn=10.2 m2 with gain of antenna is 20dBi
f=9.5*10**9;Pt=10.*10**3;c=3.*10**8;G_dBi=20.;a=10.2;r=15.*10**3;
#calculations
#Determination of received power
wl=c/f;#calculating wavelength
G=10**(G_dBi/10.);#Converting to power ratio
Pr=((wl**2)*Pt*(G**2)*a)/(((4*math.pi)**3)*(r**4));
#results
print 'The received power is',Pr,'W'
#page no 659
#prob no. 17.13a
#calculate the distance of target
#a pulse sent,returns after 15us
#given
t=15*10**-6;c=3.*10**8;
tp=10**-6;#pulse duration of pulse radar
f=10**3;#operating freq in Hz
#calculations
#Determination of distance of target
R=(c*t)/2;
#The maximum unambiguous range is
Rmax=c/(2*f);
#The minimum unambiguous range is
Rmin=c*tp/2;
#results
print 'The distance of target is',R,'m'
print 'The maximum range is ',Rmax,'m'
print 'The minimum range is ',Rmin,'m'
#page no 662
#prob no. 17.14
#calculate the doppler shift
#given
v=60.;#speed of vehicle moving towards radar in mph
c=3*10**8;#velo of light in m/s
f=10.**10;# operating frequency in Hz
#calculations
# conversion of speed from mph to km/hr
v1=60*1.6;
# conversion of speed from km/hr to m/s
v2=v1*10**3/3600.;
# Now the Doppler shift is found as
fd=2*v2*f/c;
#results
print 'The Doppler shift is ',round(fd,2),'Hz'