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link-margin-calc.py
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link-margin-calc.py
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# Adam Kimbrough - Link Margin Calculator
from math import log10, pow, pi, atan, sqrt, sin, cos
import matplotlib.pyplot as plt
import numpy as np
offset = 0
# Gains
tx_pwr = 0
tx_ant = 0
rx_ant = 0
# Pass Loss Info
path_loss = 0
tx_ant_height = 0
rx_ant_height = 0
distance = 0
freq = 0
hb = 0
hm = 0
a_hm = 0
a_hm2 = 0
# Losses
tx_feed = 0
rx_feed = 0
pwr_back_off = 0
thermal_noise_density = -174.0 # dBm
noise_figure = 0
sig_to_noise = 0
# Prop Model Booleans
fspl_bool = False
fspl2_bool = False
hms_bool = False
hl_bool = False
tx_pwr = float(input('Enter transmitter power (dBm): '))
tx_ant = float(input('Enter transmitter ant gain: '))
rx_ant = float(input('Enter receiver ant gain: '))
tx_ant_height = float(input('Enter base ant height (m): '))
rx_ant_height = float(input('Enter mobile ant height (m): '))
distance = float(input('Enter distance between TX & RX (km): '))
freq = float(input('Enter tx freq (MHz): '))
detect_bw = float(input('Enter detection bandwidth (MHz): '))
pwr_back_off = float(input('Enter power back-off: '))
tx_feed = float(input('Enter TX feed loss: '))
rx_feed = float(input('Enter RX feed loss: '))
Gr = rx_ant # Antenna Gain receiving antenna.
Gt = tx_ant # Antenna Gain transmitting antenna.
hb = tx_ant_height
hm = rx_ant_height
def sign(a):
return (a > 0) - (a < 0)
def thermal_noise_power(tnd, bw):
tnp = tnd + 10 * log10(1000000 * bw)
return tnp
def pl_calc():
global fspl_bool, fspl2_bool, hms_bool, hl_bool, thermal_noise_pwr, \
noise_figure, sig_to_noise
have_rx_sens = \
input("Enter 'Y' if you have RX sensitivity, otherwise, 'N'... "
)
if have_rx_sens.upper() == 'Y':
manual_margin = int(input('Enter RX sensitivity: '))
prop_model = \
input("Choose propagation model: 'FSPL', 'HMS'(Hata med-small), 'HL'(Hata large), 'FSPL2'(ground refl only): "
)
if prop_model.upper() == 'FSPL':
path_loss = 20 * log10(distance) + 20 * log10(freq) + 32.44
fspl_bool = True
power_at_rx = tx_pwr + tx_ant + rx_ant - path_loss \
- (pwr_back_off + tx_feed + rx_feed)
elif prop_model.upper() == 'HMS':
# Correction factor (medium-small city)
a_hm = (1.1 * log10(freq) - 0.7) * hm - (1.56 * log10(freq)
- 0.8)
# General Hata Model Equation
Lp = 46.3 + 33.9 * log10(freq) - 13.82 * log10(hb) - a_hm \
+ (44.9 - 6.55 * log10(hb)) * log10(distance)
# Hata Model (Open Area) - based on urban losses
path_loss = Lp - 4.78 * pow(log10(freq), 2) + 18.33 \
* log10(freq) - 40.94
hms_bool = True
elif prop_model.upper() == 'HL':
# Correction factor (large city)
a_hm2 = 3.2 * pow(log10(11.75 * hm), 2) - 4.97
# General Hata Model Equation
Lp = 46.3 + 33.9 * log10(freq) - 13.82 * log10(hb) - a_hm2 \
+ (44.9 - 6.55 * log10(hb)) * log10(distance)
# Hata Model (Open Area) - based on urban losses
path_loss = Lp - 4.78 * pow(log10(freq), 2) + 18.33 \
* log10(freq) - 40.94
hl_bool = True
power_at_rx = tx_pwr + tx_ant + rx_ant - path_loss \
- (pwr_back_off + tx_feed + rx_feed)
elif prop_model.upper() == 'FSPL2':
# Free Space Path Loss Model w/ Ground Reflection
G = tx_ant * rx_ant
# path_loss = 40*log10(distance*1000) - 10*log10(G*pow(hb,2)*pow(hm, 2))
fspl2_bool = True
c = 299.972458 * pow(10, 6) # Speed of light in vaccum [m/s]
Gr = rx_ant # Antenna Gain receiving antenna.
Gt = tx_ant # Antenna Gain transmitting antenna.
Pt = pow(10, tx_pwr / 10) / 1000 # Energy to the transmitting antenna [Watt]
er = 18
wave_len = c / (freq * 1000000)
phi = atan((hb + hm) / (distance * 1000)) # phi incident angle to ground.
direct_wave = sqrt(pow(abs(hb - hm), 2) + pow(distance
* 1000, 2)) # Distance, traveled direct wave
refl_wave = sqrt(pow(distance * 1000, 2) + pow(hb + hm, 2)) # Distance, traveled reflected wave
gamma = (er * sin(phi) - sqrt(er - pow(cos(phi), 2))) / (er
* sin(phi) + sqrt(er - pow(cos(phi), 2))) # Vertical polarization
length_diff = refl_wave - direct_wave
cos_phase_diff = cos(length_diff * 2 * pi / wave_len) \
* sign(gamma)
Direct_energy = Pt * Gt * Gr * pow(wave_len, 2) / pow(4
* pi * direct_wave, 2)
reflected_energy = Pt * Gt * Gr * pow(wave_len, 2) / pow(4
* pi * refl_wave, 2) * abs(gamma)
Total_received_energy = Direct_energy + cos_phase_diff \
* reflected_energy
Total_received_energy_dBm = 10 \
* log10(Total_received_energy * 1e3)
path_loss = tx_pwr + tx_ant + rx_ant \
- Total_received_energy_dBm - (pwr_back_off + tx_feed
+ rx_feed)
power_at_rx = Total_received_energy_dBm - (pwr_back_off
+ tx_feed + rx_feed)
else:
print('Invalid option')
link_margin = power_at_rx - manual_margin
print ('--------------------------------')
print ('Path loss: ', path_loss)
print ('Power left at input: ', power_at_rx)
print ('**Link Margin** ', link_margin)
elif have_rx_sens.upper() == 'N':
noise_figure = float(input('Enter receiver NF: '))
sig_to_noise = float(input('Enter receiver\'s required S/N: '))
prop_model = \
input("Choose propagation model: 'FSPL', 'FSPL2'(ground refl), 'HMS'(Hata med-small), 'HL'(Hata large): "
)
if prop_model.upper() == 'FSPL':
path_loss = 20 * log10(distance) + 20 * log10(freq) + 32.44
fspl_bool = True
power_at_rx = tx_pwr + tx_ant + rx_ant - path_loss \
- (pwr_back_off + tx_feed + rx_feed)
elif prop_model.upper() == 'HMS':
# Correction factor (medium-small city)
a_hm = (1.1 * log10(freq) - 0.7) * hm - (1.56 * log10(freq)
- 0.8)
# General Hata Model Equation
Lp = 46.3 + 33.9 * log10(freq) - 13.82 * log10(hb) - a_hm \
+ (44.9 - 6.55 * log10(hb)) * log10(distance)
# Hata Model (Open Area) - based on urban losses
path_loss = Lp - 4.78 * pow(log10(freq), 2) + 18.33 \
* log10(freq) - 40.94
hms_bool = True
power_at_rx = tx_pwr + tx_ant + rx_ant - path_loss \
- (pwr_back_off + tx_feed + rx_feed)
elif prop_model.upper() == 'HL':
# Correction factor (large city)
a_hm2 = 3.2 * pow(log10(11.75 * hm), 2) - 4.97
# General Hata Model Equation
Lp = 46.3 + 33.9 * log10(freq) - 13.82 * log10(hb) - a_hm2 \
+ (44.9 - 6.55 * log10(hb)) * log10(distance)
# Hata Model (Open Area) - based on urban losses
path_loss = Lp - 4.78 * pow(log10(freq), 2) + 18.33 \
* log10(freq) - 40.94
hl_bool = True
power_at_rx = tx_pwr + tx_ant + rx_ant - path_loss \
- (pwr_back_off + tx_feed + rx_feed)
elif prop_model.upper() == 'FSPL2':
# Free Space Path Loss Model w/ Ground Reflection
# G = tx_ant * rx_ant
# path_loss = 40*log10(distance*1000) - 10*log10(G*pow(hb,2)*pow(hm, 2))
fspl2_bool = True
c = 299.972458 * pow(10, 6) # Speed of light in vaccum [m/s]
Gr = rx_ant # Antenna Gain receiving antenna.
Gt = tx_ant # Antenna Gain transmitting antenna.
Pt = pow(10, tx_pwr / 10) / 1000 # Energy to the transmitting antenna [Watt]
er = 18
wave_len = c / (freq * 1000000)
phi = atan((hb + hm) / (distance * 1000)) # phi incident angle to ground.
direct_wave = sqrt(pow(abs(hb - hm), 2) + pow(distance
* 1000, 2)) # Distance, traveled direct wave
refl_wave = sqrt(pow(distance * 1000, 2) + pow(hb + hm, 2)) # Distance, traveled reflected wave
gamma = (er * sin(phi) - sqrt(er - pow(cos(phi), 2))) / (er
* sin(phi) + sqrt(er - pow(cos(phi), 2))) # Vertical polarization
length_diff = refl_wave - direct_wave
cos_phase_diff = cos(length_diff * 2 * pi / wave_len) \
* sign(gamma)
Direct_energy = Pt * Gt * Gr * pow(wave_len, 2) / pow(4
* pi * direct_wave, 2)
reflected_energy = Pt * Gt * Gr * pow(wave_len, 2) / pow(4
* pi * refl_wave, 2) * abs(gamma)
Total_received_energy = Direct_energy + cos_phase_diff \
* reflected_energy
Total_received_energy_dBm = 10 \
* log10(Total_received_energy * 1e3)
path_loss = tx_pwr + tx_ant + rx_ant \
- Total_received_energy_dBm - (pwr_back_off + tx_feed
+ rx_feed)
power_at_rx = Total_received_energy_dBm - (pwr_back_off
+ tx_feed + rx_feed)
else:
print ('Invalid option')
thermal_noise_pwr = thermal_noise_power(thermal_noise_density,
detect_bw)
rx_sensitivity = thermal_noise_pwr + noise_figure + sig_to_noise
link_margin = power_at_rx - rx_sensitivity
print ('--------------------------------')
print ('Path loss: ', path_loss)
print ('Power left at input: ', power_at_rx)
print ('Receiver sensitivity: ', rx_sensitivity)
print ('**Link Margin** ', link_margin)
else:
print('Invalid input')
return (
fspl_bool,
fspl2_bool,
hms_bool,
hl_bool,
tx_pwr,
tx_ant,
rx_ant,
)
def plp(
pl,
total_dist,
model1,
model2,
model3,
model4,
tx_freq,
tnp,
nf,
sn,
txp,
txant,
rxant,
offset,
):
distance2 = \
float(input('Enter assumed max FSPL distance (mi) from table: '
))
path_loss2 = 20 * log10(distance2 * 1.60934) + 20 * log10(freq) \
+ 32.44
power_at_rx2 = txp + txant + rxant - path_loss2 # neglects (pwr_back_off + tx_feed + rx_feed)
rx_sensitivity2 = tnp + nf + sn
link_margin2 = power_at_rx2 - rx_sensitivity2
print('Required link margin: ', link_margin2)
path_loss_arr = []
link_margin_arr = []
dist_arr = []
i = 0
total_dist = total_dist
for dist in np.arange(1, total_dist, 0.01):
if model1:
path_loss_arr.append(20 * log10(dist) + 20 * log10(tx_freq)
+ 32.44)
dist_arr.append(dist)
power_at_rx = float(txp + txant + rxant
- path_loss_arr[i] - (pwr_back_off
+ tx_feed + rx_feed))
rx_sensitivity = float(tnp + nf + sn)
link_margin_arr.append(power_at_rx - rx_sensitivity)
i += 1
if model2:
c = 299.972458 * pow(10, 6) # Speed of light in vaccum [m/s]
Pt = pow(10, txp / 10) / 1000 # Energy to the transmitting antenna [Watt]
er = 18
wave_len = c / (freq * 1000000)
phi = atan((hb + hm) / (dist * 1000)) # phi incident angle to ground.
direct_wave = sqrt(pow(abs(hb - hm), 2) + pow(dist * 1000,
2)) # Distance, traveled direct wave
refl_wave = sqrt(pow(dist * 1000, 2) + pow(hb + hm, 2)) # Distance, traveled reflected wave
gamma = (er * sin(phi) - sqrt(er - pow(cos(phi), 2))) / (er
* sin(phi) + sqrt(er - pow(cos(phi), 2))) # Vertical polarization
length_diff = refl_wave - direct_wave
cos_phase_diff = cos(length_diff * 2 * pi / wave_len) \
* sign(gamma)
Direct_energy = Pt * Gt * Gr * pow(wave_len, 2) / pow(4
* pi * direct_wave, 2)
reflected_energy = Pt * Gt * Gr * pow(wave_len, 2) / pow(4
* pi * refl_wave, 2) * abs(gamma)
Total_received_energy = Direct_energy + cos_phase_diff \
* reflected_energy
Total_received_energy_dBm = 10 \
* log10(Total_received_energy * 1e3)
path_loss_arr.append(txp + txant + rxant
- Total_received_energy_dBm
- (pwr_back_off + tx_feed + rx_feed))
power_at_rx = Total_received_energy_dBm - (pwr_back_off
+ tx_feed + rx_feed)
rx_sensitivity = float(tnp + nf + sn)
dist_arr.append(dist)
link_margin_arr.append(power_at_rx - rx_sensitivity)
i += 1
if model3:
# Correction factor (medium-small city)
a_hm = (1.1 * log10(freq) - 0.7) * hm - (1.56 * log10(freq)
- 0.8)
# General Hata Model Equation
Lp = 46.3 + 33.9 * log10(freq) - 13.82 * log10(hb) - a_hm \
+ (44.9 - 6.55 * log10(hb)) * log10(dist)
# Hata Model (Open Area) - based on urban losses
path_loss_arr.append(Lp - 4.78 * pow(log10(freq), 2)
+ 18.33 * log10(freq) - 40.94)
dist_arr.append(dist)
power_at_rx = float(tx_pwr + tx_ant + rx_ant
- path_loss_arr[i] - (pwr_back_off
+ tx_feed + rx_feed))
rx_sensitivity = float(tnp + nf + sn)
link_margin_arr.append(power_at_rx - rx_sensitivity)
i += 1
if model4:
# Correction factor (large city)
a_hm2 = 3.2 * pow(log10(11.75 * hm), 2) - 4.97
# General Hata Model Equation
Lp = 46.3 + 33.9 * log10(freq) - 13.82 * log10(hb) - a_hm2 \
+ (44.9 - 6.55 * log10(hb)) * log10(dist)
# Hata Model (Open Area) - based on urban losses
path_loss_arr.append(Lp - 4.78 * pow(log10(freq), 2)
+ 18.33 * log10(freq) - 40.94)
dist_arr.append(dist)
power_at_rx = float(tx_pwr + tx_ant + rx_ant
- path_loss_arr[i] - (pwr_back_off
+ tx_feed + rx_feed))
rx_sensitivity = float(tnp + nf + sn)
link_margin_arr.append(power_at_rx - rx_sensitivity)
i += 1
x1 = np.array(dist_arr)
y1 = np.array(path_loss_arr)
y2 = np.array(link_margin_arr)
if (offset == 0):
plt.plot(x1, y1, '-r', label='path loss')
plt.plot(x1, y2, '-g', label='link margin')
else:
plt.plot(x1, y1, '-r')
plt.plot(x1, y2, '-g')
j = 0
for xy in zip(x1, y1):
if round(y2[j], 1) == round(link_margin2, 1):
plt.annotate('Breakpoint: (%.2f, %.2f)' % xy, xy=xy, xytext=(x1[j]+5,y1[j]+offset),
textcoords='data')
offset = offset - 30
break
j += 1
if model1:
plt.title('Path Loss/Link Margin vs. Range (FSPL)')
if model2:
plt.title('Path Loss/Link Margin vs. Range (2-Ray GR)')
if model3:
plt.title('Path Loss/Link Margin vs. Range (Hata: med-small city)'
)
if model4:
plt.title('Path Loss/Link Margin vs. Range (Hata: large city)')
plt.xlabel('Range (km)')
plt.ylabel('Path Loss/Link Margin (dBm)')
plt.legend(loc='center right')
new_model = input('Enter new system with same BW? Y/N: ')
if (new_model.upper() == 'Y'):
(
fspl_bool,
fspl2_bool,
hms_bool,
hl_bool,
tx_pwr,
tx_ant,
rx_ant,
) = pl_calc()
plp(
path_loss,
distance,
fspl_bool,
fspl2_bool,
hms_bool,
hl_bool,
freq,
thermal_noise_pwr,
noise_figure,
sig_to_noise,
tx_pwr,
tx_ant,
rx_ant,
offset
)
else:
plt.show()
(
fspl_bool,
fspl2_bool,
hms_bool,
hl_bool,
tx_pwr,
tx_ant,
rx_ant,
) = pl_calc()
plp(
path_loss,
distance,
fspl_bool,
fspl2_bool,
hms_bool,
hl_bool,
freq,
thermal_noise_pwr,
noise_figure,
sig_to_noise,
tx_pwr,
tx_ant,
rx_ant,
offset
)