RF_modeling_mmWave_propagation

RF_modeling_mmWave_propagation.ipynb

RF_modeling_mmWave_propagation.py

# coding: utf-8

# # Exploration of wireless network RF calculations

# Free space loss equation: http://www.tapr.org/ve3jf.dcc97.html
# Assuming isotropic receiving antenna

# $$
# L_p = 32.4 + 20 log \,f + 20 log\,d\,dB\\
# f\,in\,MHz,\,d\,in\,km
# $$
# 
# 
# 

# Now lets combine this with the antenna gains and cable losses

# \begin{align}
# P_r & = P_t - L_p + G_t + G_r - L_t - L_r\\
# \\
# where &\\
# \\
# P_t & = transmitter\,power\,output\,(dBm\,or\,dBW,\,same\,units\,as\,P_r)\\
# ...&\\
# \end{align}
# 
# 
# Not taking into account refraction, defraction and reflection we can compute the loss. From [here](https://www.signalboosters.com/blog/what-is-decibel-db-gain-and-how-does-it-relate-to-cell-phone-reception) we can see that mobile phones operate in ideal conditions at - 50 dB and stop operating at - 100 dB. This post also shows you how to check your network readings from you iPhone/Android.

# In[2]:


import math


# In[3]:


L_p = 32.4 + (20 * math.log10(915)) + (20 * math.log10(10))
P_t = 24
G_t = 25
G_r = 12
L_t = 2
L_r = 2
P_r = P_t - L_p + G_t + G_r - L_t - L_r
P_r


# ### Now lets explore the loss as we increase the frequency upto millimeter wave (mmWave)

# In[4]:


def calc_loss(freq, distance, tr_pwr=24, tr_gain=10, rec_gain=10, tr_loss=2, rec_loss=2):
    """ Calculate the path loss for a frequency and distance
    
    Keyword arguments:
    freq -- the frequnecy in MHz
    distance -- the distance in km
    tr_pwr -- the transmitter power in dB
    tr_gain -- the transmitter gain in dB
    rec_gain -- the receiver gain in dB
    tr_loss - the transmitter loss in dB
    rec_loss - the receiver loss in dB
    """
    free_space_loss = 32.4 + (20 * math.log10(freq)) + (20 * math.log10(distance))
    path_loss = tr_pwr - free_space_loss + tr_gain  + rec_gain - tr_loss - rec_loss
    return path_loss


# In[5]:


import numpy as np


# In[6]:


losses = []
freq = np.arange(500, 10000, step=500)
dist = np.arange(0.00001, 20, step=0.2)
for x in freq:
    row = []
    for y in dist:
        row.append(calc_loss(x, y))
    losses.append(row)
        


# In[7]:


l_a = np.array(losses)


# In[8]:


for i in range(len(l_a)):
    print(l_a[i].mean())


# In[17]:


get_ipython().run_line_magic('matplotlib', 'inline')
import matplotlib.pyplot as plt

top = plt.plot(dist, l_a[0], 'r', label='%i MHz'% freq[0])
mid = plt.plot(dist, l_a[4], 'b', label='%i MHz'% freq[4])
bottom = plt.plot(dist, l_a[-1], 'g', label='%i MHz'% freq[-1])
plt.legend(bbox_to_anchor=(1.05, 1), loc=2, borderaxespad=0.)
plt.title("Propagation of RF frequnecy for distance (km)")
plt.ylabel('dB loss')
plt.xlabel('km')
plt.show()


# Now we want to check the distance at which each frequency hits -50 and -75 dB loss

# In[59]:


def calc_loss_at_distance(loss, distance):

    hits = []

    for c in l_a:
        for i, l in enumerate(c):
            if l <= loss:

                hits.append(distance[i])
                break
    return hits

hits_fifty = calc_loss_at_distance(-50, dist)
hits_seventy = calc_loss_at_distance(-70, dist)
        
        


# In[64]:


neg_fifty = plt.plot(freq, hits_fifty, 'r', label='distance to hit loss -50 dB')
neg_seventy = plt.plot(freq, hits_seventy, 'b', label='distance to hit loss -70 dB')
plt.legend(bbox_to_anchor=(1.05, 1), loc=2, borderaxespad=0.)
plt.title("dB loss over distance as frequency increases with 400m baseline")
plt.ylabel('distance (km)')
plt.xlabel('MHz')
plt.axhline(0.4, linestyle='--', color='k') # horizontal lines
plt.show()