Decibels. Engineers often measure the ratio of two power measurements in decibels, or \(\mathrm{dB}\). The equation for the ratio of two power measurements in decibels is $$ \mathrm{dB}=10 \log _{10} \frac{P_{2}}{P_{1}} $$ where \(P_{2}\) is the power level being measured, and \(P_{1}\) is some reference power level. a. Assume that the reference power level \(P_{1}\) is I milliwatt, and write a program that accepts an input power \(P_{2}\) and converts it into \(\mathrm{dB}\) with respect to the \(1 \mathrm{~mW}\) reference level. (Engineers have a special unit for dB power levels with respect to a \(1 \mathrm{~mW}\) reference: \(\mathrm{dBm}\).) Use good programming practices in your program. b. Write a program that creates a plot of power in watts versus power in \(\mathrm{dBm}\) with respect to a \(1 \mathrm{~mW}\) reference level. Create both a linear \(x y\) plot and a log-linear \(x y\) plot.

Short Answer

Expert verified
To calculate the power ratio in decibels (dB) with reference level P1 as 1 milliwatt, use the formula \( dBm = 10 * \log_{10}(P_2/1\,\text{mW}) \). Write a Python program to accept an input power P2, calculate the dBm, and create a linear xy plot and a log-linear xy plot of power in watts versus power in dBm. ```python import math import numpy as np import matplotlib.pyplot as plt def calculate_dBm(P2_mW): dBm = 10 * math.log10(P2_mW / 1) return dBm def create_plots(): P2_W = np.linspace(0.001, 10, 1000) P2_mW = P2_W * 1000 dBm = 10 * np.log10(P2_mW) plt.figure() plt.plot(P2_W, dBm) plt.xlabel("Power (W)") plt.ylabel("Power (dBm)") plt.title("Linear xy Plot: Power (W) vs Power (dBm)") plt.grid() plt.figure() plt.semilogx(P2_W, dBm) plt.xlabel("Power (W)") plt.ylabel("Power (dBm)") plt.title("Log-linear xy Plot: Power (W) vs Power (dBm)") plt.grid() plt.show() P2_mW = float(input("Enter the P2 power in mW: ")) dBm = calculate_dBm(P2_mW) print("The dBm value is:", dBm) create_plots() ```

Step by step solution

01

Define the formula for dBm calculation

Given the equation for dB: \( dB = 10 * \log_{10}(P_2/P_1) \) Our reference power level P1 is 1 milliwatt, so to calculate dBm, the formula becomes: \( dBm = 10 * \log_{10}(P_2/1\,\text{mW}) \)
02

Write the program

Here's a simple Python program that takes input power P2 and calculates the dBm using the above formula: ```python import math def calculate_dBm(P2_mW): dBm = 10 * math.log10(P2_mW / 1) return dBm P2_mW = float(input("Enter the P2 power in mW: ")) dBm = calculate_dBm(P2_mW) print("The dBm value is:", dBm) ``` ## Part b: Create a plot of power in watts vs power in dBm ##
03

Convert watts to milliwatts

Since the dBm formula uses milliwatts, we need to convert watts to milliwatts before using it. The conversion is given by: \( P_{2\,\text{mW}} = P_{2\,\text{W}} \times 1000 \)
04

Create the linear xy plot and the log-linear xy plot

Using the matplotlib library in Python, we can plot the linear xy and log-linear xy plots as follows: ```python import numpy as np import matplotlib.pyplot as plt def create_plots(): P2_W = np.linspace(0.001, 10, 1000) # Generate an array of powers in watts P2_mW = P2_W * 1000 # Convert watts to milliwatts dBm = 10 * np.log10(P2_mW) # Calculate dBm for each power value # Linear xy plot plt.figure() plt.plot(P2_W, dBm) plt.xlabel("Power (W)") plt.ylabel("Power (dBm)") plt.title("Linear xy Plot: Power (W) vs Power (dBm)") plt.grid() # Log-linear xy plot plt.figure() plt.semilogx(P2_W, dBm) plt.xlabel("Power (W)") plt.ylabel("Power (dBm)") plt.title("Log-linear xy Plot: Power (W) vs Power (dBm)") plt.grid() plt.show() create_plots() ``` This Python code will generate both the linear xy plot and log-linear xy plot of power in watts versus power in dBm.

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