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Ch 39: Wave Functions and Uncertainty
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 39, Problem 21

What minimum bandwidth is needed to transmit a pulse that consists of 100 cycles of a 1.0 MHz oscillation?

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1
Understand the relationship between the duration of a pulse and the bandwidth required to transmit it. The uncertainty principle in signal processing states that the product of the time duration of a signal (Δt) and its bandwidth (Δf) is approximately constant: Δt * Δf ≈ 1.
Determine the time duration of the pulse. Since the pulse consists of 100 cycles of a 1.0 MHz oscillation, calculate the total time duration (Δt) of the pulse using the formula: Δt = (number of cycles) / (frequency). Here, the frequency is 1.0 MHz, and the number of cycles is 100.
Rearrange the uncertainty principle formula to solve for the bandwidth (Δf): Δf ≈ 1 / Δt. Substitute the value of Δt obtained in the previous step into this formula.
Perform unit conversions if necessary. Ensure that the frequency and time duration are in compatible units (e.g., seconds for time and Hz for frequency) before calculating the bandwidth.
Interpret the result. The calculated bandwidth (Δf) represents the minimum frequency range required to transmit the pulse without significant distortion.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Bandwidth

Bandwidth refers to the range of frequencies that a transmission medium can carry. In the context of signal transmission, it is crucial for determining how much data can be sent over a channel in a given time. A higher bandwidth allows for the transmission of more information, while a lower bandwidth restricts the amount of data that can be transmitted.

Pulse Transmission

Pulse transmission involves sending a signal that varies in amplitude or frequency over time, typically representing data. The characteristics of the pulse, such as its duration and frequency, influence the bandwidth required for effective transmission. Understanding the relationship between pulse shape and bandwidth is essential for optimizing communication systems.
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Nyquist Theorem

The Nyquist Theorem states that to accurately transmit a signal without distortion, the sampling rate must be at least twice the highest frequency present in the signal. This principle is fundamental in determining the minimum bandwidth required for transmitting a pulse. For a signal with a frequency of 1.0 MHz, the minimum bandwidth needed would be at least 2.0 MHz to ensure proper transmission of the pulse.
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