Calculating Radar Distance from Signal Travel Time
This question asks us to determine the distance to a target based on the time it takes for a radar signal to travel to the target and return.
Understanding Radar Principles
Radar systems work by sending out electromagnetic waves (like radio waves or microwaves) and detecting the waves that are reflected back after hitting an object. The time it takes for the signal to complete this round trip (to the target and back) can be used to calculate the distance to the target.
Key principles involved:
- Speed of Signal: Radar signals travel at the speed of light ($c$).
- Travel Time: The time measured is for the signal to go to the target and return (round trip).
- Distance Formula: The fundamental relationship between distance, speed, and time is: $ \text{Distance} = \text{Speed} \times \text{Time} $
Step-by-Step Calculation
- Identify Given Values:
- Round-trip travel time ($t$) = $1 \text{ µs}$
- Speed of light ($c$) ≈ $3 \times 10^8 \text{ m/s}$
- Convert Time to Standard Units: The time is given in microseconds (µs). We need to convert this to seconds (s) for consistency with the speed of light unit (m/s). $ 1 \text{ µs} = 1 \times 10^{-6} \text{ s} $ So, $t = 1 \times 10^{-6} \text{ s}$.
- Calculate Total Round-Trip Distance: Using the distance formula, we can find the total distance the radar signal traveled. $ d_{\text{round trip}} = c \times t $ $ d_{\text{round trip}} = (3 \times 10^8 \text{ m/s}) \times (1 \times 10^{-6} \text{ s}) $ $ d_{\text{round trip}} = 3 \times 10^{(8 - 6)} \text{ m} $ $ d_{\text{round trip}} = 3 \times 10^2 \text{ m} $ $ d_{\text{round trip}} = 300 \text{ m} $
- Calculate One-Way Distance to Target: The calculated distance of 300 meters represents the path to the target and back. To find the actual distance from the radar to the target, we need to divide the round-trip distance by 2. $ d_{\text{target}} = \frac{d_{\text{round trip}}}{2} $ $ d_{\text{target}} = \frac{300 \text{ m}}{2} $ $ d_{\text{target}} = 150 \text{ m} $
Conclusion
Therefore, a round-trip travel time of $1 \text{ µs}$ for a radar signal corresponds to a distance of 150 meters to the target.
Important Questions from Antennas
Which of the following antennas is the standard reference antenna for the directiveness?
Consider the following statements:
(a) Fiber optic cable is much lighter than copper cable
(b) Fiber optic cable is not affected by power surges or electromagnetic interference
(c) Optical transmission is inherently bidirectional.
Which of the statements is (are) correct?Broadside arrays have
A. Number of dipoles of unequal size
B. Number of dipoles equally spaced
C. Collinear dipoles
D. Dipoles in phase
E. Dipoles are 90 out of phase
Choose the correct answer from the options given below:
To match the impedance of a 'ground penetrating radar antenna' to the ground, impedance of ground is given by the expression, (if ϵ r= 14, μ r= 1, σ = 10 −2 ℧/m, operating frequency = 200 MHz)
For an isotropic antenna P n(θ, φ) = 1, D = 1, for all θ and φ. The beam area for the isotropic antenna is given by:
