Podcast
Questions and Answers
What is the primary factor influencing the radar range according to the formula?
What is the primary factor influencing the radar range according to the formula?
- The square root of $P_T$
- The cube root of $P_T$
- The fourth root of $P_T$ (correct)
- The direct value of $P_T$
How is the transmitted power $P_T$ adjusted due to atmospheric attenuation in the given example?
How is the transmitted power $P_T$ adjusted due to atmospheric attenuation in the given example?
- Increased by 1.92 dBm
- Increased by 1.556 times (correct)
- Decreased by 1.556 times
- Increased by 1.92 Watts
Which of the following values is correctly calculated for the receiver sensitivity in dBW?
Which of the following values is correctly calculated for the receiver sensitivity in dBW?
- -125 dBW
- -105 dBW
- -135 dBW (correct)
- -115 dBW
What is the effective area $σ$ of the target as specified in the example?
What is the effective area $σ$ of the target as specified in the example?
What is the calculated transmitted power $P_T$ required to detect the target at the specified range?
What is the calculated transmitted power $P_T$ required to detect the target at the specified range?
Which antenna type is primarily used in TV broadcasting for the VHF and UHF bands?
Which antenna type is primarily used in TV broadcasting for the VHF and UHF bands?
What is a significant characteristic of helix and spiral antennas?
What is a significant characteristic of helix and spiral antennas?
What distinguishes linear arrays from other array types?
What distinguishes linear arrays from other array types?
Which antenna is characterized as having a composite structure for transmitting applications?
Which antenna is characterized as having a composite structure for transmitting applications?
Which array is known for its ability to be scanned over a region of space?
Which array is known for its ability to be scanned over a region of space?
What is a primary application of microwave horns?
What is a primary application of microwave horns?
Which antenna type is specifically mentioned for its broadband properties in HF communications?
Which antenna type is specifically mentioned for its broadband properties in HF communications?
Which characteristic is primarily associated with both the rhombic antenna and the log-periodic array?
Which characteristic is primarily associated with both the rhombic antenna and the log-periodic array?
What is the purpose of adjusting the amplitude and phase excitation in a linear array used for satellite communications?
What is the purpose of adjusting the amplitude and phase excitation in a linear array used for satellite communications?
How do electromagnetic waves propagate from a vertical dipole antenna?
How do electromagnetic waves propagate from a vertical dipole antenna?
What happens when the frequency at which the dipole is energized exceeds 16 kHz?
What happens when the frequency at which the dipole is energized exceeds 16 kHz?
What characterizes an isotropic radiator?
What characterizes an isotropic radiator?
What is the expression for the power density at a point Q from an isotropic radiator?
What is the expression for the power density at a point Q from an isotropic radiator?
What distinguishes the ground wave from the sky wave in electromagnetic wave propagation?
What distinguishes the ground wave from the sky wave in electromagnetic wave propagation?
What effect does the reversing field near a dipole antenna have on collapsing field lines?
What effect does the reversing field near a dipole antenna have on collapsing field lines?
In what scenarios are linear arrays particularly beneficial in satellite communication?
In what scenarios are linear arrays particularly beneficial in satellite communication?
What does the equation $P_a = E * H$ signify in relation to power density?
What does the equation $P_a = E * H$ signify in relation to power density?
In the context of radar systems, what factor does the power density $P_a$ depend on?
In the context of radar systems, what factor does the power density $P_a$ depend on?
How is the electric field strength at point Q modified by the gain of a practical antenna?
How is the electric field strength at point Q modified by the gain of a practical antenna?
What is the form of the radar equation relating transmitted power and received power?
What is the form of the radar equation relating transmitted power and received power?
In which scenario does the minimum detectable signal-to-noise ratio (S/N) come into play within radar systems?
In which scenario does the minimum detectable signal-to-noise ratio (S/N) come into play within radar systems?
Flashcards
Single-Radiator Antenna
Single-Radiator Antenna
An antenna with a single radiating element.
Multiple-Radiator Antenna
Multiple-Radiator Antenna
An antenna with multiple radiating elements, working together.
Monopole Antenna
Monopole Antenna
A basic antenna with a single wire connected to ground.
Dipole Antenna
Dipole Antenna
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Yagi Array
Yagi Array
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Yagi TV Antenna
Yagi TV Antenna
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Rhombic Antenna
Rhombic Antenna
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Log-Periodic Antenna
Log-Periodic Antenna
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Radar Range
Radar Range
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Transmitted Power (PT)
Transmitted Power (PT)
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Receiver Sensitivity
Receiver Sensitivity
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Atmospheric Attenuation
Atmospheric Attenuation
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Pulse Length
Pulse Length
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Adaptive Array Antenna
Adaptive Array Antenna
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Induction Field
Induction Field
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Radiation Field
Radiation Field
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Ground Wave
Ground Wave
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Sky Wave
Sky Wave
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Isotrope (or Point Source Radiator)
Isotrope (or Point Source Radiator)
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Power Density (Pa)
Power Density (Pa)
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Radiation Pattern
Radiation Pattern
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Relationship between E and H
Relationship between E and H
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Antenna Power Gain (G)
Antenna Power Gain (G)
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Radar Equation
Radar Equation
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Minimum Detectable Signal-to-Noise Ratio (S/N)
Minimum Detectable Signal-to-Noise Ratio (S/N)
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Study Notes
Antenna Types
- Antenna designs have evolved into single and multiple radiators
- Important types are listed
- Monopole and dipole antennas are commonly used
Table 1.1
- Single radiators: Monopole, Dipole, Wire, Helix, Spiral, Horn, Reflector
- Multiple radiators: Yagi array, Rhombic array, Log-periodic array, Linear array, Planar array, Adaptive array
Figures 1.1, 1.2, and 1.3
- Illustrate various antenna types, including Monopole, Dipole, Helix, Spiral, Horn, and Reflector
Antenna Evolution
- Complex arrays (e.g., Yagi array) are used as components
- Long wire antennas are more common in receiving applications
- Rhombic antennas are used in transmitting applications
- Helix and spiral antennas show broadband properties suitable for satellite communication
- Microwave horns and parabolic reflectors are common in radar and satellite systems
Yagi Array
- A popular TV antenna for VHF and UHF bands
- Features convenient size, useful gain, and simplicity
- Low cost
Log-Periodic Array
- Recently used in HF communication
- Attract due to broadband properties
Linear and Phased Arrays
- Constructed using basic radiators (dipole or slotted waveguide)
- One-dimensional structures called linear arrays
- Used for satellite communications as adaptive arrays
- Used to adjust amplitude and phase excitation to create nulls for signal cancellation
Wave Propagation
- Typical antenna is vertical dipole
- Electric field lines are vertical and magnetic are horizontal
- Symmetrical about antenna
- Charge on antenna reverses sign rapidly when the frequency is higher than 16kHz
Electromagnetic Waves
- Consist of ground wave (used for medium distance communication) and sky wave (used for long distance communication, refracted by ionosphere)
Point Source Radiator (Isotrope)
- Theoretical antenna
- Radiates energy equally in all directions
- Provides a basis for comparison of other antennas
- Power density at a point is calculated using the equation Pa = P/(4πr²) watts/m² (where P is power and r is distance)
Radar Equation
- Related to transmitting and receiving power in radar systems
- The equation is used to calculate the range based on the minimum range and maximum range
- The range equation depends on the fourth root of Pr(transmitted power)
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