Antenna and Wave Propagation Quiz

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Questions and Answers

What is the course code for Antenna and Wave Propagation?

EGEC4210

Who is the lecturer for the Antenna and Wave Propagation course?

Sindhu S Nair

What are the two main sets of fields produced by antennas?

  • Reactive field and Fresnel field
  • Electric field and magnetic field
  • Near field and far field (correct)
  • Radiating field and non-radiating field

The near field is characterized by the electric and magnetic fields being separate and not forming a propagating wave.

<p>True (A)</p> Signup and view all the answers

What is another name for the near field?

<p>Fresnel zone</p> Signup and view all the answers

What is the distance from the antenna where the far field begins?

<p>10 wavelengths</p> Signup and view all the answers

What are the two types of radiation patterns that antennas can produce?

<p>Field patterns and power patterns</p> Signup and view all the answers

What is the three-dimensional representation of the radiation pattern called?

<p>Spherical coordinates (D)</p> Signup and view all the answers

What is the name of the angle measured off the z-axis in a spherical coordinate system?

<p>Theta (θ)</p> Signup and view all the answers

What is the name of the angle measured counterclockwise off the x-axis in a spherical coordinate system?

<p>Phi (φ)</p> Signup and view all the answers

What is the zone or direction in which radiated power is maximum?

<p>Major lobe</p> Signup and view all the answers

What is the lobe adjacent to the major lobe?

<p>Side lobe</p> Signup and view all the answers

What is the name of the lobe that is the opposite of the major lobe?

<p>Back lobe</p> Signup and view all the answers

What two planes are typically used to measure antenna radiation patterns?

<p>E-field and H-field (D)</p> Signup and view all the answers

What does HPBW stand for?

<p>Half-power beam width</p> Signup and view all the answers

What is another name for the main lobe?

<p>Boresight</p> Signup and view all the answers

What is the mathematical expression for the half-power beam width?

<p>Half power Beam width = 70λ/D</p> Signup and view all the answers

What is the mathematical expression connecting HPBW and FNBW?

<p>FNBW = 2 * HPBW</p> Signup and view all the answers

The unit of HPBW can be either radians or degrees.

<p>True (A)</p> Signup and view all the answers

Which type of radiation pattern has a doughnut shape in 3D and a figure-of-eight shape in 2D?

<p>Omni-directional (C)</p> Signup and view all the answers

What type of radiation pattern has a sharp directional, pencil-shaped pattern?

<p>Pencil-beam pattern</p> Signup and view all the answers

What type of radiation pattern has a fan-shaped pattern?

<p>Fan-beam pattern</p> Signup and view all the answers

What type of radiation pattern is non-uniform and pattern-less and is known as a shaped beam?

<p>Shaped beam pattern</p> Signup and view all the answers

The isotropic radiation pattern is a practical and widely used pattern in real-world antennas.

<p>False (B)</p> Signup and view all the answers

What is the reference point for all types of radiation patterns?

<p>Isotropic radiation</p> Signup and view all the answers

What is the formula for calculating the directivity of an antenna?

<p>Directivity (D) = (Maximum radiation intensity (U_max)) / (Average radiation intensity (U_0))</p> Signup and view all the answers

What is the formula for calculating the directivity of an antenna in terms of effective aperture area?

<p>Directivity (D) = (4 * π * Effective aperture area (A_eff)) / (Wavelength (λ) ^ 2)</p> Signup and view all the answers

What is the formula for calculating the gain of an antenna?

<p>Gain (G) = Efficiency (η) * Directivity (D)</p> Signup and view all the answers

What is the name for the output power of a signal when it is concentrated into a smaller area by the antenna?

<p>Effective Isotropic Radiated Power (EIRP)</p> Signup and view all the answers

What is the formula for calculating EIRP?

<p>EIRP = Transmit power (P_T) - Cable loss (L_C) + Antenna gain (G_a)</p> Signup and view all the answers

What is the name for the angular width of the main lobe at half the peak power level?

<p>Half-power beam width (HPBW)</p> Signup and view all the answers

What is the name for the angular distance between the first nulls on either side of the main lobe?

<p>First null beam width (FNBW)</p> Signup and view all the answers

What is the name for the wasted radiated power in the transmit mode?

<p>Sidelobe level</p> Signup and view all the answers

What is the name for the difference between the main lobe power and the back lobe power, measured in dB?

<p>Front-to-back ratio</p> Signup and view all the answers

A well-designed antenna should have CROSSPOL components at least 20 dB below the COPOL in the main-beam region.

<p>True (A)</p> Signup and view all the answers

A well-designed antenna should have CROSSPOL components at least 5 to 10 dB below the COPOL in the side lobe regions.

<p>True (A)</p> Signup and view all the answers

The polarization of electromagnetic waves never changes during transmission over long distances.

<p>False (B)</p> Signup and view all the answers

A horizontally polarized antenna can receive circularly polarized signals, but the signal strength will be reduced.

<p>True (A)</p> Signup and view all the answers

If both the transmitter and receiver use circular polarization, the signal can be received regardless of whether they use left-hand or right-hand polarization.

<p>False (B)</p> Signup and view all the answers

What is the approximate range for the front-to-back ratio (F/B) for a well-designed antenna?

<p>20 to 30 dB (D)</p> Signup and view all the answers

What kind of antenna is used as a reference for antenna gain and has no gain in any direction?

<p>Isotropic antenna</p> Signup and view all the answers

The gain of the idealized isotropic antenna is 0 dB.

<p>True (A)</p> Signup and view all the answers

What is the name of the phenomenon where the polarization of electromagnetic waves changes slightly during transmission over long distances?

<p>Propagation effects</p> Signup and view all the answers

A transmitting station at 90° relative to an antenna with a 40° beam-width will have no interference with the antenna.

<p>True (A)</p> Signup and view all the answers

The gain of a parabolic reflector antenna is independent of the operating frequency.

<p>False (B)</p> Signup and view all the answers

The effective radiated power (ERP) of a radio station is always less than its transmit power.

<p>False (B)</p> Signup and view all the answers

What is the name for the power gain measured in dB?

<p>Decibel power gain</p> Signup and view all the answers

If a radio station has an EIRP of 25 kW and a transmit power of 1.73 kW, what is the antenna gain?

<p>14.45</p> Signup and view all the answers

What is the basic STS in SONET?

<p>STS-1</p> Signup and view all the answers

What is the data rate of an STS-3 signal?

<p>155.52 Mbps</p> Signup and view all the answers

How many DS1 channels can be multiplexed within an STS-3 frame?

<p>100</p> Signup and view all the answers

What are the two main types of SONET ring topologies?

<p>Unidirectional Path-Switched Ring (UPSR) and Bidirectional Line-Switched Ring (BLSR)</p> Signup and view all the answers

What is the difference between SONET and SDH?

<p>SONET is a digital hierarchy interface for optical transmission, while SDH is a network node interface, user-network interface, and U reference-point interface to assist BISDN. (A), SONET uses a frame structure of 9 rows and 90 columns, while SDH uses a frame structure of 9 rows and 270 columns. (B), SONET uses STS (Synchronous Transport Signal) and VT (Virtual Tributary) for transmission, while SDH uses STM (Synchronous Transport Module) and VC (Virtual Container). (C), SONET has a fixed payload rate of 51.84 Mbps, while SDH has multiple payload rates, including 155.52 Mbps, 622.08 Mbps, and 2.5 Gbps. (D), All of the above (E)</p> Signup and view all the answers

What is the purpose of an STS multiplexer?

<p>An STS multiplexer multiplexes signals from multiple electrical sources and creates the corresponding optical signal.</p> Signup and view all the answers

What is the purpose of an add/drop multiplexer?

<p>Add/drop multiplexers allow insertion and extraction of signals in an STS.</p> Signup and view all the answers

What is the responsibility of the path layer in SONET?

<p>The path layer is responsible for the movement of a signal from its source to its destination.</p> Signup and view all the answers

What is the responsibility of the section layer in SONET?

<p>The section layer is responsible for the movement of a signal across a physical section.</p> Signup and view all the answers

What is the responsibility of the photonic layer in SONET?

<p>The photonic layer corresponds to the physical layer of the OSI model, and includes physical specifications for the optical fiber channel.</p> Signup and view all the answers

What encoding scheme does SONET use?

<p>NRZ encoding</p> Signup and view all the answers

How many wavelengths away should you be to be in the far field?

<p>10 wavelengths</p> Signup and view all the answers

What is the relationship between the electric and magnetic fields in the far field?

<p>They are orthogonal to each other and to the direction of propagation.</p> Signup and view all the answers

What is the purpose of scattering parameters?

<p>Scattering parameters describe the input-output relationships between ports in an electrical system.</p> Signup and view all the answers

What does S11 represent in a two-port network?

<p>The input port voltage reflection coefficient</p> Signup and view all the answers

What is the purpose of the S-parameter matrix?

<p>The S-parameter matrix can be used to determine reflection coefficients and transmission gains from both sides of a two-port network.</p> Signup and view all the answers

What are the two common types of radiation patterns?

<p>Field patterns and power patterns (A), Omni-directional patterns and directional patterns (C), All of the above (D)</p> Signup and view all the answers

What type of antenna radiates power equally in all directions?

<p>Isotropic antenna (C)</p> Signup and view all the answers

What is the purpose of the half-power beam width (HPBW)?

<p>The HPBW is the angular separation in which the magnitude of the radiation pattern decreases by 50% (or -3dB) from the peak of the main beam.</p> Signup and view all the answers

What is the purpose of the first null beam width (FNBW)?

<p>The FNBW is the angular span between the first pattern nulls adjacent to the main lobe.</p> Signup and view all the answers

What is the purpose of the front-to-back ratio (F/B)?

<p>The F/B is a measure of how much power is radiated in the back direction compared to the front direction.</p> Signup and view all the answers

What is the purpose of the side-lobe level (SLL)?

<p>The SLL is a measure of how much power is radiated in the side lobes compared to the main lobe.</p> Signup and view all the answers

What is the purpose of the effective radiated power (ERP)?

<p>The ERP is a measure of the total power that is radiated by an antenna, taking into account the power loss from the transmission line and the antenna's gain.</p> Signup and view all the answers

What is the formula for calculating directivity?

<p>D = 4πAeff/λ²</p> Signup and view all the answers

What is the purpose of polarization?

<p>Polarization refers to the orientation of the electric and magnetic fields with respect to the earth.</p> Signup and view all the answers

What is the purpose of cross-polarization?

<p>Cross-polarization is the undesired orthogonal polarization.</p> Signup and view all the answers

Which of these is NOT a circuit quantity of an antenna?

<p>Current distribution (C)</p> Signup and view all the answers

The effective length of an antenna is the ratio of the voltage across the open terminals to the field strength of the incident wave.

<p>True (A)</p> Signup and view all the answers

What is the term for the area of the receiving antenna that captures most of the power from the incoming wave front?

<p>Effective area</p> Signup and view all the answers

The S-parameter S12 represents the power transferred from port 2 to port 1.

<p>True (A)</p> Signup and view all the answers

The ______ is approximately 10 wavelengths from the antenna and represents the radio wave with the combined electric and magnetic fields.

<p>Far field</p> Signup and view all the answers

Which of the following is NOT a common parameter used to describe antenna radiation patterns?

<p>Polarization (C)</p> Signup and view all the answers

Match these parameters with their corresponding descriptions

<p>Main lobe = The zone or direction where the radiated power is at its maximum Nulls = The zone or direction where the radiated power is at its minimum Side lobe = The lobe adjacent to the major lobe. Back lobe = The lobe opposite to the major lobe.</p> Signup and view all the answers

The radiation pattern of an antenna is typically measured in two planes: the E-field plane and the H-field plane.

<p>True (A)</p> Signup and view all the answers

What is the term for the angle between the first pattern nulls adjacent to the main lobe?

<p>First null beam width</p> Signup and view all the answers

Which of these is a type of radiation pattern?

<p>All of the above (D)</p> Signup and view all the answers

The power gain of an antenna is the ratio of the maximum power density in a given direction to the average power density over all directions.

<p>False (B)</p> Signup and view all the answers

The half-power beam width is determined by the angle at which the power density is half of the maximum power density.

<p>True (A)</p> Signup and view all the answers

What is the formula for calculating the EIRP (Effective Isotropic Radiated Power) of an antenna?

<p>EIRP = PT - LC + GA</p> Signup and view all the answers

The directivity of an antenna is directly proportional to the effective aperture area.

<p>True (A)</p> Signup and view all the answers

The gain of an antenna is equal to its directivity multiplied by the antenna's efficiency.

<p>True (A)</p> Signup and view all the answers

Co-polarization refers to the desired polarization of an antenna, while cross-polarization refers to the undesired orthogonal polarization.

<p>True (A)</p> Signup and view all the answers

What does horizontally polarized mean in terms of antenna orientation?

<p>The electric field is parallel to the ground.</p> Signup and view all the answers

Circular polarization refers to the situation where the electric and magnetic fields rotate as they leave the antenna.

<p>True (A)</p> Signup and view all the answers

What are the two types of fields that antennas produce?

<p>All of the above (D)</p> Signup and view all the answers

Which of the following is NOT a common parameter of antenna radiation patterns?

<p>Polarization (A)</p> Signup and view all the answers

The far field is the region where the electric and magnetic fields are in phase with each other.

<p>True (A)</p> Signup and view all the answers

What is the approximate distance for the far-field region?

<p>10 wavelengths from the antenna</p> Signup and view all the answers

The term Effective Radiated Power (ERP) is used when calculating the radiated power using a half-wave dipole as the reference.

<p>True (A)</p> Signup and view all the answers

What is the mathematical relationship between the First Null Beam Width (FNBW) and the Half Power Beam Width (HPBW)?

<p>FNBW = 2HPBW</p> Signup and view all the answers

What is the main purpose of using S-parameters in antenna analysis?

<p>To describe the power transfer between ports or terminals in an electrical system (D)</p> Signup and view all the answers

What is the purpose of the "Add/Drop Multiplexer" in SONET?

<p>It allows adding or removing signals from a specific path within the SONET network. (A)</p> Signup and view all the answers

What does the term "beamwidth" refer to in antenna system?

<p>The angular width of an antenna's main lobe</p> Signup and view all the answers

Which of the following is NOT a type of radiation pattern?

<p>Hemispherical (B)</p> Signup and view all the answers

The isotropic antenna is a practical and realistic antenna type used in real-world applications.

<p>False (B)</p> Signup and view all the answers

What is the term for a side lobe that has the highest strength among all side lobes?

<p>Largest side lobe</p> Signup and view all the answers

What is the difference between "co-polarization" and "cross-polarization" in terms of antenna radiation?

<p>Co-polarization refers to the desired polarization of the antenna, while cross-polarization represents the undesired orthogonal polarization.</p> Signup and view all the answers

Which of the following is NOT a benefit of using a higher side lobe level in an antenna?

<p>Reduced interference (D)</p> Signup and view all the answers

Flashcards

Near Field

This is the region around an antenna where the electric and magnetic fields are separate and not yet combined into radio waves.

Far Field

This is the region far from the antenna where the electric and magnetic fields have combined to form radio waves.

Far Field Distance

The distance from an antenna where near field effects become negligible and the radio waves are essentially plane waves.

Radiation Pattern

A graphical representation of how an antenna radiates power in different directions.

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3D Radiation Pattern

A three-dimensional plot of antenna radiation power as a function of angular position and radial distance.

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Main Lobe

The direction in which the maximum radiation power is emitted from an antenna.

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Side Lobes

Weaker radiation directions perpendicular to the main lobe of an antenna.

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Back Lobe

Radiation in the opposite direction of the main lobe of an antenna.

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Half-Power Beam Width (HPBW)

The angular width of the main lobe of an antenna where the radiation power drops to half its maximum value (-3 dB).

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First Null Beamwidth (FNBW)

The angular span between the first nulls on either side of the main lobe in an antenna's radiation pattern.

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Directivity

The ratio of the power radiated in the desired direction to the average power radiated in all directions.

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Gain

The ratio of the power radiated by an antenna in its strongest direction to the power radiated by a hypothetical isotropic antenna.

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Isotropic Antenna

A theoretical antenna that radiates power equally in all directions. It is used as a reference for comparing the performance of real antennas.

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Polarization

The orientation of the electric field of a radio wave with respect to the Earth's surface.

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Co-Polarization

When the transmitting and receiving antennas have the same polarization, resulting in optimal signal strength.

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Omni-directional Antenna

An antenna with a radiation pattern that is relatively uniform in all directions.

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Directional Antenna

An antenna that concentrates its radiation in a narrow beam.

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Directivity (D)

The ratio of the power density in the direction of maximum radiation to the power density averaged over all directions.

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Gain (G)

The ratio of the power density in the direction of maximum radiation to the power density of an isotropic antenna.

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Power Flux Density

The power density of an antenna at a particular distance from the antenna, measured in Watts per square meter (W/m²).

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Radiation Intensity

The power radiated by an antenna per unit solid angle.

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Field Strength

The strength of the electric or magnetic field at a particular point in space.

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Antenna Efficiency

A measure of the effectiveness of an antenna in converting power from the transmitter to radiated power, expressed as a ratio of the power radiated by the antenna to the power supplied to the antenna.

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Antenna Radiation Efficiency

The ratio of the power radiated by an antenna to the power supplied to the antenna.

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Antenna Feed System

A component of the antenna that couples the transmission line to the antenna element.

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Antenna Feed Point

The point at which the signal is fed into the antenna from the transmission line.

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Antenna Geometry

The physical shape and dimensions of the antenna element.

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Antenna Bandwidth

The frequency range over which the antenna can operate effectively.

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Antenna Polarization Efficiency

The ability of an antenna to produce a desired polarization.

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Synchronous Digital Hierarchy (SDH)

A standard that uses light-emitting diodes (LED) or lasers for synchronous optical fiber communication. Its purpose is to overcome synchronization problems and replace the plesiochronous digital hierarchy (PDH) system.

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Synchronous Optical Network (SONET)

The standard that transmits large data volumes over long distances using fiber optics. It combines multiple data streams using LEDs and laser beams to achieve high-speed transmission.

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STS Multiplexer

It's like a digital multiplexer that combines multiple signals from different sources, creating a single high-speed data stream. It's used in SONET systems for transmitting signals.

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STS Demultiplexer

The opposite of a multiplexer. It separates a high-speed data stream into individual signals, converting an optical signal back into electrical signals.

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Regenerator

A repeater in a SONET network. It amplifies and regenerates weakened optical signals, extending the transmission distance

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Add/Drop Multiplexer

Allows adding or removing signals within a SONET system. It can add new signals to a path or extract existing ones.

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Path Layer

The layer in SONET responsible for ensuring that the signal reaches its destination across the entire network path.

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Line Layer

This handles signal transmission over a single physical line, connecting SONET multiplexers.

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Section Layer

Handles signal transmission over a physical section, typically the distance between two regenerators in a SONET network.

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Photonic Layer

This SONET layer corresponds to the OSI model's physical layer. It defines the physical specifications for the optical fiber channel.

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STS (Synchronous Transport Signal)

A SONET signal, often referred to as a Synchronous Transport Signal. The basic unit is STS-1, with multiples of it forming higher-order signals.

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Virtual Tributary (VT)

A signal that carries the actual data payload in SONET. They can be grouped into virtual containers or carry a single client data stream.

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Unidirectional Path-Switched Ring (UPSR)

A ring network where traffic flows in one direction. If a link fails, traffic is rerouted in the opposite direction to maintain network connectivity.

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Bidirectional Line-Switched Ring (BLSR)

A ring network where traffic can flow in both directions. If a link fails, the affected traffic is rerouted to a protection path in the opposite direction.

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Add/Drop Multiplexer

The multiplexer used in SONET for adding signals to a STS path or removing signals from it. It allows for flexible access to the network.

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Plesiochronous Digital Hierarchy (PDH)

A digital transmission hierarchy that uses multiplexing to combine different bit rates into a single stream.

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Multiplexing

A method of combining multiple lower-speed signals into a single higher-speed signal.

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Optical Transceiver

A device that converts electrical signals to optical signals or vice versa.

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Synchronous Transport Signal (STS)

A fundamental unit of data in SONET, carrying a specific payload.

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STS-1

A SONET signal with a basic data rate of 51.84 Mbps.

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Higher Order STS (e.g., STS-3, STS-12)

A SONET signal with a data rate that is a multiple of STS-1, such as STS-3 or STS-12.

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Virtual Container (VC)

A SONET signal that carries a single stream of data at a specified bit rate.

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Synchronous Transport Module (STM)

A SONET signal that carries multiple streams of data, combined for efficient transmission.

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Time-Division Multiplexing (TDM)

The process of combining multiple lower-speed signals into a higher-speed signal, allowing more efficient transmission over a single channel.

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Pulse Amplitude Modulation (PAM)

A method of transmitting data by converting it into a series of pulses, where the presence or absence of a pulse represents a bit.

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Frequency Shift Keying (FSK)

A method of transmitting data by encoding the information in the frequency of a signal.

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Phase Shift Keying (PSK)

A method of transmitting data by encoding the information in the phase of a signal.

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Quadrature Amplitude Modulation (QAM)

A method of transmitting data by encoding the information in the combination of amplitude and phase of a signal.

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Multiplexed Communication System

A communication system that uses multiplexing to combine and transmit multiple data streams over a single channel.

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Digitalization

The process of converting a signal from analog to digital format, allowing for more reliable transmission over long distances.

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Binary Encoding

A method of encoding data using a combination of 0s and 1s, where each bit represents a value.

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Frame Structure

A standard way of organizing data into blocks, allowing for more efficient transmission and error detection.

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Error Detection

A method of detecting errors in data transmission by adding extra bits, allowing the receiver to verify the integrity of the received data.

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Flexibility

The ability of a communication system to handle different data rates and network configurations.

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SDH (Synchronous Digital Hierarchy)

A standard that uses LEDs or lasers to send data synchronously over optical fiber. It was developed to fix timing issues and replace the older PDH system.

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PDH (Plesiochronous Digital Hierarchy)

A digital hierarchy of multiplexing that combines various bit rates into a single stream. It uses a step-by-step approach for combining data streams.

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SONET (Synchronous Optical Network)

A standardized protocol for transmitting vast amounts of data over long distances using fiber optics. It combines multiple data streams over fiber using LEDs and lasers.

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STS-1 (Synchronous Transport Signal-1)

The basic SONET signal unit. All other STS signals are multiples of this.

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STM (Synchronous Transport Module)

SONET signals that carry multiple streams of data combined for efficient transmission.

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VC (Virtual Container)

A SONET signal that carries a single stream of data at a specific bit rate.

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UPSR (Unidirectional Path-Switched Ring)

A ring network where traffic flows in only one direction, and if a link fails, traffic is rerouted in the opposite direction for continuous connectivity.

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BLSR (Bidirectional Line-Switched Ring)

A ring network where traffic can flow in both directions. If a link fails, the affected traffic is rerouted to a protection path on the opposite side.

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Study Notes

Course Information

  • Course Code: EGEC4210
  • Lecturer: Sindhu S Nair
  • Course Title: Antenna and Wave Propagation

Course Outline

  • Outcome #4: Evaluate fundamental antenna parameters for effective radiation.
  • Outcome #5: Analyze antenna arrays for isotropic point sources and dipoles.
  • Outcome #6: Determine and analyze radiation patterns of different antenna types.

Antenna Parameters

  • Circuit Quantities: Antenna impedance (Za), Radiation resistance (Rr), Antenna temperature (Ta)
  • Physical Quantities: Size, Weight, Current distribution
  • Space Quantities: Field patterns, Polarization (LP, CP, EP), Power patterns, Beam area, Directivity (D), Gain (G), Effective aperture (Ae), Radar cross-section (σ)

Effective Length

  • Used to determine polarization efficiency.
  • Definition: The ratio of voltage at open terminals of a receiving antenna to field strength of the incident wave front (in the same polarization direction).

Effective Area

  • The area of the receiving antenna that absorbs most power from the incoming wave front.
  • Related to the maximum power obtained and the actual antenna area.

Scattering Parameters

  • Describe the input-output relationship between ports/terminals in an electrical system.
  • S12: Power transferred from port 2 to port 1.
  • S21: Power transferred from port 1 to port 2.
  • Snm: Power transferred from port m to port n in a general network.

Near Field and Far Field

  • Antennas produce near and far fields.
  • Near Field: Region directly around the antenna where electric and magnetic fields are separate; contains transmitted information, weakens with distance (approximately by the quadruple of the distance). Also referred to as the Fresnel zone.
  • Far Field: Region approximately 10 wavelengths from the antenna; is the radio wave; contains electric and magnetic fields.
  • Reactive near field ≤ 0.62 × (D3/λ)1/2
  • Radiating near field (Fresnel region) ≤ 2D2/λ
  • Far field ≥ 2D2/λ

Radiation Pattern

  • Graphically shows the radiation power pattern as a function of angular position and distance from the antenna.
  • Three-dimensional quantity, variation of field/power proportional to field squared.
  • Represented mathematically using spherical coordinates (E(θ, φ) and H(θ, φ)), where θ is the angle measured off the z-axis and φ is the angle measured counter-clockwise from the x-axis.

Different Types of Radiation Patterns

  • Isotropic: Uniform radiation in all directions.
  • Omni-directional: Doughnut shape in 3D; figure-of-eight in 2D.
  • Directional: Pencil- or fan-shaped radiated power.

Lobe Formation

  • Major lobe: Area of maximum radiated power and indicates directivity.
  • Side lobes: Areas with weaker radiation, adjacent to the major lobe.
  • Back lobe: Lobe opposite to the main lobe; often significant energy loss.

Half Power Beam Width (HPBW)

  • Angular separation where the radiation pattern magnitude decreases by 50% (or -3dB) from the main beam peak.

First Null Beam Width (FNBW)

  • Angular span between the first nulls adjacent to the main lobe.

Directivity

  • Ratio of maximum radiation intensity to the average radiation intensity over all directions.
  • equation for large antenna- D = 32400 / θeθh
  • equation for small antenna- D= 41253 / θeθh where θe, θh are in degrees.

Effective Radiated Power (ERP)

  • Radiated power calculated by reference to a half-wave dipole rather than an isotropic antenna.
  • ERP (dBW) = EIRP (dBW) – 2.15 dBi

Co-Polarization and Cross-Polarization

  • Co-polar (COPOL): Desired polarization.
  • Cross-polar (CROSSPOL): Undesired orthogonal polarization (should be low to minimize interference).

Antenna Gain

  • Given in ratio (e.g., 800) or decibels (e.g., 29 dB).
  • Gain formula for parabolic reflector: G = η(Ï€r2/λ2) where:
    • η = Efficiency
    • r = Radius of the reflector
    • λ = Wavelength

Additional Information

  • dB Calculations (Example): EIRP = Pt × G (Where G = gain in linear scale and Pt = transmitter power)

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Related Documents

Antenna and Wave Propagation PDF
Chapter 8 SONET or SDH (Revised 2s2324) PDF

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