Part 5 Flashcards by chxngy Unknown

Crucial for efficient power transfer and minimal signal reflection

Matching transmission lines

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When transmission lins are mismatched, ______ occurs due to standing waves, leading to inefficiencies in signal transmission

Power loss

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Maximizes power transfer from the source to the load, minimizing reflections that could distort the signal

Impedance matching

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oscillations of an electromagnetic wave are _______. Therefore, they are characterized by a frequency

Periodic and repetitive

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distance of one cycle occurring in space

Wave length

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Wavelength is determined from the equation

Distance = velocity x time

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Wavelength is represented by

Lambda (λ)

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Formula for wavelength

λ = v x T

Where λ = wavelength
V = velocity
T = period

But T = 1/F

Therefore, λ = v/f

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Widely used in communication systems to transmit electrical signals wherein its primary types include coaxial cable, twisted pair cable, and power cables

Metallic cables

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Structures that guide electromagnetic waves from one point to another including key parameters such as characteristic impedance (Zo), and Propagation Velocity (v)

Transmission lines

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The inherent impedance of a transmission line,
determined by its geometry and the properties of the dielectric material.

Charateristic Impedance

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The speed at which a signal propagates along the transmission
line, influenced by the dielectric constant of the insulating material

Propagation Velocity (v)

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4 Reasons why impedance matching is important

Minimizes Signal Reflection
Maximizes Power Transfer
Reduces Signal Distortion and Noise
Improving System Efficiency

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According to the ________, maximum power is delivered
from a source to a load when the load impedance matches the source impedance.

Maximum Power Transfer Theorem

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_______ can cause distortion, affecting data integrity in
communication systems.

Reflected signals

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________ cause unwanted
distortions, ringing, or even signal degradation, which is particularly
problematic in audio systems, communication networks, and digital
circuits.

Mismatched impedance

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improves the efficiency of power
transmission, especially in wireless communication, antennas, and RF
amplifiers, by ensuring that energy is not lost as heat or reflected signals

Proper impedance matching

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Components like resistors, inductors, and capacitors (L-section, π-section,
or T-section networks) adjust the impedance

Impedance Matching Networks

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Types of matching transmission lines used for impedance matching

L network
Pi-network
T-network

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basic impedance-matching circuit made up of two passive components, one in series
and one in parallel. Thus, forming an “L” shape and widely used in RF circuits, audio systems,
and power electronics to optimize power transfer and minimize signal reflection between a
source and a load.

L-network

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Types of L Networks

Low Pass L Network
High Pass L Network

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Uses an inductor and a capacitor to pass low-frequency signals while blocking high
frequencies, often used in RF applications.

Low-Pass L-Network

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Uses a capacitor and an inductor in the opposite configuration to allow high frequency signals to pass while blocking low frequencies.

High Pass L Network

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electrical circuit configuration used for impedance matching, filtering, and attenuation. It
consists of three passive components typically resistors, capacitors, or inductors arranged in the
shape of the letter “T”

T Network

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Types of T Networks

Low Pass T Network High Pass T Network Attenuator T Network Balanced T Network

Uses two inductors in series and a capacitor in parallel to allow low frequencies while blocking high frequencies.

Low Pass T Network

Uses two capacitors in series and an inductor in parallel to pass high frequencies while blocking low frequencies.

High Pass T Network

Uses resistors to reduce signal strength while maintaining impedance matching, often used in RF and audio applications.

Attenuator T Network

A symmetrical version used for balanced signal transmission, minimizing distortion and interference

Balanced T Network

A symmetrical arrangement of three components (inductors or capacitors) with one in series and two in shunt, offering wider bandwidth matching capabilities. Moreover, It is an electrical circuit used for impedance matching, filtering, and signal attenuation.

Pi Network

Types of Pi-networks

Low Pass Pi Network High Pass Pi Network Attenuator Pi Network

Uses two capacitors in parallel with an inductor in series to allow low frequencies to pass while blocking high frequencies

Low Pass Pi Network

Uses two inductors in parallel with a capacitor in series to pass high frequencies while blocking low frequencies.

High Pass Pi Network

Uses resistors to reduce signal strength while maintaining impedance matching, often used in RF circuits

Attenuator Pi Network

A special transmission line section helps match different impedances. of λ/4 (one-quarter of the wavelength)

Quarer Wave Transformer

Open or short-circuited transmission line segments (stubs) provide impedance tuning

Stub Matching

One stub to achieve impedance matching

Single stub

More flexible, uses two adjustable stubs

Double stub

Convert between balanced and unbalanced lines or step up/down impedance levels. Commonly used when connecting a coaxial cable to a balanced antenna system

Baluns and Transformers

Graphical method for impedance matching Visualize impedance transformation and find solutions easily. Used to design stub matching and L Networks

Smith chart matching

In antennas and RF amplifiers, signal reflection can cause power loss and inefficiency. The _______ ensures that the impedance of the antenna matches that of the transmission line, allowing maximum power transfer.

quarter-wave transformer

Carry signals in the form of light, and impedance mismatches at junctions between different fiber types can cause power loss and reflection.

Optical fibers

Applications in Telecommunications

RF and Microwave Circuits Optical Fiber Communications Wireless Networks

can help smooth the transition between different refractive indices, minimizing signal distortion.

A quarterwave transformer in dielectric waveguides

In these networks, signals must be transmitted efficiently across different components (antennas, amplifiers, and transmission lines)

Wireless Networks

Formula for velocity factor

Vf = Vp/C = 1/sqrt(∈r)

Most of the losses in a properly constructed and used transmission line are due to______ and, at higher frequencies, _______. Both of these losses increase with frequency.

conductor resistance dielectric conductance

Transmission line loss is usually specified in decibels for a given length which is converted in this process:

L = antilog(L(dB)/ 10)

Transmission Line Losses Formula

L = Pi / Po Where Pi =power input Po = power output

When Zo = Zl, all the incident power is absorbed by the load which is called

Matched line

When Zo is not equal to Zl, some of the incident power is absorbed by the load, and some is returned (reflected) to the source which is called an

Unmatched or mismatched line

With a mismatched line, there are 2 electromagentic waves, travelling in opposite directions, present on the line which are in fact called

Travelling waves

The two traveling waves set up an interference pattern known as

Standing wave

The standing wave has ______, which is separated by a half wavelength of the travelling waves and ______ also separated by a half wavelength

Minima (nodes) maxima (antinodes)

vector quantity that represents the ratio of reflected voltage to incident voltage or reflected current to incident current.

Reflection coefficient or coefficient of reflection

Mathematically, the reflection coefficient is _______ defined by

Γ = (ZL - Z₀) / (ZL + Z₀)

If Γ = 0, the line is

perfectly matched (no reflections)

If Γ = 1, _______ occurs

total reflection (high mismatch)

defined as the ratio of the maximum voltage to the minimum voltage or the maximum current to the minimum current of a standing wave on a transmission line

Standing wave ratio

SWR is often called the _____, wherein it Indicates the severity of impedance mismatch.

voltage standing-wave ratio (VSWR).

SWR is related to reflection coefficient by

SWR = Vmax/Vmin (unitless) Where Vmax = Ei + Er Vmin = Ei - Er

Reflections can cause the power delivered to the load to be less than it would be with a matched line for the same source because some of the power is reflected back to the source.

Power Reflection Coefficient

Since power is proportional to the square of voltage, the fraction of the power that is reflected is Γ^2, that is

P Γ =Γ^2Pi Where P Γ = power reflected from the load Pi = incident power at the load Γ = voltage reflection coefficient

In a matched transmission line, the characteristic impedance __________ regardless of the source’s distance from the load

Remains constant

For efficient transmission, only the ______, which has the lowest cutoff frequency, should be used to prevent dispersion

Dominant mode

According to the pattern of electric and magnetic fields within the waveguide, modes are designated as

transverse electric (TE) or transverse magnetic (TM) modes

In TE modes in a rectangular waveguide, the _______ is represented by the arrows, with the length of the arrows proportional to the field strength.

electric field strength

The first number following the TE designation represents the

number of half-cycles of the wave along the long dimension (a) of the rectangular guide

The second number following the TE designation represents the

Number of variations along the short dimension

In a rectangular waveguide, _____ is the dominant mode.

TE10

TE modes in rectangular waveguides

Lambda (c) = c / fc 2a = c / fc fc = c / 2a Where a = longer dimension of the waveguide cross section Lambda (c) = cutoff wavelength Lambda = wavelength in meters C = 3 x 10^6 meters per second Fm= frequency in hertz