What is RF? Basic Training and Fundamental Properties

Summary

This training script delves into the fundamentals of radio frequency (RF), explaining its nature as an electromagnetic wave and its properties like frequency and wavelength. It explores the electromagnetic spectrum, RF's power and applications, and introduces the concept of decibels and bandwidth. The script highlights the ubiquity of RF in various technologies and the challenges engineers face in managing the spectrum's complexity and allocation.

Takeaways

• 📡 RF stands for Radio Frequency and is a form of energy that travels as electromagnetic waves, capable of propagation in various media including vacuum and solid-state materials.
• 🌊 The electromagnetic spectrum is a range of frequencies and wavelengths, with RF typically defined between 1 MHz and 3 GHz, and higher frequencies classified as microwaves and millimeter waves.
• 🔍 The relationship between frequency and wavelength is inverse: as frequency increases, wavelength decreases, impacting the design and size of components used in RF engineering.
• 🔢 Common units for frequency include megahertz (MHz) and gigahertz (GHz), representing one million and one billion waves per second, respectively.
• 🌐 Power in RF is a measure of the energy per unit of time the wave can deliver, with higher power waves capable of transmitting further or penetrating deeper in applications.
• 📊 Power is often expressed in relative terms using decibels (dB), which simplifies calculations involving large or small numbers and is useful for understanding gains and losses in RF systems.
• 🔄 The bandwidth of a signal refers to the range of frequencies it occupies, with wider bandwidths allowing for more information to be transmitted, such as in FM radio and cellular communications.
• 📈 The need for increased information transmission typically leads to demands for broader bandwidths and more complex electronic components, presenting challenges for RF engineers.
• 🌍 The allocation of the electromagnetic spectrum is managed by regulatory bodies like the FCC in the US, with different frequency bands designated for various licensed, unlicensed, or government uses.
• 🆓 ISM (Industrial, Scientific, and Medical) bands are free to use within certain power limitations and are reserved for non-communication purposes, including common household appliances like microwave ovens.
• 🌐 RF and microwave engineers work within a limited slice of the spectrum, tailored to specific applications, and must consider international alignment of frequency use through organizations like the ITU.

Q & A

What does RF stand for and what type of energy is it?

RF stands for Radio Frequency. It is a form of energy that is a modification of time-dependent electronic and magnetic fields, essentially an electromagnetic wave that can propagate in vacuum or solid-state media.

What is the frequency range generally referred to as RF?

The frequency range between one megahertz (1 MHz) and three gigahertz (3 GHz) is generally called RF.

What is the relationship between frequency and wavelength in electromagnetic waves?

The relationship between frequency and wavelength is reciprocal; as frequency increases, the wavelength decreases, and vice versa. The number of waves per second is the frequency, and the distance between wave maxima is the wavelength.

What is the speed of electromagnetic waves in a vacuum?

The speed of electromagnetic waves in a vacuum is always the same regardless of frequency, which is the speed of light.

How does the size of components used in engineering vary with frequency?

Higher frequency engineers tend to design with smaller components, while lower frequency engineers use larger physical components due to the reciprocal relationship between frequency and wavelength.

What is the significance of the term 'decibel' in RF engineering?

The decibel (dB) is used to express the ratio of two values in a logarithmic scale, which is particularly useful for representing large or small numbers, and for calculating power gains and losses in RF systems.

What is the bandwidth of a signal and how does it relate to information transmission?

The bandwidth of a signal is the width of the spectral chunk covered by the signal or system. It indicates how much information the wave can carry, which is crucial for applications like FM radio and cellular communications.

What are ISM bands and why are they important in RF communication?

ISM bands are Industrial, Scientific, and Medical radio bands that are free to use within certain power limitations. They are important because they allow for the use of RF electromagnetic fields for various non-communication purposes without interference.

How does the frequency allocation map illustrate the complexity of RF usage?

The frequency allocation map shows how the electromagnetic spectrum is divided among different uses, including licensed, unlicensed, and government-only use, highlighting the diverse and complex nature of RF usage.

What is the role of the ITU in aligning frequency use across different countries?

The International Telecommunication Union (ITU) works to align frequency use across borders to ensure that all countries can operate their communication systems without interference.

Why is the demand for information transmission increasing the challenges for RF engineers?

The increasing demand for information transmission is adding to the complexity and requirements of electronic components, which in turn presents more challenges for RF engineers to design and optimize systems for higher bandwidth and efficiency.

Outlines

00:00

📡 Introduction to Radio Frequency (RF)

This paragraph introduces the concept of radio frequency (RF) as a form of energy characterized by time-dependent electronic and magnetic fields, essentially electromagnetic waves. It explains RF's propagation in various media, including vacuum and solid-state materials like metal or through cables and antennas. The script clarifies the spectrum of electromagnetic waves, distinguishing RF from microwaves and millimeter waves based on frequency ranges. It also illustrates the relationship between frequency and wavelength, using the analogy of waves on a beach, and introduces common frequency terms like megahertz and gigahertz. The constant speed of electromagnetic waves in a vacuum and the inverse relationship between frequency and wavelength are highlighted, affecting the engineering techniques used at different frequencies.

05:01

🔊 Power, Decibels, and Bandwidth in RF Communication

The second paragraph delves into the importance of power in RF communication, describing it as a measure of energy per unit time that an electromagnetic wave can deliver. It explains how power affects transmission distance and penetration depth, and the necessity of considering power in relative terms using decibels (dB). The concept of logarithmic scaling is introduced to simplify calculations involving large or small numbers, with examples provided to illustrate how gains and losses are measured in dB. The paragraph also explains the significance of bandwidth, which is the range of frequencies occupied by a signal, and how it relates to the capacity for information transmission. Examples of FM radio and cellular communication are given to demonstrate the practical applications of bandwidth in different technologies.

10:02

🌐 Frequency Allocation and RF Applications

The final paragraph discusses the complexity and diversity of electromagnetic spectrum usage, particularly focusing on frequency allocation for various applications. It mentions the preference for lower frequency allocations for systems requiring larger transmission distances due to less signal degradation by obstacles. The paragraph also highlights the Industrial, Scientific, and Medical (ISM) radio bands, which are free to use within certain power limitations, and their significance in applications like microwave ovens and Wi-Fi. The script touches on the products and technologies used by RF power and RF small signal to cover different frequency bands and applications. It concludes with a mention of the International Telecommunication Union (ITU) and the global cooperation in aligning frequency use, emphasizing the importance of understanding RF basics for engineers and businesses involved in the field.

Keywords

💡Radio Frequency (RF)

Radio Frequency, often abbreviated as RF, refers to the oscillating electromagnetic field energy that is a form of energy with properties of both electric and magnetic fields varying with time. In the context of the video, RF is the central theme, representing a specific range of frequencies used in various applications. The script explains that RF is an electromagnetic wave that can propagate through a vacuum or various media, and it is specifically the frequencies between one megahertz and three gigahertz that are generally termed as RF.

💡Frequency

Frequency is the number of oscillations or cycles per unit time of a wave, typically measured in hertz (Hz). It is a fundamental property of RF waves and is directly related to the energy of the wave. The script mentions frequency in the context of defining RF and also when discussing the electromagnetic spectrum, where it explains the relationship between frequency and wavelength, and how frequency is used to categorize different types of electromagnetic waves.

💡Wavelength

Wavelength is the physical distance between two corresponding points of a wave, such as the distance between two successive crests. The script uses the analogy of observing sea waves to explain the concept of wavelength and relates it to frequency, stating that the distance between wave maxima is the wavelength and that higher frequencies correspond to shorter wavelengths.

💡Electromagnetic Spectrum

The Electromagnetic Spectrum is the range of all possible frequencies of electromagnetic radiation. The video script introduces the spectrum to illustrate the different frequencies and their corresponding wavelengths, including visible light, X-rays, and RF waves. It also shows how RF fits within this spectrum and how different frequencies are used for various applications.

💡Power

Power, in the context of electromagnetic waves, is the measure of the energy per unit of time that the wave can deliver. The script discusses power as an important parameter for RF waves, as it affects how far a wave can be transmitted and how deeply it can penetrate materials. Power is also a key consideration in the design of RF systems.

💡Decibel (dB)

Decibel is a logarithmic unit used to express the ratio of two values of a physical quantity, often power or intensity, in decibels (dB). The script explains the use of decibels in RF engineering to describe gains and losses in signal strength, making it easier to handle large or small numbers and to perform calculations involving multiple components.

💡Bandwidth

Bandwidth refers to the range of frequencies occupied by a signal or the width of the frequency band over which a system operates. The script discusses bandwidth in relation to RF applications, such as FM radio, which has a specific bandwidth to receive signals and transmit information.

💡ISM Bands

ISM Bands, or Industrial, Scientific, and Medical radio bands, are specific frequency bands reserved for the use of RF electromagnetic fields for purposes other than communications. The script mentions ISM bands as free-to-use frequency bands with certain power limitations, highlighting their importance in various applications, including the frequency used by a magnetron.

💡Magnetron

A magnetron is a type of vacuum tube that generates high-frequency electromagnetic waves, commonly used in microwave ovens. The script uses the magnetron as an example to illustrate the concept of frequency, stating that a typical magnetron operates at 2.45 gigahertz, which corresponds to a specific wavelength.

💡Terrestrial Waves

Terrestrial waves, as mentioned in the script, refer to electromagnetic waves that propagate through the Earth's surface or through solid-state media like metal on a circuit board or through a coaxial cable. This concept is important for understanding how RF signals can be transmitted over land and the role of different media in RF communication.

💡Propagation

Propagation is the process by which electromagnetic waves spread out from their source and travel through space or a medium. The script discusses propagation in the context of RF waves, explaining how they can propagate through various media, including vacuum, space, and solid materials, which is essential for RF communication and broadcasting.

Highlights

Introduction to radio frequency (RF) and its fundamental aspects.

RF defined as a form of energy in the form of electromagnetic waves.

Frequency range of RF specified as 1 MHz to 3 GHz.

Explanation of the electromagnetic spectrum and its relation to RF.

The concept of wavelength and its reciprocal relationship with frequency.

Importance of frequency and wavelength in engineering techniques.

Power as a key parameter in RF, measuring energy per unit time.

Use of decibels (dB) for expressing power levels in a relative way.

Understanding the math behind dB calculations for signal gains and losses.

Bandwidth defined as the width of the frequency spectrum covered by a signal.

Different bandwidth requirements for various RF applications.

Frequency allocation for popular applications and the importance of ISM bands.

Challenges faced by engineers due to increasing demands on electronic components.

The role of the ITU in aligning frequency use across borders.

The complexity and diversity of electromagnetic spectrum usage today.

US frequency allocation map illustrating RF's ubiquity and importance.

Overview of RF power and small signal products covering various frequency ranges.

Conclusion summarizing the basics of RF and its applications.

Transcripts

as we said in this training block we

will do our best to explain the basic

elements of rf

this presentation will teach you the

most fundamental aspects of rf and where

these aspects play fundamental roles

we will start with an introduction on rf

as such and will continue with its

fundamental properties such as frequency

and wavelength

we'll explain the impressive

electromagnetic spectrum

the power that rf can have

the unit decibel and the term bandwidth

of rf applications

we'll zoom into a part of the spectrum

and show you some typical applications

and finally try to impress you with the

united states frequency allocation map

to give you an idea of rf's ubiquity and

importance

what is rf that we spend so much of our

time talking about it and even do

business with

rf stands for radio frequency

rf is a form of energy in the

modification of time dependent

electronic and magnetic fields

in short it's an electromagnetic wave

which propagates readily in vacuum or

rather space or in solid-state media

like metal on a circuit board or through

a coaxial cable or it can propagate out

of an antenna into space

in former times people talked about

ether as a medium to carry

electromagnetic waves

however that notion was pretty much

wrong

it simply takes space

our three-dimensional world to carry

these types of waves

we said rf is an electromagnetic wave

to be a bit more specific only the wave

frequencies between one megahertz and

three gigahertz are generally called rf

above 3 gigahertz up to 30 gigahertz we

speak about microwaves

higher frequencies between 30 and 300

gigahertz are termed millimeter waves

as we will see later when we discuss the

electromagnetic spectrum

even higher frequencies manifest

themselves as eg visible light or x-rays

or as terahertz body scanners at the

airport

this slide will clarify the relation of

the terms frequency and wavelength for

our electromagnetic rf radiation

imagine yourself as an observer on the

beach

the sea waves pass you by and you track

the distance between them that's the

wavelength

then you start counting the numbers of

waves passing by per minute say

that would give you the frequency of the

c waves per minute with our

electromagnetic rf waves it's exactly

the same

the number of waves per second is the

same as frequency

and the distance between wave maxima is

the actual wavelength

if one wave passes each second this is

known as one hertz

very common to rf and microwave are the

terms megahertz and gigahertz

this is one million and one billion

waves per second i.e the frequency

equals one megahertz and one gigahertz

respectively

it's important to note that the speed of

electromagnetic waves in vacuum is

always the same regardless of its

frequency

the waves travel with the speed of light

if the speed is constant this also means

that higher frequency waves must have

smaller wavelength

to give you an idea your magnetron at

home runs at 2.45 gigahertz frequency

which corresponds to a wavelength of

about 12 centimeters

the reciprocal relation between

frequency and wavelength is also the

fundamental reason that the techniques

that engineers use will vary depending

on the portion of the rf spectrum they

are working with

high frequency engineers design with

components that tend to be smaller

and lower frequency engineers tend to

use physical components that are of

larger size

what you see here on this slide is a

part of the electromagnetic spectrum

visualized

the table shows the frequency range

between 10 to the power of 5 100

kilohertz and 10 to the power of 21

hertz which does not at all imply that

it stops at either end

it also relates frequency to other

parameters like wavelength wave number

ie waves per centimeter and electron

volt i.e the energy of the

electromagnetic wave at a given

frequency

you should also note that as the

frequency increases more to the right

that the wavelength is dropping as we

said before

you can also see that the higher

frequency waves are more energetic by

referring to the electron volt scale

please note the examples of real

applications which are shown here as

well

on the left most of the signal

transmission kind of applications

electronics and on the right the light

based applications or optics can be

found

along with frequency and wavelength

power is another very important

parameter to consider

power is the measure of the energy per

unit of time that the electromagnetic

wave can deliver

the more power in the wave the further

the wave can be transmitted like for a

broadcast signal or the more deeply a

wave can penetrate like in certain

medical applications

more care must usually be given to

systems that operate with more power

it's important to understand power in a

relative way

the next slide shows how power and

parameters in general can more easily be

thought of in relative terms

this slide requires a lot of explanation

but will be key to understanding the

material in the more advanced rf courses

so it's important to really understand

what's going on here

this slide shows the math tricks and

vocabulary used by the engineers

if we go back to all of that forgotten

math from our younger years we remember

that instead of multiplying in the

linear domain we can add things in the

log domain remember

this becomes very useful when numbers

become very large or likewise very small

and when many multiplications are

required

for instance it becomes much easier to

add five two-digit numbers than to

multiply five six-digit numbers

this practice is common when figuring

power gains and losses through long

chains of components

so engineers will always babble in terms

of db dbm dbc etc

to know how many db some property is we

need to know how many zeros were added

to the number in the linear math domain

then to get the number of dbs we

multiply by 10.

for instance if a signal gets amplified

and becomes a thousand times larger then

three zeros were added to its value

this 3 gets multiplied by 10 to get 30

db

conversely if a signal becomes 1

millionth as big it became 10 to the

negative 6th power as big

and minus 6 times 10 is minus 60. so in

db it got affected by minus 60 db

some other nice db number facts to

remember are that every doubling of

something in the linear domain adds 3 db

in the db domain

also every time something gets cut in

half in the linear domain it drops by 3

db

or you add -3 db in the db domain

likewise if an amplifier has a gain of

20 db it amplifies the signal power by a

factor of 100 right

this allows engineers to go through the

gains and losses in a system in a very

fast way by adding numbers that are easy

to handle

i know this sounds clumsy at first but

after a few years it's easy to do math

in the db domain and you become thankful

for it you'll see how this is used in

further presentations

the bandwidth of a signal can be

considered as the width of the spectral

chunk that is being covered by the

signal or by the system

for instance an fm radio can receive

waves between 88 and 108 megahertz

the car receiver then has a 20 megahertz

bandwidth

the fm wave per radio station itself has

a certain bandwidth as well which

indicates how much information the wave

can carry so your favorite fm station

transmits a wave that is about 200

kilohertz wide

the music only covers a chunk around 20

kilohertz wide so the engineers use the

remaining frequency space in that 200

kilohertz to pack information onto the

wave to help the transmission be more

pure and to let your car navigation

system know where not to go

this same principle applies to all the

rf and microwave applications and scales

and complexity as the system needs

become more stringent

for example in highly complex third

generation cellular environments system

needs far exceed those of music

transmission for fm

this is why cellular bands operate over

broader bandwidths and each transmission

from the cell towers is more broadband

than for fm transmission

the ever increasing need for information

transmission usually adds to the demands

placed on the electronic components and

is the source of many of the challenges

for today's engineers and in fact fuels

a large part of our hprf business

this table shows a few frequency blocks

used by most popular applications

in general systems that demand larger

transmission distance will tend to be

granted lower frequency allocations

that's because using lower frequencies

has a physical advantage of having less

degradation caused by obstacles

you'll also see four ism bands called

out

these are bands that are free to use

with certain maximum power limitations

the industrial scientific and medical

ism radio bands were originally reserved

internationally for the use of rf

electromagnetic fields for industrial

scientific and medical purposes other

than communications

you will again recognize your

magnetron's frequency as an ism band

together with your wlan

in general communications equipment must

accept any interference generated by ism

equipment

the bands and applications up to 3.8

gigahertz are covered by products from

rf power

likewise the rf small signal portfolio

covers even higher frequencies and

applications up to and above 40

gigahertz

there are of course more bands defined

at higher frequencies see earlier

electromagnetic wave spectrum

these frequencies are also used for

several applications but can only be

served using other technologies than the

ones used currently by rf power and rf

small signal

this slide is just meant to illustrate

how complex and diverse the usage of

electromagnetic spectrum has become

nowadays

it is a scheme the us government the fcc

has come up with to allocate the overall

spectrum to several licensed unlicensed

or government only use

per line it gives a part of the overall

spectrum

in total it ranges between 3 kilohertz

and

gigahertz

rf and microwave engineers only have a

few small frequency slices available to

them depending on the application

in other countries this allocation might

look very different

that's also why there's not just one

single frequency in the world to do all

the cellular telephones with

in fact all countries in the world work

together in the itu body to align the

frequency use across borders the

electromagnetic waves would not just

stop there

this also finishes the presentation on

rf basics

we hope it is clear and understandable

so that you now have an idea what rf and

its associated applications are all

about