Hi there, welcome back.
In this lesson, we will see how radio frequencies are classified and their possible use in Iot architectures
and systems.
The table shows the entire classification of the radio frequency spectrum, from L.F. waves to gamma
rays, highlighting the frequency ranges and the relative wavelengths.
Let's now see the applications of radio waves to Iot devices.
Let's start with the use of infrared in remote controls for TVs and appliances or other devices.
Transmission of signal in infrared remote controllers use a modulation with a carrier frequency
typical at 38 kilohertz.
The infrared light is emitted from an IR LED controlled by the modulated signal. The modulation
used
is a digital modulation, the ASK (Amplitude Shift Keying) generally OOK (On-Off Keying) or FSK (Frequency
Shift Keying).
The limit of infrared technology is that it requires a direct and unobstructed line between the
remote control and the device to be controlled in order to function.
There are tools for detecting signals in the infrared and visible light spectrum for analysis and testing
and analyzing them on PC, such as the OpticSpy tool, shown in the figure below.
Now, let's see the frequency spectrum typically used by RF remote controls, which can be
used, for example, to control devices such as alarms, door opening systems, air conditioners, etc., Typical
transmission as RF carrier frequency is at 315 megahertz or four hundred thirty four megahertz
or eight hundred sixty eight megahertz.
Popular modulation technique used
are again Amplitude
Shift Keying, often implemented as OOK, and Frequency Shift Keying.
AM broadcasting is radio broadcasting using amplitude modulation transmissions. Commercial AM radio
stations operate at frequencies between five hundred twenty five kilohertz and one thousand six hundred
fifteen kilohertz, separated by 10 kilohertz.
Let's talk now about CB (Citizens Band) radio, used in many countries; is a land mobile radio system.
Permits short-distance person-to-person bidirectional voice communication between individuals, using
two way radios operating on 40 channels near 27 megahertz.
And FM broadcasting is a radio broadcasting using frequency modulation transmissions. Commercial FM radio
station operate generally on frequencies between eighty seven point five megahertz to 108 megahertz,
separated the channels by 200 kilohertz.
Certain subparts of the VHF band have the same use around the world.
Some national uses are detailed in this slide.
As regards the most used protocols in the Iot field, the slide shows a range of radio frequencies used.
For example, Z-wave uses the frequency eight hundred sixty eight point four megahertz. Bluetooth
uses frequencies between two point four gigahertz and two point four eight three five gigahertz and
so on for the other popular protocols such as ZigBee, wifi
HaLow, LoRa
As for the instruments that can be used for SDR that is Software Defined Radio to acquire, analyze,
retransmit radio signals in the field of security tests and diagnostics, there are several on the market,
depending on the range of frequencies that can be analyzed.
HackRF One
is capable, for example, of transmitting and receiving half duplex in the range between 1 megahertz
to 6 gigahertz.
Another popular tool for SDR is Yard Stick one that is capable of transmitting and receiving
in half duplex way at frequencies less than one gigahertz, and supporting modulations such
as ASK, OOK, GFSK, etc..
OK, thank you for your kind attention, bye.