Modulation Types & Techniques Includes:
Modulation types & techniques ITU emission designators
Modulation formats: Amplitude modulation Frequency modulation Phase modulation Quadrature amplitude modulation
The ITU, International Telecommunications Union uses an agreed set of codes or designations to easily and succinctly describe a format and modulation for a radio transmission.
The designators are used by many licencing authorities around the globe including the FCC in the USA. Accordingly they are often referred to as FCC emission designators.
These codes or emission designations are used in a variety of different areas including defining what types of transmission may be used in different portions of the radio spectrum in the ITU list agreed at the World Radio Conferences as well as defining radio transmission formats in licences and other documents.
The ITU radio emission designations define many aspects of the signal: the type of modulation, bandwidth and the type of information being carried. As such the type of radio emission, or transmission is defined in an exact manner. It should be noted that the designations describe the emission and not the transmitter or the system that is used.
The ITU designator system was agreed at the 1979 World Administrative Radio Conference, WARC 79, and superseded a previous system which has now completely fallen out of use. It is worth noting that the WARC was the old name for the conferences, they are now just called World Radio Conferences, WRC.
Radio emission types designators format
The ITU designations for the different types of radio emissions follows a standard format. This enables anyone using the system to quickly identify the parameters of the particular transmission. Although not all elements of the system may be used every time, it has been developed so that there is no ambiguity whatever part of the system for describing the types of radio emission is used.
The system has the following format:
BBBB are characters that define the bandwidth
Character "1" is a letter indicating the type of modulation
Character "2" is a digit that indicates the type of modulating signal
Character "3" is a letter indicating the type of information being transmitted
Character "4" is an optional letter indicating the practical details of the transmitted information
Character "5" is an optional letter indicating details about any multiplexing, if used.
Tables for the different characters 1 to 5 are given below.
Bandwidth designator list
The bandwidth designator has the format of three digits that express the significant figures, and a letter used for the decimal point.
The letters used are:
H: indicates hertz
k: indicates kilohertz
M: indicates Megahertz
G: indicates Gigahertz
Examples may include 200H for a 200 Hz bandwidth transmission, 6K00 for a 6 kHz bandwidth, and 1M25 for a 1.25 MHz wide transmission, etc..
Character 1 - type of modulation
This character describes the format for the modulation itself. It provides information about the way in which the signal is superimposed onto the carrier.
| List of Emission Designators for Character 1
|A||Double sideband, DSB, including DSB full carrier, i.e. amplitude modulation|
|B||Independent sideband, i.e. two sidebands present, each carrying different information|
|D||Combination of AM and FM or PM, either simultaneously or in a pre-established sequence|
|F||Frequency modulation, FM|
|G||Phase modulation, PM|
|H||Single sideband full carrier|
|J||Single sideband suppressed carrier, SSBSC|
|K||Pulse amplitude modulation, PAM|
|L||Pulse width modulation, PWM|
|M||Pulse position modulation, PPM|
|P||Series of pulses without modulation|
|Q||Sequence of pulses, phase or frequency modulation within each pulse|
|R||Single sideband with reduced or variable level carrier|
|V||Combination of pulse modulation methods|
|W||Combination of any of above|
|X||cases not covered by the above definitions|
It is worth noting that frequency modulation and phase modulation may also be referred to by the generic term: "angle modulation."
Character 2 - type of modulating signal
This character of the ITU designations for radio emissions details the characteristics of the modulating signal. It provides information including whether the modulation is analogue or digital and whether there is one channel of information or more being carried.
| List of Emission Designators for Character 2
|0||No modulating signal|
|1||One channel containing digital information without the use of modulating sub-carriers (excludes time division multiplex)|
|2||One channel containing digital information with the use of a modulating sub-carrier (excludes time division multiplex)|
|3||One channel containing analogue information|
|7||More than one channel containing digital information|
|8||More than one channel containing analogue information|
|9||Combination of analogue and digital channels|
|X||cases not covered by the above|
Character 3 - type of transmitted information
This character in the ITU designation of radio emissions details the type of information being carried. It provides some insight into the use and the way in which the information may be decoded.
| List of Emission Designators for Character 3
|A||Telegraphy for aural reception - e.g. Morse code|
|B||Telegraphy for automatic reception, i.e. machine decoded|
|D||Data transmission, telemetry or command|
|E||Telephony, i.e. voice or music intended for human listening (including sound broadcasting)|
|F||Video - television|
|W||Any combination of above|
|X||None of above|
Character 4 - details of information
This character provides some insight into the format of the information - its coding and therefore the requirements for decoding he information once it has been demodulated.
| List of Emission Designators for Character 4
|A||Two condition code - elements vary in quantity and duration|
|B||Two condition code - elements fixed in quantity and duration|
|C||Two condition code - elements vary in quantity and duration - error correction included|
|D||Four-condition code in which each condition represents a signal element (or one or more bits)|
|E||Multi-condition code in which each condition represents a signal element (of one or more bits)|
|F||Multi condition code - one character represented by one or more conditions|
|G||Monophonic broadcast quality sound|
|H||Stereophonic or quadraphonic broadcast quality sound|
|J||Commercial, non-broadcast, quality sound (but excluding K & L below)|
|K||Sound of commercial quality with the use of frequency inversion and/or band-splitting employed|
|L||Sound of commercial quality with independent FM signals to control the level of the demodulated signal, e.g. pilot tones used to control demodulation process|
|M||Monochrome images or video|
|N||Full colour images or video|
|W||Combination of the above|
|X||Cases not covered by the above descriptions|
Character 5 - details of multiplexing
Increasingly radio channels are used to carry more than one stream of information, or they may be required to share the channel with other users or streams of information. This character in the ITU designation of radio transmissions provides information about any multiplexing.
| List of Emission Designators for Character 5
|C||Code-division multiplex (including code expansion techniques such as direct sequence spread spectrum)|
|W||Combination of frequency division and time division|
|X||Other types of multiplexing - none of above|
The list of radio emission designators is widely used, especially within licences and other documentation. The ITU emission designators provide an easy method of accurately defining the form of transmission that is being used.
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