Frequency Modulation: Difference between revisions
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'''Frequency Modulation''' (or '''FM''') is an encoding technique, used | '''Frequency Modulation''' (or '''FM''') is an encoding technique, used for the encoding of both [[analog]] and [[digital]] data. | ||
In FM there is a reversal (signal level, or magnetic flux) at the start of every data bit time (i.e. every clock time); for a '1', there is an additional reversal in the middle of the bit time, with no reversal indicating a '0'. | For analog data, it typically takes a 'carrier' signal, at a fixed [[frequency]], and varies that frequency slightly, based on the analog [[signal]] to be encoded. This was the form used in 'FM radio' (hence that name). | ||
The form used for digital data is used in [[magnetic storage]], such as [[disk]]s and [[Disk#Low-cost disks|floppy drive]]s. | |||
==FM for magnetic media== | |||
In digital FM, there is a reversal (signal level, or magnetic flux) at the start of every data [[bit]] time (i.e. every [[clock]] time); for a '1', there is an additional reversal in the middle of the bit time, with no reversal indicating a '0'. | |||
Consecutive zeros show a reversal between data bit times; consecutive ones show two reversals in every bit time (i.e. doubling the frequency of reversals; hence the name). | Consecutive zeros show a reversal between data bit times; consecutive ones show two reversals in every bit time (i.e. doubling the frequency of reversals; hence the name). | ||
Latest revision as of 00:15, 23 September 2026
Frequency Modulation (or FM) is an encoding technique, used for the encoding of both analog and digital data.
For analog data, it typically takes a 'carrier' signal, at a fixed frequency, and varies that frequency slightly, based on the analog signal to be encoded. This was the form used in 'FM radio' (hence that name).
The form used for digital data is used in magnetic storage, such as disks and floppy drives.
FM for magnetic media
In digital FM, there is a reversal (signal level, or magnetic flux) at the start of every data bit time (i.e. every clock time); for a '1', there is an additional reversal in the middle of the bit time, with no reversal indicating a '0'.
Consecutive zeros show a reversal between data bit times; consecutive ones show two reversals in every bit time (i.e. doubling the frequency of reversals; hence the name).
It was mostly replaced by Modified Frequency Modulation, which can store twice as many bits in the same maximum reversal rate.
