COMMS 1-Topic 6

Angle Modulation

It is an analog modulation scheme in which the angle of a relatively high-frequency carrier signal is varied in accordance with the instantaneous amplitude of an information signal.

Frequency Deviation

It is the amount of frequency shifts that occurs when it is acted on by a modulating signal.

Phase Deviation

It is the amount of phase shifts that occurs when it is acted on by a modulating signal

Direct Frequency Modulation

An angle modulation scheme in which the frequency of a constant amplitude carrier is varied in proportion to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal.

Direct Phase Modulation

An angle modulation scheme in which the phase of a constant amplitude carrier is varied in proportion to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal.

Maximum Frequency Deviation (FM)

This occurs during the maximum positive and negative peaks of the modulating signal.

Maximum Frequency Deviation (PM)

This deviation occurs during the zero crossing of the modulating signal.

Modulator Output (FM)

The changes would occur in the output frequency in respect to changes in the amplitude of the input voltage.

Modulator Output (PM)

The changes would occur in the phase of the output frequency in respect to changes in the amplitude of the input voltage.

Instantaneous Frequency Deviation (FM)

It is directly proportional to the amplitude of the modulation signal and inversely proportional to its frequency.

Instantaneous Frequency Deviation (PM)

It is proportional to the first derivative or slope of the modulating signal.

Instantaneous Phase Deviation (FM)

It is proportional to the integral of the modulating signal voltage.

Instantaneous Phase Deviation (FM)

It is directly proportional to the amplitude of the modulation signal and unaffected by its frequency.

Modulation Index (FM)

It is proportional to the amplitude of the modulating signal and inversely proportional to the frequency of the modulating signal.

Modulation Index (PM)

It is proportional to the amplitude of the modulating signal, independent of its frequency.

Frequency Deviation (δ)

The amount of frequency shifts that occurs when it is acted on by a modulating signal.

Phase Deviation ()

It is the amount of phase shifts that occurs when it is acted on by a modulating signal.

Percent Modulation (%M)

With angle modulation, percent modulation is simply the ratio of actual frequency deviation to the maximum frequency deviation allowed by law stated in percent form.

Carrier Swing (CS)

It is the difference between the maximum positive and negative deviation of the carrier in Hz.

Deviation Ratio (DR)

The worst case (maximum) modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating signal frequency.