What is Phase Modulation | Definition Description | Tutorial
14 Illustrating the relationship between frequency modulation and phase modulation, (a) Scheme for generating an FM wave by using a phase modulator, . Differentiation of Frequency versus Phase Modulation in Angle Modulation. .. addition, from Equation it becomes clear that with a multi-PLL, the appropriate selection of The electronics group is among the world market. Phase-Frequency Relationship When Frequency is Constant. 0 θ. 0. C t ω θ+ Modulation. Frequency modulation and phase modulation are closely related!.
What is PM, Phase Modulation
The amplitude of FM carrier is constant and is independent of depth of modulation. Hence transmitter power remains constant in FM whereas it varies in AM. As against the limitation of depth of modulation in AM, in FM depth of modulation can be increased to any value, without causing any distortion. BDG xx 21 4. Because of guard bands provided in FM, adjacent channel interference is very less. Radius of propagation is limited as FM uses space waves with line of sight.
So it is possible to operate many independent transmitters on the same frequency with minimum interference. FM equipments are more complex and hence costly.
Area covered by FM is limited, to line of sight area but AM coverage area is large. FM radio was developed in the United states mainly by Edwin Armstrong in the s. Modulating differences In AM, a radio wave known as the "carrier" or "carrier wave" is modulated in amplitude by the signal that is to be transmitted In FM, a radio wave known as the "carrier" or "carrier wave" is modulated in frequency by the signal that is to be transmitted. Importance It is used in both analog and digital communication and telemetry It is used in both analog and digital communication and telemetry Frequency Range AM radio ranges from to KHz OR Up to Bits per second.
FM radio ranges in a higher spectrum from 88 to MHz. OR to bits per second. In AM radio broadcasting, the modulating signal has bandwidth of 15kHz, and hence the bandwidth of an amplitude-modulated signal is 30kHz.
FREQUENCY AND PHASE MODULATION (ANGLE MODULATION)
Twice the sum of the modulating signal frequency and the frequency deviation. If the frequency deviation is 75kHz and the modulating signal frequency is 15kHz, the bandwidth required is kHz. Transmitter and receiver are more complex as variation of modulating signal has to be converted and detected from corresponding variation in frequencies. Noise AM is more susceptible to noise because noise affects amplitude, which is where information is "stored" in an AM signal.
FM is less susceptible to noise because information in an FM signal is transmitted through varying the frequency, and not the amplitude. FM PM 1 The max frequency deviation depends on amplitude of modulating signal and its frequency The max phase deviation depends on amplitude of modulating signal 2 Frequency of the carrier is modulated by modulating signal. Phase of the carrier is modulated by modulating signal.
Modulation index remains same if modulating signal frequency is change. Modulators — Carrier frequency can be generated by LC oscillator. By varying the values of L or C of tank circuit, carrier frequency can be changed.
When these components are used with LC tank circuits, we are able to vary frequency of oscillator by changing the reactance of L or C.
FREQUENCY AND PHASE MODULATION (ANGLE MODULATION) - ppt video online download
Indirect FM — Modulation is obtained by phase modulation of the carrier An instantaneous phase of the carrier is directly proportional to the amplitude of the modulating signal. Direct FM- The frequency of carrier is varied directly by modulating signal An instantaneous frequency variation is directly proportional to the amplitude of the modulating signal. Frequency modulation using Varactor Diode — There exists small junction capacitance in the reverse biased condition of all the diodes.
The varactor diodes are designed to optimise this characteristic. As the reverse bias across varactor diode is varied, its junction capacitance changes. These changes are linear and wide 1 to pF BDG xx 30 Frequency modulation using varactor diode — All diodes show small junction capacitance in the reverse biased condition.
People versed in math will now start to point out that this equation misses an additive constant. We just assume we can work with them with a simple parameter in our synthesis engine. Please remember that last sentence, especially in the section on modulation, before you start to write to me to point out errors.
Which distance will you have covered after five seconds? The analogy here is plain: This carrier signal has properties, namely phase, frequency, and time, which all somehow depend on each other. This time dependency now surfaces in the form of the frequency being modulated by a cosine wave.
The variable, modulated component is now added to the phase. With that, we get for the phase: The proof is above. However, I can just wait for you challenging that, mostly with: So if you would use something that is not a sine or cosine, it will no longer work.
This is the moment where the scaling factors we so hastily decided to ignore above start to come back into discussion. Before, we could just rescale the entire thing and be fine. Phase modulation is also the basis for many forms of digital modulation based around phase shift keying, PSK which is a form of phase modulation.
As various forms of phase shift keying are the favoured form of modulation for digital or data transmissions, this makes phase modulation particularly important. Phase modulation basics Before looking at phase modulation it is first necessary to look at phase itself.
A radio frequency signal consists of an oscillating carrier in the form of a sine wave is the basis of the signal.
The instantaneous amplitude follows this curve moving positive and then negative, returning to the start point after one complete cycle - it follows the curve of the sine wave. This can also be represented by the movement of a point around a circle, the phase at any given point being the angle between the start point and the point on the waveform as shown.
Phase modulation works by modulating the phase of the signal, i.