Modulasi frekuensi pertemuan 4
1 / 17

Modulasi Frekuensi Pertemuan 4 - PowerPoint PPT Presentation

  • Uploaded on

Matakuliah : H0122 / Dasar Telekomunikasi Tahun : 2008. Modulasi Frekuensi Pertemuan 4. Learning Outcomes. Mahasiswa dapat menjelaskan teknik modulasi frekuensi dan karakteristiknya. Outline Materi. Prinsip Modulasi Frekuensi Bandwidth Hubungan dengan Modulasi Fasa. Angle Modulation.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Modulasi Frekuensi Pertemuan 4' - xena-gross

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Modulasi frekuensi pertemuan 4

Matakuliah : H0122 / Dasar Telekomunikasi

Tahun : 2008

Modulasi FrekuensiPertemuan 4

Modulasi frekuensi pertemuan 4

Learning Outcomes

Mahasiswa dapat menjelaskan teknik modulasi frekuensi dan karakteristiknya.

Modulasi frekuensi pertemuan 4

Outline Materi

  • Prinsip Modulasi Frekuensi

  • Bandwidth

  • Hubungan dengan Modulasi Fasa

Angle modulation
Angle Modulation

  • The angle modulation can be expressed mathematically as:

    m(t) = Vccos [ωct + (t)]

    • m(t) = angle modulated wave

    • Vc = peak carrier amplitude (Volt)

    • c = carrier radian frequency (rad/sec)

    • (t ) = instantaneous phase deviation (radians)

  • The magnitude of the frequency (f) and phase deviation ()is proportional to the amplitude of the modulating signal, Vm and the rate at which the changes are occurring is equal to the modulating signal frequency, fm.

Angle modulation1
Angle Modulation

  • Frequency & Phase Modulation (FM & PM) are both forms of Angle Modulation.

  • Because of its superior performance than AM, it is used extensively for commercial broadcasting radio broadcasting, television sound transmission, 2-way mobile radio, cellular radio, microwave and satellite communications systems.

Frequency modulation
Frequency Modulation

  • Frequency Modulation is the process of changing carrier frequency by the modulating signal while the carrier amplitude remains constant.

  • As the modulating signal amplitude increases, the carrier frequency increases and vice versa.

  • The amount of change in carrier frequency produced by the modulating signal is called Frequency Deviation (f). Meanwhile, the change in phase is called Phase Deviation ()

  • The deviation is proportional to the amplitude of the modulating signal.

Frequency modulation1
Frequency Modulation

  • FM produces pairs of sidebands spaced from the carrier in multiples of the modulating frequency.

  • The modulation index m of FM signal is the ratio of the frequency deviation fd to the modulating frequency, fm (m = fd / fm)

  • The modulation index determines the number of significant pairs of sidebands in FM signals.

Modulasi frekuensi pertemuan 4

Kfis the frequency deviation sensitivity

Frequency Modulation

The frequency of a harmonic carrier signal is varied in such a way that the instantaneous frequency deviation i.e. the difference between the instantaneous frequency and the carrier frequency is linearly related to the size of the modulating signal at a given instant of time.

Modulation index
Modulation Index

  • Frequency modulation index is defined as

    m = Kf Vm/ωm

  • Frequency deviation which is the change in carrier when acted on by a modulating signal frequency is given by:

    • Peak frequency shift in hertz

    • Peak-to-peak frequency deviation of carrier swing

  • Therefore m can be rewritten as

    m=Δf /fm

Modulasi frekuensi pertemuan 4

PM & FM Waveform






Modulasi frekuensi pertemuan 4



Jn (m) is the Bessel function of the first kind


Modulasi frekuensi pertemuan 4


  • m = modulation index

  • Vc = peak amplitude of the unmodulated carrier

  • J0(m) = carrier component

  • J1(m) = first set of side frequencies displaced from

    the carrier by ωm

  • J2(m) = second set of side frequencies displaced

    from the carrier by 2ωm

  • Jn(m) = nth set of side frequencies displaced from

    the carrier by nωm

Modulasi frekuensi pertemuan 4


FM modulator: f = 10 kHz, fm = 10 kHz, Vc = 10 V, fc = 500 kHz, m=1

Modulasi frekuensi pertemuan 4


  • Low-index modulation (narrowband FM)

    • m <1 (fm>>f), B = 2fm

    • High-index modulation (wideband FM)

    • m >10 (f >>> fm), B = 2fm

  • Actual bandwidth

  • B = 2nfm

  • (use Bessel table, n = number of significant sidebands)

  • Carson’s rule (approx 98% of power)

    • B = 2 (f + fm)

    • Δf = peak frequency deviation

    • fm = modulating frequency

Fm pm modulator
FM & PM Modulator

  • FM modulator = integrator followed by a PM Modulator

  • FM Demodulator = PM demodulator followed by a differentiator

  • PM Modulator = Differentiator followed by an FM Modulator

  • PM Demodulator = FM demodulator followed by an integrator

Modulasi frekuensi pertemuan 4

Modulating signal source

Frequency modulator


FM wave


Kf is the deviation sensitivity

Frequency Modulator

Modulasi frekuensi pertemuan 4


  • Telah dipelajari karakteristik modulasi sudut

  • Telah dipelajari modulasi frekuensi

  • Telah dipelajari peran sidebands.