elem dsar siskom

8/19/2019 elem dsar siskom

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DTG2F3

Element Dasar Siskom Radio

By Dwi Andi Nurmantris


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ELEMENT DASAR SISKOM RADIOELEMENT DASAR SISKOM RADIO

TujuanTujuan KomunikasiKomunikasi RadioRadioMengirimkan informasi dari sumber ke tujuan (dapat berjauhanletaknya) dengan memanfaatkan media udara sebagai salurantransmisi


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GoalGoal of Communication System Designof Communication System Design• To maximize transmission rate, R

• To maximize system utilization, U

• To minimize bit error rate, P e• To minimize required systems bandwidth, W

• ,• To minimize required power, E b /N o


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Type of Communication SystemsType of Communication Systems


• Types of informationVoice, data, video, music, email etc.

• Types of communication systemsPublic Switched Telephone Network (voice,fax,modem)Satellite systemsRadio,TV broadcastingCellular phonesComputer networks (LANs, WANs, WLANs)


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ClassificationClassification of Signalof Signal


q Deterministic and Random Signals A signal is deterministic means that there is no uncertainty with respect to itsvalue at any time

A signal is random means that there is some degree of uncertainty before thesignal actually occurs

q Periodic and Non-Periodic Si nals q Analog and Descrete Signals An analog signal is a continuous function of time. A discrete signal is one that exists only at discrete times

q Energy and Power Signals A signal x(t) is called an energy signal , if the energy is finite and the power iszero.(deterministic and non-periodic )

A signal x(t) is called an power signal , if the power is finite and the energy isinfinite.(periodic signals and random signals )


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Information RepresentationInformation Representation


• Communication system converts information into electricalelectromagnetic/optical signals appropriate for the transmissionmedium.

• Analog systems convert analog message into signals that can

ro a ate throu h the channel.

• Digital systems convert bits(digits, symbols) into signals

– Computers naturally generate information as characters/bits – Most information can be converted into bits

– Analog signals converted to bits by sampling and quantizing(A/D conversion)


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PenerimaPenerima / Receiver/ Receiver RRxx



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Jika diperhatikan lebih lanjut,maka terdapatbeberapa hal yang menjadi perhatian, yaitu:

– Modulator dan Demodulator (Detector)

– Oscillator

KomponenKomponen- -komponenkomponen PentingPenting dalamdalam siskomsiskom RadioRadio


– Up / Down Converter – Penguat – Modulasi (akan dibahas tersendiri) – Antenna – Saluran Transmisi


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Modulator Modulator


Berfungsi untuk memodifikasi sinyalpembawa (carrier) dari oscillator sesuaisistem modulasi yang

= – Rangkaian Modulator tergantung jenis

modulasi yang digunakan – Contoh :

• Balans Modulator • Modulator dengan Dioda Varaktor


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Berfungsi sebagai alat untuk mendapatkaninformasi yang terkandung dalam sinyalcarriertermodulasi

– Rangkaian Demodulator tergantung jenis

Demodulator/Detector Demodulator/Detector


modulasi yang digunakan – Contoh Rangkaian DeModulator :

• Envelope Detector • Quadrature Detector

• Ratio Detector • Slope Detector,dll


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Oscillator Oscillator


• Berfungsi sebagai Pembangkit SinyalPembawa (Carrier) pada Pemancar

• Jenis-jenis Oscillator : – Oscillator Umpan Balik Positif

– Oscillator Pergeseran Fase – Oscillator LC ditala : – Oscillator Hartley – Oscillator Colpitts

– Oscillator Clapps – Oscillator Tunned in/out – Oscillator Kristal Pierce


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PenguatPenguat (Amplifier)(Amplifier)


• Berfungsi memberikan penguatanterhadap sinyal yang akan dikirim/diterima

• Pada penerima, dapat berfungsi sebagaifilter karena karakteristik responsefrequency mirip band pass filter

• Pada pemancar, berfungsi menghilangkan

harmonisa dari rangkaian-rangkaianpemancar


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• Merupakan struktur transisi gelombangelektromagnetik terbimbing pada saluran keudara bebas atau sebaliknya.

• -

Antena Antena


pancaran (radiasi) yang berbeda• Macam-macam antenna :

– Loop antenna

– Dipole antenna – Yagi - Uda antenna – Parabolic antenna, dll


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SaluranSaluran TransmisiTransmisi


• Agar daya sinyal dapat dipancarkan secaramaksimal, maka impedansi output rangkaianpemancar dengan impedansi karakteristiksaluran transmisi, serta impedansi beban

• Jika tidak sama, maka akan terjadigelombang pantul

• Jika komunikasi radio dipandang dalamkonteks saluran transmisi, maka dapatdigambarkan seperti berikut


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Antenna Antenna


• Dalam konteks ini, antenna dapat berlakusebagai beban/generator


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Basic Digital Communications System


audiovideo(analogue)

dataSource

anti-aliasfilter

A/D•Nyquistsampling

ChannelCode

•FEC•ARQ•block•convolution

pulseshapingfilter•ISI

•ASK•FSK•PSK•binary•M’ary

Modulation

channelfilter

Baseband Passband

Sourcecode

g aCommunicationsChannel•loss•interference•noise•distortion

channelfilter

Transmit

Receive

Demodulation

•envelope•coherent•carrier recovery

Regeneration

•matched filter•decision threshold•timing recovery

low passfilter

D/Aquantisationnoise

ChannelDecode

•FEC•ARQ•Block•Convolution

data(digital)

audiovideo(analogue)

Sink

Sourcedecode


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