Teknik Modulasi Pertemuan 07 Matakuliah : H0484/Jaringan Komputer Tahun : 2007
Teknik Modulasi
Pertemuan 07
Matakuliah: H0484/Jaringan Komputer
Tahun: 2007
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
Menjelaskan teknik modulasiOutline Materi
Teknik Modulasi Modulasi analogModulasi digitalEncoding Techniques
Analog data, carrier analog signalDigital data, carrier analog signalAnalog Modulation
Analog data, carrier digital signalDigital Modulation
Digital data, carrier digital signalEncoding
Analog Data, Analog Signals
Why modulate analog signals?Higher frequency can give more efficient transmissionPermits frequency division multiplexing Types of modulationAmplitudeFrequencyPhaseAnalog Modulation
Modulasi
Tujuan:
Mengubah sinyal komputer yang digital menjadi sinyal analog yang diperlukan oleh saluran komunikasi.Memperbesar jarak jangkau sinyal informasi. Modem merupakan perangkat keras untuk kedua proses iniLST/FASKD/CINQ
Type Modulasi Digital /Analog
Modulation Techniques
Frequency Shift Keying
Most common form is binary FSK (BFSK)Two binary values represented by two different frequencies (near carrier)Less susceptible to error than ASKUp to 1200bps on voice grade linesHigh frequency radioEven higher frequency on LANs using coaxPhase Shift Keying
Phase of carrier signal is shifted to represent dataBinary PSKTwo phases represent two binary digitsDifferential PSKPhase shifted relative to previous transmission rather than some reference signalQuadrature PSK
More efficient use by each signal element representing more than one bite.g. shifts of /2 (90o)Each element represents two bitsCan use 8 phase angles and have more than one amplitude9600bps modem use 12 angles , four of which have two amplitude4-PSK Constellation
Quadrature Amplitude Modulation
QAM used on asymmetric digital subscriber line (ADSL) and some wirelessCombination of ASK and PSKLogical extension of QPSKSend two different signals simultaneously on same carrier frequencyUse two copies of carrier, one shifted 90Each carrier is ASK modulatedTwo independent signals over same mediumDemodulate and combine for original binary output4-QAM and 8-QAM
PULSE AMPLITUDE MODULATION
Pulse amplitude modulation has some applications, but it is not
used by itself in data communication. However, it is the first step
in another very popular conversion method called
pulse code modulation.
Pulse Code Modulation (PCM)