Digital Modulation oleh Risanuri Hidayat

Digital Modulation Three basic forms of digital modulation Analog Digital AM Amplitude ASK FM Frequency FSK PM Phase PSK 06/11/61 Digital Modulation

Amplitude Shift Key 06/11/61 Digital Modulation 1 1 1 1 1 0 1 0 0 0 1 1 0 1 0 1 0 0 1 0 1 1 1 t (logic 1) (logic 0) 06/11/61 Digital Modulation

Amplitude Shift Key[1] 06/11/61 Digital Modulation The ASK waveform for one pulse (logic 1) In order to find an Energy Spectrum of The Autocorrelation technique is used Delay Energy Spectrum Therefore Energy Spectrum of ASK sinc2 function 06/11/61 Digital Modulation

Power Spectral Density Detection of ASK : detect present (logic 1) or of the carrier absent (logic 0) 06/11/61 Digital Modulation

Frequency Shift Key 06/11/61 Digital Modulation 1 1 1 1 1 0 1 0 0 0 1 1 0 1 0 1 0 0 1 0 1 1 1 t Output for 1 Output for 0 06/11/61 Digital Modulation

Power Spectral Density Frequency separation Note: To prevent significant overlapping of the bandpass of two filters in detection process frequency separation Data rate 06/11/61 Digital Modulation

Power Spectral Density[1] The Actual shape of Power Spectral Density of FSK Detection of FSK Bandpass Filter is used to detect f1 (1) and f2 (0) In general for frequency separation; ; or where m is an integer 06/11/61 Digital Modulation

Phase Shift Key 06/11/61 Digital Modulation ~ 1 1 1 1 1 0 1 0 0 0 1 1 0 1 0 1 0 0 1 0 1 1 1 t ~ 06/11/61 Digital Modulation

Power Spectral Density 06/11/61 Digital Modulation

Detection of PSK Phase Reversal Key (PRK) Since information is in the phase, only synchronous detection is possible Receiver: To data detection Matched filter detection carrier Synchronize (coherent) Local oscillator e.g. Crystal oscillator known as Voltage Control Oscillator VCO 06/11/61 Digital Modulation