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Chapter 5 AM, FM, and Digital Modulated Systems Binary Bandpass Signalling Techniques OOK BPSK FSK

Chapter 5 AM, FM, and Digital Modulated Systems Binary Bandpass Signalling Techniques OOK BPSK FSK. Huseyin Bilgekul Eeng360 Communication Systems I Department of Electrical and Electronic Engineering Eastern Mediterranean University. Binary B andpass S ignaling t echniques.

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Chapter 5 AM, FM, and Digital Modulated Systems Binary Bandpass Signalling Techniques OOK BPSK FSK

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  1. Chapter 5 • AM, FM, and Digital Modulated Systems • Binary Bandpass Signalling Techniques • OOK • BPSK • FSK Huseyin Bilgekul Eeng360 Communication Systems I Department of Electrical and Electronic Engineering Eastern Mediterranean University Principle of Communication

  2. Binary Bandpass Signaling techniques • On–Off keying (OOK) [amplitude shift keying (ASK)] - Consists of keying (switching) a carrier sinusoid on and off with a unipolar binary signal. • - Morse code radio transmission is an example of this technique. • - OOK was one of the first modulation techniques to be used and precedes analog communication systems. • Binary Phase-Shift Keying (BPSK) - Consists of shifting the phase of a sinusoidal carrier 0o or 180o with a unipolar binary signal. - BPSK is equivalent to PM signaling with a digital waveform. • Frequency-Shift Keying (FSK) - Consists of shifting the frequency of a sinusoidal carrier from a mark frequency (binary 1) to a space frequency (binary 0), according to the baseband digital signal. - FSK is identical to modulating an FM carrier with a binary digital signal. Principle of Communication

  3. Binary Bandpass Signaling techniques Principle of Communication

  4. On-Off Keying (OOK) Carrier Cos(2fct) OOK output Acm(t)Cos(2fct) Message m(t) • Also known as Amplitude Shift Keying (ASK) • The complex envelope is • The OOK signal is represented by • The PSD of this complex envelope is given by where m(t) has a peak value of So that s(t) has an average normalized power of Principle of Communication

  5. On-Off Keying (OOK) 1 0 1 0 1 0 1 Message m(t) Unipolar Modulation m(t) Bipolar Modulation s(t) OOK signal Tb – bit period ; R – bit rate Principle of Communication

  6. On-Off Keying (OOK) • PSD of the bandpass waveform is given by • Null-to-Null bandwidth is and absolute bandwidth is • The Transmission bandwidth is Where B is the baseband bandwidth Principle of Communication

  7. Binary output Envelope Detector OOK in Detection of OOK • Non-Coherent Detection • Coherent Detection with Low-pass filter Binary output LPF OOK in Principle of Communication

  8. Binary Phase Shift Keying (BPSK) Message: m(t) Carrier:Cos(2fct) BPSK output AcCos(2fct+Dpm(t)) -90 Phase shift 1 0 1 0 1 0 1 Message m(t) Unipolar Modulation m(t) Bipolar Modulation s(t) BPSK output Generation: Principle of Communication

  9. Binary Phase Shift Keying (BPSK) • The BPSK signal is represented by let pilot carrier term data term • The level of the pilot carrier term is set by the value of the peak deviation • The digital modulation index ‘h’ is given by 2∆θ – maximum peak-to-peak deviation during time Ts • If Dp is small, then there is little power in data term & more in pilot term • To maximize performance (minimum probability of error) Optimum case : BPSK signal : Principle of Communication

  10. Binary Phase Shift Keying (BPSK) • The complex envelope for this BPSK is given by • The PSD for this complex envelope is given by • PSD of the bandpass waveform is given by Average normalized power of s(t) : Null-to-Null BW Principle of Communication PSD of optimum BPSK

  11. Binary Phase Shift Keying (BPSK) If Dp /2 Pilot exists fc 2R = 2/Tb Power Spectral Density (PSD) of BPSK: Principle of Communication

  12. Frequency Shift Keying (FSK) Message: m(t) Cos(2f1t) FSK output AcCos(2f1t+1) or AcCos(2f2t+2) Osc. f1 Cos(2f2t) Osc. f2 • Discontinuous FSK : • The discontinuous-phase FSK signal is represented by for t during a binary ‘1’ signal for t during a binary ‘0’ signal Principle of Communication

  13. Frequency Shift Keying (FSK) • Continuous FSK : Frequency Modulator fc FSK output Message: m(t) • The Continuous-phase FSK signal is represented by or where for FSK Principle of Communication

  14. Frequency Shift Keying (FSK) 1 0 1 0 1 0 1 Message m(t) Unipolar Modulation Bipolar Modulation m(t) s(t) FSK output (Discontinuous) s(t) FSK output (Continuous) Mark(binary 1) frequency: f1 Space(binary 0) frequency: f2 Principle of Communication

  15. Frequency Shift Keying (FSK) Digital data Dial up phone line Computer FSK modem (Originate) f1 = 2225Hz f2 = 2025Hz PSTN Computer Center FSK modem (Answer) f1 = 1270Hz f2 = 1070Hz FSK modem with 300bps Principle of Communication

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