Elektronik Öğretmenliği EBB 333 Haberleşme Sistemleri-I 2013-2014 Güz Yarıyılı Öğretim Üyesi Prof. Dr. Yunus E. Erdemli Ofis: 1011, Tel: 303-2238 E-posta: yunusee@kocaeli.edu.tr Arş. Gör. Mustafa H. B. Uçar Ders Programı Pz.tesi: 12:00-15:00 (Teo) 15:00-16:50 (Lab) Referanslar: 1) Modern Digital & Analog Communication Systems B. P. Lathi, Oxford University Press, 1998 2) Analog Haberleşme A. H. Kayran, E. Panayırcı, Ü. Aygölü; Birsen Yayın, İstanbul http://www.birsenyayin.com 3) Analog ve Sayısal İletişim H. P. Hsu (Çeviri: E. Afacan) Schaum s Outline Series, McGraw-Hill Nobel Yayın Dağıtım, Ankara 2003 www.nobelyayin.com 4) http://www.clee.freehomepage.com/teaching.html
Ders İçeriği Haberleşme Sistemlerinde Temel Kavramlar Matematiksel Temeller İşaret ve Sistemlerin Sınıflandırılması Fourier Dönüşümü ve Özellikleri Sinyallerin Doğrusal ve Doğrusal Olmayan Haberleşme Kanallarında İletimi Modülasyon Çeşitleri Genlik Modülasyonu (AM) Açı Modülasyonu (FM/PM) Değerlendirme: Dönem İçi Notu = Ara Sınav (%26) + Laboratuar (%14) Dönem Sonu Notu = Final Sınavı (%60)
Telekomünikasyon Trafiği Gelişimi
Haberleşme Servislerindeki Artış
Concept and Model of Communications Electronic Communications: Telephone, wireless phone, TV, radar, etc. General Communication Model Source Transmitter Transmission System Receiver Destination Microphone Telephone Computer Scanner Transformer Encoder Compress Modulator Line/Cable Fiber/Air Satellite Network Transformer Decoder Uncompress Demodulator Speaker Earphone Computer Printer Basic Communication Criteria: Performance, Reliability, Security
Signal Frequency, Spectrum & Bandwidth s(t) Signal in time domain cos(2πf1t) T period t T=1/f1 f: frequency s(t)=acos(2πf1t) + Bcos(2πf2t) s(t) Periodic Aperiodic Signal in frequency domain Spectrum S(f) f1 S(f) A B f1 f2 S(f) f f s(t) Analog Signal Digital Signal t Fourier Transform S(f)=ʃs(t)e -j2πft dt S(f) Bandwidth f t Bandwidth f
Time-Frequency Relation & Signal Bandwidth General Relations: Time Domain Frequency Domain Signal Bandwidth Change Slow Low Frequency Small Change Fast High Frequency Large s1(t) s2(t)? BW1 < BW2 t t Earthquake wave: 0.01 ~ 10 Hz Nuclear explosion signal: 0.01 ~ 10 Hz Electrocardiogram (ECG): 0 ~ 100 Hz Wind noise: 100 ~ 1000 Hz Speech: 100 ~ 4000 Hz (4 KHz) Audio: 20 ~ 20000 Hz (20 KHz) NTSC TV: 6 MHz HDTV: > 10 MHz
System Frequency Response & Bandwidth Input Signal x(t) Input Spectrum: X(f) System: H() Output Signal y(t) =H[x(t)] Output Spectrum: Y(f) System Frequency Response: H(f) = Y(f)/X(f) H(f) System Bandwidth Signal can pass Signal can t pass f
Important Reasons for Modulation: Ease of Radiation: c=l f Simultaneous Transmission of Several Signals FDM/TDM Effecting the Exchange of SNR with B Signal-to-Noise Ratio: S_ N Channel Capacity Channel Bandwidth
Modulation Carrier: Acos(2πfct+φ) where fc is called carrier frequency Modulation: change or modify values of A, fc, φ according to input signal m(t) - modify A A[m(t)]: Amplitude Modulation (AM) - modify fc fc[m(t)]: Frequency Modulation (FM) - modify φ φ[m(t)]: Phase Modulation (PM) m(t) Modulator modulated signal: s(t) Acos(2πfct+φ)
rms value: P g C / 2 rms value: ( t) gg P C C (constant,dc) 2 rms value: C
- Lowpass signals
g(t) G(w) h(t) H(w) LTI y(t) Y(w)
w 0 min 203,229 203 krad/sn
Ideal High-Pass Filter Frequency Response Ideal Band-Pass Filter Frequency Response
Physically Realizable Filter
SIGNAL DISTORTION OVER A COMMUNICATION CHANNEL g(t) G(w) h(t) H(w) LTI y(t) Y(w)
.
USB (upper sideband) LSB (lower sideband) DSB: LSB+USB (double sideband)
LPF
DSB spectrum + E(w)
Series-Bridge Diode Modulato Diode-Bridge Electronic Switch Shunt-Bridge Diode Modulato
Ring Modulator
Switching Demodulator: LPF
t = m(t) min Modulation Index: A=1
DC blockage
t t Upper limit for RC:
i q = 0 for i=1 & q = -p/2 for i=2
cos(w c t) LPF
DSB-SC BPF USB
& m(t) DC blockage
below.
. V s
LPF
k
Instantaneous Frequency:
f c 100 MHz k f 5 2p 10 F
f c 100 MHz k p 10p
f c 100 MHz k f 5 2p 10 frequency-shift keying (FSK)
f c 100 MHz k p p / 2 phase-shift keying (PSK)
k p m( t) 1
NBPM Modulator NBFM Modulator
Bandwidth bandwidth of baseband signal m(t) Wide-Band FM (WBFM) or Wide-Band PM (WBPM) Narrow-Band FM (NBFM) or Narrow-Band PM (NBPM
k f 2p 10 5
k f 2p 10 5 2-2 k f 2p 10 5 4 7.5
maximum: Features of Angle Modulation In AM, the transmission bandwidth (B T ) cannot be changed. There do not have the feature of exchanging signal power for B T. However, in angle modulation, B T can be adjusted by adjusting Df. modulated systems, SNR a (B T ) 2.
.. f
-.
.
For AM:
m(t)
2 2