Week 5 (Spring 2024) – Sample-and-hold, PAM/PWM/PPM, TDM and PCM

Sample and Hold Operation (Örnekle ve tut işlemi)

Flat Top Sampling (FTS)

(Düz Tepeli Örnekleme)

Sample and Hold Operation

Flat Top Sampling (FTS)

x_s(t) : Pulse Amplitude Modulation (PAM)

Discrete time analog modulation

Sample / Hold (Dump) circuit (Örnekle ve tut devresi)

Equalizing LPF (Dengeleyici AGF)

advance in time → h_eq(t) is not causal

For this reason, is chosen

A PAM signal is produced as shown in the figure below. a) If the bandwidth of x(t) is 1 kHz, what is the maximum value of T_s to obtain x(t) without distortion at the receiver? b) For T_s=T_s() , sketch PAM demodulator. Find the transfer function of demodulator.

PWM: Pulse Width Modulation (Darbe Genişlik Modülasyonu)

PPM: Pulse Position Modulation (Darbe Pozisyon Modülasyonu)

Time Division Multiplexing (TDM)

Zaman Bölmeli Çoklama (ZBÇ)

Multiple PAM signals are transmitted without overlapping.

At the receiver, PAM signals are separated by synchronization.

Advantages: 1) Easier to implement. 2) Less crosstalk than FDM

Disadvantages: 1) strict synchronization

Çok kaynaklı (Multi-source) Multiplexing (Çoklama)

Çok kullanıcılı (Multi-user) Multiple Access (Çoklu Erişim)

Pulse Code Modulation (PCM)

(Darbe Kod Modülasyonu - DKM)

x_p=maks |x(t)| Peak value (Tepe değer)

Kuantalayıcı adımı = Δ v=2x_pL Kuantalayıcıdaki seviye sayısı (# of levels in quantizer)

L=8 (mid-rise quantizer)

* Each sample is approximated with a quantized value, the approximation will result in an error less than Δ v/2 in the positive direction or -Δ v/2 in the negative

Quantization error range: (-Δ v/2, Δ v/2)

Average quantization noise power =N_q=E[q^2]

(Ort. kuantalama gürültüsü gücü)

İşaretin Gürültüye Oranı (İGO)

Signal-to-Noise Ratio (SNR)

Signal-to-Quantization Noise Ratio (SQNR)

* Each sample is quantized to the middle of the quantization interval.