إتصالات

Table of Contents
CH I. Radio Frequency Basics
1Analog transmission chain …….…………………………………………….. 01
1.1 Information……...….…………………………………………………………………….. 01
1.2 Transmission Chain…...…...…..………………………………………………………… 01
1.2.1 Transducer at the transmitter…………………………………………………………. 01
1.2.2 Transmitter……………………………………………………………………………... 01
1.2.3 Transmission channel………………………………………………………………….. 02
1.2.4 The Receiver……………………………………………………………………………. 02
1.2.5 Transducer at the receiver…………………………………………………………….. 03
2 Why Modulate?................................................................................................. 03
2.1 Base band transmission……...……….………………………………………………….. 03
2.2 Transposed band transmission (modulation)…...…………….………………………... 04
3 Allocation of radio frequency bands…...…..……………………………….. 05
4 Bandwidth for a system………………...……………………………………. 07
5 Behavior of radio waves…………………..…………………………………. 08
6 Calculate with decibels (dB):…….....……………………………………….. 08
CH II. Oscillator Circuits
RLC, LC Oscillators and Quartz…………………..….……………………… 10
1 Description of a coil…………………………………………………………. 10
1.1 Behavior of the coil……………………………………………...………………………... 10
1.2 Modeling the behavior of a coil…………………………………...……………………... 11
1.3 The magnetic energy of the coil (stored energy)…………………...…………………… 11
2 Description of a capacitor…………………………………………………… 12
The electrical energy given to the capacitor………………………………...……………… 12
3 RLC Oscillators…………………..…………………………………………... 13
4 Free oscillators……………………………………………………...………... 14
4.1 Undamped oscillating discharge of the LC circuit…………………………...……….... 14
4.2 Solution of the differential equation…………………………………………….............. 15
4.3 Graphical representations……………………………………………………………...... 16
4.4 Conservation of the energy transferred between the capacitor and the coil………..... 17
5 Forced Oscillations…………………………………………………………… 17
6 Quartz oscillators…………………………………………………………...... 18
CH III. AM Modulation and Demodulation
1 AM Modulation………………………………………………………………. 19
1.1 Double SideBand - Large Carrier DSB-LC or (Full Carrier (FC))………………....... 19
1.1.1 Principle………………………………………………………………………………… 19
1.1.2 Graphical presentation in time domain and trapezoidal display of AM signal……. 20
1.1.3 The modulated signal types (for only DSB-LC):……………………………………... 21
1.1.4 Spectrum of the modulated signal…………………………………………………...... 22
1.1.5 Transported power by Uam(t)………………………………………………………….. 23
1.2 Double SideBand - Suppressed Carrier DSB-SC………………………………………. 24
2 AM Demodulation……………………………………………………………. 26
2.1 Envelop detector (for DSB-LC)…………………………………………………………. 26
CH IV. Angular Modulation and Demodulation (FM and PM)
1 Frequency modulation (FM)………………………………………………… 27
FM signal shape in time domain ……………………………………………………………. 27
2 Phase modulation (PM)………………………………………………………
28
3 Frequency modulation with a sinusoidal signal……………………………. 28
3.1 Sinusoidal modulating signal…………………………………………………………….. 28
3.2 Narrowband modulation………………………………………………………………… 28
3.3 Calculation of the spectrum of the frequency modulated signal……………………… 29
3.3.1 Bessel functions and properties………………………………………………………... 30
3.3.2 Bessel functions of 1st kind…………………………………………………………….. 31
3.3.3 Power of modulated signal…………………………………………………………….. 32
3.3.4 Spread spectrum VS modulation index……………………………………………….. 32
4 Frequency demodulation……………………………………………………..
33
4.1 Frequency discriminator (slope detector)………………………………………………. 33
4.2 Quadrature FM demodulator (or coincidence detector)………………………………. 35
4.3 FM receiver using PLL (Phase-Locked Loop) ………………………………………… 37
5 Conversion between FM and PM…………………………………………… 38
CH V. Performance of the Different Modulations in the
Presence of Noise
1 Signal to Noise Ratio (SNR)…………………………………………………. 39
2 Additive white Gaussian noise (AWGN)……………………………………. 39
3 Noise sources………………………………………………………………….. 40
4 SNR in baseband communications …………………………………………. 40
5 SNR in communication with carrier signal ………………………………... 41
5.1 Figure of Merit…………………………………………………………………………… 41
5.2 SNR in AM System (DSB-LC)…………………………………………………………... 41
5.3 SNR in FM System……………………………………………………………………….. 44
6 Pre-Emphasis and De-Emphasis in FM system…………………………….
48
7 Comparisons between angular modulation and AM modulation…………
49
CH VI. Superheterodyne Receivers
1 Direct Amplification Receiver………………………………………………. 50
2 Superheterodyne Receivers………………………………………………….. 52
2.1 Minimum Detectable Signal (MDS)……………………………………………………... 52
2.2 Pre-selection Filter……………………………………………………………………….. 53
2.3 RF Amplifier (Low Noise Amplifier, LNA)…………………………………………….. 53
2.4 Mixer and Local Oscillator………………………………………………………………. 54
2.5 IF Filter…………………………………………………………………………………… 55
2.6 IF Amplifier………………………………………………………………………………. 55
2.7 Demodulator……………………………………………………………………………… 56
2.8 AF Amplifier……………………………………………………………………………… 56
4 Problem of Image Frequency………………………………………………... 57
5 Applications of Superheterodyne Receivers………………………………... 57
CH VII. Phase-Locked Loop (PLL)
1 PLL with a fixed frequency (sinusoidal signal)……………………………..
58
1.1 PLL Unlocked…………………………………………………………………………….. 59
1.2 PLL Locked………………………………………………………………………………. 60
1.3 Capture range and hold (lock) range…………………………………………………… 60
1.4 Estimation of the hold (lock) range……………………………………………………... 61
1.5 Capture range estimation……………………………………………………………....... 63
2 PLL in dynamic regime (variable frequency)……………………………… 63
3 Frequency synthesizers………………………………………………………. 63
References………………………………………………………………………. 64