1. Eeng 360 1 Chapter4 Transmitters and Receivers  Generalized Transmitters  AM PM Generation  Inphase and Quadrature Generation  Superheterodyne Receiver  Frequency Division Multiplexing Huseyin Bilgekul Eeng360 Communication Systems I Department of Electrical and Electronic Engineering Eastern Mediterranean University

2. Eeng 360 2 Generalized Transmitters Any type of modulated signal can be represented by The complex envelope g(t) is a function of the modulating signal m(t) Transmitter Modulating signal Modulated signal Example:

3. Eeng 360 3 Generalized Transmitters R(t) and θ(t) are functions of the modulating signal m(t) as given in TABLE 4.1  Two canonical forms for the generalized transmitter: 1. AM- PM Generation Technique: Envelope and phase functions are generated to modulate the carrier as Figure 4–27 Generalized transmitter using the AM–PM generation technique.

4. Eeng 360 4 Generalized Transmitters x(t) and y(t) are functions of the modulating signal m(t) as given in TABLE 4.1 2. Quadrature Generation Technique: Inphase and quadrature signals are generated to modulate the carrier as Fig. 4–28 Generalized transmitter using the quadrature generation technique.

5. Eeng 360 5 IQ (In-phase and Quadrature-phase) Detector

6. Eeng 360 6 Generalized Receivers Receivers Tuned Radio Frequency (TRF) Receiver: Composed of RF amplifiers and detectors. No frequency conversion It is not often used. Difficult to design tunable RF stages. Difficult to obtain high gain RF amplifiers Superheterodyne Receiver: Downconvert RF signal to lower IF frequency Main amplifixcation takes place at IF  Two types of receivers:

7. Eeng 360 7 Tuned Radio Frequency (TRF) Receivers Active Tuning Circuit Detector Circuit Local Oscillator Bandpass Filter Baseband Audio Amp  Composed of RF amplifiers and detectors.  No frequency conversion. It is not often used.  Difficult to design tunable RF stages.  Difficult to obtain high gain RF amplifiers

8. Eeng 360 8 Heterodyning (Upconversion/ Downconversion) Subsequent Processing (common) All Incoming Frequencies Fixed Intermediate Frequency Heterodyning

9. Eeng 360 9 Superheterodyne Receivers Superheterodyne Receiver Diagram

10. Eeng 360 10 Superheterodyne Receiver

11. Eeng 360 11 Superheterodyne Receivers  The RF and IF frequency responses H 1 (f) and H 2 (f) are important in providing the required reception characteristics.

12. Eeng 360 12 Superheterodyne Receivers f IF RF Response IF Response

13. Eeng 360 13 Superheterodyne Receivers

14. Eeng 360 14 Superheterodyne Receiver Frequencies

15. Eeng 360 15 Superheterodyne Receiver Frequencies

16. Eeng 360 16 Frequency Conversion Process

17. Eeng 360 17 Image Frequencies Image frequency not a problem. Image frequency not a problem. Image frequency is also received Image frequency is also received

18. Eeng 360 18 AM Radio Receiver

19. Eeng 360 19 Superheterodyne Receiver Typical Signal Levels

20. Eeng 360 20 Double-conversion block diagram.