Modulation demodulation assignment

Sania Bilal
Studying at UOS bhakkar

1. “ Modem & it’s function ” Subject: Digital Logic Design Submitted to: Sir Kamran Shah Submitted by: Sania Bilal Roll No: BCSF 19 BM 005 Date: 11 th June 2020 University of Sargodha Bhakkar Campus Title:

2. Contents: Introduction to Modem Modulation Demodulation Analog to digital conversion Digital to Ana log conversion

3. Modem: Modem stands for Modulator and Demodulator. Allow a computer to communicate over a telephone line. The goal of modem is to produce a signal that can be transmitted easily and decoded to reproduce original data signal. It has two working phase: Modulation Demodulation There are two types of modem: Internal Modem External Modem It can be used over any means of transmitting analog signals from light emitting diodes to radio.

4. Types of Modem(According to use): External Modem Internal Modem   Wireless Modem in PC Cable Modem Satellite Modem ADSL Modem

5. External Modem: Internal Modem: An external modem is a network device that is in a self-contained enclosure external to a computer. This is in contrast to an internal modem that is contained on a printed circuit board with a computer. An  internal modem  is basically an external  modem  and serial port mounted upon a PC bus card. These are cheaper than external  modems  as they do not require a power supply or a chassis.  Internal modems  work fine for remote serial console applications.

6. Wireless Modem: Cable Modem: A  wireless modem  is a  modem  that bypasses the telephone system and connects directly to a  wireless  network, through which it can directly access the Internet connectivity provided by an Internet service provider (ISP). A  cable modem  is a type of network bridge that provides bi-directional data communication via radio frequency channels on a hybrid fiber-coaxial  (HFC), radio frequency over glass ( RFOG ) and coaxial cable infrastructure.

7. Satellite Modem: ADSL Modem: A  satellite modem  or sat modem is a  modem  used to establish data transfers using a communications  satellite  as a relay. A  satellite modem's  main function is to transform an input bit stream to a radio signal and vice versa. Asymmetric digital subscriber line is a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide.

8. Types of Modem(According to working function): Directional capacity: half duplex modem and full duplex modem. Connection to the line: 2-wire modem and 4-wire modem. Transmission mode: asynchronous modem and synchronous modem.

9. transmission in one direction at a time. If a carrier is detected on the line by the modem, It gives an indication of the incoming carrier to the DTE( Data terminal equipment  ) through a control signal of its digital interface. As long as the signal is being received; the modem does not give permission to the DTE to transmitted data. HALF DUPLEX M O D E M A half du p lex modem permits

10. FULL DUPLEX A full duplex modem allows simultaneous transmission in both directions. Therefore, there are two carriers on the line, one outgoing and the other incoming.

11. 2-WIRE MODEM 2-wire modems use the same pair of wires for outgoing and incoming carriers. The data connection established through telephone exchange is also a 2-wire connection. In 2-wire modems, half duplex mode of transmission that uses the same frequency for the incoming and outgoing carriers can be easily implemented.

12. 4-WIRE MODEM In a 4-wire connection, one pair of wires is used for the outgoing carrier and the other pair is used for incoming carrier. Full duplex and half duplex modes of data transmission are possible on a 4- wire connection. As the physical transmission path for each direction is separate, the same carrier frequency can be used for both the directions

13. ASYNCHRONOUS MODEM: Asynchronous modems can handle data bytes with start and stop bits. There is no separate timing signal or clock between the modem and the DTE. The internal timing pulses are synchronized repeatedly to the leading edge of the start pulse . start

14. SYNCHRONOUS MODEM: Synchronous modems can handle a continuous stream of data bits but requires a clock signal. The data bits are always synchronized to the clock signal. There are separate clocks for the data bits being transmitted and received.

15. “Modulation And It’s Types”

16. Modulation: First phase of modem. Operation of varying amplitude, frequency or phase of carrier signal accordingly with the instantaneous amplitude of the message signal is called modulation. Modulation = Adding information to a carrier signal. Modulation is usually applied to electromagnetic signals: radio waves, lasers/optics and computer networks.

17. Modulation System:

18. Types of Modulation: Amplitude modulation (AM ): In which the height -- i.e., the strength or intensity -- of the signal carrier is varied to represent the data being added to the signal. Frequency modulation (FM): Frequency modulation  (FM) is the encoding of information in a carrier wave by varying the instantaneous  frequency  of the wave. The term and technology is used in both telecommunications and signal processing.

19. Phase modulation (PM): Polarization modulation: . In which the phase of the carrier waveform is varied to reflect changes in the frequency of the data. In PM, the frequency is unchanged while the phase is changed relative to the base carrier frequency . It is similar to FM. In which the angle of rotation of an optical carrier signal is varied to reflect transmitted data.

20. Pulse-code modulation : Quadrature amplitude modulation ( QAM ): In which an analog signal is sampled to derive a data stream that is used to modulate a digital carrier signal . Which uses two AM carriers to encode two or more bits in a single transmission

21. Why we use modulation? Multiple carriers of different frequencies can often be transmitted over a single media, with each carrier being modulated by an independent signal. For example, Wi-Fi uses individual channels to simultaneously transmit data to and from multiple clients. To increase the bandwidth of the signals. To reduce the antenna size.

22. “Demodulation And It’s Types”

23. Demodulation: Demodulation  is extracting the original information-bearing signal from a  carrier wave . A   demodulator  is an  electronic circuit  that is used to recover the information content from the modulated carrier wave . The signal output from a demodulator may represent sound (an  analog   audio signal ), images (an analog  video signal ) or  binary  data (a  digital signal ).

24. Types of Demodulation: AM radio: An  AM  signal encodes the information into the carrier wave by varying its amplitude in direct sympathy with the analogue signal to be sent. There are two methods used to demodulate AM signals : envelope detector   product detector SSB  is a form of AM in which the carrier is reduced or suppressed entirely, which require coherent demodulation. 

25. FM Radio: It is a process of getting back or generating original modulating signal from modulated FM signal. It can be achieved by converting the frequency deviation of FM signal to the variation of equivalent voltage. The demodulator will produce an output where its instantaneous amplitude is proportional to the instantaneous frequency of its input FM signal.

26. “ Analog to Digital Conversion ”

27. Analog to digital conversion(ADC): ADC ( Analog to Digital Converter ) is an electronic device that converts a continuous analog input signal to discrete digital numbers (binary ). Analog Real world signals that contain noise Continuous in time D igi t al Discrete in time and value Binary digits that contain values 0 or 1

28. Why is ADC Important? All microcontrollers store information using digital logic. Compress information to digital form for efficient storage. Medium for storing digital data is more robust. Digital data transfer is more efficient . Digital data is easily reproducible. Provides a link between real-world signals and data storage.

29. Flash A/D Converter Successive Approximation A/D Converter Example of Successive Approximation Dual Slope A/D Converter Delta – Sigma A/D Converter Types of A/D Converters :

30. “ Digital to Analog Conversion ”

31. Digital to Analog conversion(DAC): Digital-to-analog conversion is the process of changing one of the characteristics of an analog signal based on the information in digital data. Digital data needs to be carried on an analog signal. A carrier signal (frequency f c ) performs the function of transporting the digital data in an analog waveform. The analog carrier signal is manipulated to uniquely identify the digital data being carried.

32. System diagram of DAC:

33. Types of DAC:

34. Thank You!