COMMUNICATION SYSTEMS

Report on

FREQUENCY SHIFT KEYING

Akash R

2009A3PS034G

Section 1

Date: 21 March 2012

Objective:

To implement frequency shift keying.

Theory:

FSK (Frequency Shift Keying) is also known as frequency shift modulation and frequency shift signaling. Frequency Shift Keying is a data signal converted into a specific frequency or tone in order to transmit it over wire, cable, optical fiber or wireless media to a destination point. But FSK, with some modifications, is still effective in many instances including the digital world where it is commonly used in conjunction with computers and low speed modems. In fact, the contributions of FSK are much more far reaching. For example, the principle of FSK has laid the path to the development of other similar techniques such as the Audio Frequency Shift Keying (AFSK) and Multiple Frequency Shift Keying (MFSK) just to name a few.

In Frequency Shift Keying, the modulating signals shift the output frequency between predetermined levels. Technically FSK has two classifications, the non-coherent and coherent FSK. In non-coherent FSK, the instantaneous frequency is shifted between two discrete values named mark and space frequency, respectively. On the other hand, in coherent Frequency Shift Keying or binary FSK, there is no phase discontinuity in the output signal.

In this digital era, the modulation of signals are carried out by a computer, which converts the binary data to FSK signals for transmission, and in turn receives the incoming FSK signals and converts it to corresponding digital low and high, the language the computer understands best.

The basic principle of Frequency Shift Keying is at least a century old. Despite its age, FSK has successfully maintained its use during more modern times and has adapted well to the digital domain, and continues to serve those that need to transfer data via computer, cable, or wire. There is no doubt that FSK will be around as long as there is a need to transmit information in a highly effective and affordable manner.

Observation:

Input F1(corresponding to 0) F2(corresponding to 1)TTL 5v, 100Hz 1.25 KHz 12.5 KHzTTL 5v, 200Hz 2.78 KHz 11.1 KHz

SIMULINK BLOCK DIAGRAM:

OUTPUT WAVEFORM: