Design of narrow band pass filter

Design of narrow - Demodulator(or Receiver Modulator(or Transmitter M-ary FSK Modulator MICRO-CONTROLLER PC Power Amplifier Transducer ED 16

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Unformatted text preview: Demodulator (or) Receiver Modulator (or) Transmitter M-ary FSK Modulator MICRO-CONTROLLER PC Power Amplifier Transducer ED 16 NBPF-16 LS 2 ED 2 NBPF-2 LS 1 ED 1 NBPF-1 LNA + AGC Trans- ducer Micro- Controller rential amplifier mon source amplifier ential amplifier mon source amplifier C HAPTER – І INTRODUCTION 1 Communication is the process of establishing connection or link between two points for information exchange. A device that performs modulation is known as a modulator and a device that performs the inverse operation of modulation is known as a demodulator. A device that can do both operations is a modem (short for "Modulator-Demodulator"). Modem encodes the signal to be transmitted and also decodes the received data. Receiver is an element of the communication system. Basic block diagram of a Modem : A data transmission system using binary encoding transmits a sequence of binary digits, that is, 1’s and 0’s. These digits may be represented in a number of ways. The resulting signal is used to modulate a carrier. A data transmission system using binary encoding transmits a sequence of binary digits, that is, 1’s and 0’s. These digits may be represented in a number of ways. The resulting signal is used to modulate a carrier. There are different modulation techniques like Phase Shift Keying (PSK) Amplitude Shift Keying (ASK) Frequency Shift Keying (FSK) Phase Shift Keying : In this modulation the phase of the carrier is varied in accordance with the input bit i.e., for logic 1 the phase of the carrier Amplitude Shift Keying : The amplitude of an analog carrier signal varies in accordance with the bit stream (modulating signal), keeping frequency and phase constant. The level of amplitude can be used to represent binary logic 0s and 1s. We can think of a carrier signal as an ON or OFF switch. In the modulated signal, logic 0 is represented by the absence of a carrier, thus giving OFF/ON keying operation and hence the name given. 2 Frequency Shift Keying : Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. The simplest FSK is binary FSK (BFSK). BFSK literally implies using a pair of discrete frequencies to transmit binary (0s and 1s) information. In this modem design the frequency shift keying concept was used with a slight modification. Here corresponding to input bit sequence the corresponding frequency signal was sent to output . TRANSMITTER: Figure 1.1 The transmitting unit shown in circuit1 is built around a microcontroller. It is connected to PC via RS232 connection. The data (message) to be transmitted by the transmitting unit will be downloaded to the unit from the PC.Different frequencies are generated during the on periods of these square pulses depending on the input bit combination. The frequencies were selected to be in low range as this project was designed for being applied in under water communication....
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This note was uploaded on 02/13/2011 for the course EE 438 taught by Professor Dr.d.s.murthy during the Winter '09 term at SUNY Buffalo.

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Design of narrow - Demodulator(or Receiver Modulator(or Transmitter M-ary FSK Modulator MICRO-CONTROLLER PC Power Amplifier Transducer ED 16

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