Modulation Techniques for Mobile Radio

Modulation Techniques for Mobile Radio UNIT-3

What is modulation ,[object Object],[object Object],[object Object],[object Object]

Modulation Techniques ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Analog/Digital Modulation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Goal of Modulation Techniques ,[object Object],[object Object],[object Object],[object Object],[object Object]

Digital Modulation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Digital Modulation The modulating signal is respresented as a time-sequence of symbols or pulses. Each symbol has m finite states: That means each symbol carries n bits of information where n = log 2 m bits/symbol. ... 0 1 2 3 T One symbol (has m states – voltage levels ) ( represents n = log 2 m bits of information ) Modulator

Factors that Influence Choice of Digital Modulation Techniques ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Power Efficiency of Modulation ,[object Object],[object Object],[object Object],[object Object],E b : signal energy per bit N 0 : noise power spectral density PER : probability of error

Bandwidth Efficiency of Modulation ,[object Object],[object Object],R: the data rate (bps) B: bandwidth occupied by the modulated RF signal

Linear Modulation Techniques ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Binary Phase Shift Keying ,[object Object],[object Object],[object Object],[object Object],Q 0 State 1 State

BPSK Example Data Carrier Carrier+  BPSK waveform 1 1 0 1 0 1

Quadrature Phase Shift Keying ,[object Object],[object Object],[object Object],Q 11 State 00 State 10 State 01 State Phase of Carrier:  /4, 2  /4, 5  /4, 7  /4

4 different waveforms 11 01 00 10 cos+sin -cos+sin cos-sin -cos-sin

Constant Envelope Modulation ,[object Object],[object Object],[object Object],[object Object],[object Object]

Frequency Shift Keying (FSK) ,[object Object],Continues FSK Integral of m(x) is continues.

FSK Example 1 1 0 1 Data FSK Signal

SPREAD SPECTRUM MODULATION TECHNIQUES

Modulation Techniques for Mobile Radio

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Modulation Techniques for Mobile Radio