Phase Modulation

Najeeb Haider Zaidi

Basics

• Definition• What it does Look Like? Definition

Change in the Phase of the Carrier Wave proportional to the change in the Amplitude of the Message Signal;

Definition

Change in the Phase of the Carrier Wave proportional to the change in the Amplitude of the Message Signal;

Mathematics

mPSK

PSK

mPSK

VKVvolt

radsK

tvKt

ttVtv

Index modulation

)()(

))(sin()(

Mathematical Representation

]sinsin[)(

]sinsin[)(

)](sin[)(

tmtVtv

tVKtVtv

ttVtv

mPSKccm

mmPSKccm

ccm

The Similarity between FM and PM

• In FM Frequency Deviates from its Center.

• If Input Voltage is kept constant for a while, Output frequency shall be constant.

• An Exercise…….• Same equipment can be

used to generate both FM and PM.

At 96.3 MHz center Frequency,

And K=10KHz/V

If Vm=1V, it will generate 96.31MHz Frequency.

At 96.3 MHz center Frequency,

And K=10KHz/V

If Vm=1V, it will generate 96.31MHz Frequency.

Difference Between FM and PM

• If I change the Message Signal Frequency, – It will change the Modulation Index, in FM.– It will change the Frequency Deviation in PM.