QAM system A quadrature amplitude modulation (QAM) system is a communication sys

Question

QAM system A quadrature amplitude modulation (QAM) system is a communication system capable of transmitting two messages m1 (t), m2(t) at the same time. The transmitted signal s(t) is s(t) =m1(t)cos(ohm ct) + m2(t)sin(ohm ct) Carefully draw a block diagram for the QAM system. Determine if the system is time invariant or not. Assume m1(r) = m2(t) = m(t)-that is. we are sending the same message using two different modulators. Express the modulated signal in terms of a cosine with carrier frequency ohm. amplitude A, and phase 0. Obtain A and theta. Is the system linear? Explain.

Explanation / Answer

s(t)   = m1(t)cos(ct) +m2(t)sin(ct)

a) if we dealy the input by sec ,then s(t) =m1(t-)cos(ct) +m2(t-)sin(ct)   ......(1)

if we delay delay the out put by sec, then

s(t-) =m1(t-)cos(c{t-}) +m2(t-)sin(c{t-}) .......(2)

from (1) and (2) it is claer that system is not time invarient

b)   s(t) = m(t)cos(ct) +m(t)sin(ct)

            let m(t) =Acoswmt

       s(t) = m(t)2[1/2 cos(ct) +1/2sin(ct)]

            = m(t)2 cos(ct - /4)

   A =m(t)2

   =/4

      system is linear , because it flow the super position and homogeneouty

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.