Homework 1_1
ECET310

1. Add:

(a) 60 dB + 25 dB= 85 dB

(b) 20 dBW + 5 dBW= 25 dBW

(c) 22 dB - 4 dB= 18 dB

2. Convert:

(a) 65 W into dB= 18.1 dB

(b) 10 dB into watts= 10/10 = log x => 10W

(c) – 5 dB into watts= 5 = 10 log x x=10 ^(-5/10) = 0.316W

(d) –30 dBm into dBrn= 30 dBrun

(e) 15 dBrn into dBm= 10 log (p/1mW)
15/10= log (p/1mW)
1.5 =log (p/mW) = -15dB

2. A three-stage amplifier is shown with power gains. Calculate total power gain in decibels, and as a number.

Ap(tot)=(Ap1)(Ap2)(Ap3)=7500
Ap(tot) (dB) = 10 log(10) +10 log (25) +10 log(30) = 38.75dB

3.

(a) Determine the overall power gain.
(b) Find the output power if Pin = 15 mW

a) Ap(t) = (10)(10)(20) = 2000 b) Po = (Pin)(Ap(t)) = (15mW)(2000) = 30W

4. If Pin = -20 dBm, determine the output power in dBm and watts.

Ap(t) = 13+16-6 = 23dB
Ap(t) = log^-1 (23/10) = 199.526
Pin = -20dBm = (1mW)(log^-1(-20/10)) = 1mW* 10^-2 = 10 uW
Po = (Pin)(Ap(t)) = 10u*199.526 = 1.995 mW
Po(dBm) = 10 log (Po)/1mW = 10 log (1.995mW/1mW) = - 27dBm

5. Determine:

(a) Net gain (b) Net gain in dBs (c) Power output
(a) Net gain (b) Net gain in dBs (c) Power output

a) Ap(t) = (Ap1)(1/L)(Ap2) = 400*(1/2000)*500 = 100

b) Ap(t)(dB)= 10 log (100) = 20dB

c) Po = (Pin)(Ap(t)) = 0.1W*100 = 10W

6. Determine:

(b) Net gain (b) Net gain in dBs (c) Power