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diff --git a/3161/CH8/EX8.1/Ex8_1.sce b/3161/CH8/EX8.1/Ex8_1.sce
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+clc;

+//page 436

+//problem 8.1

+

+//Given frequency range fc= 1MHz to fc = 1.0005Mhz

+//Single side message bandwidth is fM

+fM= (1.0005 - 1)*10^6;

+disp('Message bandwidth is '+string(fM)+' Hz');

+//The textbook contains a calculation error here. The calculated fM in the textbook is 500kHz instead of 5kHz, following which all the solutions are erroneous  

+

+//Given input signal strength Si= 1mW

+//Let output signal strength be So

+//So=Si/4

+Si= 10^(-3);

+So= Si/4;

+disp('Signal output strength is '+string(So)+' dB');

+

+//Given Power Spectral Density n = 10^-9 W/Hz

+//Let output noise strength be No

+n= 10^-9;

+No= (n*fM)/4;

+disp('Output Noise Strength is '+string(No)+' dB');

+

+//Let SNR at filter output be SNR

+SNR= So / No;

+disp('Output SNR is '+string(SNR)+' dB');

+

+//By reduction of message signal Bandwidth the Output Noise strength changes

+//Let the new output noise strength, bandwidth and SNR be be No_new, fM_new and SNR_new respectively

+fM_new = 75/100*fM;

+No_new = n*fM_new/4;

+SNR_new = So / No_new;

+

+disp('Changed SNR is '+string(SNR_new)+' dB');

+

+

diff --git a/3161/CH8/EX8.2/Ex8_2.sce b/3161/CH8/EX8.2/Ex8_2.sce
new file mode 100644
index 000000000..b9feabfd0
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+++ b/3161/CH8/EX8.2/Ex8_2.sce
@@ -0,0 +1,37 @@
+clc;

+//page 436

+//problem 8.2

+

+//Given frequency range fc - fm = 0.995MHz to fc + fm = 1.005Mhz

+//Double side message bandwidth is fM

+fM= (1.005 - 0.995)*10^6 / 2;

+disp('Message bandwidth is '+string(fM)+' Hz');

+//The textbook contains a calculation error here.

+//The calculated fM in the textbook is 500kHz instead of 5kHz,

+//Following which all the solutions obtained here are erroneous.

+

+//Given input signal strength Si= 1mW

+//Let output signal strength be So

+//So=Si/2

+Si= 10^(-3);

+So= Si/2;

+disp('Signal output strength is '+string(So)+' dB');

+

+//Given Power Spectral Density n = 10^-9 W/Hz

+//Let output noise strength be No

+n= 10^-9;

+No= (n*fM)/2;

+disp('Output Noise Strength is '+string(No)+' dB');

+

+//Let SNR at filter output be SNR

+SNR= So / No;

+disp('Output SNR of the DSB-SC wave is '+string(SNR)+' dB');

+

+//By reduction of message signal Bandwidth the Output Noise strength changes

+//Let the new output noise strength, bandwidth and SNR be be No_new, fM_new and SNR_new respectively

+fM_new = 75/100*fM;

+No_new = n*fM_new/4;

+SNR_new = So / No_new;

+disp('Changed SNR is '+string(SNR_new)+' dB');

+

+

diff --git a/3161/CH8/EX8.3/Ex8_3.sce b/3161/CH8/EX8.3/Ex8_3.sce
new file mode 100644
index 000000000..042dfa9ce
--- /dev/null
+++ b/3161/CH8/EX8.3/Ex8_3.sce
@@ -0,0 +1,24 @@
+clc;

+//page 446

+//problem 8.3

+

+//Given bandwidth of signal is fM = 4kHZ

+fM = 4*10^3;

+//Given power spectral density of white noise n = 2*10^-9 W/Hz

+n = 2*10^-9;

+//Also given that minimum output SNR is 40dB

+//Signal undergoes a loss of 30dB

+

+//For SSB:

+// Required minimum output SNR = Si_min_SSB / (n*fM) = 40 dB = 10^4

+Si_min_SSB = (10^4)*n*fM;

+// Required minimum signal strength at transmitter output Si_tran = Si_min * 30 dB

+Si_tran_SSB = Si_min_SSB * 10^3;

+disp('Required minimum SSB signal strength at transmitter output is'+string(Si_tran_SSB)+' W');

+

+//For DSB-SC:

+// Required minimum output SNR = (Si_min_DSB/3) / (n*fM) = 40 dB = 10^4

+Si_min_DSB = 3*(10^4)*n*fM;

+// Required minimum signal strength at transmitter output Si_tran = Si_min * 30 dB

+Si_tran_DSB = Si_min_DSB * 10^3;

+disp('Required minimum DSB signal strength at transmitter output is'+string(Si_tran_DSB)+' W');

diff --git a/3161/CH8/EX8.4/Ex8_4.sce b/3161/CH8/EX8.4/Ex8_4.sce
new file mode 100644
index 000000000..7bf00c03b
--- /dev/null
+++ b/3161/CH8/EX8.4/Ex8_4.sce
@@ -0,0 +1,33 @@
+clc;

+//page 447

+//problem 8.4

+

+//Given bandwidth of signal is fM = 60 kHZ

+fM = 60*10^3;

+

+//Given power spectral density of white noise n = 2*10^-6 W/Hz

+n = 2*10^-6;

+

+//Given time average of square of mssg signal P = 0.1W

+P = 0.1;

+

+//Noise power at input baseband range NM

+NM = n * fM;

+

+//Threshold occurs at carrier power Pc = 2.9 * NM

+Pc_Threshold = 2.9 * NM;

+

+//For carrier power Pc = 10W, output SNR

+Pc = 10;

+SNRo = Pc * P / NM ;

+disp('Output SNR is '+string(SNRo)+' dB');

+

+//Carrier power is reduced by 100 times making the new power Pc_new

+Pc_new = Pc / 100;

+

+//In the given solutions the NM value is 1.2W instead of 0.12W

+//The corect answer is 0.0925926 instead of 0.000926

+SNR_new = (4/3) * P * (Pc_new/NM)^2;

+disp('Output SNR when carrier power is reduced is '+string(SNR_new)+' dB');

+

+