# In the communication system, if for a given rate of information transmission requires channel bandwidth, B1 and signal-to-noise ratio SNR1. If the cha

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In the communication system, if for a given rate of information transmission requires channel bandwidth, B1 and signal-to-noise ratio SNR1. If the channel bandwidth is doubled for same rate of information then a new signal-to-noise ratio will be

1. SNR1
2. 2SNR1
3. $\sqrt {SN{R_1}}$
4. $\frac{{SN{R_1}}}{2}$

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Correct Answer - Option 3 : $\sqrt {SN{R_1}}$

Shannon-Hartley Theorem- It tells the maximum rate at which information can be transmitted over a communications channel of a specified bandwidth in the presence of noise.

$C = B{\log _2}\left( {1 + \frac{S}{N}} \right)$

Where C is the channel capacity in bits per second

B is the bandwidth of the channel in hertz

S is the average received signal power over the bandwidth

N is the average noise

S/N is the signal-to-noise ratio (SNR)

For transmitting data without error R ≤ C where R = information rate

Assume information Rate = R

Form Shanon hartley theorem

Rmax = C

$R = B{\log _2}\;\left( {1 + SNR} \right)$

When channel Band width (B) = B1

Signal to noise ratio = SNR1

${R_1} = {B_1}{\log _2}\left( {1 + SNR} \right)$

If SNR ≫ 1

${R_1} = {B_1}{\log _2}SN{R_1}$       ---(1)

When channel B ⋅ ω = 2B1

Let signal to noise Ration = SNR2

Information Rate = R2

${R_2} = 2{B_1}{\log _2}SN{R_2}$     ---(2)

Given- R2 = R1

$2{B_1}{\log _2}SN{R_2} = {B_1}{\log _2}SN{R_1}$

$SN{R_2} = {\left( {SN{R_1}} \right)^{\frac{1}{2}}}$