Bandwidth to send signal FSK question, question about terminology

[pokie_panda]

Homework Statement

A binary encoded signal with a bit-rate of Rb = 112 kbps is now encoded using polar NRZ baseband encoding and then modulated using binary FSK with a carrier frequency spacing of 10 kHz. What is the bandwidth required to transmit this modulated signal?

a.132 kHz
b.224 kHz
c.234 kHz
d.112 kHz

Homework Equations

w = 2 ×Δfmax + 2rb

The Attempt at a Solution

Δf = 10kHz

w = 2 ×Δfmax + 2rb

w= 2 x 10 + 2 x 112= 244 kHz.


I think my mistake is to do with Δf max freq. deviation.
carrier frequency spacing of 10 kHz.

Does this mean the distance between f0 - f1 = 10k, making Δf = 5k giving me 234 k

 

[KataKoniK]

?

Hi there,

Your attempt at a solution is on the right track, but there are a few things that need to be clarified.

Firstly, for binary FSK, the carrier frequency spacing refers to the difference between the two carrier frequencies used for the two different bits (0 and 1). So in this case, the carrier frequencies would be 10 kHz apart, but the actual spacing would be 20 kHz (since the carrier frequency for bit 1 would be 10 kHz higher than the carrier frequency for bit 0).

Secondly, the formula you have used is correct, but it is usually written as:

w = 2 × Δfmax + Rb

where Δfmax is the maximum frequency deviation and Rb is the bit rate. In this case, Δfmax would be 10 kHz (since that is the spacing between the carrier frequencies) and Rb would be 112 kbps.

So putting it all together, we get:

w = 2 × 10 kHz + 112 kbps = 132 kHz

So the correct answer to the question would be a. 132 kHz.

Hope this helps!