Re: [Discuss-gnuradio] LPF in FM receiver

[Aditya Dhananjay]

To continue: It is always easier to process signals in baseband (centered around 0) than it is to process RF signals (due to the high sampling rates required).

Given that the bandwidth you are interested in is in the order of 100kHz (typical of FM radio signals), it is easy to see why radio receivers are designed the way they are.

On Tue, Feb 11, 2014 at 11:31 AM, Aditya Dhananjay <address@hidden> wrote:

In the FM receiver: Why a LPF is used instead of a BPF in order to select the Radio channel that we want to hear? That is the only part I don't understand.

Hello Pablo,

Let's say you are trying to receive an FM signal centered around 100MHz. In other words, the signal of interest is from (100-delta)MHz through (100+delta)MHz.

My understanding is that at the receiver, you are first demodulating the signal by multiplying the incoming signal with the carrier frequency of 100MHz. This leads to two bands:

a) Centered around 0: (-delta through +delta)

b) Centered around 200MHz: (200-delta) Mhz through (200+delta) MHz.

Signal (a) is what you are interested in, while signal (b) needs to be eliminated. This is where the LPF comes in.

Best,

Aditya