A digital fsk equipment transmits bipolar return to zero data. when sending a sequence of alternating ones and zeros how many different frequenies will be transmitted?
The fsk is actually sending mark and space signals, isn't it? The actual frequncies depnends on the technique of modulation (quad fsk?) and the filters on the transmitter at the output. Ideally, there are two frequencies involved, but in practice, there are more. Actually, in practice, the mark and space spectrum is not a single frequency, but spectrum. The bandwidth of the mark/space signal is dependent on keying frequency. So you have several parameters which matter. Normally, we try to filter these bandwidths, mainly to get the power into the center information band (either mark or space), but it does also reduce interference. In my modem on my HAM radio station, I have a built in active filter to do this.
http://rfwireless.rell.com/pdfs/TN_WJfsk.pdf
1 answer