Another RF curiousity - Electronic Circuits Projects Diagrams Free

zachtheterrible · 28th August 2004, 04:37 AM

Hello, I read in one of my books that a change in the amplitude of an input signal will change the frequency of an RF oscillator. But it never explained what a change in frequency of an input signal will do to the oscillator output. Please 2 be explaining

Thanx so much :lol:

checkmate · 28th August 2004, 08:21 AM

The actual process is called Frequency Modulation (FM). Essentially, a voltage-controlled oscillator (VCO) is used. The value of a signal is then encoded in the frequency of the FM signal.
If you want to know why this is done, you'll have to know a host of other concepts ie signal spectrums, fourier transforms, bandwidth etc. This forms the integral part of communications theory.
I'll try to give a summarised version. In the wireless domain, bandwidth is a premium, hence signals are always manipulated to be confined within their allocated bandwidths. In FM, this is precisely what is being done. The signal is "modulated" to occupy a small range of the frequency spectrum, ie its bandwidth.

zachtheterrible · 28th August 2004, 05:22 PM

so what youre saying is that the bandwith of the FM signal is controlled by the frequency of the input signal, and the frequency deviation is controlled by the amplitude of the signal. Ive been studying quite a bit about radio n stuff like that that you mentioned.

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28th August 2004, 04:37 AM	(permalink)
zachtheterrible	Another RF curiousity Hello, I read in one of my books that a change in the amplitude of an input signal will change the frequency of an RF oscillator. But it never explained what a change in frequency of an input signal will do to the oscillator output. Please 2 be explaining Thanx so much :lol: __________________ I'm no electronics god, i just talk too much.

28th August 2004, 08:21 AM	(permalink)
checkmate	The actual process is called Frequency Modulation (FM). Essentially, a voltage-controlled oscillator (VCO) is used. The value of a signal is then encoded in the frequency of the FM signal. If you want to know why this is done, you'll have to know a host of other concepts ie signal spectrums, fourier transforms, bandwidth etc. This forms the integral part of communications theory. I'll try to give a summarised version. In the wireless domain, bandwidth is a premium, hence signals are always manipulated to be confined within their allocated bandwidths. In FM, this is precisely what is being done. The signal is "modulated" to occupy a small range of the frequency spectrum, ie its bandwidth.

28th August 2004, 05:22 PM	(permalink)
zachtheterrible	so what youre saying is that the bandwith of the FM signal is controlled by the frequency of the input signal, and the frequency deviation is controlled by the amplitude of the signal. Ive been studying quite a bit about radio n stuff like that that you mentioned. __________________ I'm no electronics god, i just talk too much.