converting square into Sin for wireless transmission???

[Hisham2005]

hello guys,

I need help, I'm making an fsk transmitter that should be connected to an Antenna for wireless transmission, but this circuit I'm working with, has an output of a square wave fsk, so, I guess I need to convert this square into sine for wireless transmission with an antenna, how?
the site which has the simple fsk modulator is here :
**broken link removed**

try to check the pdf version, (last page in the pdf file)

so, how i can convert it?, an RF amplifier in this case won't be sufficient!
thanks

 

[echo47]

To convert square into sine, build a low-pass filter that passes the desired frequencies and blocks everything above three times that frequency.

 

[rfmw]

What frequency are we talking about here?

The simplest way to get FSK modulated carrier frequency is to FM modulate the VCO (LC oscillator with varactor diode) with a (digital) squarewave signal. But this design will probably need PLL control for frequency stability, so its complicated for unexperienced designer.

Perhaps a better way and still simple to get frequency stable, FSK modulated RF signal is to FM modulate crystal-based oscillator with a couple of multiplier stages to get higher frequencies.

 

[cesare]

I think you do not need to convert the sqare wave (modulating signal) into a sinusoidal one.

Usually RF signals are modulated from square wave using a pin diode, a varicap or a PLL Modulator.