how to encode IR signals ?

Hey everyone,

I have a transmitter circuit which sends a continuous wave at close to 38KHz but the problem is that standard TSOP1xxx suppress cw.

They need a suitable data format to work which means encoded signals.

I m using this circuit :
http://www.tkk.fi/Misc/Electronics/circuits/ir_send.gif

I was thinking of using the LM555 timer in astable mode to generate a pulse.
Need help on how to use it in astable mode.

Any other means would be okay too.

Thanx
Cheers