I was searching the web to get full knowledge of IR remote controls. My satellite receiver (Humax)'s remote control got ruined. So, I unscrewed the remote control took a look inside it. I know IR operates on 36KHz but what modulation techniques is being used. I just need to know the circuitry of the transmitter.
You don't mention the word "protocol" in your question, but you must know that there's a number of protocols around, not everybody uses the same coding. That makes "full knowledge" a tall order. RC-5 Telaclavo refers to (as one of the most used) is totally different from the Sony SIRC protocol, for instance.
This page suggests Humax uses the NEC protocol:
"The Hex Code Generator for Yamaha is for NEC IR Protocol which is the same for Onkyo and many other manufacturers e.g. Toshiba,Humax etc."
Modulation is at 38kHz, not 36.
Building a replacement remote controller would be a silly idea; for a few dollar you can buy a universal, programmable RC.
If you really want to you'll need little more than a microcontroller. In the old days there were specific ICs for remote controls, the SAA3010 was the standard for RC-5, and was used in 100s of millions of remote controls. But today a microcontroller is as cheap. The program is easy: when you wake up on interrupt scan the keypad, and if a key is detected, send a serial datastream of the modulated code to the output. Repeat until the button is released and go to sleep.
There will be a transistor which drives the IR LED(s), and that's it. Most of the time a series resistor for the LEDs isn't even used.
Using the Philips 87LPC76x microcontroller as a remote control transmitter, NXP application note for an RC-5 remote controller.
As far as the circuitry of the transmitter is concerned, an MCU that reads the keyboard (of the remote control) and drives an infrared LED is all is needed.