suitable transmitter type and design

[quaternion]

I am new in the field of transmitting and receiving.
The transmitter is a wireless one.
It is a part of a project and not stand alone one and so minimizing complexity and cost is a must. It is used as a control for a semi on-off operation.It is contained in a device (also under design and can be changed) that operates with a PIC micro-controller that checks for a secret code and if the code is right control is enabled,and the Tx transmit signals that control the on-off operation which is also controlled by a PIC µC(i.e. a Rx give the info to the PIC and the PIC controls the operation ).Noting that there are other work in the same project that i didn't talk about so the design needed to be less complex as I said before.Also noting that the PICs are small ones that are used in normal control applications.
I work at 40MHz carrier. As a start I think to transmit the digital info as ASK(amplitude shift keying) but I face some problems that make me to rethink about the modulation type to be used.Also the transmitter and its PIC info source are wanted to operate with a DC source in the range of 9 to 12 V (is this sufficient knowing that the transmitter operating range is no more than 20 meters).Also I decided to use a class B power amplifier to drive the antenna, which is chosen to be a normal loop antenna (coil around a ferrite rod that is used for FM detection).

Which modulation type is recommended in this case and if a suitable IC for modulation and mixing is available please I need its number,also any recommended IC's or implementations.

Many thanks in advance.

 

[VVV]

Since you have already thought about ASK, I think you should take a look at the rfPIC. **broken link removed**

It uses ASK or FSK modulation and it is not expensive.
However, it runs in the 400MHz range. If you can change that, then you can use this part, which has everything you need inside.

If the frequency must be 40MHz, then you will have to build the transmitter yourself. Ideas here http://www.discovercircuits.com/R/rftrans.htm

 

[quaternion]

Thank you very much.
But I have changed the design to suit my case as I control on-off operation,so according to the PIC output I will modulate the carrier with constant two frequencies i.e for on operation 2 frequencies and changing one of them for off operation and changing the other frequency for lock and unlock operation and reapeting change of the first freq.
Something like DTMF(dual tone multiple frequncy that is used in telephone set)
Again thanks very much.