ASK demodulation using DSP I need to implement an ASK (ampliltude shift keying) demodulation using a DSP ( a dsPIC ) and programming in C. Especifically talking, I need to demodulate a signal from a car's key transponder. I already have a circuit of antenna that receive the signal and I already can sample it, but I still have a doubt of how could be the best way, faster and reliable, to filter the signal. 
I was using a FIR filter using Kaiser windowing and 13 taps, but it demanded a lot of processing time and I still have some errors. Is there a better way to do it ?

With my best regards,
Daniel.
In general, a receiver would consist of these blocks:


An analog band-pass filter centered around the carrier frequency.
A low-noise amplifier to bring the signal above the receiver's sensitivity.
Optionally, an analog intermediate frequency stage.
A sampler. You can do bandpass sampling if the carrier frequency is too large for the ADC.
In a DSP, implement:


Final downconversion if needed.
Downsampling to reduce the sampling rate
Carrier, frame and symbol synchronization
Matched filtering to recover the bits with optimum BER (in the case of ASK with rectangular pulse shaping, the matched filter is just an integrate &amp; dump filter)



I highly recommend that you get and read Telecommunications Breakdown, by Johnson and Sethares, which is available for free (as a draft) from the authors' website here.