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burst FSK demodulation

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ddt694

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fsk demodulation algorithm

Hello,

I want to search for some demodulatin algorithms for burst FSK.

I had built a FSK transmitter and two FSK receivers to do burst data communication between two computer via wireless channel. The data rate is 9600kbps/19200kbps. One receiver is analog demodulator and using philips SA605 fsk demodulation chip, the other using ADC/FPGA to do the fully digital FSK demodulator. The total carrier frequency offset is not high (about 1kHz). The analog demodulator work well, it's sensitivity is about -113dBm. The fully digital demodulator's sensitivity is only -103dBm for i am not familiar to burst FSK demodulation algorithm.
In burst FSK receiver, the PLL technique may be not suitable, Anyone has the idea for the burst FSK demod?

thanks
 

flatulent

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fsk receiver algorithm

You should try using a FM discriminator with passive parts. Follow this by a comparator to get the logic levels.
 

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burst fsk demodulator

flatulent said:
You should try using a FM discriminator with passive parts. Follow this by a comparator to get the logic levels.

Thanks, Flatulent
That is what the sa606 does. In the digital demod, i use match filter algorithm, say,
using two filters to filter f1 and f2 separately, detect the f1 and f2's energy, then decide the current symbol. Textbook say this is the optimum algorithm but i can not reach the optimum performance. Another problem is i donot know how to correct the frequency offset. In burst communication, this is really a trouble thing.

Best regards
 

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I was suggesting that you do this in hardware. The filters should be relative wide so you are operating on the selective slopes on the sides towards each other. Look up discriminators for analog FM demodulation in any text book for examples.

On the burst offset, If you can sample the detector output at many times the bit rate and store it, you can then process the information by finding the average value and then using that value for slicing (determining a one or zero logic level) the data.
 

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