how to realize demodulation module in FPGA

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The signal flow is as following:

analog signal from Ultrosonic Probe -> A/D -> FPGA(using digital demodulation shceme)

Generally,Hillbert convert is used to demodulation,but it is difficult to be realized in FPGA,i think.So I am searching other ways which are not so difficult.

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Ok, so your signal is analog.

Just to be clear; your ultrasonic signal has 10kHz bandwidth on a 2.5MHz carrier? Are you transmitting and receiving the signal, i.e., is this an active ultrsonic system? Do you need to pulse compress the received signal, eg., if the transmit signal is a linear FM chirp. Do you have an array of receivers, or just one?

Hilbert transforms can be used to convert a real-valued signal to a complex-valued (analytic) signal. However, demodulation to baseband followed by filtering and decimation achieves much the same thing, but the filters are symmetric, so the response is better.

What is your ADC sample rate? If you are sampling DC to ~2.5MHz, I would expect something higher than 2.5MHz, but if you are bandpass filtering your 2.5MHz signal, you could sub-sample and digitally alias the signal.

What are you planning on doing?

Cheers,

Dave