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Do you also have to make a digital tuner?Iam working my thesis....iam supposed to build a digital fm demodulator with FPGA so i need a bandpass filter and an amplifier as the rf front in of ADC and fpga!!!Is there anything in the market or i have to build them myself?
Yes but a cheap circuit has a poor capture ratio and a good circuit has an excellent capture ratio. The capture ratio helps to avoid distortion caused by multipath.Capture is automatic. The stronger signal wins.
This is my thesis!!I want to implement a software defined radio fm broadcast receiver!!! I consider to sample at 80 Msps!!
This is my thesis!!I want to implement a software defined radio fm broadcast receiver!!! I consider to sample at 80 Msps!!I already find by the way the bandpass filter....https://www.electro-tech-online.com/custompdfs/2009/03/2722-1-1.pdf i consider to use an amplifier with 20dB gain at range of 20-500 Mhz from analog devices....so the rf front end circuit would be antenna-b.p filter-amp-b.p filter!!!
This filter looks very good and should do the job well, although it is likely more expensive than doing it yourself.
80 Msps may be acceptable. This is Undersampling and is commonly done for bandpass signals. A quick review of Wikipedia on this even gives an example of sampling an FM band signal:
**broken link removed**)
The article points out there are several choices for a good sampling frequency and their example mentions 44 and 56 MHz. Usually one seeks to use the lowest practical sampling frequency in order to keep the hardware as cheap and simple as possible. I wonder why you chose a freqeuncy as high as 80 MHz?
Yes i use a sub sampling procedure due to the fact that my signal is band limited!! You are right i can use even smaller sample rate!!Another question is there a circuit that i can use to limit the amplitude of my singal to avoid noise amplitude variations? As we know frequency modulation is invariant of amplitude....so variations of amplitude will cause errors in demodulation.
If i consider to implement the rf front end the same way that super hetero dyne receiver works with IF at 10.7 Mhz, where i can find staff like an rf amplifier an if amplifier filters and a local oscillator-mixer? Is there anybody know the implementation method-procedure I am supposed to use for mixing the rf signal to if?