Hello everyone,

I would like to learn more about digital IF filter (10.7 and 21.7 MHz) and especially find a solution at the same price, size and performance as an analog filtering.
To begin, I already have try to use my LimeSDR mini with GNUradio to create an IF filter of 12.5 KHz. It works, it's enough easy but with too much delay, low embedded capacity and higher price.

So, after a lot of research on internet, I have discovered few potentials solutions:
-A chip with integrated FIR filter but with too low working frequency for my application.
-A microcontroller with DSP functionality, like STM32F7 but with too low working frequency.
-A FPGA (XC7Z020-1CLG484C) with fully configurable FIR filter and baseband transceiver (AD9361) but with too higher price (350$):
https://wiki.analog.com/resources/fpga/docs/hdl/fmcomms2_fir_filt

I know that high performance are often not in linked with a low price, but It's essentialy for radioamator use.
I'm looking for advices, recommendations and experiences about digital IF filter

Have a good day!
Joss

 

Don't use a digital filter. The analog ones are better. The advantages of the "DSP TigerShark" filters that I have made are only to be able to control the filtration more.

 

I understand your mind, but my first goal is to use a digital filter to get a taking in hand. My second goal is to use a digital filter in system which required a digital filter. Like a digital receiver channelizer with 50 channels, not achievable with analog technology in tiny package for example and especially, in the end, to have a fully configurable system.


This type of project should participate to increase the accessibility of high-performance SDR system for radio amateur use or other.
What do you think about this idea?

 

I think the licenses will be a problem and you haven't consider that. Also digital filters are a relatively new field.

Making the filter itself is not that hard, you have to pick the MCU properly and make the programming(this part is hard). What the frequencies that you want to use?

 

For amateur use, most bandwidths are narrow. The DSP is done with software on the baseband.

Have you ever heard of a Tayloe detector or mixer? You might find that interesting.

It has some amazing specs compared to detectors of old classical design. And it's easily modulated for transceiver operation. The detector acts like a modulator/demodulator.