Synaps3
Member level 1
So right now I am building an FM audio transmitter based on the ADF4360-8. I have the evaluation board for this device and what I am working on right now is changing the loop filter that they included on the board with my own that will work best for audio modulation. What they have included on the board is a third-order, passive, low pass filter. They say the filter was was designed for a bandwidth of 40kHz. So from what I've read, it seems like if I want to have the audio transmitter have good bass-response in the audio, I have to make the loop bandwidth as small as possible (essentially as small as the lowest audio frequency I want to transmit?) So if that's true, the 40kHz that they have isn't going to work. I did some calculations using some software and I chose the option for third-order, passive because I want to replace what is on the board. The problem is that when I set loop bandwidth to 50Hz (which I think is acceptable for my audio). The values of the capacitors go up way too high - unrealistically - they don't make SMD capacitors of that size.
So what am I doing wrong? Do I need to choose a different loop bandwidth (maybe it's OK to choose a higher?) Do I need to use a different topology or an active filter for this purpose instead? I would rather keep the same design because then I can test on this board, but if it is necessary to choose a different, let me know.
Thank you and best regards!
So what am I doing wrong? Do I need to choose a different loop bandwidth (maybe it's OK to choose a higher?) Do I need to use a different topology or an active filter for this purpose instead? I would rather keep the same design because then I can test on this board, but if it is necessary to choose a different, let me know.
Thank you and best regards!