On Sun, 20 May 2018 20:54:34 -0400 "Marcus D. Leech" <[email protected]> wrote:
> Does anyone here know how various high-integration tuners achieve > more-or-less continuously-variable corner low-pass frequency on the > baseband outputs? > > I'm aware of switched-capacitor filters, but my understanding is that > due to the high branch ratios, you need a clock with a very high ratio > relative to the corner frequency (like 50:1 or 100:1), and so > doing these for RF/IF filters isn't that practical. > > Another approach is to have a little matrix of Ls and Cs and Rs, and > switch different ones in to get a tailored response. But again, CMOS > chips aren't that good at producing Ls and Cs of significant value. > > Inquiring minds want to know.... > > -Marcus > Can you be more specific about the corner frequency? Cell phones use chips that have switchable banks of capacitors for antenna tuning. st.com IIRC is a source. I used to design switched capacitor filter chips in the 80/90s. The technology was killed by oversampled converters and DSP. The SCF players went into continuous time video filters using transconductance amps and such. _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
