Hi Most communications systems also have constraints based on signals in adjacent channels. That pretty much forces a solution of "lots of filter before lots of gain". Distributing both gain and filtering across multiple stages gets you into a variety of issues that map junk into the passband. Once the junk is there, you can't get rid of it later.
Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of ehydra Sent: Monday, January 24, 2011 3:35 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] power spectrum of hard limiter output The classical approach is to heavily band-limit the input of an following hard-limiter. But would it possible to merge both functions in several stages of an IF-strip? I think most individuals cannot follow much of this idea but time-nuts have the same problem :-) My main interest is a practical (reduced to standard parts to buy) CMOS inverter IF-strip where the individual stages are ac-coupled. So it is possible to integrate a high-pass filter via the coupling capacitor and low-pass via the cross connected capacitor over the inverters. I think the interstage capacitor also removes 1/f noise of the signal from the individual pre-stage inverter. CMOS having more 1/f noise than bipolar transistors under approx. 1 KHz but can be comfortable from 100 KHz to 1 MHz. The nice thing with CMOS is cheapness and simplicity. So the questions are: 1. maximum useful amplification 2. depends on noise in first stage 3. compression on MOSFET inverter gives spectral regrowth 4. limiting of burst noise in rf signals 5. trying to avoid any form of automatic gain control 6. etc. I played with SPICE models in LTspice and practical with SpectrumLab using CD4007 inverters as IF-strip at 25 KHz. I try to be practical and avoid heavy mathematicals. It works fine if one think of the price of such simple parts! But I'm a little over my edge how to optimize it further. Any suggestions are welcome. I don't have access to IEEE papers. This paper is interesting because it mentions main aspects but looses itself in CDMA specific aspects: www4.ncsu.edu/~kggard/kg_papers/MTT_05_FrontEnd_Distortion.pdf regards - Henry (Sorry for bad english) _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
