); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY John Miles wrote: >> Am I missing something here? >> >> I always thought mixers were non linear by definition, and >> relying on that >> non linearity to function:-) >> > > Sure, a mixer is nonlinear with respect to the multiplicative function it > applies to its two inputs to obtain the desired output. It should, however, > behave linearly with respect to multiple frequency components that may be > present at any *one* input. You don't want it to modify either input > signal, just multiply them together. > > Think of a mixer with a perfect sine wave at its RF input and a square wave > at its LO input. It's nonlinear with respect to the switching action caused > by the LO signal, but it had better be linear with respect to how it handles > the sine wave being switched on and off. If it distorts the sine wave > input, it will generate harmonics that you probably didn't want. And if you > apply two or more tones to the mixer's input at once, you want only those > same tones coming out, with the usual +/- translation by the LO frequency. > To the extent that the mixer allows the RF input tones to interact or > multiply with each other, it's nonlinear. > > This wasn't such a big deal in the old days when your radio had a high-Q > tuned circuit in front of its first mixer, but modern designs work by > shovelling a large portion of the spectrum into the mixer at once. > Nonlinearity is a bad thing in that case. > > -- john, KE5FX > > John
At drive levels below saturation, the loss of a mixer depends on the LO signal level. Consequently the feedback loop gain of a regenerative divider depends on the input signal level. Hence one would expect there to be a well defined threshold at which the lop gain is sufficient for regeneration to occur. Bruce _______________________________________________ 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.
