This and related topics are presented in : [BOOK] The design of modern microwave oscillators for wireless applications: theory and optimizationUL Rohde, AK Poddar, G Böck - 2005 - books.google.com Delivering the best possible solution for phase noise and output power efficiency in oscillators This complete and thorough analysis of microwave oscillators investigates all aspects of design, with particular emphasis on operating conditions, choice of resonators and transistors, phase noise, and output power. It covers both bipolar transistors and FETs. Following the authors' guidance, readers learn how to design microwave oscillators and … Cited by 198 Related articles All 6 versions 73 de Ulrich , N1 UL In a message dated 1/7/2018 7:07:56 AM Eastern Standard Time, [email protected] writes:
Does any limiter, soft or hard, [and perhaps any nonlinearity of power term 3 or greater in the amplifier of an oscillator] cause the "baseband 1/f noise to translate up to the resonator frequency [a form of crossmodulation]?. I wonder this because phase noise vs freq plots look a bit like the 1/f plots of a resistor, or active device, or power supply. Ceramic caps, and resonators [I`m thinking of quartz crystals] don`t pass much DC, and as I understand it, 1/f noise is associated with dc passing through resistors, or semiconductors. So the best way to go might be to have a very linear amplifier, which exhibits very low noise [perhaps 150dB below the operating level], with an AGC loop, that sets the operating levela little below the level at which the amp starts to clip - this could be done with a thermistor to avoid the AGC loop altering the [optimised] operating conditions of the amp. Alternatively you might be able to use a tetrode device like a dual gate MOSFET, and apply the AGC to the second gate. Thus you could keep the extremely linear amp extremely linear. [150dB below 1Volt RMS is 0.032uV RMS]. Cheers!........................................................................................................................................................................Don ZL4GX <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Sun, Jan 7, 2018 at 3:12 PM, Dana Whitlow <[email protected]> wrote: > One point about oscillator design I've not yet seen mentioned is this: the > limiter > must not degrade the resonator Q when in action. Hence, a pair of diodes > connected in parallel back to back, across a shunt resonator, would be a > bad > thing to do from the perspective of low phase noise. A differential > amplifier > that limits by running out of current on peaks, driving a shunt resonator, > is > a much better way even though one pays a price in having more transistor > noise in the circuit. > > I've long wondered if a very slow AGC might avoid the nonlinear mechanisms > issue except, of course, for things happening within the AGC loop's > bandwidth. > Is anybody reading this aware of what the truth really is? > > Dana > > > On Sat, Jan 6, 2018 at 4:29 PM, Magnus Danielson < > [email protected] > > wrote: > > > > > > > On 01/06/2018 10:31 PM, Joseph Gwinn wrote: > > >> ------------------------------ > > >> > > >> Message: 2 > > >> Date: Sat, 6 Jan 2018 09:19:31 -0500 > > >> From: Bob kb8tq <[email protected]> > > >> To: Discussion of precise time and frequency measurement > > >> <[email protected]> > > >> Subject: Re: [time-nuts] AM vs PM noise of signal sources > > >> Message-ID: <[email protected]> > > >> Content-Type: text/plain; charset=utf-8 > > >> > > >> Hi > > >> > > >> The key point missing is the fact that any real oscillator must have > > >> a limiter > > >> in the loop. Otherwise it will “create one” by going over the max > > >> output of this or > > >> that amplifier. To the degree that the limiter has issues (limits > > >> poorly) you will get > > >> AM noise. > > > > > > Hmm. Not strictly true. One can also use an AGC loop, like a wein > > > bridge oscillator. That said, some kind of softish limiter is commonly > > > used. > > > > Regardless what non-linear mechanism in play, this remains a non-linear > > mechanism that achieves the goal. Choose wisely. > > > > Cheers, > > Magnus > > _______________________________________________ > > 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. > _______________________________________________ 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.
