ODP: thru zero VCO questions

[mbartkow at ET.PUT.Poznan.PL]

> And how can one make stable VCO running so high?
> I mean if we want to tune it at, say, 50Hz (afer downconversion)
> and have reasonable stability, it must run at 20050Hz, and no 0.1Hz
> less. It's almost crystal stability...
> Of course, such thing would be used only for deep modulation,
> but how can we tune it anyhow?
> 
> BTW, better to put 'braking point at 40kHz (LO=40kHz, VCO=20..60kHz,
> IF=20kHz..0..20kHz) which makes stability problem bigger.

Well, we need very hi-spec VCOs here, it's the price of the pleasure ;-)

BTW while OTA-based triangle VCOs are claimed to be tracking up to
ultrasonic scale, I think the temperature dependency of the gm may
affect their stability. I have a solution in my drawer, but I am not
going to present it here, because it uses a PLL and I don't want you
to cry out you don't like one :-)

regards,

MB


--

Maciej Bartkowiak, PhD
========================================================================
Institute of Electronics and Telecommunication     fax: (+48 61) 8782572
Poznan University of Technology          phone: (+48 61) 8791016 int.171
Piotrowo 3A                             email: mbartkow at et.put.poznan.pl
60-965 Poznan POLAND               http://www.et.put.poznan.pl/~mbartkow
========================================================================