Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!sdd.hp.com!hplabs!hpfcso!hpfcbig!bame From: bame@hpfcbig.SDE.HP.COM (Paul Bame) Newsgroups: sci.electronics Subject: Re: Oscillators with extra-large frequency ranges Message-ID: <6560003@hpfcbig.SDE.HP.COM> Date: 2 Jan 91 18:02:19 GMT References: Organization: HP SESD, Fort Collins, CO Lines: 34 > As a hobbyist electronician I have come across a real problem. > For a certain project, I would need an oscillator with digital, > LOGARITHMIC adjusting (32-bit, 1000 x log) and a HUGE range, > 1 kHz to 100 MHz. Is this at all possible? Your "HUGE" range is probably not a big problem. You could probably use fairly standard PLL synthesis techniques. You might want to consider running an oscillator at, say 200-300 MHz and mixing it with 200 MHz to obtain 0-100 MHz. This way you get to use a VCO which covers a small range (1.5:1) which is not difficult. The incredibly precise logarithmic control may be a real pain - just consider the problem of accurately measuring 1 (log) bit in 32 bits with a frequency counter - you might need an expensive counter with a very long capture time to resolve 1KHz from 1KHz + 1 bit. You didn't mention how fast this thing is required to change frequency. > Then the next problem would be just to divide this signal into eight > lines, so that the lines would pulse (change state, whichever would be > the easiest) alternately, in order. I mean: Line 1,then line 2, then line 3, > and at each input pulse from the oscillator the next line would be activated. A fast shift register might do the trick - or (gasp!) a state machine. > This oscillator-divider pair would be used to control 8 memories, whose > signals would be each in turn given to a D/A converter. It sounds like you might get more help if you described what your design is supposed to do at a high level rather than a low level. It sounds like perhaps what you're doing could be solved other ways and maybe has been done before. -Paul "Spice is the Variety of Life" bame@hpfcbig.sde.hp.com N0KCL