What's inside a wide band VCO?

Jay Kickliter

I've been working on a design centered around this VCO. I've looked for images of VCO packages cracked open, and can't find one. At $6 each, I don't want to destroy one. What's inside of it, and how do they get such a wide tuning range?

Leon

139 MHz to 159 MHz isn't a wide range. I've made VCOs with a much wider range than that.

Wide-range VCOs use hyper-abrupt tuning diodes.

LoopyByteloose

"The Art of Electronics" by Horowitz, et al might explain things best for you.

Phil Pilgrim (PhiPi)

I think it's instructive to see what range of capacitance is necessary to achieve such a tuning range. Given a constant value for the inductance in the oscillator's presumptive LC tuning circuit, the capacitance ratio can be derived from the equation:

f1 / f2 = sqrt(c2 / c1), or
(f1 / f2)² = c2 / c1

In this case, the square of the high/low frequency ratio is 1.3:1, which is easily achieved by a tuning diode.

-Phil

Jay Kickliter

Thanks. So they're just regular LC oscillators with an RF shield around them?

Phil Pilgrim (PhiPi) wrote: »

I think it's instructive to see what range of capacitance is necessary to achieve such a tuning range. Given a constant value for the inductance in the oscillator's presumptive LC tuning circuit, the capacitance ratio can be derived from the equation:

f1 / f2 = sqrt(c2 / c1), or
(f1 / f2)² = c2 / c1

In this case, the square of the high/low frequency ratio is 1.3:1, which is easily achieved by a tuning diode.

-Phil

Phil Pilgrim (PhiPi)

I don't know for sure; but, given the parameters, it's well within reason.

-Phil