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Looking for cheap solution to build GHz VCO

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Full Member level 5
Apr 1, 2002
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Low_cost GHz VCO

Hi there,

I'm looking for a solution to build a cheap microstrip-VCO for 24GHz. The
frequency span has to be about +/-150MHz and more or less linear. The
output-power should be in the range of 0dBm and should not change
significant over frequency.
My current implementation is a parallel coupled oscillator with a comb-
filter. The frequency change is done by changing the drain-current of the
GaAs Fet. So I change the S21 phase and also the frequency. This is not
very linear and the output-power changes...
The use of a varactor-diodes gives a linear frequency but is a problem
because of the price. Because I need no 'high-end' oscillator we also tried
UHF varactors. This works but the frequency-span is low because of the
parasitic inductance.
Any idea?

Have you tried a DRO. If you cannot design a DRO what about designing the oscillator at around 1GHz and then mulitply it by 24. You can multiply it quite successfully by designing multipliers with BPF's.

Did you try searching

There are some references to VCO's in the forum such as 18 Ghz push-push. These articles and or links may give you some ideas for consideration.

Hi shogun,

The use of a DRO and/or multiplier sections is not possible because of the
price. This oscillator has to be implemented in a ultra-low cost sensoric
system. Anyway thanks for you answers.
Has anybody else another idea to change the frequency?


Ultra low cost 24 GHz oscillator

It seems you have to select 'a ultra low cost' transistor first of all. It must have sufficient gain at 24 GHz to be useful as an oscillator active element.

When you have found a device having an acceptable price, please let us know which one and we'll try to help you find a suitable oscillator topology.

Hi GaAs FET,

One FET I'm currently using for such an application is NE3210S01 from
NEC / CEL. It costs about 0.70$ / pce. With this device it's possible to
build such an oscillator. My problem is to tune the frequency for about
+/- 150MHz "without" (or not too much) additional cost...


Could you tell me what will you use for? perhaps, I can give sth for you.


Perhaps you can get a better solution if you change (tune) the collector or drain voltage of the transistor instead of changing its current.

Hi shou,
the use of this VCO is in a low-cost doppler sensor with distance measure-
ment. This is done with FMCW.

Hi g579,
good idea, I will try. Do you have any experience how much the frequency
can be pushed/pulled?


Hi mr_ghz,

I think 5 - 10 % tuning (depending on the actual construction ) can be easily obtained.

use a vco from mini circuit ,it's pretty work in small size

Re: Low_cost GHz VCO

The most important thing is the price. So the minicircuit module is not possible.


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