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specific varactor diodes required

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kazim

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can some one help me to find a varactor diode that can tune from 700 MHz freq to 3 GHz

i mean to say that if i keep my circuit operating freq to 1800 MHz the varactor tuning should shift it to 900 or upper 2100.

more in detail like when voltage is v1 freq is at 1800 when v2 freq shifts to 900 and when voltage is kept v3 freq is then 2100
 

It depends on many factors, particularly when the frequency swing is so large.
Work out the capacitance needed to tune your circuit at the ends of the range, 700MHz and 3000MHz, taking into account stray capacitance already present. Then look for varactors which cover that capacitance range in the voltage range you can provide.

Brian.
 

i know this formula but what is the value of L in case of varactor diodes...its just voltage and capacitance
 

VCO has 3 class: Lumped resonator, printed resonator, and ceramic resonator. What's your VCO requirement?

I think you can buy a VCO from vendor, that's more easy and a lot of cheap VCO for selling.
 

If you are looking for a maximum tuning range of 700MHz to 3000MHz, I think you need an LC tuned circuit. A resonator wouldn't 'pull' that far. It might be worth considering an alternative to just a VCO, such as generating at half frequency where physical restraints are less then using a wide-band frequency doubler, or mixing with a fixed frequency to reach your target. I assume the reason for using a varactor is that you have PLL control so you have some freedom in software to adjust the direction and size of frequency steps.
Answering your question though, L is an inductance you provide as part of the tuned circuit, it isn't a property of the varactor.

Brian.
 

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