[SOLVED] How can i bias Varactor Diode in my design?

[biff44]

Your varactors look very large compared to the coupler size. They will not behave like capacitors if you build this.

You can try a lower permittivity substrate to have larger line/coupler dimensions. Then you also have more room for bias coupling/decoupling.

this is a very important point. a circuit, once laid out, has to "look right". when you glance at it, it has to have things that clearly look like transmission lines .... i.e. with a width that is much smaller than the lengths, etc. If it looks odd, and you do not know where one portion of the circuit starts and the other ends....well you just have a "blob" of metal, and who knows how that will react? In some cases you can analyze that "blob" with an EM simulator and luck-out to have the desired response. But if the analysis does not show the response you want, there is no way to guess how to modify it to make it work. So try to get circuit elements that have the proper "aspect ratio" always.

 

[redcrystalline]

this is a very important point. a circuit, once laid out, has to "look right". when you glance at it, it has to have things that clearly look like transmission lines .... i.e. with a width that is much smaller than the lengths, etc. If it looks odd, and you do not know where one portion of the circuit starts and the other ends....well you just have a "blob" of metal, and who knows how that will react? In some cases you can analyze that "blob" with an EM simulator and luck-out to have the desired response. But if the analysis does not show the response you want, there is no way to guess how to modify it to make it work. So try to get circuit elements that have the proper "aspect ratio" always.

all you said is new for me. Thanks for sharing your comment.