@BigBoss How to choose the right value of the capacitor? Based on what? Are there mathematical equation to calculate the value?If you wanna see the effect of the capacitor, use s-parameters or equivalent modeled circuit of the capacitor.
You will see how a capacitor effects the PA.
There should practically be few capacitors connected in parallel there.@BigBoss How to choose the right value of the capacitor? Based on what? Are there mathematical equation to calculate the value?
Where I can find equivalent RLCk circuit of the capacitor? Can be used in ADS simulation?There should practically be few capacitors connected in parallel there.
-High value for low frequencies ( DC to few hundred kHz and uF range )
-Medium value for medium frequencies ( nF or few hundred pF range)
-Low value for high frequencies.( pF range )
Because every capacitor has a highest admissible frequency limit due to ESR.Therefore we use few capacitors to cover overall frequency band.
But in simulations, the practical effects can be seen as if the capacitors are very well modeled or used with their equivalent circuits.
The most important parameter is ESR for capacitor then series inductance ( for high frequency capacitors ) plus parasitic capacitors at each terminal to GND.
However there isn't any empirical formulae for them. You should simulate with their equivalent circuits or s-parameters ( s-parameters can cause some troubles in simulations that's why I prefer using equivalent RLCk circuit ) then you have to decide which type and what value of capacitor must be used by observing circuit metrics.( Noise,Non-linearity,Output Power, Band Flatness,Reflections etc. )
View attachment 163445
You should request from the vendor or download Design Kit of the vendor and install it. The Design Kit will include all necessary parameters of the component.For instance..( small ceramic capacitors only )Where I can find equivalent RLCk circuit of the capacitor? Can be used in ADS simulation?
Where I can find equivalent RLCk circuit of the capacitor? Can be used in ADS simulation?
How if I used one piece for each power supply with 10 PF capacitance? As I could not find the RLC circuit for the component? Only available S2P file?There should practically be few capacitors connected in parallel there.
-High value for low frequencies ( DC to few hundred kHz and uF range )
-Medium value for medium frequencies ( nF or few hundred pF range)
-Low value for high frequencies.( pF range )
Because every capacitor has a highest admissible frequency limit due to ESR.Therefore we use few capacitors to cover overall frequency band.
But in simulations, the practical effects can be seen as if the capacitors are very well modeled or used with their equivalent circuits.
The most important parameter is ESR for capacitor then series inductance ( for high frequency capacitors ) plus parasitic capacitors at each terminal to GND.
However there isn't any empirical formulae for them. You should simulate with their equivalent circuits or s-parameters ( s-parameters can cause some troubles in simulations that's why I prefer using equivalent RLCk circuit ) then you have to decide which type and what value of capacitor must be used by observing circuit metrics.( Noise,Non-linearity,Output Power, Band Flatness,Reflections etc. )
View attachment 163445
How to determine the number of required caps? Are there any equations?There should practically be few capacitors connected in parallel there.
-High value for low frequencies ( DC to few hundred kHz and uF range )
-Medium value for medium frequencies ( nF or few hundred pF range)
-Low value for high frequencies.( pF range )
Because every capacitor has a highest admissible frequency limit due to ESR.Therefore we use few capacitors to cover overall frequency band.
But in simulations, the practical effects can be seen as if the capacitors are very well modeled or used with their equivalent circuits.
The most important parameter is ESR for capacitor then series inductance ( for high frequency capacitors ) plus parasitic capacitors at each terminal to GND.
However there isn't any empirical formulae for them. You should simulate with their equivalent circuits or s-parameters ( s-parameters can cause some troubles in simulations that's why I prefer using equivalent RLCk circuit ) then you have to decide which type and what value of capacitor must be used by observing circuit metrics.( Noise,Non-linearity,Output Power, Band Flatness,Reflections etc. )
View attachment 163445
"undesired frequencies", in my case are the harmonics 2nd, and 3rd harmonics. How about the relationship between these caps and the desired frequencies. Can you please explain more as I still have no clear vision about selection of these caps? What will happen if don't select the values and numbers of caps properly?Hi,
usually you would estimate your required capacitance value according to your expected undesired frequencies by Z = 1/(2 . pi . f. C). To get rid of this frequencies a low impedance Z is desired. But at high frequencies capacitors may already act like an inductor (increasing impedance with increasing frequency). Larger valued capacitors start “earlier“ (at lower frequencies) to act as inductor than caps with a low value. Thus serveral caps are used in parallel to cover a desried frequency band. The final number depends on your frequency band as well on the chosen capacitor types/values.
Have a look at the ksim simulator I linked at post #10. There you can have a direct look at the impedance vs. frequency behaviour for individual caps. It is also possible to export the corresponding Spice and S2P file. Or you have a look at the datasheet of other manufacturer.
BR
@stenzer How much this low Z should be? specific range or value?Hi,
usually you would estimate your required capacitance value according to your expected undesired frequencies by Z = 1/(2 . pi . f. C). To get rid of this frequencies a low impedance Z is desired. But at high frequencies capacitors may already act like an inductor (increasing impedance with increasing frequency). Larger valued capacitors start “earlier“ (at lower frequencies) to act as inductor than caps with a low value. Thus serveral caps are used in parallel to cover a desried frequency band. The final number depends on your frequency band as well on the chosen capacitor types/values.
Have a look at the ksim simulator I linked at post #10. There you can have a direct look at the impedance vs. frequency behaviour for individual caps. It is also possible to export the corresponding Spice and S2P file. Or you have a look at the datasheet of other manufacturer.
BR
Regarding this, which frequencies should I consider while I am selecting the caps? Let's say, i want to measure s-paramrter over 2 to 6 GHz. My target frequency band is 3.4 to 3.6 GHz. So, in this case which freqiency should i consider in terms of ESL & ESR? Is it all frequrncies from 2 to 6 GHz or only 3.4-3.6 GHz band of interset? In other words, what are the frequency of noise that we need to suppres using decoupling caps or how to be determined? Thank youThere should practically be few capacitors connected in parallel there.
-High value for low frequencies ( DC to few hundred kHz and uF range )
-Medium value for medium frequencies ( nF or few hundred pF range)
-Low value for high frequencies.( pF range )
Because every capacitor has a highest admissible frequency limit due to ESR.Therefore we use few capacitors to cover overall frequency band.
But in simulations, the practical effects can be seen as if the capacitors are very well modeled or used with their equivalent circuits.
The most important parameter is ESR for capacitor then series inductance ( for high frequency capacitors ) plus parasitic capacitors at each terminal to GND.
However there isn't any empirical formulae for them. You should simulate with their equivalent circuits or s-parameters ( s-parameters can cause some troubles in simulations that's why I prefer using equivalent RLCk circuit ) then you have to decide which type and what value of capacitor must be used by observing circuit metrics.( Noise,Non-linearity,Output Power, Band Flatness,Reflections etc. )
View attachment 163445
How if some of these components does not have model especially through hole caps? As I use combination of smd and through hole capsIf you wanna see the effect of the capacitor, use s-parameters or equivalent modeled circuit of the capacitor.
You will see how a capacitor effects the PA.
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