LPF filter power considerations (components)
This LPF will REPEL RF back instead of CONSUME it by shunting it to the ground. Please correct me if this is not the case, as this property is desired in my application.
I wonder if I could use standard SMD inductors and capacitors (0805?) if I feed the filter with 5W of RF power at 50R, or if "power" components are needed, as I have used.
It's complicated to evaluate. Fortunately we have simulators. They're just the thing to predict response of a filter network containing several linear components.
Your filter rolls off around 50-60 MHz.
My simulation has an input which is a mix of two sinewaves (each 15V amplitude). One sinewave is unchanging at 15 MHz (a guess), because it seemed to make sense to have a constant signal in the input.
Then to examine response, 'noise' is added in the form of a sine sweep from 30 to 130 MHz.
Scope traces tell current levels through all components. (No doubt this is different from your setup.) Volt levels are a guess. To result in 1/3 A through C1 & C3, your high frequency noise needs to be 15V amplitude or so. Your input signal may not have that great degree of noise.
Missing information: Frequency of the 5W signal. I presume 144 MHz.
SMD capacitors should be O.K. with 100V DC rating.
SMD inductors can work, depending on the specification. Wirewound air coil inductors have high SRF and no core saturation problems, e.g. Murata LQN21 or Wuerth WE-KI 0805C.
Thank you very much for the simulation!
As far as I can understand from your results and FvM comments, there would be no problem to use ordinary SMD capacitors and inductors that have an anameled wire coil, am I right?
The capacitors carry chiefly high frequencies to ground. They withstand whatever is the voltage*Amperes of the content. Obviously if the noise content is low power then you can get by with low power capacitors.
The inductors carry your 5W signal (and some high frequencies). The Ampere level looks as though it might be 1/3 A.
1/3 A would be true for frequencies below the LPF cut-off that pass the filter. For higher frequencies, e.g. 144 MHz, only a smaller fraction of the 5W/50 ohm current is loading the first inductor and about noting the others.
That's exactly my point.
The input to the filter (from left to right) will be 144MHz and 440MHz at 5W, which will be blocked by the filter. Because of the filter topology the filter will reflect these frequencies (VSWR) and not shunt them to Ground. Please correct me if this is wrong.
However <60MHz will pass from the other direction (right to left) of the filter (during receive). This is just a minor power signal, not 5W.
So I guess using SMD components is ok right?