Electronics > RF, Microwave, Ham Radio

RF switch power supply noise

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sadboi:
Hey,

I'm looking to use the SKYA21003 RF switch for sharing an antenna with a GNSS module and RF transmitter.

Just wondering if the power for an RF switch requires low noise. Will power supply noise from a switching converter couple onto the RF signals?

Cheers.

radiolistener:
yes, noise leakage can happens even if you put single ground wire to SMPS, it will be enough to get noise interference

p.larner:
imho any switching psu is bad news anywhere near a radio!.they belong in landfill.

radiogeek381:
Modern switch mode power supplies can be quite suited to high performance radios.  I have several on my desk right now - an Ettus B210, B200mini, N200, and a N321. All with switch mode power supplies.  Some with several. The ADALM-PLUTO has one too. I do a whole lot of work looking for spurs. The power supplies aren’t contributing in any perceptible way.

In the 70’s it was hard to find quiet supplies.  It still is if we’re talking down-market PC supplies and such.  But well designed switch mode supplies can be quite good.

In any case the RF devices should be mounted over an appropriate ground plane, with appropriate decoupling between power and ground, and careful layout.  The app note from the vendor is often very helpful here. Some notes even suggest various RF choke schemes. Such practices are important whether the power source is a battery or a wall wart.

p.larner: Have you encountered actual problems in a modern radio with a purpose-designed SMPS? I have not.  And I have more than a few modern radios.

EggertEnjoyer123:
Considering the supply current is <1mA, I'd use a RC filter to get rid of most of the noise.

Something like a 200 ohm resistor and a 100nF capacitor should do the trick.

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