RF switches

Hi,

What are some good, low noise transmit/receive RF switches to use for low power 2.4GHz ISM band? I haven't had much luck finding the SPM321 RF switches used in this circuit: (from a Nordic Semiconductor appnote) "

Anyone know of some nice parts from TI, National, Maxim-ic etc that may work well?

cheers, Jamie

The best line I know of is by MaCom.

Cheers

PeteS

Hi,

I used Mini-Circuits GSWA-4-30DR on a recent project. They performed admirably once I figured out how to decouple them properly.

Good Luck, Tom

Checked out MiniCircuits?

Ken

Hello Jamie,

As John mentioned NEC may have suitable devices. Check out their UPG series.

Other than that, how about PIN diodes? These make fantastic RF switches but they do require a few mA for a "closed switch".

Regards, Joerg

I found a couple of these at digikey but am not sure if they are suitable for 2.4GHz operation: MA2JP0200LCT-ND MMBV3700LT1OSCT-ND

I checked out the Mini-Circuits GSWA-4-30DR, but it is listed at $20 each, and these PIN diodes from digikey are under a dollar each! :)

How would the pin diodes be layed out for transmit/receive switching, similiar to this circuit:

How many PIN diodes would be required?

cheers, Jamie

Hello Jamie,

The old HP app notes are really good. Examples on how to arrange PIN diodes can be found in these notes, such as:

For some reason it has become tough to find some of the HP app notes on the Agilent server (sigh...) so it may be better to use Google.

It depends on whether you want to do SPST, SPDT or a larger mux. Also, it depends on off isolation requirements. For mundane stuff a single diode in the RF path might do, for higher isolation a T-switch with three diodes is favorable.

With respect to cost, check out other mainstream suppliers as well. I have designed with PIN diodes that were more in the penny range rather than a Dollar. They are not always called PIN diodes. Occasionally marketeers prefer to label them "band switching diodes" and the like.

Of course, at 2.4GHz strict RF layout guidelines apply.

Regards, Joerg

Minicircuits have already gone to the trouble of putting the PIN diodes into a package and making it work. Depends how much your time is worth, or how much fun you can have for your money. :-)

The Minicircuits website has data on the devices, including the circuits for the devices themselves, showing exactly what you want. See:

Cheers.

Ken