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I want to connect multiple GPS antennas to a single GPS module and select one of them based on some logic. Basically, I want the module to receive signals from only the selected antenna.

Is there an inexpensive/generic/common IC that can act as a Demultiplexer for GPS RF signal (without distorting it too much)?

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    \$\begingroup\$ I'm sure there is such IC. But I don't think such answer would suffice. Please rephrase to ask something useful. Keep in mind though, that selection of a particular chip/IC is off topic. \$\endgroup\$ – Dzarda Aug 6 '14 at 11:38
  • \$\begingroup\$ Hi Dzarda, The question is useful to me that's why I have asked it. Could you care to explain why chip selection is off topic since ultimately one has to decide on a chip to materialize a design? Anyway, I have edited the question title and made it more descriptive. \$\endgroup\$ – Dojo Aug 6 '14 at 11:43
  • \$\begingroup\$ To be honest, I don't quite know why chip selection is off topic, but it quite makes sense, as these things/trends change quite often, so the information may get obsolete quite quickly. \$\endgroup\$ – Dzarda Aug 6 '14 at 11:47
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I believe the component you are looking for is called an RF switch. They are used for example for switching the TX path of bluetooth and wifi chips to a single antenna. RF switches are quite inexpensive (relative term, I know), and come for many purposes.

The terminology for RF switch classifications is similar to regular switches, i.e. SPDT means single-pole-dual-throw, i.e. a single common signal can be routed to two locations.

Here's a relatively generic one which works over a relatively large frequency band (incl. GPS) http://fi.mouser.com/ProductDetail/Skyworks-Solutions-Inc/SKY13270-92LF/?qs=sGAEpiMZZMtsfndvJ9ArQ1GAoWUJ3yIM3lKzNTG0W6Y%3d

Datasheet: http://www.mouser.com/ds/2/472/200128G-23362.pdf

Please note that RF switches are nowadays often minuscule components and can be difficult to solder manually for the unexperienced.

Here's a more generic article about RF switches by digikey: http://www.digikey.com/en/articles/techzone/2012/aug/rf-switches-simplify-multi-antenna-systems

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You need an RF mux or RF switches (DPST, DP3T etc). These are available from several manufacturers in various form factors. As for the control logic, you can use a micro controller. Take into account that GPS signals reaching Earth surface have roughly a -120dBm power level, your switching circuit will add losses to this figure. An alternative approach would be to use active antennas and enable/disable their LNA.

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I'd suggest using an RF relay, which will allow you easily keep the signal path shielded, which is a major factor when dealing with signal levels this low.

The only way I'd use an IC here would be after an amplification stage.

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At GPS frequencies, you could hand-build PIN diodes into switches. On, with a few mA passing through, it's an ohm. Off, with 5v reverse across it, it's 1pF or thereabouts.

With leaded PIN diodes, with care you could actually string them in space between the tabs on the backs of connectors, or between the ends of co-ax cables, there's no need to get everything into and out of a board.

Because GPS is spread spectrum, you don't need super isolation to make the receiver see one rather than another antenna. Model what you get with 1pF off and 1 ohm on in a 50ohm system at that frequency.

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