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Dual Band WLAN Diplexer?

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aaron_do

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Hi all,


in a dual-band WLAN, a diplexer is normally used after to combine the 2GHz and 5GHz bands after their FEMs. I'm just wondering why do we use a diplexer and not an SPDT? The two bands don't seem to operate concurrently...



thanks,
Aaron
 

SunnySkyguy

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a properly designed Diplex filter can have adequate Return Loss (>15dB) and transmission band loss (<0.2dB) and be cheaper and lower loss than a good SPDT RF switch with Pin diodes.
 

aaron_do

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I see. I didn't realize a diplexer would be cheaper. Not sure about the lower loss though. Both are on the order of 0.5 dB. Also, its a waste because most FEMs already have a SPDT to cover TX/RX, so an SP4T would cover dual-band TX/RX with not much increase in the loss...


Aaron
 

aaron_do

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Are you sure there's no functional reason for having a diplexer instead of a switch? I'm looking at the SE5516A from Skyworks, which is a dual-band FEM, and they still use a diplexer between the two PAs...
 

volker@muehlhaus

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in a dual-band WLAN, a diplexer is normally used after to combine the 2GHz and 5GHz bands after their FEMs. I'm just wondering why do we use a diplexer and not an SPDT? The two bands don't seem to operate concurrently...

In any case, with a diplexer the receiver than search for base stations on both bands simultaneously (without switching).
 
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