Hi Guys-
 I'm brand new to this forum.  I've got a design for a 2.4 GHz radio that requires a PA.  For my PA I'm using the Sige PA2423L (http://www.sige.com/support/files/datasheets/PA2423Lds.pdf).  I've built and stuffed the board, but am not getting any significant power output.  In fact I have a version of the same board sans PA and I achieve MUCH better power output without the PA than with the PA.  I've debugged enough to say with 99% certainty that the problem is in the output circuitry on the PA (see Figure 1 @ http://www.sige.com/support/files/datasheets/PA2423L_3_1.pdf).  Has anyone here used this part for a design?  If not, can anyone please explain to me why in Figure 1 of the previous URL they've chosen L1 = 1.5nH and C4 = .5pF?  They say that it's a 3rd harmonic shunt, but it seems to me that the LC resonant frequency is tuned to 7.1GHz which means that 7.1GHz is actually passed to the antenna while 2.4 GHz has a path to ground via C7.  What am I missing here?  Thanks a lot!!

D

Hi mg777-

Thanks for the info.  I don't have the vendor's evaluation board.  I simply used the reference schematic and followed good layout practices in my own board.  Vctl is set to Vcc in my board via a ucontroller's I/O.

My board is 10 mil FR-4.  What RF choke are you referring to?  In their reference schematic I don't see a choke listed...  All my Ls and Cs are murata RF components.  I'm going to try to sweep them on a network analyzer and make sure that @ 2.4GHz they are the correct inductance/capacitance.

I was indeed thinking that I should measure S12 of the PA by biasing the PA with a larger inductor and no C4.  I'm going to try to do that tomorrow, but the equipment is pretty tied up these days

In general though, am I correct in stating that at the particular values for C4 and L1 given in the reference schematic that 2.4GHz will find a nice path to ground while 7.1GHz will easily be passed to the antenna?  Thanks a lot for your help,

D