THS4509EVM

Yes, that should do it. Verify the R5, R6 values to give you the gain that you want. --RJH

Hi RJ,

With the about setting ( Vs+ to +5V, Vs- to 0V, GND to 0V, TP2 to 1.7V; with R7, R8 removed, putting 0 ohms for R9, R10), the input single ended signal is 200MHz sine wave, -1.5 dBm.  

We got the following results from the J8 (green) and J7(purple), the first picture is Board #1, the second Board #4.  

The questions are the following:

1. should the outputs at J8 and J7 180 degress shifted?
2. signal from J7 of Board #4 has lower DC bias than the one from J8.  Is the board damaged?

Best regards,

Mark Liang

Hi RJ,

The other board (Board #5) has a lower outputs.  Is it damaged?  

Mark:

The I/Q inputs to the modulator must be in quadrature (i.e. 90 degrees out of phase from each other).  This must be generated from the source.  The amp cannot do it.

The common mode voltage (i.e. mean on the screen captures) does not look correct.  One plot had 2.6V and the above one had 1.3V.  These should be 1.7V to interface with the modulator properly.  The amplitude difference may be a gain setting difference.  I doubt the EVM is damaged as there is still an output.  Check the impedance values of the resistors in the circuit and compare between each board.

--RJH

Hi RJ,

I understand that the I/Q inputs to the modulator must be in quadrature, and from two sources.

The question is for the differential outputs: p and n of the THS4509EVM, for the differential outputs, the p and n should be 180 degrees out of phase from each other. 

But we do not see that when the R7, R8 are removed; although while R7 and R8 are connected, the p: Vo+ and n:Vo- of the THS4509 do have 180 degrees out of phase from each other.

The second question is the TRF370417: in point 4 of 1.4 on page 6 of SLWU062, it talks about using 0.85 V for TRF370x17 to set the common mode on the ESG; when we use a 4 channel AWG, should we set each channel DC offset to 0.85V (ch1 is for I, ch2 for I bar, ch3 for Q, ch4 for Q bar)?

Best regards,

Mark Liang

Mark:

Agreed.  The differential outputs should be 180 degrees out of phase with each other.  I do not understand why having a load dictates differential operation.

The datasheet states 0.85 V because the test equipment was the Agilent ESG.  The front panel setting expects a 50 ohm load on the BB outputs but with the '04 that is not the case so the voltage is doubled from the front panel setting, hence 1.7V.

You can ping the High Speed Amplifier forum relative the THS4509 operation to get access to the application experts on that device.

--RJH

RJ,

Thank you for the reply. What is BB stands for, when you said "a 50 ohm load on the BB outputs"?

The AWG, which we have, is 50 ohm output for all channels.

Best regards,
Mark Liang