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TRF370317 Sideband and carrier suppression issue

Other Parts Discussed in Thread: TRF370317

The In-Phase and Quadrature-Phase baseband signal (150MHz) output from DAC are fed  to the modulator TRF370317. The LO given to the Modulator is 1.62GHz with 0dBm level from a clean source. The bias given to the modulator is 1.7V and the resistors in the resistor divider, used to provide this bias, are of 0.1% precision.

With this the results what we observed are,  

1)  Sideband suppression of 12dBc

Carrier suppression of 31dBm

As far as level at modulator input is considered, capacitors in between the DAC and modulator will remove the DC, if any, on the DAC output, before feeding it to the Modulator. At Modulator input we are shifting the level to 1.7V, (as said in the datasheet [page no. 4]). The voltage levels at the input point of modulator, as measured in the oscilloscope, are  IVIN = 1.749V IREF = 1.752V, QVIN = 1.748V , QREF = 1.752V.

So the difference in the levels is 0.004V, which is negligible.

Here i am attaching you my schematics and layout for reference.



The output level what we are targeting are

1)  Sideband suppression of more than 50dBc.

2)  Carrier suppression of more than 50dBm.


Let us know how to improve the performance.