Implementing a bias tee
According to the schematic, inductor L5 (56uH) has nothing to do with the upconverter integrated circuits...it supplies DC power to the signal source via the input SMA connector. If the input signal source doesn't need this "Bias-T", then L5 is not needed and should be removed.

DC input +5V should have a direct path to all these points:


NE612 pin 8
D3 anode
C16
C15(+)
C1


There's another possibility: The signal source is also the source of +5V. In this case, the bias-T is required, and L5 feeds +5v to the nodes mentioned above.