Frequency response of amplifier

I tried to simulate the frequency response of a amplifier circuit in AWR MWO (emp file attached). I'm using vendor-supplied s-parameter data for the GALI-39+ amplifier and the TCCH-80+ choke. I am considering putting the bias tee on another board, so I wanted to see what the response would look like if I made the line from the amplifier to the bias tee ~500 mm. I got a noisy response for the 500 mm line compared to a 1 mm line. Is this normal behavior or am I doing something wrong?

~ 500mm (~19.7inches) microstrip... really?

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The "hopefully" coax connecting the two boards will help you out. Coax is a shielded, impedance controlled medium. Microstrip does not handle RF well on very long lines (500mm). I had a ~5 inch (127mm) long line that preformed fairly well to 6GHz but that is pushing it and not a desirable design.

I replaced the line with a coax element of same length in the schematic, but it's still making those ripples. Is there a way to reduce their amplitude?