Decoupling capacitors introduce more noise on transmitter power amplifier
The spectral plot shows a huge spurious at 700MHz.
Get some bypassing UNDER THE package, perhaps on backside; or atop the ICs pins, with 1mm*2mm SMT cap

I'd suggest your initial circuit was an oscillator; those capacitors are not close enough, given you want a 6 GHz power amplifier to be happy/stable/good-data-eye/emit a UWB burst.

The Bead provides some loss, and quenches/dampens the parasitics.

I'd get a tiny 10pF and solder that right across the leads.

To estimate the Fresonate, assume 1nH/millimeter. Thus 6mm (plus lead frame and bondwires), for total of 10nH.

The Fresonate of 10nH and 10pF is only 500MHz, thus your onchip parasitics are part of the energy circulating path. You bead(s) provided dampening.







simulate this circuit &ndash; Schematic created using CircuitLab

You can install capacitors INSIDE the footprint, on back side of the PCB. This may help.