I was soldering the HMC928LP5E using my own duroid 5880 board (Grounded CPW, signal width 4.3mm, gap 1mm). I measured the insertion loss of the board with the phase shifter and found out that the insertion loss is fluctuate with frequency. The fluctuation seems has a period of around 0.2GHz and amplitude 1dB. I don't know what is wrong with my board. Do you have any suggestions?