UltraPAC500 is new generation IQ signal instrument in UltraFLEXPlus tester. One UltraPAC500 instrument have 16 diff source/16 diff capture (8 IQ pairs), I/Q channel have 250 MHz BW to provide 500 MHz IQ BW. It have higher channel density and higher bandwidth compared to UltraPAC300 and UltraPAC80 in UltraFLEX tester. The Ultra Precision Analog Channel have native IQ capabilities for IQ waveform AWG generator and IQ waveform capture. The user model for UPAC500 is different from UPAC300 and UPAC80. The I and Q channels will be programmed as a IQ pair. In this paper, we will introduce this new generation of IQ signal instrument – UPAC500 and key best practices and loopback performance experiments result.