In datasheet, output of ad9739 is connected to TC1-33-75G2+, using 90Ω to GND in figure 65. Now，i want to amplify the amplitude of output, can i use bigger resistor here, i.e, 100Ω，150Ω？
The AD9739 is a 14-bit, 2.5 GSPS high performance RF digital-to-analog converter (DAC) capable of synthesizing wideband signals from dc up to 3.0 GHz....
AD9739 on Analog.com
thanks for the question. I don't recommend changing the 90ohm. (70ohm // (90+90)ohm ) = 50ohm, this is the impedance driving by the DAC for an optimal match.
If you like to amplify the signal, you could use Figure 67 with RF differential amp
what type of application is that?