Hi Jinxie,
You need your existing splitter (or better a 2 resistor 1 in 2 out one) an a Return Loss Bridge (RLB) either professional or one like this
Connect the SA output to the splitter, 1 splitter output to SA R input, other splitter output to RLB input (terminate any unused splitter outputs) RLB output to SA A input. RLB "REF" to known good load. and loa under test to RLB "Test".? zero and infinate calibration use another known good load and short on RLB test post.
A Reflection test set like the HP 8502A contains these parts and an attenuator in a handy package.
Robert G8RPI.
