about test equipments

what are the differences between oscilloscope, vector signal analyzer, network analyzer? what are the advantages and disadvantages of each of them ?

They're all used for different purposes so you really can't talk about advantages or disadvantages. If you need to take a particular measurement generally only one instrument will do it well. Here is a brief overview of the different instruments.

An oscilloscope is the most basic and it only measures a signal's amplitude over time. Then comes the spectrum analyzer which measures a signals frequency spectrum, a vector signal analyzer adds demodulation to determine the signal phase. The network analyzer adds a signal source and measures the phase and amplitude response through a component, module or system.

This is the short answer but I'm Wikipedia has better explanations than mine.

Ray