how to measur PA's output VSWR

vswr measur network

Now I am designing a WCDMA 2W PA, and I donnt know how to measure output VSWR,because I am afraid of damaging network analyzer under having powe supply.

how to measure output vswr

Why do you need to measure this parameter? Commercial systems use circulators and isolators in the feed and so no energy reflected or picked up by the antenna reaches the power amplifier.

If you did measure it and you had a quadrature hybrid type of amplifier topology the SWR would be very close to 1.0. If it is a single amplifier it will be very high since amplifiers are designed for efficiency first and not output impedance being 50 ohms.

Actually I think that you are looking to measure ruggedness of the PA under different VSWR’s.
For this you can use a simple line-stretcher (or tuning stub, whatever you want to name it). You have to calibrate this device, at one frequency (mid band), and one Phase (0 degrees) using the Network Analyzer, and record the VSWR (1:1, 2:1, 4:1, 6:1, 10:1 etc), for each position of the stub.
Put the line-stretcher at the output of the PA, an attenuator at the other side, and check the behavior of the PA for different VSWR’s and Phases.

From what I know, is no 2W (33dBm) WCDMA PA for mobile phones, on the market. The max power what I saw is 28dBm, to be able to reach 24dBm at the antenna connector, after filtering, switching (if is dual mode) and duplexer.

Sorry but PA haas no SWR , it has an charateristic impedance and the device you connect to it introduced swr or not.
You can test it impedance.

I think you can use a dual-directional coupler to test PA output VSWR approximatively, compare with both couple value to get it.

Just Bias the amplifier in its nominal bias point, terminate the input of the power amp ( no input power), then emit a power to the output and measure the reflection