in our developed board
when connect with short Antennas,the system crash
but when we connect with antennas by line,the system is ok
but we test the wsr in board,it's 2~4
I think even if not match,the system may not crash
please give me some advice
In simple systems, the oscillator is directly connected to the antenna. In those, if you present the wrong antenna impedance the oscillator stops oscillating. You might have one of those.
Your problem is the antenna, it looks like it has a short or open and because of that you have high VSWR, when you use a cable the VSWR is redused because of the attenuation ans it come to the range you can deal with.
I would check the VSWR of the short antenna.
Another less likely option is that you have feedback because the antenna is to close to the circuit.