In order to research the interference rules of step-forward sweep frequency wave（SSFW） on a certain decimeter wave fuze

we theoretically deduced and analyzed the startup characteristics of the fuze in SSFW irradiation.Irradiation effect experiments were done

and interference rules and mechanism were confirmed.Experiment results show that:（1） SSFW irradiation can make the test fuze accidental fire;（2） sensitivity factors of SSFW on test fuze include the sweep frequency band

sweep frequency step

irradiation energy

and frequency stay time;（3） the sweep frequency step and frequency stay time can affect the demodulation voltage amplitude and the repetition period

respectively.When other parameters satisfy the requirements

the step length should be not shorter than 3 kHz and the frequency stay time should be not long than 20 ms in the fuze misaction;（4） the threshold interference field（TIF） is not affected by the sweep parameters;（5） the interference mechanism is that the frequency change of SSFW causes the state change of oscillatory abruptly

which will make the output voltage of the high frequency circuit to fluctuate.Then

the changing state will force the executive circuit mis-action.