  Reducing the in-band and co-polarization radar cross section (RCS) of
antennas is a widely concerned problem, especially for bistatic RCS reduction
of a single antenna. Therefore, this letter presents a design method to control
the null of the in-band scattering field by controlling the load impedance of
the antenna, so as to effectively reduce the bistatic RCS. First, the
relationship between the null position and the load impedance is calculated by
analyzing the in-band scattering field of the antenna. Then, the load impedance
of the traditional patch antenna is controlled by cascading an open-circuit
stub of different lengths on the feeding line, so as to realize the null
tunning of the in-band scattering field. Simulated and measured results show
that the designed patch antenna can tune the scattering pattern null from
0{\deg} to 60{\deg} thus effectively reduce the bistatic RCS under the premise
that the radiation performance is basically unchanged.
