This paper presents a novel technique for mitigation of flange effect and antenna transmit to receive isolation improvement methodology using RF choke for the bistatic radars of aerospace vehicles. The presence of flange causes variation in antenna radiation pattern, by an increase in sidelobe level, decrease in gain and dip in roll pattern, thereby degradation in the performance of the antenna. An RF choke adjacent to the waveguide wall is introduced to nullify the undesirable effects of the flange. This Paper demonstrates through simulation and experimentation that this choke effectively suppresses the surface wave and can be applied in many types of antennas to improve the radiation pattern deteriorated by parasitic elements. It is also demonstrated through measurements that the isolation from transmit to receive antenna is improved by introducing choke, with this technique antenna isolation is enhanced by 23 dB with 11 dB antenna gain. The gain and sidelobe improvement of the antenna with RF choke is 2 dB, and 6 dB, respectively. The proposed array antenna is fabricated with and without choke, measurements are performed and test results are presented. The isolation test between transmit & receive antenna is performed in an anechoic chamber and test results are presented. © 2022 Elsevier GmbH