Abstract: The transmitting multi-beam forming technique of wideband LFM radar is studied in this paper. To deal with the aperture effects in wideband phased array radar, a low cost and low complexity method based on time-varying weighting is proposed. An S-band 4-element protype system is designed and tested, which fractional bandwidth is over 20% and the center frequency is 2.45 GHz. In this system, the weighting coefficients of beamforming and channel calibration are modulated to the LFM signal in the transmit radio-frequency (RF) path, and the measured channel performances and far-field radiation patterns can prove the feasibility of the proposed method.