In wireless communication systems with array antennas, direction of arrival (DOA) of received signal is required for signal detection to obtain enough signal to noise ratio (SNR). However, without knowledge of DOA of signal, joint DOA estimation and signal detection are required for successful data transmission in beamforming system. Hybrid beamforming system composing of analog radio frequency (RF) combiner and digital baseband combiner has been proposed to reduce high complexity of digital beamforming system by using small number of RF chains which reduce dimension of signal. In spite of enefits in hardware complexity, reduced dimension may yield both performance degradation of DOA estimation and loss of received SNR. To reduce SNR loss and improve both DOA estimation and signal detection performance, we propose an adaptive method for RF combiner design. Simulation results show the performance improvement by using proposed method in both line of sight (LOS) channel and multipath channel.