A 15GHz-band 4-channel transmit/receive RF core-chip is presented for high SHF wide-band massive MIMO in 5G. In order to realize small RF frontend for 5G base stations, both 6bit phase shifters (PS) and 0.25 dB resolution variable gain amplifiers (VGA) are integrated in TX and RX paths of 4-channels on the chip. A PS calibration technique is applied to compensate the error of 6bit PS caused by process variations. A common gate current steering topology with tail current control is used for VGA to enhance the gain control accuracy. The 15GHz-band RF core-chip fabricated in 65 nm CMOS process achieved phase control error of 1.9deg. rms., and amplitude control error of 0.23 dB. rms.