Vector modulator technology in active phased array antenna has been used as a replacement of conventional digital phase shifter and digital attenuator. In this paper, vector modulator is realized by a vector modulation HMC500LP3 chip from Hittite company using Agilent ADS software. The HMC500LP3 is a Vector Modulator RFIC with high dynamic range and differential input. As a demonstration of the vector modulator’s flexibility, the HMC500LP3 chip has been fabricated and characterized by means of S-parameter measurements. What’s more, this paper systematically presents the vector modulator measurement step which uses Agilent USB/GPIB control module 82357B to have logic control of vector network analyzer and DC Power Analyzer by MATLAB software. The DEEMBDING calculation for SMA connector is completed by the MATLAB software. Finally, the measurement results show that the chip of the HMC500LP3 vector modulator can realize a continuously controlled 360◦ phase shifting range and a range of (−9 dB)–(−41 dB) for the amplitude over the 1.8 GHz–2.2 GHz band. Measured S11 and S22 are below −17 dB and −15 dB.