Direct conversion quadrature demodulator analysis based on recently fabricated V-band six-port circuit operating over 60 GHz band is presented in this paper. In order to obtain realistic system simulation results, the computer model of the six-port demodulator is implemented using Advanced Design System (ADS) software and S-parameter measurements of the integrated six-port circuit on thin alumina substrate. The performance of the proposed model is characterized in terms of the Error Vector Magnitude (EVM) for various M-PSK/M-QAM modulated signals. Very good demodulation results have been obtained over a 5 GHz band, from 60 to 65 GHz. These results provide further evidence that the six-port quadrature demodulator is a successful approach for homodyne or heterodyne transceivers designed for high-speed short-range wireless communication systems, such as today's WiGig or future millimeter wave 5G.