With recent enhancements in semiconductor technology the microwave frequency range beyond 50 GHz becomes more and more attractive especially for wideband communication applications like 802.11ad, microwave links or automotive RADAR. Low phase noise is essential for these applications to work properly. Accurate measurement of phase noise is needed to improve the performance. However, test setups at these frequencies become difficult, especially when cross correlation of two receive paths is needed to suppress additional phase noise added by the local oscillators or mixer stages. Two external harmonic mixers in combination with a commercially available phase noise tester are used for phase noise analysis. Signal sources with frequencies up to 500 GHz can theoretically be measured with this setup.