A millimeter wave H-plane duplexer with E-plane filters has been designed. The channel filters are connected via a T-junction which is compensated by a cylindrical post and analyzed by integral contour method. Moreover, the junction discontinuity effects have been taken into account. The combination of filters and compensated T-junction allows for low-cost manufacturing. The E-plane filters are analyzed separately, by the mode matching method. The scattering parameters of the combination of filters and T-junction are obtained. The diameter and position of the compensating post and the length of the T-junction arms are optimized in order to achieve the desired performance. This procedure saves computational time and memory. The duplexer has been built for 38GHz and the theory was verified by measurements.