Our solution uses a coaxial-waveguide version of the finline array.  A flared coaxial line, composed of 32 wedge-shaped circuit trays, is loaded radially with tapered slotlines in the direction of wave propagation. Each input slotline provides a gradual transition from the coaxial TEM field to a planar transmission line, for compatibility with standard microwave integrated circuitry. This combiner is based on an extension of the tapered slotline array design to the coaxial waveguide and has a broad bandwidth of more than 14GHz. Spectral Domain Method (SDM) is exploited to compute the propogation constant. A new circuit tray scheme with sector intersection is applied in this system. 1 Watt output power is reached with good linearity by integrating 32 low power MMICs. Test results prove that the coaxial waveguide power combiner is a desirable candidate for ultra-broadband high power combining.