Abstract: According to the recently developed travelling wave interaction concepts, a TW FET with suitable electrode structure for a monolithic realization has been designed and investi-gated by a microstrip line hybrid model together with individual FETs. A coplanar meander line slow wave electrode system was chosen, since it can be easily integrated into a monolithic FET structure. The active length of the model was 3 guided wave length long. With 21 individual FETs the output power of the model was higher by more than one order in magnitude as compared to an individual FET. A rather flat gain characteristic with broad-band-width of 1:15 was obtained. The small signal S parameters showed useful values. The RF field distribution along the active meander line electrodes was measured. The distribution reveals the TW interaction nature. The phase shift and two tone third order intermodulation with the input power level were also observed. No efforts had been spent to optimize the model design, but the measured characteristic was still attractives; there is much room for improvement in performance of the TW FET.