Distributed oscillator for generating a high frequency third harmonic microwave signal having high power output. The oscillator comprises a plurality of gain cells in a parallel configuration. Each of the gain cells comprises a bottom n-MOSFET (metal oxide semiconductor field effect transistor and a top n-MOSFET (metal oxide semiconductor field effect transistor)  each having a gate length of 0.18µm. The drain  of each bottom n-MOSFET of each gain cell is connected to the gate  of the top n-MOSFET thereof.  The drain of each top n-MOSFET is connected to a drain transmission line and the gate of each bottom n-MOSFET is connected to a gate transmission line . The drain transmission line comprises a coplanar waveguide (CPW) at each end thereof and a coplanar waveguide (CPW) between every two drains and the gate transmission line comprises a coplanar waveguide (CPW)  at each end thereof and a coplanar waveguide (CPW)  between every two gates. The output end of the drain transmission line is connected to the input end of the gate transmission line through a feed back path . The body (and source  of each bottom n-MOSFET and top n-MOSFET are earthed. The input end of the drain transmission line is connected to a voltage supply .  The output end of the gate transmission line is connected to a frequency collector . A peeking inductor  is connected across the gate and drain of the bottom n-MOSFET of each of the odd number gain cells. The length of each of the end CPWs in the drain transmission line and gate transmission line is half the length of the CPW between every two drains or gates and the inductance of the peeking inductor connected across the gate and drain of the bottom n-MOSFET of each of the odd gain cells is 1nH.