High frequency oscillator second harmonic

A high frequency oscillator second harmonic comprises a transistor (16), a first signal line (30) which is connected at one end to the base or gate of the transistor, a first shunt capacitor (34) connected at one end to the other end first signal line is connected and grounded at the other end, a second signal line (32) which is connected at one end to the collector or drain of the transistor, a second shunt capacitor (36) connected at one end to the other end of the second signal line is connected and grounded at the other end, and a capacitor (38) of high capacitance which is connected between the first signal line and the second signal line. The first signal line has a length which is equal to one wavelength between an odd multiple of a quarter of the wavelength of the fundamental signal plus and minus one-sixteenth of the wavelength of the fundamental signal.