OPTIMIZATION OF SECOND HARMONIC INPUT IMPEDANCE FOR HIGH CONVERSION GAIN FREQUENCY DOUBLER

Design of a high conversion gain frequency doubler has been presented in this paper by optimizing the input impedance at the second harmonic frequency. A LC tank resonator, as a second harmonic impedance optimizer at input side, properly adjusts the harmonic impedance without affecting matching performance at fundamental frequency. In practice, a stepped impedance resonator was utilized for realizing the designed input impedances at both fundamental and the second harmonic frequency. Based on this design technique, a 5 to 10 GHz single-ended GaAs FET frequency doubler was designed, fabricated, and tested. For the frequency doubler configuration, conversion gain of 7.34 dB and saturated output power of 8.17 dBm was achieved when the FET was biased in pinch-off region, rich second harmonic. 1