A novel frequency doubler using a feedforward structure and DGS microstrip for fundamental and high order components suppression

A novel design of a frequency doubler, using a feedforward technique and a defected ground structure (DGS), is described. In the proposed frequency doubler, the feedforward loop suppresses the fundamental component (f ₀), and the DGS attenuates the higher order harmonics such as third, fourth and so on. Due to the combination of the feedforward structure and the DGS, only the doubled frequency component (2f ₀) appears at the output port; the other unwanted components are suppressed effectively. A frequency doubler is designed at 1.87 GHz by the proposed technique and measured. The measured output power at 2f ₀ is -3 dBm when the input power is 0 dBm. Compared with a -conventional frequency doubler, the suppressions obtained at f ₀, 3f ₀ and 4f ₀ are improved by 42.9 dB, 19.2 dB and 29.7 dB, respectively. The phase noise at 2f ₀ is increased by only 3.8 dB above that of f ₀.