A Ka-band GaAs MMIC quadrupler with high conversion gain and efficient rejection of undesired harmonics

A Ka-band monolithic frequency quadrupler with high conversion gain and efficient rejection of undesired harmonics based on 0.15um GaAs PHEMT process is presented in this paper. The quadrupler is constructed cascading an input power amplifier, a one-stage active quadrupling part and an amplifier of the fourth harmonic. Input power amplifier with one stage is designed for guarantee of proper input power of the quadrupler, so that the quadrupling part takes in its least conversion loss. Coupled with amplifying of the fourth harmonic by the amplifier behind the quadrupling part, the whole circuit realizes a high conversion gain. Efficient rejection of undesired harmonics can be reached by harmonic restrain structure inside the quadrupling part and a open stub between the quadrupling part and the amplifier behind it. According to the simulation results, when power of input signal at 8.5 GHz is -2 dBm, the conversion gain of the MMIC quadrupler is 18.23 dB. The rejection of fundamental is 61 dBc and rejection of unwanted harmonic is 45 dBc for second harmonic, 33 dBc for the third and 40 dBc for the fifth. The overall chip size is 2.88×2.06 mm2.