| This paper presents the detailed design and implementation of an ultra-wide band active MMIC doubler on the basis of 0.18μm pHEMT GaAs process. This doubler consists of three parts: active balun, balanced FET doubler and distributed amplifiers. The commonly used topologies of active balun and distributed amplifier have been discussed and compared to instruct the selection of architecture of this doubler; Electromagnetic simulation on critical passive components and layouts have also been carefully studied to instruct the specific layout design. Furthermore, theory of doubler has been given and the qualitative analysis on selection of bias voltage of FET's gate has been roughly studied. The experimental results show the specific gate voltage needed to provide maximum output power at second harmonic. The input frequency of this doubler ranges from 2GHz to 25GHz. However, confined by the available measurement device and rigid time, the input frequencies between 2GHz and 20GHz have been experimentally tested. The measured results show that when the input frequency ranges from 2GHz to 6GHz or from 9GHz to 18GHz, the doubler has a second harmonic output power of greater than 3dBm with 3dBm input power. The fundamental rejection is greater than 20dB in these two bands. The second harmonic output power and the fundamental rejection is greater than 2dBm and greater than 15dB for the input frequency between 7 and 8GHz, respectively. When the input frequency goes up to 19GHz, the second harmonic output power and fundamental rejection is about -2dBm and 10dB, respectively. Nevertheless, provided that the losses caused by coaxial line, wire bonding, and radiation and so on, the measured results are in good accordance with the simulation results during the input frequencies between 2GHz and 18GHz, while the differences are bigger with the input frequency higher than 19GHz. This phenomenon is caused by the relatively high loss generated by the connectors etc in high frequencies. |
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