A monolithic four-stage low-noise amplifier (LNA) was successfully demonstrated for direct broadcast satellite (DBS) down-converters using 0.3 µm gate pulse-doped GaAs MESFET's This paper presents the design and test results of the LNA. The key feature of the research is a detailed demonstration of the difference between a noise figure of the four-stage LNA and an optimal noise figure of an employed FET with simulation and experiments. This LNA shows VSWR's of below 1.5: 1 as well as a noise figure of 1.1 dB and a gain of 28 dB at 12 GHz. To the best of our knowledge, it is the lowest noise figure reported so far in 12 GHz-band MMIC amplifiers. In the power characteristics, a 1 dB compression point (P1dB) of 10 dBm and a third order intercept point (IP3) of 19 dBm were shown.

Process-related variation of optimal noise figures (Fo) in pulse-doped GaAs MESFET's is discussed in this paper. Fluctuation in gate length of the proposed devices is shown to be a dominant source of variation in noise parameters. The statistical distribution of the optimal noise figure is modeled by using the gaussian approximation of the distribution in gate length; the probability density function of Fo is derived. A comparison between the calculated results by the derived probability density function and the measured distribution of Fo showed good agreement.

The application of pulse-doped GaAs MESFET's to a power amplifier module is discussed in this paper. The epitaxial layer structure was redesigned to have a dual pulse-doped structure for power applications, achieving a sufficient gate-drain brakdown voltage with excellent linearity. The measured load-pull characteristics of the redesigned device for the minimum power consumption design was presented. This device was shown to have almost twice the power-added efficiency of a conventional ion-implanted GaAs MESFET. Two kinds of power amplifiers were designed and fabricated, achieving Pout of 28.6 dBm at IM3 of -40 dBc with Pdc of 8 W and Pout of 33.0 dBm at IM3 of -40 dBc with Pdc of 32 W, respectively.