Design Of GaAs HBT Power Amplifiers For Satellite Mobile Communication

Satellite mobile communication as a complementary industry of mobile communication has obtained a rapid development recent years because of its long-haul communication, strong anti-interference ability and signal stability. Radio frequency transmitter is a main block of the satellite mobile communication terminal whose function is the up-conversion and amplification of the base band signal. Power amplifier as a component to amplify the signal, its efficiency, harmonic performance, ruggedness determines the power dissipation, linearity of the transmitter. So it is significant to do some research on the power amplifier which is used for satellite mobile communication.Aiming at the harmonic performance of S band power amplifier, this project proposed a high harmonic suppression output matching network and designed a S band power amplifier using GaAs HBT technology. Three stage structure was used in this S band power amplifier and the size of it was 4mm*4mm. For the high harmonic suppression output match network, there exited three LC series resonance networks to trap the harmonic component of the power amplifier. The LC series resonance networks not only trapped the harmonic component but also took part in the impedance transformer in fundamental frequency, thus it reduced the size of the power amplifier. The measure results showed that a gain of 35dB was achieved and the gain flatness was ±0.2dB when the input signal power is from-15dBm to 4dBm. The saturate power was 35.2dBm and output P1dB was 34dBm. From second to fifth order, the harmonic suppression was -53.7dBc,-58.15dBc,-65.57dBc,-60.87dBc.For the beidou satellite navigation power amplifier, two kinds of power combination networks were used for achieved the 5 W output power. One was for improving the harmonic performance and the other was for improving the ruggedness of the power amplifier. To improve the ruggedness,90° phase shift of the two path was introduced in the output matching network. The measure results showed that the output power of the PA with harmonic suppression combination network was 38.3dBm and the PAE was 43.7%. From second to fifth order, the harmonic suppression was -66dBc,-64dBc, -74dBc, -47dBc. For the PA whose output combination network exited 90° phase shift achieved 37.6dBm output power and the PAE was 42.6%. Furthermore, the experimental results showed that PA ruggedness was improved(open with a supply voltage up to 5V) while maintained the output power and power-added efficiency under a 50 Ohms load.