| This thesis mainly focuses on designing an appropriate power amplifier for transmitter section of a homemade radar system in S band. This common-source amplifier works under 32V in Class AB to realize power amplification. The chip is GaN HEMT which has a high operating voltage, high output power, wide operating band, high efficiency and a small volume. The package is made up of metal-ceramic non-hermetical shell and has excellent heat conduction and heat stability. The amplifier is matched to 50Ω by internal matching network and external matching network, which has very good power and gain performances in a broad band.The thesis work is divided into following parts:The first part is designing an internal matching network from the chip to package. Because of a relative small input and output impedance of GaN devices, input matching network inside the package shell is needed to increase the impedance that facilitates the design of the external matching circuit. DC analysis and load-pull simulation 1 are made in ADS, the package modeling and bonding-wires are simulated is HFSS. The packaged chips are finally verified by load-pull measurement, which fits well the simulations.The second part is about the external matching network design based on load-pull measurement of the package chips. Distributed components and conjugate matching are used to match the input and output impedance to 50Ω.Finally, to improve the RF measurement accuracy, a set of testing fixtures that meet TRL standards are designed. The manufactured demo board is tuned and tested on small-signal testing system and large-signal load-pull system. Measurement results show that within the entire band, the small-signal gain is over 10.5dB, the input return loss and output return loss are both smaller than-lOdB, the saturated output power is over 88 watts, the drain efficiency is over 57%, and the droop is smaller than 0.6dB. These parameters all meet the primary design requirements. |
PDF Full Text Request