S-band High-power Solid State Power Amplifier And The Radial Waveguide Synthesis Research

Solid state power amplifier(SSPA) is widely used in remote sensing, radar, electronic jamming, electronic identification, mobile communications and other RF systems, because of its high reliability, long life, small size, high efficiency and good linearity. With the development of semiconductor technology, the technology of SSPA has become more sophisticated. However, because the limited output power of single transistor is difficult to meet the requirement in some fields, in which requires the use of power combining technology.This paper focuses on the reaserch of S-band high-power solid state power amplifier system, and the output power of 800W is combined by a 4-way radial-waveguide power combiner with four 250W power amplifier modules. Its operating frequency is from 2.3 GHz to 2.6 GHz. The 250W high-power amplifier module consists of eight 50W LDMOS FETs through the structure of balanced amplifier.Starting from the basic principle, firstly, this paper introduces the key characteristics of power amplifier and the questions needed in amplifier designing. It puts emphasis on the design of matching network, for its design directly affects the performance of power amplifier. In-depth study of those basic theories benefits the design of power amplifier. After that, this paper designs the matching network of final stage transistor using ADS software, and gives a detailed design. Finally, completing the PCB layout and testing the amplifier is the next work. The 1dB compression point of the power amplifier is more than 54dBm, the gain is greater than 67.8dB, and the gain flatness is less than 1.8dB, harmonic wave and clutter is greater than 60dBc. The testing results showed that all the characteristics of the power amplifier meet the technical requirements.Secondly, this paper introduces several power combining methods and compares their advantages and disadvantages, it focuses on the theory about radial waveguide spatial power combining technology. By the combination of theoretical methods and software, this paper designs a 4-way radial-waveguide high power combiner using HFSS. The innovation of this power combiner is that the inner conductor of the input and output connectors to the probe is a whole, so there is no inaccuracy caused by the depth of probe putting into the cavity. It improves the performance of the power combiner, and its stability is also better than the traditional radial-waveguide power combiner. The result of simulation shows that the output return loss of power combiner is less than -30dB, the insertion loss less than 0.1dB, the isolation less than -8dB, and its combining efficiency is up to 96% with great power capacity. The final testing results and simulation results are consistent.