Broadband high power amplifiers using spatial power combining technique

High power, broad bandwidth, high linearity and low noise are among the most important features in amplifier design. Realizing all these features in one amplifier remained as a big challenge for RF engineers. Broadband spatial power combining technique addresses all these issues by combining the output power of a large quantity of Microwave Monolithic Integrated Circuit (MMIC) amplifiers in a broadband environment, while maintaining good linearity and improving phase noise of the MMIC amplifiers. The intent of this research is to extend the waveguide based combiner design to broadband applications with emphasis on linearity improvement and phase noise reduction. Coaxial waveguide was used as the host of the combining circuits for broader bandwidth and better uniformity by equally distributing the input power to each element. The goal also includes the standardization of the modeling technique. Meanwhile, thermal management, efficiency, noise figure, phase noise and linearity analyses are all covered in this work.; A broadband low noise medium power amplifier is first presented. The coaxial waveguide combiner is utilized to combine the output power of 32 low noise MMIC amplifiers. A bandwidth from 3.5 to 14 GHz is achieved with a maximum power of 1 watt. The residue noise of the amplifier is lower than −150 dBc at a 10 KHz offset from the carrier with 15 dB reduction compared to the residual phase noise of a MMIC amplifier.; A new compact coaxial combiner with much smaller size is further investigated. Broadband slotline to microstrip line transition is integrated for better compatibility with commercial MMIC amplifiers. Thermal simulations are performed and a new thermal management scheme is employed to improve the heat sinking in high power application. A high power amplifier using the compact combiner design is built and demonstrated to have a bandwidth from 6 to 17 GHz with 45-watt maximum output power. Linearity measurement has shown a high IP3 of 54 dBm. Residual phase noise is −140 dBc at a 10 KHz offset from carrier.