Ka-band Solid State Power Synthesis Technology Research

The effective distance and anti-jamming ability of a microwave application system are greatly determined by the transmitter's output power, and high power amplifier is the key component of wireless transmitter. In the millimeter-wave band, the DC transition efficiency is very low, so a single component's output power is limited. In order to make solid-state power amplifier (SSPA) partially substitute the stodgy TWT component, we must use power combining technique to increase its output power.After researching a lot of paper about power combining technique, we designed and assembled a Ka-band solid-state power amplifier. The main contents are the follows:1. By analyzing and comparing the characteristics of various power combing techniques, we chose a waveguide four paths spatial power combining structure as the scheme of the SSPA.2. Analyzed the principle of the power dividing-combining structure. Then designed a Ka-band 2×2 power dividing-combing structure which is based on a double antipodal finline-to-microstrip transition. After modeling and optimizing by the software CST Microwave Studio, we made a practical structure which back-to-back insertion loss is less than 1.5 decibels and return loss is better than 10 decibels in the frequency range 30 to 40 GHz. Also, we designed a Ka-band finline-to-microstrip transition for the driver amplifiers.3. We chose a new material to substitute the conventional Kovar as the carrier of the MMIC. By thermal simulating and optimizing in the finite element analyzing software ANSYS, we got the proper size of the carrier. It greatly improved the heat conduction form the MMIC to the Aluminum house.4. Designed and assembled the Ka-band SSPA. In the frequency range 33 to 37 GHz, its highest saturation output power is up to 10.33 watts (40.14 dBm). And the 10 watts output power bandwidth is about 1 GHz (from 34 to 35 GHz). We can estimate the highest power combining efficiency is up to 85%. 5. Forecasted the promising outlook of the SSPA design for millimeter-wave applications. And also, this structure could be used as a basic unit to realize further power combining.