Design Of Microwave Power Dividing Or Combining Circuit

With millimeter-wave technology more and more widely applied in radar, satellitecommunications, electronic warfare, navigation control and other military electronic systems, there isincreasing demand for the output power of the signal source. Only when the output power is highenough, can it be achieved that good communication quality of communication systems, fartransmission distance and strong enough anti-interference ability of radar. But in the millimeter-waveband, the output power of a single solid-state power device is often limited, so that it cannot meet therequirement of high power output. Then, a particular circuit which is called power combining circuit,to combine the power of multiple solid state devices is needed. Therefore, it’s of great significance tostudy of power combining circuits with features of broadband, high efficiency, high power, easy toimplement, miniaturization and good heat dissipation.In this thesis, the basic theory of power combining and main factors that have influence on outputpower and combining efficiency are discussed. Based on the theory, two Ka-band four-way powercombining circuits are designed. The main works in this thesis can be summarized as follows:The combining efficiency of the combining circuit is analyzed and the required conditions toobtain the maximum combining efficiency are deduced. The influence of branch failure on outputpower is analyzed. The chain type power combining circuit and binary type power combining circuitare analyzed.Two Ka-band four-way chain type power combining circuits based on waveguide are designed torealize equal power coupling from four microstrip probes. Capacitive iris and stepped waveguide areused to realize impedance matching with the probes. The cause of the spikes on the S-parameter curveof the back-to-back structure is discussed and their eliminate methods are proposed. The chain typecircuit based on stepped waveguide is fabricated and measured.Using waveguide T-junction, waveguide to coaxial-cable converter and waveguide steppedimpedance matching network, a novel3dB waveguide-coaxial bridge is constructed. Based on this3dB bridge and the structure of waveguide to double probe transition, a Ka-band four-way binary typepower combining network is designed. In the29GHz to36GHz band, the simulated insertion loss ofthe power combining circuit is less than0.05dB and the combining efficiency is more than98.9%.