Study Of Solid-state Millimeter-wave Waveguide Spatial Power Combining Technology

Recently, a millimeter-wave waveguide-based spatial power combining technique using MMIC Pas (Monolithic Microwave Integrated Circuit Power Amplifiers) has gradually become a hot point in millimeter-wave solid-state high power electronic field, In these researching works, the realization of millimeter-wave broadband solid-state high power combining has been cumbered by problems about maintaining a high efficiency and a broad bandwidth under a large number of combining ways. These problems are deeply studied in this thesis. The mainly achievements are described below:1 .Based on circuit theory, the effect on combining efficiency taken by imbalances in amplitude and in phase, combining network loss and combining stages are studied in multi-stage power combining circuit and in N-way power combining circuit respectively, which builds a theoretical foundation for multi-way solid-state high power combining.2.A millimeter-wave ultra-broadband spatial power combining circuit with high efficiency is presented based on coupling between waveguide and multi-way micro-strip probes located in a same phase plane. Taking advantage of symmetry of circuit, broadband multi-way power combining is achieved in millimeter-wave band. This technique breaks through the limitations of loss and of bandwidth in a traditional millimeter-wave integrated hybrid and avoids additional loss of transition between waveguide and microstrip line. Then a 180°-3dB hybrid and a 0°-3dB hybrid with broadband and low loss performance in millimeter-wave frequencies are studied and applied in waveguide-based solid-state high power spatial combining circuits respectively. Using the 180°-hybrid, a two-way high power combining amplifier is realized. The CW output power measured is more than 36dBm in 31-35GHz, the peak of 37.5dBm occurs at 32GHz, and a power combining efficiency about 80% is obtained in the operating frequency range. Combined with a conventional waveguide hybrid, the 0°-hybrid is used in a millimeter-wave four-way high power combining amplifier. In 32-37GHz, the measured pulsed (10%) output power is more than 40dBm, and the peak of 42dBm (15.8 Watt) is obtained at 32GHz. The combining efficiency is more than 77% in 32-38GHz, and more than 85% in 34-35GHz.3.With an ultra-broadband low loss performance, a novel millimeter-wave waveguide-based spatial four-way power combining/dividing network is presented. This network has equally combining/dividing character and fixed phase difference performance between branches and is convenience of integrating solid-state high power devices, which meet requirement of higher power in an ultra-broad bandwidth at millimeter-wave frequencies. The simulated and measured results show that in full Ka-band, this four-way network exhibits a consistent branches' performance and has a measured loss about 0.2dB. Using this network, an ultra-broadband four-way power combining amplifier is fabricated. The combining efficiency of 70-80% is obtained in full Ka-band. For the first time, the excellent broadband performances are achieved, which exhibited by the compact four-way power combining/dividing network and by the four-way power combining amplifier.4.For the first time, the amplitude and phase conditions of chain-style power combining network are deduced and network performance in each stage coupling unit is ascertained, when power combining and power dividing are realized by the same network. Then a millimeter-wave waveguide-based broadband four-stage-four-way chain-style power combining technique is studied. In this technique, the bandwidth limitation to a conventional millimeter-wave waveguide-based chain-style power combining is broken through by the broadband low loss characteristic of E-plane probe coupling with waveguide. According to the simulated results, a power combining efficiency more than 97% is obtained in a bandwidth of 23.5% at Ka frequency, due to influence by imbalance among branches of combining network.5.For the first time, to avoid a sharply increase in loss with more combining ways in a traditional chain-style power combining circuit, a new idea is proposed that multi-way branches are included in one coupling stage and a high efficiency is obtained with more combining ways. Accordingly, a novel millimeter-wave waveguide-based spatial multi-way chain-style power combining circuit is presented. To obtain multiple ways in one stage under the chain-style combining conditions, this circuit takes advantage of symmetrically coupling of multi-way microstrip probes located in a same phase plane in waveguide. And then with a high efficiency, the combining ways with times of stages are obtained. To validate the idea and the scheme proposed, two novel millimeter-wave broadband low loss four-stage chain-style power combining/dividing networks with eight ways and with sixteen ways are presented respectively. The simulated and measured results show that in Ka-band with more than 20% bandwidth, this two millimeter-wave multi-way chain-style networks both have a loss less than 0.3dB. With the two networks used in millimeter-wave solid-state multi-way chain-style power combining respectively, high power combining efficiencies of 91.8% and 86% are obtained, when the inconsistency of the amplifier devices is ignored. For the first time, the excellent multi-way broadband performance is achieved at millimeter-wave frequencies, and the compact multi-way chain-style combining/dividing network is easy in fabricating and convenience of integrating multi-way solid-state high power devices. As a possible prediction, with high power MMIC PAs manufactured in a same wafer, this waveguide-based multi-way chain-style power combining technique could be used to obtain a higher millimeter-wave solid-state power.