With the spread of the 5th generation mobile phone, the increase of the output power of PA (power amplifier) has become important, and in recent years, differential amplifiers that can increase the output voltage amplitude for the power supply voltage have been examined from the viewpoint of power synthesis. In the case of a differential PA, in addition to the advantage of voltage amplitude, the load impedance can be set 4 times as much as that of a single-ended PA, which makes it possible to reduce the impact of parasitic resistance. With the study of the differential PA, many transformer matching circuits have been studied in addition to the LC matching circuits that have been widely used in the past. The transformer matching circuit can easily realize the differential-single conversion, and the transformer matching circuit is an indispensable technology in the differential PA. As with the LC matching circuit, widening the bandwidth of the transformer matching circuit is at issue. In this paper, characteristics of basic transformer matching circuits are analyzed by adding input/output shunt capacitance to transformers and the conditions of bandwidth improvement are clarified. In addition, by comparing the FBW (fractional bandwidth) with the LC 2-stage matching circuit, it is shown that the FBW can be competitive.

A TM010 cavity power combiner is presented, which achieves direct interface to microstrip lines via magnetic field coupling. A prototype is fabricated and its S-matrix measured. From the S-parameters we calculate that it shows less than 0.85 dB insertion loss over 250 MHz bandwidth at X-band. The return power to the input ports is less than -15 dB over this bandwidth. We verify the insertion loss estimation using S-matrix, by measuring transmission S-parameter of a concatenated 2-port divider-combiner network. Similarly analyzed is the case of performance of power combiner when one of the input fails. We find that we can achieve graceful degradation provided we ensure some particular reflection phase at the degraded port.

In this paper, we propose a wideband four-way turnstile-junction waveguide divider/combiner in the Ka-band. The proposed divider/combiner has an insertion loss of less than 0.8 dB over the frequency range of 28–39.5 GHz. A power combiner amplifier using this circuit and four MMIC amplifiers has been demonstrated with 83% combining efficiency at 34.9 GHz. The measured results show that the turnstile-junction waveguide divider-combiner is a suitable element for developing a broadband millimeter-wave spatial power combiner amplifier.

In this letter, a novel wideband traveling wave power divider/combiner based on the finline with irises is presented and studied. Experiments on the four-way passive divider/combiner demonstrate a minimum overall insertion loss of 1.5 dB at 35.8 GHz, and the insertion loss across 32-38 GHz is less than 2.5 dB.

A novel resonant eight-way divider/combiner based on a double-layer finline is presented and studied. Experiments on the compact eight-way passive divider/combiner demonstrate a minimum overall insertion loss of 1 dB at 35.3 GHz, and the inserting loss across 34-36 GHz is less than 1.9 dB.

A novel resonant four-way divider/combiner based on finline is presented and studied. This divider/combiner designed in 34-36 GHz is composed of new probe coupling units between finline to microstrip lines. The measured power-combining efficiency of this circuit at 34.85 GHz is 83%.

In this letter, a novel 4-way X-band spatial power divider/combiner has been developed using a modified quasi-Yagi antenna transition. The divider has an insertion loss of less than 0.5 dB and a power balance of +/-0.8 dB over a bandwidth of 3.5 GHz in the X-band. A power combiner amplifier using this circuit and four MMIC amplifiers has been demonstrated with 84% combining efficiency. The obtained results show that the modified quasi-Yagi antenna is a suitable element to develop a broadband spatial power combiner.

In this paper, a novel eight-way Ka-band spatial power combining structure based on SIW/HMSIW is presented and studied. The power-combining structure is realized by transitions between HMSIW and parallel multiport planar microstrip lines. The power combiner is designed and fabricated in 33.5-35 GHz. The measured results show a good agreement with simulation and a combining efficiency of 72% is achieved at 34.3 GHz.

A low-loss serial power combiner using suspended stripline is described. It consists of novel broadside-coupled directional couplers which have shunt capacitances at the edges of the coupled sections. These additional shunt capacitances compensate for poor directivities of the couplers because of inhomogeneous dielectric in suspended stripline structure. The fabricated three-way power combiner has achieved good performance with insertion loss less than 0.23 dB over a bandwidth of 10% in 2 GHz band.

This paper describes multi-branch Wilkinson power dividers using multilayer MMIC technology. Circuit configuration is simplified and the circuit area is effectively minimized using thin film microstrip lines. An impedance transformer between the input port and the divided point is introduced to complete impedance matching and reduce insertion loss in multi-branch power dividers. Size-reduced planar-type 2-, 4-, and 8-branch Wilkinson power dividers are produced and performed well.