A Wideband Doherty Combiner with Phase Variation Compensation Using LTCC Applicable for High Power Transmission

In this paper, we propose a small-sized Doherty combiner with phase variation compensation using low temperature co-fired ceramic (LTCC) substrate. The proposed design theory for the Doherty combiner is derived using the phase calculation of the S-parameter based on the relation between the input and output ports. The proposed circuit is designed after determining the band edge frequency and the targeted degree of the phase balance. The proposed circuit is verified using the microstrip line and the LTCC substrate. The implemented structure, using LTCC as the substrate, is operated under a high-power test of continuous wave 50 W, the results of which also show that the amplitude and phase balance have variations within 0.2 dB and ±1°, respectively. The high-power test shows that the implemented structure is applicable for high power Doherty amplifiers or combiners.