High-efficiency three-way Ka-band waveguide unequal power combiner

• Published in: IET microwaves, antennas & propagation Vol. 6; no. 11; pp. 1195 - 1199
• Main Authors: Simons, R.N., Abraham, A.J., Freeman, J.C., Wintucky, E.G., Chevalier, C.T.
• Format: Journal Article
• Language: English
• Published: Stevenage The Institution of Engineering & Technology 21.08.2012
• Subjects: Amplitudes; Constants; Deep space; Modulation; Noise levels; Ports; Serials; Waveguides
• ISSN: 1751-8725; 1751-8733
• DOI: 10.1049/iet-map.2012.0207

This article presents the design, simulation and characterisation of a novel high-efficiency Ka-band rectangular waveguide three-way serial combiner for monolithic microwave integrated circuit power amplifiers (PA) with unequal output power. The combiner presented here is suited for low data rate communications from deep space using a single carrier with constant envelope type modulation. The three-way combiner consists internally of two branch-line hybrids connected in series by a short length of waveguide. The two branch-line hybrids were each designed to combine two input signals that are equal in phase and with an amplitude ratio of two, although in general the amplitude ratio could be arbitrary. S-parameter measurements demonstrated a close achievement of the design goals. The measured return loss at the output port was greater than 16 dB and the isolation between the three input ports of the three-way combiner were greater than 22 dB. The combining of three PAs was successfully demonstrated, in which the measured combining efficiency was greater than 90% at the centre frequency of 32.05 GHz.