Abstract
This paper presents a novel design of an eight-port directional coupler with a very compact structure and simple manufacturing, working in the Ku frequency band. One of the main goals of the design was to ease the manufacturing with a simple structure: the coupler consisted of four rectangular waveguide input ports, four rectangular waveguide output ports, and a central coupling region with only H-plane variation. A prototype was fabricated using additive manufacturing, with a combination of 3D printing and silver coating metallization. The obtained performance showed a theoretical bandwidth of 6.6% with 20 dB return loss for the input/output ports. Good agreement between simulations and measurements was obtained, validating the proposed coupler as a good trade-off for low cost 3D printing, compactness, and high performance for systems requiring a high number of ports as in phase arrays or Butler matrices.
Highlights
Power distribution networks at microwave frequencies are widely used in satellite communications, radars, mobile systems, and measurement
The proposed structure introduces another suitable configuration for couplers with eight ports, with a good trade-off between fractional bandwidth, return loss, and isolation
Routing arms with H-plane discontinuities in the waveguide width were used to transfer the signal from the input ports to the central coupling region. These elements were designed to have a coupling with the same transmission to all the output ports
Summary
Power distribution networks at microwave frequencies are widely used in satellite communications, radars, mobile systems, and measurement. The short-slot couplers are one of the most well-known topologies for compact couplers [2] They are traditionally designed with four or six physical ports [2,3,4,5,6], playing a very important role in several microwave systems such as antenna feeders or Butler matrices [7,8,9], since they provide several advantages related to low insertion loss, good isolation, and high power handling capability. In several previous studies such as in [2] and [4], E- and H-plane couplers were designed with an equal or arbitrary (i.e., non-3 dB division) power distribution These couplers have four physical ports, with one electrical port or mode at each physical port and with a 15% relative frequency bandwidth measured at 25 dB of return loss. The proposed structure introduces another suitable configuration for couplers with eight ports, with a good trade-off between fractional bandwidth, return loss, and isolation
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