Novel Coupler Using Dissimilar Lines for Monitoring High-Output Microwave Sources

In the search for a compact device to monitor the high-power output of devices such as magnetrons, the plausibility of devising a coupler consisting of the output coaxial line of the magnetron and a stripline, was investigated. The coupling was achieved by bringing a small hole on the outer conductor of the coaxial line directly under a small hole on the ground plane of a stripline. A mechanical housing that guarantees reproducibility of angular adjustments and undisturbed electromagnetic performance is necessary to investigate the coupling properties of a coaxial line to stripline coupler. A reliable mechanical housing with good mechanical and electromagnetic properties was devised for a 60-Ohm coaxial line to 50-Ohm stripline. The important features of this mechanical housing and details of the same are also presented here. The theoretical indications of a high directivity and coupling in the range of 60 dB are proved to be true using the specially designed mechanical device that enables reproducible angular adjustments of the two lines. The design specification of minimum 20 dB directivity was found experimentally to be realizable with such couplers. Theoretical predictions and experimental results are found to tally very well.