Directional microwave coupled-line couplers with high lateral coupling level

Classic сoupled-line couplers with a high lateral coupling level by type of directivity are counterdirectional. Restrictions on their synthesis are imposed by the gap between transmission lines, which must be extremely small (tens of microns), the difference in the phase velocities of even and odd modes, which must be compensated and others. This makes it difficult of manufacturing couplers. Described in technical literature сoupled-line couplers with a high lateral coupling level with changed types of directivity are either quite bulky or have small dimensions due to the use of discrete inductors and capacitances, which complicates the technological process with surface mounting when implementing the final device. In this article we propose a compact сoupledline coupler with a high lateral coupling level, which implements power transfer to a single port (0 dB, crossover). The coupler topology uses periodic loops that are located between сoupled-line. The equivalent circuit of the coupled lines was calculated and analyzed for a single periodic stub. This allowed us to determine the necessary parameters and dimensions of the topology. The device is narrow-band (3 GHz ± 5 %), transmission coefficient minus 0.44 dB at the center frequency of 3 GHz, isolation for isolated ports is not less than 35 dB. The proposed compact coupler with a coupling level of 0 dB suits building distribution circuits in which it is necessary to exclude the intersection of transmission lines. The information on the synthesis of the 3 dB co-directional microwave coupler on coupled strip lines with lateral electromagnetic coupling is given. The coupler is characterized by a high isolation level with an isolated port, not less than 40 dB. The imbalance of the amplitudes between the working (through and connected) and the input port is minus (3.4 ± 0.8) dB.

Design of a 324 MHz 200 kW CW Waveguide-to-Coaxial Adaptor for Radio Frequency Quadrupole Microwave System

A 324 MHz 200 kW waveguide-to-coaxial adaptor has been designed and fabricated for a microwave coupler in a radio frequency quadrupole system. Optimization of the adaptor is performed by the numerical study and experimental test. High-power measurements show that the reflection coefficient of the adaptor is less than −30 dB at the RFQ operating frequency, and there is no breakdown in the 228 kW pulse test. The measurement results are consistent with the simulation results, indicating that the adaptor has good high-power transmission performance. This work provides theoretical and experimental bases for a rectangular-to-coaxial adaptor design, especially in high-power steady-state operation.