A highly directional eight‐hole coupling circular waveguide coupler

Abstract

Aiming at the system noise temperature calibration of the K-band seven-beam cryogenic receiver on Tianma Radio Telescope, a design of K-band highly directional coupler is proposed in this paper. Based on the hole coupling principle proposed by Gian Guido Gentili, an eight-hole coupling circular waveguide directional coupler is designed by ANSYS HFSS software. Through the distribution mode of eight coupling holes, the excellent performance and compact structure have been realized. Measurement shows that the reflection coefficient is less than À25 dB, coupling degree is stable within À25 ± 1 dB, isolation degree is lower than À35 dB, and directivity coefficient is greater than 10 dB in its operating frequency range.

A Compact Circular Waveguide Directional Coupler for High-Order Mode Vacuum Electronic Devices

“…Until recently, the mainstream research into directional couplers applied for the power monitoring of VEDs has mainly been focused on traditional aperture-type directional couplers [12][13][14][15][16][17][18][19][20][21][22], which are conventionally composed of a high-order mode circular waveguide (main waveguide) and a standard or non-standard rectangular waveguide (secondary waveguide), connected in a parallel or orthogonal way through two or more coupling apertures with various shapes. For structures where the primary and secondary waveguides are connected in a parallel arrangement, it is necessary to adjust the size, spacing, and number of the coupling holes to obtain excellent performance.…”

“…Another traditional structure is to connect the main and secondary waveguides of the coupler in an orthogonal way, which has the advantage of greatly reducing the axial length of the device. However, because the orthogonal connection mode limits the length of its coupling region, the disadvantage of this kind of structure is that its relative bandwidth is generally less than 10%, which means it can only work in a narrow band [21,22] so there are fewer studies on this structure.…”