Theoretical and Experimental Investigations on Input Couplers for a Double Confocal Gyro-Amplifier

Two types of double confocal waveguide
${\mathrm {TE}}_{06}^{anti} $
-mode input couplers operating at 140 and 220 GHz are theoretically and experimentally investigated in this article, respectively. The 140 GHz input coupler is based on a power division network structure, while the 220 GHz input coupler is based on a coaxial resonant cavity structure. The field pattern of these two input couplers are analyzed and discussed. The prototypes were fabricated and tested. Back-to-back transmission experimental results agree well with the results of the theoretical simulations. The experimental results show that the 3 dB bandwidth of the power division input coupler at 140 GHz is about 9 GHz and the maximum transmission is −1.4 dB. The 3 dB bandwidth of the coaxial cavity input coupler at 220 GHz is about 3.5 GHz and the maximum transmission is −0.9 dB. It means that a wider bandwidth can be obtained from the power division input coupler, while a higher conversion efficiency can be obtained fromthe coaxial cavity input coupler. The proposed methodology can be applied to the design of an arbitrary
${\mathrm {TE}}_{0{n}}^{\text{anti}} $
(
${n} >=2$
) mode input coupler for a double confocal structure gyro-amplifier.