Compact probe design for power monitoring from the narrow side of the reduced height waveguide

Due to confined space in a stack of reduced height waveguides, power detection of the incident and reflected wave in the reduced height waveguide is extremely difficult. A new compact probe to monitor the incident and reflected wave from the narrow side of the reduced height waveguide has been developed. This compact probe consists of 2 current loops, a directional coupler, and a small trimmer capacitor. The two current loops are placed on the narrow side of the waveguide with a quarter guide wavelength (λ_g/4) spacing. The outputs of the current loops are connected to the directional coupler. In order to optimize phase adjustment, a trimmer capacitor is attached in series with one of the current loops. Test results show that more than 30 dB directivity at 4.6 GHz is achieved by using this compact probe.