IEC 60154: Waveguide Flanges — Zero-Leakage Microwave Connections Through Quarter-Wave Chokes

Waveguide Flanges — The “Zero Leakage” Microwave Connection Standard

IEC 60154-7 specifies waveguide flange dimensions and electrical requirements. A waveguide flange is not an ordinary mechanical connection — it must ensure electromagnetic continuity across the waveguide cross-section. Any gap or misalignment causes reflection (increased VSWR) and leakage (EMI).

Key requirements: (1) Flange flatness — typically ≥0.01 mm; unevenness creates gap leakage. (2) Choke groove — an annular groove machined into the flange face, depth = λ/4, creating a high-impedance short-circuit that prevents microwave leakage through flange gaps — even with imperfect mechanical contact, electrical continuity is maintained. (3) Alignment pins — ensures waveguide cross-section alignment; broad and narrow walls must not be swapped (affects polarization).