Short note: E-plane tee against H-plane tee

A waveguide tee is a three-port junction made by joining a side arm to a main rectangular waveguide. In an E-plane tee the side arm lies in the plane of the E-field. In an H-plane tee it lies in the plane of the H-field.

 E-plane tee (series)     H-plane tee (shunt)
        port 3                   port 3
         ||                       ||
 ====[  top  ]====       ====[ side  ]====
 port 1      port 2      port 1      port 2
 arm on broad wall       arm on narrow wall

E-plane tee (series tee)

• The side arm is joined to the broad wall, parallel to the E-field of the main guide.
• A signal fed into port 3 splits equally into ports 1 and 2, but the two outputs are 180° out of phase.
• In-phase equal signals at ports 1 and 2 cancel at port 3. Out-of-phase signals add at port 3, so port 3 gives the difference (Δ) of the inputs.
• It acts like a series connection.

H-plane tee (shunt tee)

• The side arm is joined to the narrow wall, so its axis is parallel to the H-field plane.
• A signal fed into port 3 splits equally into ports 1 and 2 in phase.
• In-phase signals at ports 1 and 2 add at port 3, so port 3 gives the sum (Σ).
• It acts like a shunt (parallel) connection.

Combining the two gives the magic tee (hybrid tee), used in mixers, duplexers and impedance bridges.