The 3-dB coupler can be used:

– as a decoupled power splitter with a ratio of 1:1,

– for the decoupled combining of two transmitters

with frequency spacing as narrow as

desired (at 3 dB loss),

– for the decoupled combining of two receivers

with frequency spacing as narrow as desired,

– for the decoupled combining of two transmitter/

receiver units, whose integrated

duplexers are within the same frequency

range,

– as a frequency-independent 90° phase shifter,

– as a component to form combiners.

Function:

The 3-dB coupler has four ports, two of which

are decoupled from each other. For example

effective power entering into port 1 is distributed

into ports 2 and 3. Port 4 is decoupled and

without power if ports 2 and 3 are ideally

matched. In practice an absorber of suitable

power at port 4 is to be planned in accordance

with the mismatch of ports 2 and 3.

Decoupled combining can be achieved via the

diagonally opposite ports 2 and 3 or 1 and 4.