Directional couplers are useful for monitoring and measuring
power levels from antennas and at different points in a
communications system. Designing a microstrip or stripline
directional coupler requires a clear understanding of the
physics of coupled lines and the limitations of a printed-
circuitboard (PCB) process. What follows is the design of a
novel microstrip/coplanar-to-stripline directional coupler that
is convenient for simultaneous monitoring of power transmitted
to and reflected from an antenna. The coupler can be designed
with coupling coefficients from 20 to 40 dB and features unique
wideband compensation for optimum performance. The compensation
is achieved by proper displacement of a tuning ground plane
between the coupled lines. Using the design approach shown here,
30- and 40-dB couplers will be constructed and tested.
Directional couplers are an important part of modern radar and
wireless-communications equipment, for monitoring power
transmitted to and reflected from an antenna. The requi