Microstrip configuration with inductive pickup loop for VSWR meter

In an instrument for detecting and measuring directional RF voltage wave levels on a coaxial transmission line having a tubular outer conductor and a coaxial inner conductor, said instrument being adapted to be inserted in the line and having a D'Arsonval meter movement, the improvement which comprises:

• a microstrip circuit board with a ground plane conductive layer on one surface in electrical contact with the ends of said tubular outer conductor and a conductive path printed on the other surface thereof connected to the ends of said coaxial inner conductor, said conductive path having a circular loop portion formed therein,
• an inductive sensing loop printed on said other surface within and coaxial with said loop portion of said conductive path and closely spaced thereto for sensing the RF voltage wave level on said transmission line,
• circuit means between said sensing loop and said meter movement to process the signal sensed by said sensing loop, and
• rotary switch means operationally associated with said microstrip circuit board and having a first position wherein said sensing loop is connected to said circuit means to sense the forward voltage wave on said transmission line and a second position wherein said sensing loop is connected to said circuit means to sense the reflected voltage wave on said transmission line.