DEVICE FOR MEASURING MOISTURE IN OVERLAYS (LIKE HAIR) OF A MICROSTRIP DIRECTIONAL COUPLER

摘要

A sensor for measuring moisture content of a sample like hair, comprising: a micorstrip line; a directional coupler having a pair of generally parallel first (3) and second (4) strips defining a coupling gap therebetween; and a high frequency signal generator electrically coupled to said first strip (3) and operable to couple power to said second strip (4) with the sample placed as an overlay across said coupling gap to thereby generate a coupled power signal in said second strip having an amplitude related to moisture content of the sample. The coupled power signal from strip (4) is phase (13) shifted by the microstrip line and coupled to one port of a mimixer (12). The forward power signal from strip (3) is coupled to the other part of mixer (12).