Metal-length sensor with antenna resonant detector for prescription guidance of oral pill medication

A method of measuring the length of a small piece of metal without any physical contact has been developed. The metal can be considered to be an antenna with a resonant frequency that depends on its electrical length. When two pieces of metal are placed near each other, they are coupled via electromagnetic waves in the radio frequency (RF) region; and they influence each other by means of energy transfer. If one piece of metal is driven by an RF source, energy is transferred to the other piece, even if the pieces are not physically touching each other. The energy transfer is efficient when the frequency of the RF source matches the resonant frequency of the second piece of metal. If the voltage standing wave ratio (VSWR) of the RF source side is monitored, a clear dip in the VSWR curve is observed at the resonant frequency of the second piece of metal because of energy transfer. That frequency can be used to calculate the length of the second piece of metal. A new sensing antenna that provides efficient coupling to the target and is fairly insensitive to the far environment has been developed with the goal of making a practical system. A scanning RF signal generator and a VSWR detection unit were also developed for the experiments and were housed in a small, handy module. As a practical application, a system for detecting the removal of pills from thermoformed blister packaging was developed that can help to ensure that a person takes the proper amount of medication at the proper times.