Wireless Impedance Spectrometer

摘要

A system and method for measuring the permittivity and/or the impedance of a material are based on transmitting a first RF signal to a transponder coupled to the material. The transponder is equipped with a resonant antenna coupled to the material such that the response of the antenna is affected by the material. The signal strength of a second RF signal transmitted by the transponder in response to the first RF signal, and received by an interrogator, is measured. The interrogator can calculate both the real part and the imaginary part of the complex impedance of the material from multiple measurements of the signal strength of the second RF signal taken at a plurality of frequencies of the first RF signal.

主权项

1. An apparatus for measuring both the real and the imaginary components of the impedance of a material, the apparatus comprising:
an interrogator comprising a transmitter for transmitting a first radio-frequency (RF) signal; and a first transponder comprising a first resonant antenna coupled to the material such that a resonant frequency and a quality factor of the first resonant antenna are affected by the real and imaginary components of the impedance of the material; wherein the first resonant antenna is for receiving the first RF signal and for transmitting a second RF signal based on the first RF signal; wherein the interrogator further comprises a receiver for receiving the second RF signal; wherein the interrogator further comprises a frequency generator for generating a first frequency of the first RF signal at a first time and a second frequency of the first RF signal at a second time; wherein the interrogator further comprises an impedance calculator for calculating the real and imaginary components of the impedance of the material based on (a) a first measurement of the second RF signal as received by the interrogator at the first time, and (b) a second measurement of the second RF signal as received by the interrogator at the second time; and wherein the first frequency is different from the second frequency.