An indirect impedance characterization method for monolithic THz antennas

We present an impedance characterization method for THz antennas using coplanar probe measurements. The antenna structure, which is typically monolithically integrated with detector diodes, is represented as a two-port network. The impedance seen by the diode can be analytically extracted using reflection coefficient measurements from the other remote location of the antenna. The diode port is replaced with three terminations (short, open, and a resistive load) and measured S₁₁ data is used to compute the impedance seen by the diode. The results show that the approach gives an accurate estimate of the antenna impedance except when the electrical length between two ports is near a multiple of one-half wavelength.