Antenna Matching at Harmonic Frequencies to Complex Load Impedance

Analysis of a self-resonant, dual-frequency-matched antenna is presented. The operating frequencies of the antenna are harmonically separated, and 1-GHz fundamental and 2-GHz second harmonic frequencies are used. This type of antenna can be used, e.g., in harmonic transponder applications, where the antenna is loaded with a nonlinear element, which is typically a Schottky diode. In this letter, the impedance properties of the studied antenna are investigated using an example Schottky diode. Compared to conventional 50- Ω environments, the frequency-dependent impedance of the Schottky diode provides additional challenges for antenna matching, which are also addressed. Rather than providing a design for an application-specific antenna, the current study presents certain “building blocks” that may be useful for particular antenna designs.