Small Antennas Remote Impedance Measurement Using Electrostatic Discharge
The conventional techniques to measure the input impedance of an antenna are based on comparing the reflected signal to the incident signal at the antenna port at a given frequency. A network analyzer connected to the antenna under test through a feeding cable is the most common impedance measurement setup. The induced current on the outer surface of the feeding cable in the electrically small antenna (ESA) case, however, significantly interferes with this process. Therefore, the traditional methods to measure the input impedance such as using a network analyzer may not be suitable for an ESA. A remote impedance measurement technique based on the impulse responses of an ESA terminated to three standard loads, short/open/matched load, is introduced. Two different types of antennas are designed and simulated using a full-wave simulator and then the impulse responses are computed using a transient simulator software. Thereafter, two different circuit models are introduced and the parameters of these models are computed using three impulse responses. The input impedance of both antennas are computed directly from the full-wave simulations as well as the remote measurement technique and the results are compared. Finally, both antennas are prototyped, measured, and the input impedances of the antennas are compared for the direct measurement using a network analyzer and the proposed technique. The presented results confirm the accuracy of the proposed method.