Impedance Measurement of Properly Excited Small Balanced Antennas

This paper presents a new method for measuring the input impedance of properly fed small balanced antennas using a conventional vector network analyzer. The measurement setup includes a balun which allows driving the balanced antenna properly. This measurement method allows analysis of proximity effects on the input return loss of balanced antennas. For this purpose, a formula to extract the antenna impedance by measuring the reflection coefficient at the balun input is developed. To verify the proposed method, a balanced antenna with known simulated differential impedance has been measured and compared with the simulation results. The achieved good agreement validates the developed formula and thus the new measurement procedure.