Measuring the Antenna Factor in a TEM Waveguide at Low Frequencies

Considering the low radiation efficiency of antennas at low frequencies (e.g., below 200 MHz), and the poor absorption of radio absorbing materials in an anechoic chamber. An alternative method for antenna factor (AF) measurement in a transverse electromagnetic (TEM) waveguide is proposed. By using a vector network analyzer to perform $S_{21}$ measurement, the AF can be calculated accurately, which eliminates the testing uncertainties in anechoic chambers and makes the testing process more efficient. Relevant tests are conducted in a self-made open TEM waveguide from 100 kHz to 200 MHz, and the reliability of the proposed approach is validated by comparing the measured and simulated results.