Load impedance of electrically small receiving antenna providing minimal group delay time irregularity

The accuracy of determining coordinates in terrestrial radio navigation systems (RNS) depends on the receiving antenna frequency response irregularity: received signal power and group delay time (GD). Due to the limited space on the carrier, the RNS receiving antennas are small and cannot be effectively matched with feeder over the entire operating frequency band. The paper considers two options for the RNS receiver input circuit. First is a classical matching scheme and second is direct connection of the antenna to the receiver input. It is shown that the most uniform frequency characteristics are achieved when the antenna is connected directly to reciever. In this case, the maximum received signal power occurs when the antenna input resistance module and the load resistance are equal. At the same time, high load resistance increases the frequency response irregularity. Therefore, the choice of load resistance should be made compromising manner, taking into account signal level, available input amplifier gain and the allowed frequency response irregularity.