Long Range In-Well Radar Measurements utilizing Higher-order Propagation Modes

Long range in-well radar measurements are presented in this contribution. Using an FMCW radar at 24 GHz, the benefits of higher-order propagation modes are demonstrated by a comparison between standard TE
11
and advantageous TE
01
-mode. The TE
01
-mode is excited by a compact in-line mode converter, which can be mounted directly between radar and horn antenna. Hence, the achievable distance of the radar system in long subsurface pipe applications can be increased. Due to its field distribution, the TE
01
-mode reduces wall losses and the excitation of further higher modes is reduced. Consequently, the resulting reflection at the end of a test pipe measuring over 500 m in length, is increased by more than 35 dB.